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proc(4)

proc(4)                          File Formats                          proc(4)



NAME
       proc - /proc, the process file system

DESCRIPTION
       /proc  is  a  file  system  that  provides  access to the state of each
       process and light-weight process (lwp) in the system. The name of  each
       entry  in  the  /proc  directory is a decimal number corresponding to a
       process-ID. These entries  are  themselves  subdirectories.  Access  to
       process  state  is  provided  by additional files contained within each
       subdirectory; the hierarchy is described more completely below. In this
       document,  ``/proc  file''  refers  to  a non-directory file within the
       hierarchy rooted at /proc. The owner of each /proc file  and  subdirec‐
       tory is determined by the user-ID of the process.


       /proc  can  be  mounted on any mount point, in addition to the standard
       /proc mount point, and can be mounted  several  places  at  once.  Such
       additional mounts are allowed in order to facilitate the confinement of
       processes to subtrees of the file system via chroot(1M) and  yet  allow
       such processes access to commands like ps(1).


       Standard  system  calls  are  used  to  access  /proc  files:  open(2),
       close(2),  read(2),  and  write(2)  (including   readv(2),   writev(2),
       pread(2),  and  pwrite(2)).  Most  files describe process state and can
       only be opened for reading.  ctl  and  lwpctl  (control)  files  permit
       manipulation  of  process  state and can only be opened for writing. as
       (address space) files contain the image of the running process and  can
       be  opened  for  both  reading  and writing. An open for writing allows
       process control; a read-only open allows inspection but not control. In
       this  document,  we refer to the process as open for reading or writing
       if any of its associated /proc files is open for reading or writing.


       In general, more than one process can open the same /proc file  at  the
       same  time.  Exclusive  open is an advisory mechanism provided to allow
       controlling processes to avoid collisions with each  other.  A  process
       can obtain exclusive control of a target process, with respect to other
       cooperating processes, if it successfully opens any /proc file  in  the
       target  process for writing (the as or ctl files, or the lwpctl file of
       any lwp) while specifying O_EXCL in the open(2). Such an open fails  if
       the target process is already open for writing (that is, if an as, ctl,
       or lwpctl file is already open for writing). There can be any number of
       concurrent  read-only opens; O_EXCL is ignored on opens for reading. It
       is recommended that the first open for writing by a controlling process
       use  the  O_EXCL flag; multiple controlling processes usually result in
       chaos.


       If a process opens one of its own /proc files  for  writing,  the  open
       succeeds  regardless  of  O_EXCL  and  regardless of whether some other
       process has the process open for writing. Self-opens do not count  when
       another process attempts an exclusive open. (A process cannot exclude a
       debugger by opening itself for writing and the application of a  debug‐
       ger  cannot  prevent a process from opening itself.) All self-opens for
       writing are forced to be close-on-exec (see the  F_SETFD  operation  of
       fcntl(2)).


       Information  and  control  operations  are  provided through additional
       files. <procfs.h> contains definitions of data structures  and  message
       formats  used  with  these files. Some of these definitions involve the
       use of sets of flags. The set types sigset_t,  fltset_t,  and  sysset_t
       correspond,  respectively,  to  signal, fault, and system call enumera‐
       tions defined in <sys/signal.h>,  <sys/fault.h>,  and  <sys/syscall.h>.
       Each  set  type  is large enough to hold flags for its own enumeration.
       Although they are of different sizes, they have a common structure  and
       can be manipulated by these macros:

         prfillset(&set);             /* turn on all flags in set */
         premptyset(&set);            /* turn off all flags in set */
         praddset(&set, flag);        /* turn on the specified flag */
         prdelset(&set, flag);        /* turn off the specified flag */
         r = prismember(&set, flag);  /* != 0 iff flag is turned on */



       One  of  prfillset()  or  premptyset()  must  be used to initialize set
       before it is used in any other operation. flag must be a member of  the
       enumeration corresponding to set.


       Every  process contains at least one light-weight process, or lwp. Each
       lwp represents a flow of execution that is independently  scheduled  by
       the  operating system. All lwps in a process share its address space as
       well as many other attributes. Through the use of lwpctl and ctl  files
       as  described  below,  it  is  possible  to affect individual lwps in a
       process or to affect all of them at once, depending on the operation.


       When the process has more than one lwp, a representative lwp is  chosen
       by  the system for certain process status files and control operations.
       The representative lwp is a stopped lwp only if all  of  the  process's
       lwps are stopped; is stopped on an event of interest only if all of the
       lwps are so stopped (excluding PR_SUSPENDED lwps); is in a PR_REQUESTED
       stop  only  if  there  are no other events of interest to be found; or,
       failing everything else, is in a PR_SUSPENDED stop (implying  that  the
       process is deadlocked). See the description of the status file for def‐
       initions of stopped states. See the PCSTOP control  operation  for  the
       definition of ``event of interest''.


       The  representative  lwp  remains fixed (it is chosen again on the next
       operation) as long as all of the lwps are stopped on events of interest
       or  are  in  a PR_SUSPENDED stop and the PCRUN control operation is not
       applied to any of them.


       When applied to the process control file, every /proc control operation
       that  must act on an lwp uses the same algorithm to choose which lwp to
       act upon. Together with synchronous stopping (see PCSET), this  enables
       a  debugger  to  control a multiple-lwp process using only the process-
       level status and control files if it so chooses. More fine-grained con‐
       trol can be achieved using the lwp-specific files.


       The  system  supports  two  process data models, the traditional 32-bit
       data model in which ints, longs and pointers are all 32 bits wide  (the
       ILP32 data model), and on some platforms the 64-bit data model in which
       longs and pointers, but not ints, are 64 bits in width (the  LP64  data
       model).  In the LP64 data model some system data types, notably size_t,
       off_t, time_t and dev_t, grow from 32 bits to 64 bits as well.


       The /proc interfaces described here are available to  both  32-bit  and
       64-bit  controlling  processes. However, many operations attempted by a
       32-bit controlling process on a 64-bit target process fails with EOVER‐
       FLOW  because the address space range of a 32-bit process cannot encom‐
       pass a 64-bit process or because the data in some  64-bit  system  data
       type  cannot  be  compressed  to fit into the corresponding 32-bit type
       without loss of information. Operations that fail in this  circumstance
       include  reading and writing the address space, reading the address-map
       files, and setting the target process's registers. There is no restric‐
       tion  on operations applied by a 64-bit process to either a 32-bit or a
       64-bit target processes.


       The format of the contents of any /proc file depends on the data  model
       of the observer (the controlling process), not on the data model of the
       target process. A 64-bit debugger does not have to translate the infor‐
       mation it reads from a /proc file for a 32-bit process from 32-bit for‐
       mat to 64-bit format. However, it usually has to be aware of  the  data
       model  of  the  target process. The pr_dmodel field of the status files
       indicates the target process's data model.


       To help deal with system data structures that are read from 32-bit pro‐
       cesses,  a  64-bit  controlling program can be compiled with the C pre‐
       processor symbol _SYSCALL32 defined  before  system  header  files  are
       included.  This makes explicit 32-bit fixed-width data structures (like
       cstruct stat32) visible to the 64-bit program. See types32.h(3HEAD).

DIRECTORY STRUCTURE
       At the top level, the directory /proc contains entries  each  of  which
       names  an  existing process in the system. These entries are themselves
       directories. Except where otherwise noted, the  files  described  below
       can  be  opened  for  reading only. In addition, if a process becomes a
       zombie (one that has exited but whose parent has not  yet  performed  a
       wait(3C)  upon  it),  most of its associated /proc files disappear from
       the hierarchy; subsequent attempts to open them, or to  read  or  write
       files opened before the process exited, elicits the error ENOENT.


       Although process state and consequently the contents of /proc files can
       change from instant to instant, a single read(2) of  a  /proc  file  is
       guaranteed  to return a sane representation of state; that is, the read
       is atomic with respect to the state of the process. No  such  guarantee
       applies  to  successive  reads  applied  to  a /proc file for a running
       process. In addition, atomicity is not guaranteed for  I/O  applied  to
       the  as  (address-space)  file  for  a running process or for a process
       whose address space contains memory shared by another running process.


       A number of structure definitions are used to describe the files. These
       structures  may  grow  by the addition of elements at the end in future
       releases of the system and it is not legitimate for a program to assume
       that they are not.

STRUCTURE OF /proc/pid
       A  given  directory /proc/pid contains the following entries. A process
       can use the invisible alias /proc/self if it wishes to open one of  its
       own /proc files (invisible in the sense that the name ``self'' does not
       appear in a directory  listing  of  /proc  obtained  from  ls(1),  get‐
       dents(2), or readdir(3C)).

   contracts
       A directory containing references to the contracts held by the process.
       Each entry is a symlink to the contract's directory under  /system/con‐
       tract. See contract(4).

   as
       Contains  the  address-space image of the process; it can be opened for
       both reading and writing. lseek(2) is used to position the file at  the
       virtual  address of interest and then the address space can be examined
       or changed through  read(2)  or  write(2)  (or  by  using  pread(2)  or
       pwrite(2) for the combined operation).


       Data  may  be transferred from or to any locations in the address space
       of the traced process by applying lseek(2) to position the as  file  at
       the  virtual address of interest followed by read(2) or write(2) (or by
       using pread(2) or pwrite(2) for the combined operation).  The  address-
       map files /proc/pid/map and /proc/pid/xmap can be read to determine the
       accessible areas (mappings) of the address  space.  I/O  transfers  may
       span  contiguous  mappings.  An  I/O request extending into an unmapped
       area is truncated at the boundary. A  write  request  beginning  at  an
       unmapped virtual address fails with EIO; a read request beginning at an
       unmapped virtual address returns zero (an end-of-file indication).

   ctl
       A write-only file to which structured messages  are  written  directing
       the  system to change some aspect of the process's state or control its
       behavior in some way. The seek offset is not relevant when  writing  to
       this file. Individual lwps also have associated lwpctl files in the lwp
       subdirectories.  A  control  message  may  be  written  either  to  the
       process's ctl file or to a specific lwpctl file with operation-specific
       effects. The effect of a control message is  immediately  reflected  in
       the  state of the process visible through appropriate status and infor‐
       mation files. The types of control messages  are  described  in  detail
       later. See CONTROL MESSAGES.

   status
       Contains  state  information  about  the process and the representative
       lwp. The file contains a pstatus structure which contains  an  embedded
       lwpstatus structure for the representative lwp, as follows:

         typedef struct pstatus {
              int pr_flags;            /* flags (see below) */
              int pr_nlwp;             /* number of active lwps in the process */
              int pr_nzomb;            /* number of zombie lwps in the process */
              pid_tpr_pid;             /* process id */
              pid_tpr_ppid;            /* parent process id */
              pid_tpr_pgid;            /* process group id */
              pid_tpr_sid;             /* session id */
              id_t pr_aslwpid;         /* obsolete */
              id_t pr_agentid;         /* lwp-id of the agent lwp, if any */
              sigset_t pr_sigpend;     /* set of process pending signals */
              uintptr_t pr_brkbase;    /* virtual address of the process heap */
              size_t pr_brksize;       /* size of the process heap, in bytes */
              uintptr_t pr_stkbase;    /* virtual address of the process stack */
              size_tpr_stksize;        /* size of the process stack, in bytes */
              timestruc_t pr_utime;    /* process user cpu time */
              timestruc_t pr_stime;    /* process system cpu time */
              timestruc_t pr_cutime;   /* sum of children's user times */
              timestruc_t pr_cstime;   /* sum of children's system times */
              sigset_t pr_sigtrace;    /* set of traced signals */
              fltset_t pr_flttrace;    /* set of traced faults */
              sysset_t pr_sysentry;    /* set of system calls traced on entry */
              sysset_t pr_sysexit;     /* set of system calls traced on exit */
              char pr_dmodel;          /* data model of the process */
              taskid_t pr_taskid;      /* task id */
              projid_t pr_projid;      /* project id */
              zoneid_t pr_zoneid;      /* zone id */
              lwpstatus_t pr_lwp;      /* status of the representative lwp */
         } pstatus_t;



       pr_flags  is a bit-mask holding the following process flags. For conve‐
       nience, it also contains the lwp  flags  for  the  representative  lwp,
       described later.

       PR_ISSYS     process is a system process (see PCSTOP).


       PR_VFORKP    process is the parent of a vforked child (see PCWATCH).


       PR_FORK      process has its inherit-on-fork mode set (see PCSET).


       PR_RLC       process has its run-on-last-close mode set (see PCSET).


       PR_KLC       process has its kill-on-last-close mode set (see PCSET).


       PR_ASYNC     process has its asynchronous-stop mode set (see PCSET).


       PR_MSACCT    Set   by   default  in  all  processes  to  indicate  that
                    microstate accounting is enabled. However, this  flag  has
                    been  deprecated  and no longer has any effect. Microstate
                    accounting may not be disabled; however, it is still  pos‐
                    sible to toggle the flag.


       PR_MSFORK    Set   by   default  in  all  processes  to  indicate  that
                    microstate accounting is enabled for processes  that  this
                    parent forks(). However, this flag has been deprecated and
                    no longer has any effect. It is possible  to  toggle  this
                    flag;  however,  it  is not possible to disable microstate
                    accounting.


       PR_BPTADJ    process  has  its  breakpoint  adjustment  mode  set  (see
                    PCSET).


       PR_PTRACE    process has its ptrace-compatibility mode set (see PCSET).



       pr_nlwp  is the total number of active lwps in the process. pr_nzomb is
       the total number of zombie lwps in the process. A zombie lwp is a  non-
       detached  lwp  that  has  terminated  but  has  not  been  reaped  with
       thr_join(3C) or pthread_join(3C).


       pr_pid, pr_ppid, pr_pgid, and pr_sid are, respectively, the process ID,
       the ID of the process's parent, the process's process group ID, and the
       process's session ID.


       pr_aslwpid is obsolete and is always zero.


       pr_agentid is the lwp-ID for the /proc agent lwp (see the PCAGENT  con‐
       trol operation). It is zero if there is no agent lwp in the process.


       pr_sigpend identifies asynchronous signals pending for the process.


       pr_brkbase is the virtual address of the process heap and pr_brksize is
       its size in bytes. The address formed by the sum of these values is the
       process  break  (see  brk(2)).  pr_stkbase  and pr_stksize are, respec‐
       tively, the virtual address of the process stack and its size in bytes.
       (Each  lwp  runs on a separate stack; the distinguishing characteristic
       of the process stack is that the operating system grows it when  neces‐
       sary.)


       pr_utime,  pr_stime,  pr_cutime,  and  pr_cstime are, respectively, the
       user CPU and system CPU time consumed by the process, and  the  cumula‐
       tive  user  CPU and system CPU time consumed by the process's children,
       in seconds and nanoseconds.


       pr_sigtrace and pr_flttrace contain, respectively, the set  of  signals
       and  the set of hardware faults that are being traced (see PCSTRACE and
       PCSFAULT).


       pr_sysentry and pr_sysexit contain, respectively, the  sets  of  system
       calls being traced on entry and exit (see PCSENTRY and PCSEXIT).


       pr_dmodel indicates the data model of the process. Possible values are:

       PR_MODEL_ILP32     process data model is ILP32.


       PR_MODEL_LP64      process data model is LP64.


       PR_MODEL_NATIVE    process data model is native.



       The  pr_taskid,  pr_projid,  and pr_zoneid fields contain respectively,
       the numeric IDs of the task, project, and zone in which the process was
       running.


       The constant PR_MODEL_NATIVE reflects the data model of the controlling
       process, that is, its value is PR_MODEL_ILP32 or PR_MODEL_LP64  accord‐
       ing  to  whether  the controlling process has been compiled as a 32-bit
       program or a 64-bit program, respectively.


       pr_lwp contains the status information for the representative lwp:

         typedef struct lwpstatus {
           int pr_flags;              /* flags (see below) */
           id_t pr_lwpid;             /* specific lwp identifier */
           short pr_why;              /* reason for lwp stop, if stopped */
           short pr_what;             /* more detailed reason */
           short pr_cursig;           /* current signal, if any */
           siginfo_t pr_info;         /* info associated with signal or fault */
           sigset_t pr_lwppend;       /* set of signals pending to the lwp */
           sigset_t pr_lwphold;       /* set of signals blocked by the lwp */
           struct sigaction pr_action;/* signal action for current signal */
           stack_t pr_altstack;       /* alternate signal stack info */
           uintptr_t pr_oldcontext;   /* address of previous ucontext */
           short pr_syscall;          /* system call number (if in syscall) */
           short pr_nsysarg;          /* number of arguments to this syscall */
           int pr_errno;              /* errno for failed syscall */
           long pr_sysarg[PRSYSARGS]; /* arguments to this syscall */
           long pr_rval1;             /* primary syscall return value */
           long pr_rval2;             /* second syscall return value, if any */
           char pr_clname[PRCLSZ];    /* scheduling class name */
           timestruc_t pr_tstamp;     /* real-time time stamp of stop */
           timestruc_t pr_utime;      /* lwp user cpu time */
           timestruc_t pr_stime;      /* lwp system cpu time */
           uintptr_t pr_ustack;       /* stack boundary data (stack_t) address */
           ulong_t pr_instr;          /* current instruction */
           prgregset_t pr_reg;        /* general registers */
           prfpregset_t pr_fpreg;     /* floating-point registers */
         } lwpstatus_t;



       pr_flags is a bit-mask holding the  following  lwp  flags.  For  conve‐
       nience, it also contains the process flags, described previously.

       PR_STOPPED    The lwp is stopped.


       PR_ISTOP      The lwp is stopped on an event of interest (see PCSTOP).


       PR_DSTOP      The lwp has a stop directive in effect (see PCSTOP).


       PR_STEP       The  lwp  has  a  single-step  directive  in  effect (see
                     PCRUN).


       PR_ASLEEP     The lwp is in an  interruptible  sleep  within  a  system
                     call.


       PR_PCINVAL    The lwp's current instruction (pr_instr) is undefined.


       PR_DETACH     This  is  a  detached  lwp  (see  pthread_create(3C)  and
                     pthread_join(3C)).


       PR_DAEMON     This is a daemon lwp (see pthread_create(3C)).


       PR_ASLWP      This flag is obsolete and is never set.


       PR_AGENT      This is the /proc agent lwp for the process.



       pr_lwpid names the specific lwp.


       pr_why and pr_what together describe, for a stopped lwp, the reason for
       the stop. Possible values of pr_why and the associated pr_what are:

       PR_REQUESTED     indicates that the stop occurred in response to a stop
                        directive, normally  because  PCSTOP  was  applied  or
                        because  another  lwp  stopped on an event of interest
                        and the asynchronous-stop flag (see PCSET) was not set
                        for the process. pr_what is unused in this case.


       PR_SIGNALLED     indicates  that the lwp stopped on receipt of a signal
                        (see PCSTRACE); pr_what holds the signal  number  that
                        caused  the  stop  (for  a newly-stopped lwp, the same
                        value is in pr_cursig).


       PR_FAULTED       indicates that the lwp stopped on incurring a hardware
                        fault  (see  PCSFAULT); pr_what holds the fault number
                        that caused the stop.


       PR_SYSENTRY      indicate a stop on entry to or exit from a system call
       PR_SYSEXIT       (see  PCSENTRY  and PCSEXIT); pr_what holds the system
                        call number.


       PR_JOBCONTROL    indicates that the lwp  stopped  due  to  the  default
                        action  of  a  job  control  stop  signal  (see sigac‐
                        tion(2)); pr_what holds the stopping signal number.


       PR_SUSPENDED     indicates that the lwp stopped due  to  internal  syn‐
                        chronization  of  lwps  within the process. pr_what is
                        unused in this case.



       pr_cursig names the current signal, that is,  the  next  signal  to  be
       delivered  to  the  lwp,  if any. pr_info, when the lwp is in a PR_SIG‐
       NALLED or PR_FAULTED stop, contains additional information pertinent to
       the particular signal or fault (see <sys/siginfo.h>).


       pr_lwppend  identifies  any synchronous or directed signals pending for
       the lwp. pr_lwphold identifies those signals whose  delivery  is  being
       blocked by the lwp (the signal mask).


       pr_action contains the signal action information pertaining to the cur‐
       rent signal (see sigaction(2)); it is undefined if pr_cursig  is  zero.
       pr_altstack contains the alternate signal stack information for the lwp
       (see sigaltstack(2)).


       pr_oldcontext, if not zero, contains the address on the lwp stack of  a
       ucontext  structure  describing  the  previous  user-level context (see
       ucontext.h(3HEAD)). It is non-zero only if the lwp is executing in  the
       context of a signal handler.


       pr_syscall  is the number of the system call, if any, being executed by
       the lwp; it is non-zero if and only if the lwp is stopped on  PR_SYSEN‐
       TRY  or  PR_SYSEXIT,  or  is asleep within a system call ( PR_ASLEEP is
       set). If pr_syscall is non-zero, pr_nsysarg is the number of  arguments
       to the system call and pr_sysarg contains the actual arguments.


       pr_rval1, pr_rval2, and pr_errno are defined only if the lwp is stopped
       on PR_SYSEXIT or if the PR_VFORKP flag is set.  If  pr_errno  is  zero,
       pr_rval1  and  pr_rval2 contain the return values from the system call.
       Otherwise, pr_errno contains the error number for  the  failing  system
       call (see <sys/errno.h>).


       pr_errpriv is a missing privilege.


       pr_clname contains the name of the lwp's scheduling class.


       pr_tstamp,  if  the  lwp is stopped, contains a time stamp marking when
       the lwp stopped, in real time seconds and nanoseconds  since  an  arbi‐
       trary time in the past.


       pr_utime is the amount of user level CPU time used by this LWP.


       pr_stime is the amount of system level CPU time used by this LWP.


       pr_ustack is the virtual address of the stack_t that contains the stack
       boundaries for this LWP. See getustack(2) and _stack_grow(3C).


       pr_instr contains the machine instruction to which  the  lwp's  program
       counter  refers.  The  amount  of  data  retrieved  from the process is
       machine-dependent. On SPARC based machines, it is  a  32-bit  word.  On
       x86-based  machines,  it is a single byte. In general, the size is that
       of the machine's smallest instruction. If PR_PCINVAL is  set,  pr_instr
       is  undefined;  this occurs whenever the lwp is not stopped or when the
       program counter refers to an invalid virtual address.


       pr_reg is an array holding the contents of a stopped lwp's general reg‐
       isters.

       SPARC                On  SPARC-based machines, the predefined constants
                            R_G0 ... R_G7, R_O0 ... R_O7, R_L0 ... R_L7,  R_I0
                            ...  R_I7,  R_PC,  R_nPC,  and  R_Y can be used as
                            indices to refer to the  corresponding  registers;
                            previous  register  windows can be read from their
                            overflow locations on the stack (however, see  the
                            gwindows file in the /proc/pid/lwp/lwpid subdirec‐
                            tory).


       SPARC V8 (32-bit)    For SPARC V8 (32-bit) controlling  processes,  the
                            predefined  constants  R_PSR, R_WIM, and R_TBR can
                            be used as indices to refer to  the  corresponding
                            special  registers. For SPARC V9 (64-bit) control‐
                            ling processes, the  predefined  constants  R_CCR,
                            R_ASI,  and R_FPRS can be used as indices to refer
                            to the corresponding special registers.


       x86 (32-bit)         For 32-bit x86 processes, the predefined constants
                            listed belowcan be used as indices to refer to the
                            corresponding registers.

                              SS
                              UESP
                              EFL
                              CS
                              EIP
                              ERR
                              TRAPNO
                              EAX
                              ECX
                              EDX
                              EBX
                              ESP
                              EBP
                              ESI
                              EDI
                              DS
                              ES
                              GS

                            The   preceding   constants    are    listed    in
                            <sys/regset.h>.

                            Note  that  a  32-bit  process  can  run on an x86
                            64-bit system, using the constants listed above.


       x86 (64-bit)         To read  the  registers  of  a  32-  or  a  64-bit
                            process,  a 64-bit x86 process should use the pre‐
                            defined constants listed below.

                              REG_GSBASE
                              REG_FSBASE
                              REG_DS
                              REG_ES
                              REG_GS
                              REG_FS
                              REG_SS
                              REG_RSP
                              REG_RFL
                              REG_CS
                              REG_RIP
                              REG_ERR
                              REG_TRAPNO
                              REG_RAX
                              REG_RCX
                              REG_RDX
                              REG_RBX
                              REG_RBP
                              REG_RSI
                              REG_RDI
                              REG_R8
                              REG_R9
                              REG_R10
                              REG_R11
                              REG_R12
                              REG_R13
                              REG_R14
                              REG_R15

                            The   preceding   constants    are    listed    in
                            <sys/regset.h>.



       pr_fpreg is a structure holding the contents of the floating-point reg‐
       isters.


       SPARC registers, both general and floating-point, as seen by  a  64-bit
       controlling  process  are the V9 versions of the registers, even if the
       target process is a 32-bit (V8) process. V8 registers are a  subset  of
       the V9 registers.


       If the lwp is not stopped, all register values are undefined.

   psinfo
       Contains  miscellaneous information about the process and the represen‐
       tative lwp needed by the ps(1) command. psinfo remains accessible after
       a  process becomes a zombie. The file contains a psinfo structure which
       contains an embedded lwpsinfo structure for the representative lwp,  as
       follows:

         typedef struct psinfo {
             int pr_flag;             /* process flags (DEPRECATED: see below) */
             int pr_nlwp;             /* number of active lwps in the process */
             int pr_nzomb;            /* number of zombie lwps in the process */
             pid_t pr_pid;            /* process id */
             pid_t pr_ppid;           /* process id of parent */
             pid_t pr_pgid;           /* process id of process group leader */
             pid_t pr_sid;            /* session id */
             uid_t pr_uid;            /* real user id */
             uid_t pr_euid;           /* effective user id */
             gid_t pr_gid;            /* real group id */
             gid_t pr_egid;           /* effective group id */
             uintptr_t pr_addr;       /* DEPRECATED was address of process */
             size_t pr_size;          /* size of process image in Kbytes */
             size_t pr_rssize;        /* resident set size in Kbytes */
             dev_t pr_ttydev;         /* controlling tty device (or PRNODEV) */
             ushort_t pr_pctcpu;      /* % of recent cpu time used by all lwps */
             ushort_t pr_pctmem;      /* % of system memory used by process */
             timestruc_t pr_start;    /* process start time, from the epoch */
             timestruc_t pr_time;     /* cpu time for this process */
             timestruc_t pr_ctime;    /* cpu time for reaped children */
             char pr_fname[PRFNSZ];   /* name of exec'ed file */
             char pr_psargs[PRARGSZ]; /* initial characters of arg list */
             int pr_wstat;            /* if zombie, the wait() status */
             int pr_argc;             /* initial argument count */
             uintptr_t pr_argv;       /* address of initial argument vector */
             uintptr_t pr_envp;       /* address of initial environment vector */
             char pr_dmodel;          /* data model of the process */
             lwpsinfo_t pr_lwp;       /* information for representative lwp */
             taskid_t pr_taskid;      /* task id */
             projid_t pr_projid;      /* project id */
             poolid_t pr_poolid;      /* pool id */
             zoneid_t pr_zoneid;      /* zone id */
             ctid_t pr_contract;      /* process contract id */
         } psinfo_t;



       Some  of the entries in psinfo, such as pr_addr, used to refer to refer
       to internal kernel data structures  addresses.   In  this  release  the
       value of pr_addr is always 0 unless running with all privilege.


       psinfo_t.pr_flag  is  a  deprecated  interface that should no longer be
       used. Applications currently relying on the SSYS bit in pr_flag  should
       migrate to checking PR_ISSYS in the pstatus structure's pr_flags field.


       pr_pctcpu and pr_pctmem are 16-bit binary fractions in the range 0.0 to
       1.0 with the binary point to the right of the high-order  bit  (1.0  ==
       0x8000). pr_pctcpu is the summation over all lwps in the process.


       pr_lwp  contains  the  ps(1) information for the representative lwp. If
       the process is a zombie, pr_nlwp,  pr_nzomb,  and  pr_lwp.pr_lwpid  are
       zero and the other fields of pr_lwp are undefined:

         typedef struct lwpsinfo {
             int pr_flag;             /* lwp flags (DEPRECATED: see below) */
             id_t pr_lwpid;           /* lwp id */
             uintptr_t pr_addr;       /* DEPRECATED was internal address of lwp */
             uintptr_t pr_wchan;      /* DEPRECATED was wait addr for sleeping lwp */
             char pr_stype;           /* synchronization event type */
             char pr_state;           /* numeric lwp state */
             char pr_sname;           /* printable character for pr_state */
             char pr_nice;            /* nice for cpu usage */
             short pr_syscall;        /* system call number (if in syscall) */
             char pr_oldpri;          /* pre-SVR4, low value is high priority */
             char pr_cpu;             /* pre-SVR4, cpu usage for scheduling */
             int pr_pri;              /* priority, high value = high priority */
             ushort_t pr_pctcpu;      /* % of recent cpu time used by this lwp */
             timestruc_t pr_start;    /* lwp start time, from the epoch */
             timestruc_t pr_time;     /* cpu time for this lwp */
             char pr_clname[PRCLSZ];  /* scheduling class name */
             char pr_name[PRFNSZ];    /* name of system lwp */
             processorid_t pr_onpro;  /* processor which last ran this lwp */
             processorid_t pr_bindpro;/* processor to which lwp is bound */
             psetid_t pr_bindpset;    /* processor set to which lwp is bound */
             lgrp_id_t pr_lgrp        /* home lgroup */
             hrtime_t pr_last_onproc; /* Timestamp of when thread last ran on */
                                      /* a processor */
         } lwpsinfo_t;



       Some  of  the  entries  in  lwpsinfo,  such  as pr_stype, pr_state, and
       pr_name, refer to internal kernel data structures  and  should  not  be
       expected  to  retain  their  meanings  across different versions of the
       operating system.


       In prior releases the lwpsinfo pr_addr and  pr_wchan  fields  contained
       kernel memory addresses for the corresponding kernel data structures in
       this release those fields are now always  0  unless  running  with  all
       privilege.


       lwpsinfo_t.pr_flag  is  a deprecated interface that should no longer be
       used.


       pr_pctcpu is a 16-bit binary fraction, as described  above.  It  repre‐
       sents  the  CPU  time  used  by  the specific lwp. On a multi-processor
       machine, the maximum value is 1/N, where N is the number of CPUs.


       pr_contract is the id of the process contract of which the process is a
       member. See contract(4) and process(4).


       pr_last_onproc is the time when thread last ran on a processor.

   cred
       Contains a description of the credentials associated with the process:

         typedef struct prcred {
              uid_t pr_euid;      /* effective user id */
              uid_t pr_ruid;      /* real user id */
              uid_t pr_suid;      /* saved user id (from exec) */
              gid_t pr_egid;      /* effective group id */
              gid_t pr_rgid;      /* real group id */
              gid_t pr_sgid;      /* saved group id (from exec) */
              int pr_ngroups;     /* number of supplementary groups */
              gid_t pr_groups[1]; /* array of supplementary groups */
         } prcred_t;




       The  array  of associated supplementary groups in pr_groups is of vari‐
       able length; the cred file contains all of  the  supplementary  groups.
       pr_ngroups  indicates the number of supplementary groups. (See also the
       PCSCRED and PCSCREDX control operations.)

   priv
       Contains a description of the privileges associated with the process:

         typedef struct prpriv {
              uint32_t        pr_nsets;      /* number of privilege set */
              uint32_t        pr_setsize;    /* size of privilege set */
              uint32_t        pr_infosize;   /* size of supplementary data */
              priv_chunk_t    pr_sets[1];    /* array of sets */
         } prpriv_t;



       The actual dimension of the pr_sets[] field is

         pr_sets[pr_nsets][pr_setsize]



       which is followed by additional information  about  the  process  state
       pr_infosize bytes in size.


       The    full   size   of   the   structure   can   be   computed   using
       PRIV_PRPRIV_SIZE(prpriv_t *).

   sigact
       Contains an array of sigaction structures describing the current dispo‐
       sitions  of  all signals associated with the traced process (see sigac‐
       tion(2)). Signal numbers are displaced by 1 from array indices, so that
       the action for signal number n appears in position n-1 of the array.

   auxv
       Contains  the initial values of the process's aux vector in an array of
       auxv_t structures (see <sys/auxv.h>). The values are  those  that  were
       passed  by  the  operating system as startup information to the dynamic
       linker.

   ldt
       This file exists only on x86-based machines. It is  non-empty  only  if
       the  process  has  established  a local descriptor table (LDT). If non-
       empty, the file contains the array of currently active LDT  entries  in
       an array of elements of type struct ssd, defined in <sys/sysi86.h>, one
       element for each active LDT entry.

   map, xmap
       Contain information about the virtual address map of the  process.  The
       map file contains an array of prmap structures while the xmap file con‐
       tains an array of prxmap structures. Each structure  describes  a  con‐
       tiguous  virtual  address  region  in  the  address space of the traced
       process:

         typedef struct prmap {
              uintptr_tpr_vaddr;         /* virtual address of mapping */
              size_t pr_size;            /* size of mapping in bytes */
              char pr_mapname[PRMAPSZ];  /* name in /proc/pid/object */
              offset_t pr_offset;        /* offset into mapped object, if any */
              int pr_mflags;             /* protection and attribute flags */
              int pr_pagesize;           /* pagesize for this mapping in bytes */
              int pr_shmid;              /* SysV shared memory identifier */
         } prmap_t;



         typedef struct prxmap {
              uintptr_t pr_vaddr;        /* virtual address of mapping */
              size_t pr_size;            /* size of mapping in bytes */
              char pr_mapname[PRMAPSZ];  /* name in /proc/pid/object */
              offset_t pr_offset;        /* offset into mapped object, if any */
              int pr_mflags;             /* protection and attribute flags */
              int pr_pagesize;           /* pagesize for this mapping in bytes */
              int pr_shmid;              /* SysV shared memory identifier */
              dev_t pr_dev;              /* device of mapped object, if any */
              uint64_t pr_ino;           /* inode of mapped object, if any */
              size_t pr_rss;             /* pages of resident memory */
              size_t pr_anon;            /* pages of resident anonymous memory */
              size_t pr_locked;          /* pages of locked memory */
              uint64_t pr_hatpagesize;   /* pagesize of mapping */
         } prxmap_t;




       pr_vaddr is the virtual  address  of  the  mapping  within  the  traced
       process  and  pr_size  is its size in bytes. pr_mapname, if it does not
       contain a null string, contains the name of a file in the object direc‐
       tory (see below) that can be opened read-only to obtain a file descrip‐
       tor for the mapped file associated with the  mapping.  This  enables  a
       debugger  to  find object file symbol tables without having to know the
       real path names of the executable file  and  shared  libraries  of  the
       process. pr_offset is the 64-bit offset within the mapped file (if any)
       to which the virtual address is mapped.


       pr_mflags is a bit-mask of protection and attribute flags:

       MA_READ          Mapping is readable by the traced process.


       MA_WRITE         Mapping is writable by the traced process.


       MA_EXEC          Mapping is executable by the traced process.


       MA_SHARED        Mapping changes are shared by the mapped object.


       MA_ANON          Mapping is anonymous memory.


       MA_ISM           Mapping  is  intimate  shared   memory   (shared   MMU
                        resources).


       MAP_NORESERVE    Mapping does not have swap space reserved (mapped with
                        MAP_NORESERVE).


       MA_SHM           Mapping System V shared memory.


       MA_OSM           Mapping shared memory created with shmget_osm(2)



       A contiguous area of the  address  space  having  the  same  underlying
       mapped  object  may  appear  as  multiple mappings due to varying read,
       write, and execute attributes. The underlying mapped  object  does  not
       change  over  the range of a single mapping. An I/O operation to a map‐
       ping marked MA_SHARED fails if applied at a virtual address not  corre‐
       sponding  to a valid page in the underlying mapped object. A write to a
       MA_SHARED mapping that is not marked MA_WRITE fails. Reads  and  writes
       to  private  mappings  always  succeed.  Reads  and  writes to unmapped
       addresses fail.


       pr_pagesize is the page size for the mapping, currently always the sys‐
       tem pagesize.


       pr_shmid  is the shared memory identifier, if any, for the mapping. Its
       value is −1  if  the  mapping  is  not  System  V  shared  memory.  See
       shmget(2).


       pr_dev is the device of the mapped object, if any, for the mapping. Its
       value is PRNODEV (-1) if the mapping does not have a device.


       pr_ino is the inode of the mapped object, if any, for the mapping.  Its
       contents are only valid if pr_dev is not PRNODEV.


       pr_rss  is  the number of resident pages of memory for the mapping. The
       number of resident bytes for the mapping may be determined by multiply‐
       ing pr_rss by the page size given by pr_pagesize.


       pr_anon  is  the number of resident anonymous memory pages (pages which
       are private to this process) for the mapping.


       pr_locked is the number of locked pages for the  mapping.  Pages  which
       are locked are always resident in memory.


       pr_hatpagesize  is the size, in bytes, of the HAT (MMU) translation for
       the mapping. pr_hatpagesize may be different than pr_pagesize. The pos‐
       sible  values are hardware architecture specific, and may change over a
       mapping's lifetime.

   rmap
       Contains information about the reserved address ranges of the  process.
       The  file  contains  an array of prmap structures, as defined above for
       the map file. Each structure describes  a  contiguous  virtual  address
       region  in  the address space of the traced process that is reserved by
       the system in the sense that an mmap(2) system call that does not spec‐
       ify  MAP_FIXED  do not use any part of it for the new mapping. Examples
       of such reservations  include  the  address  ranges  reserved  for  the
       process  stack  and  the  individual  thread stacks of a multi-threaded
       process.

   cwd
       A symbolic  link  to  the  process's  current  working  directory.  See
       chdir(2). A readlink(2) of /proc/pid/cwd yields a null string. However,
       it can be opened, listed, and searched as a directory, and can  be  the
       target of chdir(2).

   root
       A  symbolic  link  to  the process's root directory. /proc/pid/root can
       differ from the system root directory if the  process  or  one  of  its
       ancestors  executed  chroot(2) as super user. It has the same semantics
       as /proc/pid/cwd.

   fd
       A directory containing references to the open  files  of  the  process.
       Each entry is a decimal number corresponding to an open file descriptor
       in the process.


       If an entry refers to a regular file, it can be opened with normal file
       system  semantics  but,  to  ensure that the controlling process cannot
       gain greater access than the controlled process, with  no  file  access
       modes  other  than its read/write open modes in the controlled process.
       If an entry refers to a directory, it can be  accessed  with  the  same
       semantics  as /proc/pid/cwd. An attempt to open any other type of entry
       fails with EACCES.

   object
       A directory containing read-only files with names corresponding to  the
       pr_mapname  entries  in the map and pagedata files. Opening such a file
       yields a file descriptor for the underlying mapped file associated with
       an address-space mapping in the process. The file name a.out appears in
       the directory as an alias for the process's executable file.


       The object directory makes it possible for  a  controlling  process  to
       gain  access  to  the  object file and any shared libraries (and conse‐
       quently the symbol tables) without having to know the actual path names
       of the executable files.

   path
       A  directory  containing symbolic links to files opened by the process.
       The directory includes one entry for cwd and root. The  directory  also
       contains  a  numerical  entry for each file descriptor in the fd direc‐
       tory, and entries matching those  in  the  object  directory.  If  this
       information  is  not available, any attempt to read the contents of the
       symbolic link fails. This is most common for files that do not exist in
       the filesystem namespace (such as FIFOs and sockets), but can also hap‐
       pen for regular files. For the file descriptor entries, the path may be
       different from the one used by the process to open the file.

   pagedata
       Opening the page data file enables tracking of address space references
       and modifications on a per-page basis.


       A read(2) of the page data file descriptor returns structured page data
       and atomically clears the page data maintained for the file by the sys‐
       tem. That is to say, each read returns data collected  since  the  last
       read;  the first read returns data collected since the file was opened.
       When the call completes, the read buffer contains the following  struc‐
       ture  as  its header and thereafter contains a number of section header
       structures and associated byte arrays that must be accessed by  walking
       linearly through the buffer.

         typedef struct prpageheader {
             timestruc_t pr_tstamp; /* real time stamp, time of read() */
             ulong_t pr_nmap;       /* number of address space mappings */
             ulong_t pr_npage;      /* total number of pages */
         } prpageheader_t;



       The  header  is  followed  by pr_nmap prasmap structures and associated
       data arrays. The prasmap structure contains the following elements:

         typedef struct prasmap {
             uintptr_t pr_vaddr;        /* virtual address of mapping */
             ulong_t pr_npage;          /* number of pages in mapping */
             char pr_mapname[PRMAPSZ];  /* name in /proc/pid/object */
             offset_t pr_offset;        /* offset into mapped object, if any */
             int pr_mflags;             /* protection and attribute flags */
             int pr_pagesize;           /* pagesize for this mapping in bytes */
             int pr_shmid;              /* SysV shared memory identifier */
         } prasmap_t;



       Each section header is followed by pr_npage bytes, one  byte  for  each
       page  in  the  mapping, plus 0-7 null bytes at the end so that the next
       prasmap structure begins on an eight-byte aligned boundary.  Each  data
       byte may contain these flags:

       PG_REFERENCED    page has been referenced.


       PG_MODIFIED      page has been modified.



       If the read buffer is not large enough to contain all of the page data,
       the read fails with E2BIG  and  the  page  data  is  not  cleared.  The
       required  size  of  the read buffer can be determined through fstat(2).
       Application of lseek(2) to the page data file  descriptor  is  ineffec‐
       tive;  every  read  starts  from the beginning of the file. Closing the
       page data file descriptor terminates  the  system  overhead  associated
       with collecting the data.


       More  than  one  page  data file descriptor for the same process can be
       opened, up to a system-imposed limit per traced process. A read of  one
       does  not affect the data being collected by the system for the others.
       An open of the page data file fails with ENOMEM if  the  system-imposed
       limit would be exceeded.

   watch
       Contains  an  array  of  prwatch  structures, one for each watched area
       established by the PCWATCH control operation. See PCWATCH for details.

   usage
       Contains process usage information described  by  a  prusage  structure
       which contains at least the following fields:

         typedef struct prusage {
             id_t pr_lwpid;           /* lwp id.  0: process or defunct */
             int pr_count;            /* number of contributing lwps */
             timestruc_t pr_tstamp;   /* real time stamp, time of read() */
             timestruc_t pr_create;   /* process/lwp creation time stamp */
             timestruc_t pr_term;     /* process/lwp termination time stamp */
             timestruc_t pr_rtime;    /* total lwp real (elapsed) time */
             timestruc_t pr_utime;    /* user level CPU time */
             timestruc_t pr_stime;    /* system call CPU time */
             timestruc_t pr_ttime;    /* other system trap CPU time */
             timestruc_t pr_tftime;   /* text page fault sleep time */
             timestruc_t pr_dftime;   /* data page fault sleep time */
             timestruc_t pr_kftime;   /* kernel page fault sleep time */
             timestruc_t pr_ltime;    /* user lock wait sleep time */
             timestruc_t pr_slptime;  /* all other sleep time */
             timestruc_t pr_wtime;    /* wait-cpu (latency) time */
             timestruc_t pr_stoptime; /* stopped time */
             ulong_t pr_minf;         /* minor page faults */
             ulong_t pr_majf;         /* major page faults */
             ulong_t pr_nswap;        /* swaps */
             ulong_t pr_inblk;        /* input blocks */
             ulong_t pr_oublk;        /* output blocks */
             ulong_t pr_msnd;         /* messages sent */
             ulong_t pr_mrcv;         /* messages received */
             ulong_t pr_sigs;         /* signals received */
             ulong_t pr_vctx;         /* voluntary context switches */
             ulong_t pr_ictx;         /* involuntary context switches */
             ulong_t pr_sysc;         /* system calls */
             ulong_t pr_ioch;         /* chars read and written */
         } prusage_t;



       Microstate  accounting is now continuously enabled. While this informa‐
       tion was previously an estimate,  if  microstate  accounting  were  not
       enabled,  the  current  information is now never an estimate represents
       time the process has spent in various states.

   lstatus
       Contains a prheader structure followed by an array of lwpstatus  struc‐
       tures,   one   for   each   active   lwp   in  the  process  (see  also
       /proc/pid/lwp/lwpid/lwpstatus, below). The prheader structure describes
       the number and size of the array entries that follow.

         typedef struct prheader {
             long pr_nent;        /* number of entries */
             size_t pr_entsize;   /* size of each entry, in bytes */
         } prheader_t;



       The lwpstatus structure may grow by the addition of elements at the end
       in future releases of the system. Programs must use pr_entsize  in  the
       file  header  to  index  through the array. These comments apply to all
       /proc files that include a  prheader  structure  (lpsinfo  and  lusage,
       below).

   lpsinfo
       Contains  a  prheader structure followed by an array of lwpsinfo struc‐
       tures, one for eachactive and zombie  lwp  in  the  process.  See  also
       /proc/pid/lwp/lwpid/lwpsinfo, below.

   lusage
       Contains  a  prheader  structure followed by an array of prusage struc‐
       tures, one for each active lwp in the process, plus an additional  ele‐
       ment at the beginning that contains the summation over all defunct lwps
       (lwps that once existed but no longer exist in the process).  Excluding
       the  pr_lwpid, pr_tstamp, pr_create, and pr_term entries, the entry-by-
       entry summation over all these structures  is  the  definition  of  the
       process  usage  information  obtained  from  the  usage file. (See also
       /proc/pid/lwp/lwpid/lwpusage, below.)

   lwp
       A directory containing entries each of which names an active or  zombie
       lwp  within  the process. These entries are themselves directories con‐
       taining additional files as described below.  Only  the  lwpsinfo  file
       exists in the directory of a zombie lwp.

STRUCTURE OF /proc/pid/lwp/ lwpid
       A given directory /proc/pid/lwp/lwpid contains the following entries:

   lwpctl
       Write-only  control  file. The messages written to this file affect the
       specific lwp rather than the representative lwp, as is the case for the
       process's ctl file.

   lwpstatus
       lwp-specific state information. This file contains the lwpstatus struc‐
       ture for the specific lwp as described above for the representative lwp
       in the process's status file.

   lwpsinfo
       lwp-specific  ps(1) information. This file contains the lwpsinfo struc‐
       ture for the specific lwp as described above for the representative lwp
       in  the  process's  psinfo  file.  The lwpsinfo file remains accessible
       after an lwp becomes a zombie.

   lwpusage
       This file contains the  prusage  structure  for  the  specific  lwp  as
       described above for the process's usage file.

   gwindows
       This  file  exists only on SPARC based machines. If it is non-empty, it
       contains a gwindows_t structure, defined in  <sys/regset.h>,  with  the
       values  of those SPARC register windows that could not be stored on the
       stack when the lwp stopped. Conditions under which register windows are
       not  stored  on  the stack are: the stack pointer refers to nonexistent
       process memory or the stack pointer is improperly aligned. If  the  lwp
       is  not  stopped  or if there are no register windows that could not be
       stored on the stack, the file is empty (the usual case).

   xregs
       Extra state registers. The extra state  register  set  is  architecture
       dependent;  this  file  is  empty  if the system does not support extra
       state registers. If the file is non-empty, it contains an  architecture
       dependent  structure  of  type prxregset_t, defined in <procfs.h>, with
       the values of the lwp's extra  state  registers.  If  the  lwp  is  not
       stopped,  all  register values are undefined. See also the PCSXREG con‐
       trol operation, below.

   cxregs
       CPU-specific extended registers. The CPU specific extended register set
       is  architecture-dependent;  this  file is empty if the system does not
       support extended registers. If the file is non-empty,  it  contains  an
       architecture  dependent  structure  of  type prcpuxregset_t, defined in
       <procfs_isa.h>, with the values of the lwp's extended registers. If the
       lwp  is  not  stopped,  all register values are undefined. See also the
       PCSCXREG control operation, below.

   asrs
       This file exists only for 64-bit SPARC V9  processes.  It  contains  an
       asrset_t structure, defined in <sys/regset.h>, containing the values of
       the lwp's platform-dependent ancillary state registers. If the  lwp  is
       not  stopped,  all  register values are undefined. See also the PCSASRS
       control operation, below.

   templates
       A directory which contains references to the active templates  for  the
       lwp,  named  by  the  contract type. Changes made to an active template
       descriptor do not affect the original  template  which  was  activated,
       though  they do affect the active template. It is not possible to acti‐
       vate an active template descriptor. See contract(4).

CONTROL MESSAGES
       Process state changes  are  effected  through  messages  written  to  a
       process's  ctl  file or to an individual lwp's lwpctl file. All control
       messages consist of a long that names the specific  operation  followed
       by additional data containing the operand, if any.


       Multiple  control  messages  may  be  combined in a single write(2) (or
       writev(2)) to a control file, but no partial writes are permitted. That
       is,  each control message, operation code plus operand, if any, must be
       presented in its entirety to the write(2) and not in pieces  over  sev‐
       eral  system  calls. If a control operation fails, no subsequent opera‐
       tions contained in the same write(2) are attempted.


       Descriptions of the allowable control messages follow.  In  all  cases,
       writing  a message to a control file for a process or lwp that has ter‐
       minated elicits the error ENOENT.

   PCSTOP PCDSTOP PCWSTOP PCTWSTOP
       When applied to the process control file, PCSTOP directs  all  lwps  to
       stop and waits for them to stop, PCDSTOP directs all lwps to stop with‐
       out waiting for them to stop, and PCWSTOP simply waits for all lwps  to
       stop.  When applied to an lwp control file, PCSTOP directs the specific
       lwp to stop and waits until it has stopped, PCDSTOP  directs  the  spe‐
       cific  lwp  to  stop without waiting for it to stop, and PCWSTOP simply
       waits for the specific lwp to stop. When  applied  to  an  lwp  control
       file,  PCSTOP  and  PCWSTOP  complete when the lwp stops on an event of
       interest, immediately if  already  so  stopped;  when  applied  to  the
       process  control  file, they complete when every lwp has stopped either
       on an event of interest or on a PR_SUSPENDED stop.


       PCTWSTOP is identical to PCWSTOP except that it enables  the  operation
       to  time  out,  to  avoid waiting forever for a process or lwp that may
       never stop on an event of interest. PCTWSTOP takes a long operand spec‐
       ifying a number of milliseconds; the wait terminates successfully after
       the specified number of milliseconds even if the process or lwp has not
       stopped;  a timeout value of zero makes the operation identical to PCW‐
       STOP.


       An ``event of interest'' is either a PR_REQUESTED stop or a  stop  that
       has  been  specified  in  the process's tracing flags (set by PCSTRACE,
       PCSFAULT, PCSENTRY, and PCSEXIT). PR_JOBCONTROL and PR_SUSPENDED  stops
       are  specifically not events of interest. (An lwp may stop twice due to
       a stop signal, first showing PR_SIGNALLED if the signal is  traced  and
       again  showing PR_JOBCONTROL if the lwp is set running without clearing
       the signal.) If PCSTOP or PCDSTOP is applied to an lwp that is stopped,
       but  not  on an event of interest, the stop directive takes effect when
       the lwp is restarted by the competing mechanism. At that time, the  lwp
       enters a PR_REQUESTED stop before executing any user-level code.


       A  write  of a control message that blocks is interruptible by a signal
       so that, for example, an alarm(2) can be set to avoid  waiting  forever
       for  a  process  or lwp that may never stop on an event of interest. If
       PCSTOP is interrupted, the lwp stop directives remain  in  effect  even
       though  the write(2) returns an error. (Use of PCTWSTOP with a non-zero
       timeout is recommended over PCWSTOP with an alarm(2).)


       A system process (indicated by the PR_ISSYS  flag)  never  executes  at
       user  level, has no user-level address space visible through /proc, and
       cannot be stopped. Applying one of these operations to a system process
       or any of its lwps elicits the error EBUSY.

   PCRUN
       Make  an  lwp  runnable again after a stop. This operation takes a long
       operand containing zero or more of the following flags:

       PRCSIG      clears the current signal, if any (see PCCSIG).


       PRCFAULT    clears the current fault, if any (see PCCFAULT).


       PRSTEP      directs the lwp to execute a single machine instruction. On
                   completion of the instruction, a trace trap occurs. If FLT‐
                   TRACE is being traced, the lwp stops; otherwise, it is sent
                   SIGTRAP. If SIGTRAP is being traced and is not blocked, the
                   lwp stops. When the lwp stops on an event of interest,  the
                   single-step directive is cancelled, even if the stop occurs
                   before the instruction is executed. This operation requires
                   hardware and operating system support and may not be imple‐
                   mented on all processors. It is implemented  on  SPARC  and
                   x86-based machines.


       PRSABORT    is  meaningful  only if the lwp is in a PR_SYSENTRY stop or
                   is marked PR_ASLEEP; it instructs the lwp to  abort  execu‐
                   tion of the system call (see PCSENTRY and PCSEXIT).


       PRSTOP      directs  the  lwp  to  stop again as soon as possible after
                   resuming execution (see PCDSTOP). In particular, if the lwp
                   is  stopped  on  PR_SIGNALLED  or PR_FAULTED, the next stop
                   shows PR_REQUESTED, no other stop intervenes, and  the  lwp
                   does not execute any user-level code.



       When  applied  to  an  lwp  control  file, PCRUN clears any outstanding
       directed-stop request and makes the specific lwp runnable.  The  opera‐
       tion fails with EBUSY if the specific lwp is not stopped on an event of
       interest or has not been directed to stop or if the  agent  lwp  exists
       and this is not the agent lwp (see PCAGENT).


       When  applied to the process control file, a representative lwp is cho‐
       sen for the operation as described for /proc/pid/status. The  operation
       fails  with  EBUSY if the representative lwp is not stopped on an event
       of interest or has not been directed  to  stop  or  if  the  agent  lwp
       exists.  If  PRSTEP  or PRSTOP was requested, the representative lwp is
       made runnable and its outstanding  directed-stop  request  is  cleared;
       otherwise all outstanding directed-stop requests are cleared and, if it
       was stopped on an event of interest, the representative lwp  is  marked
       PR_REQUESTED. If, as a consequence, all lwps are in the PR_REQUESTED or
       PR_SUSPENDED  stop  state,  all  lwps  showing  PR_REQUESTED  are  made
       runnable.

   PCSTRACE
       Define a set of signals to be traced in the process. The receipt of one
       of these signals by an lwp causes the lwp to stop. The set  of  signals
       is  defined using an operand sigset_t contained in the control message.
       Receipt of SIGKILL cannot be  traced;  if  specified,  it  is  silently
       ignored.


       If  a  signal  that is included in an lwp's held signal set (the signal
       mask) is sent to the lwp, the signal is not received and does not cause
       a  stop until it is removed from the held signal set, either by the lwp
       itself or by setting the held signal set with PCSHOLD.

   PCCSIG
       The current signal, if any, is cleared from the specific or representa‐
       tive lwp.

   PCSSIG
       The  current  signal and its associated signal information for the spe‐
       cific or representative lwp are set according to the  contents  of  the
       operand  siginfo structure (see <sys/siginfo.h>). If the specified sig‐
       nal number is zero, the current signal is  cleared.  The  semantics  of
       this  operation  are different from those of kill(2) in that the signal
       is delivered to the lwp immediately after execution is resumed (even if
       it  is  being  blocked)  and  an  additional PR_SIGNALLED stop does not
       intervene even if the signal is traced. Setting the current  signal  to
       SIGKILL terminates the process immediately.

   PCKILL
       If applied to the process control file, a signal is sent to the process
       with semantics identical to those of kill(2). If applied to an lwp con‐
       trol file, a directed signal is sent to the specific lwp. The signal is
       named in a long operand contained in the message. Sending SIGKILL  ter‐
       minates the process immediately.

   PCUNKILL
       A  signal  is  deleted,  that is, it is removed from the set of pending
       signals. If applied to the process control file, the signal is  deleted
       from  the process's pending signals. If applied to an lwp control file,
       the signal is deleted from the lwp's pending signals. The current  sig‐
       nal  (if  any)  is unaffected. The signal is named in a long operand in
       the control message. It is an  error  (EINVAL)  to  attempt  to  delete
       SIGKILL.

   PCSHOLD
       Set  the  set  of  held  signals for the specific or representative lwp
       (signals whose delivery is blocked if sent to the lwp). The set of sig‐
       nals  is  specified with a sigset_t operand. SIGKILL and SIGSTOP cannot
       be held; if specified, they are silently ignored.

   PCSFAULT
       Define a set of hardware faults to be traced in the process. On  incur‐
       ring  one of these faults, an lwp stops. The set is defined via the op‐
       erand fltset_t structure. Fault names are defined in <sys/fault.h>  and
       include  the  following. Some of these may not occur on all processors;
       there may be processor-specific faults in addition to these.

       FLTILL       illegal instruction


       FLTPRIV      privileged instruction


       FLTBPT       breakpoint trap


       FLTTRACE     trace trap (single-step)


       FLTWATCH     watchpoint trap


       FLTACCESS    memory access fault (bus error)


       FLTBOUNDS    memory bounds violation


       FLTIOVF      integer overflow


       FLTIZDIV     integer zero divide


       FLTFPE       floating-point exception


       FLTSTACK     unrecoverable stack fault


       FLTPAGE      recoverable page fault



       When not traced, a fault normally results in the posting of a signal to
       the lwp that incurred the fault. If an lwp stops on a fault, the signal
       is posted to the lwp when execution is  resumed  unless  the  fault  is
       cleared  by  PCCFAULT or by the PRCFAULT option of PCRUN. FLTPAGE is an
       exception; no signal is posted. The  pr_info  field  in  the  lwpstatus
       structure  identifies  the  signal to be sent and contains machine-spe‐
       cific information about the fault.

   PCCFAULT
       The current fault, if any, is cleared; the  associated  signal  is  not
       sent to the specific or representative lwp.

   PCSENTRY PCSEXIT
       These  control  operations instruct the process's lwps to stop on entry
       to or exit from specified system calls. The set of system calls  to  be
       traced is defined via an operand sysset_t structure.


       When  entry to a system call is being traced, an lwp stops after having
       begun the call to the system but before the system call arguments  have
       been  fetched  from  the  lwp.  When  exit  from a system call is being
       traced, an lwp stops on completion of the system  call  just  prior  to
       checking  for  signals  and returning to user level. At this point, all
       return values have been stored into the lwp's registers.


       If an lwp is stopped on entry to a system call  (PR_SYSENTRY)  or  when
       sleeping  in an interruptible system call (PR_ASLEEP is set), it may be
       instructed to go  directly  to  system  call  exit  by  specifying  the
       PRSABORT  flag  in a PCRUN control message. Unless exit from the system
       call is being traced, the lwp returns to user level showing EINTR.

   PCWATCH
       Set or clear a watched area in the controlled process  from  a  prwatch
       structure operand:

         typedef struct prwatch {
             uintptr_t pr_vaddr;  /* virtual address of watched area */
             size_t pr_size;      /* size of watched area in bytes */
             int pr_wflags;       /* watch type flags */
         } prwatch_t;



       pr_vaddr  specifies  the  virtual  address  of  an area of memory to be
       watched in the controlled process. pr_size specifies the  size  of  the
       area,  in  bytes.  pr_wflags  specifies the type of memory access to be
       monitored as a bit-mask of the following flags:

       WA_READ         read access


       WA_WRITE        write access


       WA_EXEC         execution access


       WA_TRAPAFTER    trap after the instruction completes



       If pr_wflags is non-empty, a watched area is established for  the  vir‐
       tual  address  range specified by pr_vaddr and pr_size. If pr_wflags is
       empty, any previously-established watched area starting at  the  speci‐
       fied virtual address is cleared; pr_size is ignored.


       A  watchpoint  is  triggered  when an lwp in the traced process makes a
       memory reference that covers at least one byte of a  watched  area  and
       the memory reference is as specified in pr_wflags. When an lwp triggers
       a watchpoint, it incurs a watchpoint trap. If FLTWATCH is being traced,
       the  lwp  stops;  otherwise, it is sent a SIGTRAP signal; if SIGTRAP is
       being traced and is not blocked, the lwp stops.


       The watchpoint trap occurs  before  the  instruction  completes  unless
       WA_TRAPAFTER  was specified, in which case it occurs after the instruc‐
       tion completes. If it occurs before completion, the memory is not modi‐
       fied.  If  it  occurs  after completion, the memory is modified (if the
       access is a write access).


       Physical i/o is an exception for watchpoint traps.  In  this  instance,
       there  is  no guarantee that memory before the watched area has already
       been modified (or in the case of WA_TRAPAFTER, that the memory  follow‐
       ing  the  watched  area has not been modified) when the watchpoint trap
       occurs and the lwp stops.


       pr_info in the lwpstatus structure contains  information  pertinent  to
       the watchpoint trap. In particular, the si_addr field contains the vir‐
       tual address of the memory reference that triggered the watchpoint, and
       the   si_code  field  contains  one  of  TRAP_RWATCH,  TRAP_WWATCH,  or
       TRAP_XWATCH, indicating read, write, or execute  access,  respectively.
       The  si_trapafter  field  is  zero unless WA_TRAPAFTER is in effect for
       this watched area; non-zero indicates that the current  instruction  is
       not  the instruction that incurred the watchpoint trap. The si_pc field
       contains the virtual address of the instruction that incurred the trap.


       A watchpoint trap may be triggered while executing a system  call  that
       makes reference to the traced process's memory. The lwp that is execut‐
       ing the system call incurs the watchpoint trap while still in the  sys‐
       tem call. If it stops as a result, the lwpstatus structure contains the
       system call number and its arguments. If the lwp does not stop,  or  if
       it  is set running again without clearing the signal or fault, the sys‐
       tem call fails with EFAULT. If WA_TRAPAFTER was specified,  the  memory
       reference  s  completed and the memory is modified (if the access was a
       write access) when the watchpoint trap occurs.


       If more than one of WA_READ, WA_WRITE, and WA_EXEC is specified  for  a
       watched  area,  and  a  single  instruction incurs more than one of the
       specified types, only one is reported when the watchpoint trap  occurs.
       The  precedence is WA_EXEC, WA_READ, WA_WRITE (WA_EXEC and WA_READ take
       precedence over WA_WRITE), unless WA_TRAPAFTER was specified, in  which
       case it is WA_WRITE, WA_READ, WA_EXEC (WA_WRITE takes precedence).


       PCWATCH  fails with EINVAL if an attempt is made to specify overlapping
       watched areas or if pr_wflags contains flags other than those specified
       above.  It  fails  with  ENOMEM if an attempt is made to establish more
       watched areas than the system can support (the system can support thou‐
       sands).


       The  child  of  a  vfork(2)  borrows the parent's address space. When a
       vfork(2) is executed by a traced process, all watched areas established
       for  the parent are suspended until the child terminates or performs an
       exec(2). Any watched areas established independently in the  child  are
       cancelled  when  the  parent  resumes  after the child's termination or
       exec(2). PCWATCH fails with  EBUSY  if  applied  to  the  parent  of  a
       vfork(2)  before  the child has terminated or performed an exec(2). The
       PR_VFORKP flag is set in  the  pstatus  structure  for  such  a  parent
       process.


       Certain accesses of the traced process's address space by the operating
       system are immune to watchpoints. The initial construction of a  signal
       stack  frame  when  a  signal is delivered to an lwp does not trigger a
       watchpoint trap even if the new  frame  covers  watched  areas  of  the
       stack.  Once the signal handler is entered, watchpoint traps occur nor‐
       mally. On SPARC based machines, register window overflow and  underflow
       does  not  trigger  watchpoint  traps, even if the register window save
       areas cover watched areas of the stack.


       Watched areas are not inherited by child processes, even if the  traced
       process's inherit-on-fork mode, PR_FORK, is set (see PCSET, below). All
       watched areas are cancelled when the traced process performs a success‐
       ful exec(2).

   PCSET PCUNSET
       PCSET sets one or more modes of operation for the traced process. PCUN‐
       SET unsets these modes. The modes to be set or unset are  specified  by
       flags in an operand long in the control message:

       PR_FORK      (inherit-on-fork):  When  set, the process's tracing flags
                    and its inherit-on-fork mode are inherited by the child of
                    a  fork(2),  fork1(2), or vfork(2). When unset, child pro‐
                    cesses start with all tracing flags cleared.


       PR_RLC       (run-on-last-close): When set and the last writable  /proc
                    file  descriptor referring to the traced process or any of
                    its lwps is closed, all of the process's tracing flags and
                    watched areas are cleared, any outstanding stop directives
                    are canceled, and if any lwps are  stopped  on  events  of
                    interest,  they  are  set running as though PCRUN had been
                    applied to them. When unset, the process's  tracing  flags
                    and  watched  areas are retained and lwps are not set run‐
                    ning on last close.


       PR_KLC       (kill-on-last-close): When set and the last writable /proc
                    file  descriptor referring to the traced process or any of
                    its  lwps  is  closed,  the  process  is  terminated  with
                    SIGKILL.


       PR_ASYNC     (asynchronous-stop):  When  set,  a  stop  on  an event of
                    interest by one lwp does not directly affect any other lwp
                    in the process. When unset and an lwp stops on an event of
                    interest other than PR_REQUESTED, all other  lwps  in  the
                    process are directed to stop.


       PR_MSACCT    (microstate accounting): Microstate accounting is now con‐
                    tinuously enabled. This flag is deprecated and  no  longer
                    has  any  effect  upon microstate accounting. Applications
                    may  toggle  this  flag;  however,  microstate  accounting
                    remains enabled regardless.


       PR_MSFORK    (inherit microstate accounting): All processes now inherit
                    microstate accounting, as it is continuously enabled. This
                    flag  has  been  deprecated  and its use no longer has any
                    effect upon the behavior of microstate accounting.


       PR_BPTADJ    (breakpoint trap pc adjustment): On x86-based machines,  a
                    breakpoint  trap  leaves  the  program  counter  (the EIP)
                    referring to the breakpointed instruction plus  one  byte.
                    When  PR_BPTADJ  is  set,  the  system adjusts the program
                    counter back to the location of the breakpointed  instruc‐
                    tion  when the lwp stops on a breakpoint. This flag has no
                    effect on SPARC based  machines,  where  breakpoint  traps
                    leave  the  program  counter referring to the breakpointed
                    instruction.


       PR_PTRACE    (ptrace-compatibility): When set, a stop on  an  event  of
                    interest  by  the traced process is reported to the parent
                    of the traced process by wait(3C), SIGTRAP is sent to  the
                    traced  process  when  it  executes  a successful exec(2),
                    setuid/setgid flags are not honored for execs performed by
                    the  traced  process,  any exec of an object file that the
                    traced process cannot read fails,  and  the  process  dies
                    when  its parent dies. This mode is deprecated; it is pro‐
                    vided only to allow ptrace(3C)  to  be  implemented  as  a
                    library function using /proc.



       It  is  an  error  (EINVAL) to specify flags other than those described
       above or to apply these operations to a  system  process.  The  current
       modes  are  reported  in  the  pr_flags  field  of /proc/pid/status and
       /proc/pid/lwp/lwp/lwpstatus.

   PCSREG
       Set the general  registers  for  the  specific  or  representative  lwp
       according to the operand prgregset_t structure.


       On  SPARC based systems, only the condition-code bits of the processor-
       status register (R_PSR) of SPARC V8 (32-bit) processes can be  modified
       by PCSREG. Other privileged registers cannot be modified at all.


       On x86-based systems, only certain bits of the flags register (EFL) can
       be modified by PCSREG: these include the  condition  codes,  direction-
       bit, and overflow-bit.


       PCSREG fails with EBUSY if the lwp is not stopped on an event of inter‐
       est.

   PCSVADDR
       Set the address at which execution resumes for the specific  or  repre‐
       sentative  lwp  from the operand long. On SPARC based systems, both %pc
       and %npc are set, with %npc set to the instruction following  the  vir‐
       tual  address.  On  x86-based systems, only %eip is set. PCSVADDR fails
       with EBUSY if the lwp is not stopped on an event of interest.

   PCSFPREG
       Set the floating-point registers for the specific or representative lwp
       according  to  the operand prfpregset_t structure. An error (EINVAL) is
       returned if the system does not support floating-point  operations  (no
       floating-point  hardware and the system does not emulate floating-point
       machine instructions). PCSFPREG fails with EBUSY  if  the  lwp  is  not
       stopped on an event of interest.

   PCSXREG
       Set  the  extra  state registers for the specific or representative lwp
       according to the architecture-dependent operand prxregset_t  structure.
       An  error  (EINVAL)  is  returned  if the system does not support extra
       state registers. PCSXREG fails with EBUSY if the lwp is not stopped  on
       an event of interest.

   PCSCXREG
       Set the CPU-specific extended registers for the specific or representa‐
       tive lwp according to the architecture-dependent operand prcpuxregset_t
       structure. An error (EINVAL) is returned if the system does not support
       extra state registers. PCSCXREG fails with EBUSY  if  the  lwp  is  not
       stopped on an event of interest.

   PCSASRS
       Set  the  ancillary  state registers for the specific or representative
       lwp according to  the  SPARC  V9  platform-dependent  operand  asrset_t
       structure.  An  error (EINVAL) is returned if either the target process
       or the controlling process is not a 64-bit SPARC V9  process.  Most  of
       the  ancillary  state registers are privileged registers that cannot be
       modified. Only those that can be  modified  are  set;  all  others  are
       silently ignored. PCSASRS fails with EBUSY if the lwp is not stopped on
       an event of interest.

   PCAGENT
       Create an agent lwp in the controlled process with register values from
       the operand prgregset_t structure (see PCSREG, above). The agent lwp is
       created in the stopped state showing PR_REQUESTED  and  with  its  held
       signal  set  (the  signal  mask)  having all signals except SIGKILL and
       SIGSTOP blocked.


       The PCAGENT operation fails with EBUSY  unless  the  process  is  fully
       stopped  via  /proc, that is, unless all of the lwps in the process are
       stopped either on events of interest or on PR_SUSPENDED, or are stopped
       on  PR_JOBCONTROL and have been directed to stop via PCDSTOP.  It fails
       with EBUSY if an agent lwp already exists. It fails with ENOMEM if sys‐
       tem resources for creating new lwps have been exhausted.


       Any  PCRUN operation applied to the process control file or to the con‐
       trol file of an lwp other than the agent lwp fails with EBUSY  as  long
       as  the  agent lwp exists. The agent lwp must be caused to terminate by
       executing the SYS_lwp_exit system call trap before the process  can  be
       restarted.


       Once  the  agent lwp is created, its lwp-ID can be found by reading the
       process status file. To facilitate opening the agent lwp's control  and
       status  files,  the  directory name /proc/pid/lwp/agent is accepted for
       lookup operations as an invisible alias for /proc/pid/lwp/lwpid,  lwpid
       being the lwp-ID of the agent lwp (invisible in the sense that the name
       ``agent'' does not appear  in  a  directory  listing  of  /proc/pid/lwp
       obtained from ls(1), getdents(2), or readdir(3C)).


       The purpose of the agent lwp is to perform operations in the controlled
       process on behalf of the controlling process: to gather information not
       directly  available  via /proc files, or in general to make the process
       change state in ways not directly available via  /proc  control  opera‐
       tions.  To  make  use  of an agent lwp, the controlling process must be
       capable  of  making  it  execute  system   calls   (specifically,   the
       SYS_lwp_exit  system call trap). The register values given to the agent
       lwp on creation are typically the registers of the representative  lwp,
       so that the agent lwp can use its stack.


       The  agent  lwp is not allowed to execute any variation of the SYS_fork
       or SYS_exec system call traps. Attempts to do so yield ENOTSUP  to  the
       agent lwp.


       Symbolic  constants  for system call trap numbers like SYS_lwp_exit and
       SYS_lwp_create can be found in the header file <sys/syscall.h>.

   PCREAD PCWRITE
       Read or write the target process's address space via a  priovec  struc‐
       ture operand:

         typedef struct priovec {
             void *pio_base;      /* buffer in controlling process */
             size_t pio_len;      /* size of read/write request in bytes */
             off_t pio_offset;    /* virtual address in target process */
         } priovec_t;



       These  operations  have  the  same  effect  as  pread(2) and pwrite(2),
       respectively, of the target process's address space file.  The  differ‐
       ence  is  that more than one PCREAD or PCWRITE control operation can be
       written to the control file at once, and they can be interspersed  with
       other control operations in a single write to the control file. This is
       useful, for example, when planting many breakpoint instructions in  the
       process's  address space, or when stepping over a breakpointed instruc‐
       tion. Unlike pread(2) and pwrite(2), no provision is made  for  partial
       reads  or  writes;  if the operation cannot be performed completely, it
       fails with EIO.

   PCNICE
       The traced process's nice(2) value is incremented by the amount in  the
       operand  long.  Only  a process with the {PRIV_PROC_PRIOCNTL} privilege
       asserted in its effective set can better a process's priority  in  this
       way,  but  any user may lower the priority. This operation is not mean‐
       ingful for all scheduling classes.

   PCSCRED
       Set the target process credentials  to  the  values  contained  in  the
       prcred_t  structure  operand (see /proc/pid/cred). The effective, real,
       and saved user-IDs and group-IDs of the target  process  are  set.  The
       target  process's  supplementary groups are not changed; the pr_ngroups
       and pr_groups members of the structure operand are  ignored.  Only  the
       privileged  processes  can  perform  this  operation; for all others it
       fails with EPERM.

   PCSCREDX
       Operates like PCSCRED but  also  sets  the  supplementary  groups;  the
       length  of  the  data  written  with  this  control operation should be
       "sizeof (prcred_t) + sizeof (gid_t) * (#groups - 1)".

   PCSPRIV
       Set the target  process  privilege  to  the  values  contained  in  the
       prpriv_t operand (see /proc/pid/priv). The effective, permitted, inher‐
       itable, and limit sets are all changed. Privilege  flags  can  also  be
       set. The process is made privilege aware unless it can relinquish priv‐
       ilege awareness. See privileges(5).


       The limit set of the target process cannot be grown. The  other  privi‐
       lege  sets  must be subsets of the intersection of the effective set of
       the calling process with the new limit set of  the  target  process  or
       subsets of the original values of the sets in the target process.


       If any of the above restrictions are not met, EPERM is returned. If the
       structure written is improperly formatted, EINVAL is returned.

PROGRAMMING NOTES
       For security reasons, except for the psinfo,  usage,  lpsinfo,  lusage,
       lwpsinfo,  and lwpusage files, which are world-readable, and except for
       privileged processes, an open of a /proc file  fails  unless  both  the
       user-ID  and  group-ID  of the caller match those of the traced process
       and the process's object file is readable by the caller. The  effective
       set of the caller is a superset of both the inheritable and the permit‐
       ted set of the target process. The limit set of the caller is a  super‐
       set  of the limit set of the target process. Except for the world-read‐
       able files just mentioned, files corresponding  to  setuid  and  setgid
       processes can be opened only by the appropriately privileged process.


       A  process  that is missing the basic privilege {PRIV_PROC_INFO} cannot
       see any processes under /proc that it cannot send a signal to.


       A process that has {PRIV_PROC_OWNER} asserted in its effective set  can
       open any file for reading. To manipulate or control a process, the con‐
       trolling process must have at least as many privileges in its effective
       set  as  the target process has in its effective, inheritable, and per‐
       mitted sets. The limit set of the controlling process must be a  super‐
       set  of  the  limit  set of the target process. Additional restrictions
       apply if any of the uids of  the  target  process  are  0.  See  privi‐
       leges(5).


       Even  if  held  by  a  privileged  process, an open process or lwp file
       descriptor (other than file descriptors for the  world-readable  files)
       becomes  invalid  if  the  traced  process  performs  an  exec(2)  of a
       setuid/setgid object file or an object file  that  the  traced  process
       cannot  read.  Any  operation  performed on an invalid file descriptor,
       except close(2), fails with EAGAIN. In this situation, if  any  tracing
       flags  are  set  and the process or any lwp file descriptor is open for
       writing, the process is directed to stop and its run-on-last-close flag
       is  set (see PCSET). This enables a controlling process (if it has per‐
       mission) to reopen the /proc files to get new valid  file  descriptors,
       close  the  invalid  file descriptors, unset the run-on-last-close flag
       (if desired), and proceed. Just closing the  invalid  file  descriptors
       causes  the  traced  process to resume execution with all tracing flags
       cleared. Any process not currently open for writing via /proc, but that
       has  left-over  tracing flags from a previous open, and that executes a
       setuid/setgid or unreadable object file, are not stopped but  have  all
       its tracing flags cleared.


       To wait for one or more of a set of processes or lwps to stop or termi‐
       nate, /proc file descriptors (other than those obtained by opening  the
       cwd  or root directories or by opening files in the fd or object direc‐
       tories) can be used in  a  poll(2)  system  call.  When  requested  and
       returned,  either of the polling events POLLPRI or POLLWRNORM indicates
       that the process or lwp stopped on an event of interest. Although  they
       cannot  be requested, the polling events POLLHUP, POLLERR, and POLLNVAL
       may be returned. POLLHUP indicates that the process or lwp  has  termi‐
       nated.  POLLERR  indicates that the file descriptor has become invalid.
       POLLNVAL is returned immediately if POLLPRI or POLLWRNORM is  requested
       on  a  file  descriptor referring to a system process (see PCSTOP). The
       requested events may be empty to wait simply for termination.

FILES
       /proc

           directory (list of processes)


       /proc/pid

           specific process directory


       /proc/self

           alias for a process's own directory


       /proc/pid/as

           address space file


       /proc/pid/ctl

           process control file


       /proc/pid/status

           process status


       /proc/pid/lstatus

           array of lwp status structs


       /proc/pid/psinfo

           process ps(1) info


       /proc/pid/lpsinfo

           array of lwp ps(1) info structs


       /proc/pid/map

           address space map


       /proc/pid/xmap

           extended address space map


       /proc/pid/rmap

           reserved address map


       /proc/pid/cred

           process credentials


       /proc/pid/priv

           process privileges


       /proc/pid/sigact

           process signal actions


       /proc/pid/auxv

           process aux vector


       /proc/pid/ldt

           process LDT (x86 only)


       /proc/pid/usage

           process usage


       /proc/pid/lusage

           array of lwp usage structs


       /proc/pid/path

           symbolic links to process open files


       /proc/pid/pagedata

           process page data


       /proc/pid/watch

           active watchpoints


       /proc/pid/cwd

           alias for the current working directory


       /proc/pid/root

           alias for the root directory


       /proc/pid/fd

           directory (list of open files)


       /proc/pid/fd/*

           aliases for process's open files


       /proc/pid/object

           directory (list of mapped files)


       /proc/pid/object/a.out

           alias for process's executable file


       /proc/pid/object/*

           aliases for other mapped files


       /proc/pid/lwp

           directory (list of lwps)


       /proc/pid/lwp/lwpid

           specific lwp directory


       /proc/pid/lwp/agent

           alias for the agent lwp directory


       /proc/pid/lwp/lwpid/lwpctl

           lwp control file


       /proc/pid/lwp/lwpid/lwpstatus

           lwp status


       /proc/pid/lwp/lwpid/lwpsinfo

           lwp ps(1) info


       /proc/pid/lwp/lwpid/lwpusage

           lwp usage


       /proc/pid/lwp/lwpid/gwindows

           register windows (SPARC only)


       /proc/pid/lwp/lwpid/xregs

           extra state registers


       /proc/pid/lwp/lwpid/cxregs

           CPU-specific extended registers


       /proc/pid/lwp/lwpid/asrs

           ancillary state registers (SPARC V9 only)


SEE ALSO
       ls(1),  ps(1),  chroot(1M),  alarm(2),  brk(2),  chdir(2),   chroot(2),
       close(2),  creat(2),  dup(2),  exec(2),  fcntl(2),  fork(2),  fork1(2),
       fstat(2),  getdents(2),  getustack(2),  kill(2),   lseek(2),   mmap(2),
       nice(2),  open(2),  poll(2),  pread(2), ptrace(3C), pwrite(2), read(2),
       readlink(2),   readv(2),   shmget(2),   sigaction(2),   sigaltstack(2),
       vfork(2),    write(2),    writev(2),    _stack_grow(3C),   readdir(3C),
       pthread_create(3C),    pthread_join(3C),     siginfo.h(3HEAD),     sig‐
       nal.h(3HEAD),  thr_create(3C),  thr_join(3C),  types32.h(3HEAD),  ucon‐
       text.h(3HEAD), wait(3C), contract(4), process(4), lfcompile(5),  privi‐
       leges(5)

DIAGNOSTICS
       Errors  that  can  occur  in addition to the errors normally associated
       with file system access:

       E2BIG        Data to be returned in a read(2) of  the  page  data  file
                    exceeds  the size of the read buffer provided by the call‐
                    er.


       EACCES       An attempt was made to examine a process that ran under  a
                    different   uid   than   the   controlling   process   and
                    {PRIV_PROC_OWNER} was not asserted in the effective set.


       EAGAIN       The  traced  process  has  performed  an  exec(2)   of   a
                    setuid/setgid  object  file  or  of an object file that it
                    cannot read; all further operations on the process or  lwp
                    file descriptor (except close(2)) elicit this error.


       EBUSY        PCSTOP,  PCDSTOP,  PCWSTOP,  or  PCTWSTOP was applied to a
                    system process; an exclusive open(2) was  attempted  on  a
                    /proc  file for a process already open for writing; PCRUN,
                    PCSREG, PCSVADDR, PCSFPREG, or PCSXREG was  applied  to  a
                    process  or  lwp  not  stopped on an event of interest; an
                    attempt was made  to  mount  /proc  when  it  was  already
                    mounted;  PCAGENT  was  applied  to a process that was not
                    fully stopped or that already had an agent lwp.


       EINVAL       In general, this means that some invalid argument was sup‐
                    plied  to  a  system call. A non-exhaustive list of condi‐
                    tions eliciting this error  includes:  a  control  message
                    operation code is undefined; an out-of-range signal number
                    was specified with PCSSIG, PCKILL,  or  PCUNKILL;  SIGKILL
                    was  specified  with  PCUNKILL;  PCSFPREG was applied on a
                    system that does not  support  floating-point  operations;
                    PCSXREG  was  applied  on  a  system that does not support
                    extra state registers.


       EINTR        A signal was received by  the  controlling  process  while
                    waiting  for the traced process or lwp to stop via PCSTOP,
                    PCWSTOP, or PCTWSTOP.


       EIO          A write(2) was attempted at  an  illegal  address  in  the
                    traced process.


       ENOENT       The  traced  process  or  lwp  has  terminated after being
                    opened.  The  basic  privilege  {PRIV_PROC_INFO}  is   not
                    asserted  in  the effective set of the calling process and
                    the calling process cannot send a  signal  to  the  target
                    process.


       ENOMEM       The  system-imposed  limit on the number of page data file
                    descriptors was reached on an open of  /proc/pid/pagedata;
                    an attempt was made with PCWATCH to establish more watched
                    areas than the system can support; the  PCAGENT  operation
                    was issued when the system was out of resources for creat‐
                    ing lwps.


       ENOSYS       An attempt was made to perform  an  unsupported  operation
                    (such  as  creat(2), link(2), or unlink(2)) on an entry in
                    /proc.


       EOVERFLOW    A 32-bit controlling process attempted to  read  or  write
                    the  as  file or attempted to read the map, rmap, or page‐
                    data file of a 64-bit target process. A 32-bit controlling
                    process  attempted  to apply one of the control operations
                    PCSREG,  PCSXREG,  PCSVADDR,  PCWATCH,  PCAGENT,   PCREAD,
                    PCWRITE to a 64-bit target process.


       EPERM        The  process that issued the PCSCRED or PCSCREDX operation
                    did not have the {PRIV_PROC_SETID} privilege  asserted  in
                    its  effective  set, or the process that issued the PCNICE
                    operation did not have  the  {PRIV_PROC_PRIOCNTL}  in  its
                    effective set.

                    An  attempt  was made to control a process of which the E,
                    P, and I privilege sets were not a subset of the effective
                    set  of  the  controlling  process or the limit set of the
                    controlling process is not a superset of limit set of  the
                    controlled process.

                    Any  of the uids of the target process are 0 or an attempt
                    was made to change any of the uids to 0 using PCSCRED  and
                    the  security  policy imposed additional restrictions. See
                    privileges(5).


NOTES
       Descriptions of structures in this document  include  only  interesting
       structure  elements,  not  filler and padding fields, and may show ele‐
       ments out of order for descriptive clarity. The actual structure  defi‐
       nitions are contained in <procfs.h>.

BUGS
       Because  the old ioctl(2)-based version of /proc is currently supported
       for binary compatibility with old applications, the top-level directory
       for  a  process,  /proc/pid,  is  not  world-readable, but it is world-
       searchable. Thus, anyone can open /proc/pid/psinfo  even  though  ls(1)
       applied to /proc/pid fails for anyone but the owner or an appropriately
       privileged process. Support for the old ioctl(2)-based version of /proc
       will be dropped in a future release, at which time the top-level direc‐
       tory for a process will be made world-readable.


       On SPARC based machines, the types gregset_t and fpregset_t defined  in
       <sys/regset.h> are similar to but not the same as the types prgregset_t
       and prfpregset_t defined in <procfs.h>.



SunOS 5.11                        9 Apr 2015                           proc(4)
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