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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
       subdirectory 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 will fail
       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
       debugger 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)).

       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 file /proc/pid/map 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).

       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
       enumerations 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
       definitions of stopped states. See the PCSTOP control operation for the
       definition of ``event of interest''.

       The representative lwp remains fixed (it will be 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
       control 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 will fail with
       EOVERFLOW because the address space range of a 32-bit process cannot
       encompass 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 file, and setting the target process's registers. There is
       no restriction 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
       information it reads from a /proc file for a 32-bit process from 32-bit
       format 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
       processes, a 64-bit controlling program can be compiled with the C
       preprocessor 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(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(2) 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, will elicit 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
       will be 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 will 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),
       getdents(2), or readdir(3C)).

   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).

   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
       information 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 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 r_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 */
          lwpstatus_t pr_lwp;       /* status of the representative lwp */
       } pstatus_t;

       pr_flags is a bit-mask holding the following process flags. For
       convenience, 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
             process has microstate accounting enabled (see PCSET).

       PR_MSFORK
             process microstate accounting is inherited on fork (see PCSET).

       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 lwps in the process.

       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
       control 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,
       respectively, 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 will
       grow it when necessary.)

       pr_utime, pr_stime, pr_cutime, and pr_cstime are, respectively, the
       user CPU and system CPU time consumed by the process, and the
       cumulative 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 constant PR_MODEL_NATIVE reflects the data model of the controlling
       process, that is, its value is PR_MODEL_ILP32 or PR_MODEL_LP64
       according 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 */
        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
       convenience, it also contains the process flags, described previously.

       PR_STOPPED
             lwp is stopped.

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

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

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

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

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

       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

       PR_SYSEXIT
             indicate a stop on entry to or exit from a system call (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 sigaction(2)); pr_what holds the
             stopping signal number.

       PR_SUSPENDED
             indicates that the lwp stopped due to internal synchronization 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_SIGNALLED 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
       current 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(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_SYSENTRY 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_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
       arbitrary time in the past.

       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 IA
       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
       registers.

       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 subdirectory).

       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)
             controlling processes, the predefined constants R_CCR, R_ASI, and
             R_FPRS can be used as indices to refer to the corresponding
             special registers.

       IA    On IA based machines, the predefined constants SS, UESP, EFL, CS,
             EIP, ERR, TRAPNO, EAX, ECX, EDX, EBX, ESP, EBP, ESI, EDI, DS, ES,
             FS, and GS can be used as indices to refer to the corresponding
             registers.

       pr_fpreg is a structure holding the contents of the floating-point
       registers.

       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
       representative lwp needed by the ps(1) command. psinfo is 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 */
            int pr_nlwp;              /* number of 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;        /* 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 */
            taskid_t pr_taskid;       /* task id */
            projid_t pr_projid;       /* project id */
            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 */
       } psinfo_t;

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

       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 and pr_lwp.pr_lwpid are zero and the
       other fields of pr_lwp are undefined:

       typedef struct lwpsinfo {
            int pr_flag;              /* lwp flags */
            id_t pr_lwpid;            /* lwp id */
            uintptr_t pr_addr;        /* internal address of lwp */
            uintptr_t pr_wchan;       /* 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 */
       } lwpsinfo_t;

       Some of the entries in lwpsinfo, such as pr_flag, pr_addr, pr_wchan,
       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.

       pr_pctcpu is a 16-bit binary fraction, as described above. It
       represents 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.

   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
       variable length; the cred file contains all of the supplementary
       groups. pr_ngroups indicates the number of supplementary groups. (See
       also the PCSCRED control operation.)

   sigact
       Contains an array of sigaction structures describing the current
       dispositions of all signals associated with the traced process (see
       sigaction(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 IA 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
       Contains information about the virtual address map of the process. The
       file contains an array of prmap structures, each of which describes a
       contiguous 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;

       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
       directory (see below) that can be opened read-only to obtain a file
       descriptor 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_ISM
             mapping is intimate shared memory (shared MMU resources).

       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
       mapping marked MA_SHARED fails if applied at a virtual address not
       corresponding 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
       system 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).

   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
       specify MAP_FIXED will 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 appears as a symbolic link and
       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
       consequently the symbol tables) without having to know the actual path
       names of the executable files.

   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
       system. 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
       structure 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
       ineffective; 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 will fail 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_tpr_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;

       If microstate accounting has not been enabled for the process (see the
       PR_MSACCT flag for the PCSET operation, below), the usage file contains
       only an estimate of times spent in the various states. The usage file
       is accessible after a process becomes a zombie.

   lstatus
       Contains a prheader structure followed by an array of lwpstatus
       structures, one for each 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
       structures, one for each lwp in the process. (See also
       /proc/pid/lwp/lwpid/lwpsinfo, below.)

   lusage
       Contains a prheader structure followed by an array of prusage
       structures, one for each lwp in the process plus an additional element
       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 lwp within the
       process. These entries are themselves directories containing additional
       files as described below.

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
       structure 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
       structure for the specific lwp as described above for the
       representative lwp in the process's psinfo file.

   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
       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.

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
       several system calls. If a control operation fails, no subsequent
       operations 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
       terminated 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
       without 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 specific 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
       specifying a number of milliseconds; the wait will terminate
       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 PCWSTOP.

       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 FLTTRACE
             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 implemented on all processors. It is
             implemented on SPARC and IA 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 execution 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 will show PR_REQUESTED,
             no other stop will have intervened, and the lwp will not have
             executed 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
       operation 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
       chosen 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
       representative lwp.

   PCSSIG
       The current signal and its associated signal information for the
       specific or representative lwp are set according to the contents of the
       operand siginfo structure (see <sys/siginfo.h>). If the specified
       signal 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
       control file, a directed signal is sent to the specific lwp. The signal
       is named in a long operand contained in the message. Sending SIGKILL
       terminates 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
       signal (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 will be blocked if sent to the lwp). The set of
       signals 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
       incurring one of these faults, an lwp stops. The set is defined via the
       operand 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-
       specific information about the fault.

   PCCFAULT
       The current fault, if any, is cleared; the associated signal will not
       be 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
       virtual address range specified by pr_vaddr and pr_size. If pr_wflags
       is empty, any previously-established watched area starting at the
       specified 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
       instruction completes. If it occurs before completion, the memory is
       not modified. If it occurs after completion, the memory is modified (if
       the access is a write access).

       pr_info in the lwpstatus structure contains information pertinent to
       the watchpoint trap. In particular, the si_addr field contains the
       virtual 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
       executing the system call incurs the watchpoint trap while still in the
       system 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
       system call fails with EFAULT. If WA_TRAPAFTER was specified, the
       memory reference will have completed and the memory will have been
       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
       thousands).

       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 will 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
       normally. On SPARC based machines, register window overflow and
       underflow will 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
       successful exec(2).

   PCSET PCUNSET
       PCSET sets one or more modes of operation for the traced process.
       PCUNSET 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 processes 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
             running 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): When set, microstate accounting is
             enabled for the process. This allows the usage file to contain
             accurate values for the times the lwps spent in their various
             processing states. When unset (the default), the overhead of
             microstate accounting is avoided and the usage file can only
             contain an estimate of times spent in the various states.

       PR_MSFORK
              (inherit microstate accounting): When set, and microstate
             accounting is enabled for the process, microstate accounting will
             be enabled for future child processes. When unset, child
             processes start with microstate accounting disabled.

       PR_BPTADJ
              (breakpoint trap pc adjustment): On IA 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 will adjust the program counter back to the
             location of the breakpointed instruction 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 via wait(2), 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
             provided only to allow ptrace(2) 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 IA 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
       interest.

   PCSVADDR
       Set the address at which execution will resume for the specific or
       representative lwp from the operand long. On SPARC based systems, both
       %pc and %npc are set, with %npc set to the instruction following the
       virtual address. On IA 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.

   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
       system resources for creating new lwps have been exhausted.

       Any PCRUN operation applied to the process control file or to the
       control 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 _lwp_exit(2) system call 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 /propc/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
       operations. To make use of an agent lwp, the controlling process must
       be capable of making it execute system calls (specifically, the
       _lwp_exit(2) system call). 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 fork(2),
       exec(2), or _lwp_create(2) system calls. Attempts to do so yield
       ENOTSUP to the agent lwp.

   PCREAD PCWRITE
       Read or write the target process's address space via a priovec
       structure 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
       difference 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 instruction. 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 the super-user may better a process's priority in
       this way, but any user may lower the priority. This operation is not
       meaningful 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
       super-user may perform this operation; for all others it fails with
       EPERM.

PROGRAMMING NOTES
       For security reasons, except for the psinfo, usage, lpsinfo, lusage,
       lwpsinfo, and lwpusage files, which are world-readable, and except for
       the super-user, 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. Except for the world-
       readable files just mentioned, files corresponding to setuid and setgid
       processes can be opened only by the super-user.

       Even if held by the super-user, 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
       will have been directed to stop and its run-on-last-close flag will
       have been set (see PCSET). This enables a controlling process (if it
       has permission) 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, will not be
       stopped but will have all its tracing flags cleared.

       To wait for one or more of a set of processes or lwps to stop or
       terminate, /proc file descriptors (other than those obtained by opening
       the cwd or root directories or by opening files in the fd or object
       directories) 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
       terminated. 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/rmap
             reserved address map

       /proc/pid/cred
             process credentials

       /proc/pid/sigact
             process signal actions

       /proc/pid/auxv
             process aux vector

       /proc/pid/ldt
             process LDT (IA only)

       /proc/pid/usage
             process usage

       /proc/pid/lusage
             array of lwp usage structs

       /proc/pid/pagedata
             process page data

       /proc/pid/watch
             active watchpoints

       /proc/pid/cwd
             symlink to the current working directory

       /proc/pid/root
             symlink to 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/asrs
             ancillary state registers (SPARC V9 only)

SEE ALSO
       ls(1), ps(1), chroot(1M), _lwp_create(2), _lwp_exit(2), 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), kill(2), lseek(2),
       mmap(2), nice(2), open(2), poll(2), pread(2), ptrace(2), pwrite(2),
       read(2), readlink(2), readv(2), shmget(2), sigaction(2),
       sigaltstack(2), vfork(2), wait(2), write(2), writev(2), readdir(3C),
       siginfo(3HEAD), signal(3HEAD), types32(3HEAD), ucontext(3HEAD),
       lfcompile(5)

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

       ENOENT
             The traced process or lwp has terminated after being opened.

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

       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.

       EPERM Someone other than the super-user issued the PCSCRED operation;
             someone other than the super-user attempted to better a process's
             priority by applying PCNICE.

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

       EINVAL
             In general, this means that some invalid argument was supplied to
             a system call. A non-exhaustive list of conditions 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.

       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 creating lwps.

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

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

       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.

       EOVERFLOW
             A 32-bit controlling process attempted to read or write the as
             file or attempted to read the map, rmap, or pagedata 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.

NOTES
       Descriptions of structures in this document include only interesting
       structure elements, not filler and padding fields, and may show
       elements out of order for descriptive clarity. The actual structure
       definitions 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 will fail for anyone but the owner or the super-
       user. Support for the old ioctl(2)-based version of /proc will be
       dropped in a future release, at which time the top-level directory 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 5.9                         23 Jul 2001                          proc(4)

NAME | DESCRIPTION | DIRECTORY STRUCTURE | CONTROL MESSAGES | PROGRAMMING NOTES | FILES | SEE ALSO | DIAGNOSTICS | NOTES | BUGS

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