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 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).
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 files, 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.h(3HEAD).
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)).
contracts
A directory containing references to the contracts held by the process. Each entry is a symlink to the contract's directory under /system/contract. 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).
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 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 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
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 possible to toggle the flag.
PR_MSFORK
Set by default in all processes to indicate that microstate accounting will be 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 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
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 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 */
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 convenience, 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
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.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_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_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 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.
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 predefined 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 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 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; /* 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, refer to internal kernel data structures and should not be expected to retain their meanings across different versions of the operating system.
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; /* 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 */
lgrp_id_t pr_lgrp /* home lgroup */
} lwpsinfo_t;
Some of the entries in
lwpsinfo, such as
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.
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 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.
pr_contract is the id of the process contract of which the process is a member. See
contract(4) and
process(4).
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 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 *).
secflags
This file contains the security-flags of the process. It contains a description of the security flags associated with the process.
typedef struct prsecflags {
uint32_t pr_version; /* ABI Versioning of this structure */
secflagset_t pr_effective; /* Effective flags */
secflagset_t pr_inherit; /* Inheritable flags */
secflagset_t pr_lower; /* Lower flags */
secflagset_t pr_upper; /* Upper flags */
} prsecflags_t;
The
pr_version field is a version number for the structure, currently
PRSECFLAGS_VERSION_1.
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 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 contains an array of
prxmap structures. Each structure 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;
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 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)
MAP_NORESERVE
mapping does not have swap space reserved (mapped with MAP_NORESERVE)
MA_SHM
mapping System V shared memory
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).
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 multiplying
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 possible 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 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 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.
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 directory, and entries matching those in the object directory. If this information is not available, any attempt to read the contents of the symbolic link will fail. This is most common for files that do not exist in the filesystem namespace (such as FIFOs and sockets), but can also happen 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 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_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 information 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 structures, 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 structures, 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 structures, one for each active 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 active or zombie lwp within the process. These entries are themselves directories containing additional files as described below. Only the lwpsinfo file exists in the directory of a zombie lwp.
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 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 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).
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 following 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 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): Microstate accounting is now continuously enabled. This flag is deprecated and no longer has any effect upon microstate accounting. Applications may toggle this flag; however, microstate accounting will remain 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 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 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 provided 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 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 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.
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
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
/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
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.
If the controlling process neglects to force the agent lwp to execute the
SYS_lwp_exit system call (due to either logic error or fatal failure on the part of the controlling process), the agent lwp will remain in the target process. For purposes of being able to debug these otherwise rogue agents, information as to the creator of the agent lwp is reflected in that lwp's
spymaster file in
/proc. Should the target process generate a core dump with the agent lwp in place, this information will be available via the
NT_SPYMASTER note in the core file (see
core(4)).
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 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 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 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 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, inheritable, and limit sets are all changed. Privilege flags can also be set. The process is made privilege aware unless it can relinquish privilege awareness. See
privileges(5).
The limit set of the target process cannot be grown. The other privilege 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.