The process file system, or
,
implements a view of the system process table inside the file system.
It is normally mounted on
/proc
and is required for the complete operation of programs such as
ps(1)
and
w(1).
The
provides a two-level view of process space, unlike the previous
Fx 1.1
implementation.
At the highest level, processes themselves are named, according to
their process ids in decimal, with no leading zeros.
There is also a
special node called
curproc
which always refers to the process making the lookup request.
Each node is a directory which contains the following entries:
Each directory contains several files:
ctl
a write-only file which supports a variety
of control operations.
Control commands are written as strings to the
ctl
file.
The control commands are:
attach
stops the target process and arranges for the sending
process to become the debug control process.
detach
continue execution of the target process and
remove it from control by the debug process (which
need not be the sending process).
run
continue running the target process until
a signal is delivered, a breakpoint is hit, or the
target process exits.
step
single step the target process, with no signal delivery.
wait
wait for the target process to come to a steady
state ready for debugging.
The target process must be in this state before
any of the other commands are allowed.
The string can also be the name of a signal, lower case
and without the
SIG
prefix,
in which case that signal is delivered to the process
(see
sigaction(2)).
The
procctl(8)
utility can be used to clear tracepoints in a stuck process.
dbregs
The debug registers as defined by
struct dbregs
in
In machine/reg.h .
dbregs
is currently only implemented on the i386 architecture.
etype
The type of the executable referenced by the
file
entry.
file
A symbolic link to the file from which the process text was read.
This can be used to gain access to the process' symbol table,
or to start another copy of the process.
If the file cannot be found, the link target is
`unknown'
fpregs
The floating point registers as defined by
struct fpregs
in
In machine/reg.h .
fpregs
is only implemented on machines which have distinct general
purpose and floating point register sets.
map
A map of the process' virtual memory.
mem
The complete virtual memory image of the process.
Only those address which exist in the process can be accessed.
Reads and writes to this file modify the process.
Writes to the text segment remain private to the process.
note
Used for sending signals to the process.
Not implemented.
notepg
Used for sending signal to the process group.
Not implemented.
regs
Allows read and write access to the process' register set.
This file contains a binary data structure
struct regs
defined in
In machine/reg.h .
regs
can only be written when the process is stopped.
rlimit
This is a read-only file containing the process current and maximum
limits.
Each line is of the format
rlimit current max
with -1
indicating infinity.
status
The process status.
This file is read-only and returns a single line containing
multiple space-separated fields as follows:
command name
process id
parent process id
process group id
session id
major , minor
of the controlling terminal, or
-1,-1
if there is no controlling terminal.
a list of process flags:
ctty
if there is a controlling terminal,
sldr
if the process is a session leader,
noflags
if neither of the other two flags are set.
the process start time in seconds and microseconds,
comma separated.
the user time in seconds and microseconds,
comma separated.
the system time in seconds and microseconds,
comma separated.
the wait channel message
the process credentials consisting of
the effective user id
and the list of groups (whose first member
is the effective group id)
all comma separated.
the hostname of the jail in which the process runs, or
`-'
to indicate that the process is not running within a jail.
In a normal debugging environment,
where the target is fork/exec'd by the debugger,
the debugger should fork and the child should stop
itself (with a self-inflicted
SIGSTOP
for example).
The parent should issue a
wait
and then an
attach
command via the appropriate
ctl
file.
The child process will receive a
SIGTRAP
immediately after the call to exec (see
execve(2)).
Each node is owned by the process's user, and belongs to that user's
primary group, except for the
mem
node, which belongs to the
kmem
group.
FILES
/proc
normal mount point for the
.
/proc/pid
directory containing process information for process
pid
/proc/curproc
directory containing process information for the current process
An -nosplit
This manual page written by
An Garrett Wollman ,
based on the description
provided by
An Jan-Simon Pendry ,
and revamped later by
An Mike Pritchard .
