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/* $OpenBSD: README,v 1.6 2002/03/14 00:42:25 miod Exp $ */
/* $NetBSD: README,v 1.4 1994/06/29 06:34:43 cgd Exp $ */
saute procfs lyonnais
procfs supports two levels of directory. the filesystem root
directory contains a representation of the system process table.
this consists of an entry for each active and zombie process, and
an additional entry "curproc" which always represents the process
making the lookup request.
each of the sub-directories contains several files. these files
are used to control and interrogate processes. the files implemented
are:
file - xxx. the exec'ed file.
status - r/o. returns process status.
ctl - w/o. sends a control message to the process.
for example:
echo hup > /proc/curproc/note
will send a SIGHUP to the shell.
whereas
echo attach > /proc/1293/ctl
would set up process 1293 for debugging.
see below for more details.
mem - r/w. virtual memory image of the process.
parts of the address space are readable
only if they exist in the target process.
a more reasonable alternative might be
to return zero pages instead of an error.
comments?
note - w/o. writing a string here sends the
equivalent note to the process.
[ not implemented. ]
notepg - w/o. the same as note, but sends to all
members of the process group.
[ not implemented. ]
regs - r/w. process register set. this can be read
or written any time even if the process
is not stopped. since the bsd kernel
is single-processor, this implementation
will get the "right" register values.
a multi-proc kernel would need to do some
synchronisation.
fpregs - r/w. same as regs, but for floating point registers
when available.
cmdline - r/o. process command line parameters, separated
by NULs
Note that regs and fpregs are not available if the kernel is compiled
without option PTRACE.
this then looks like:
% ls -li /proc
total 0
9 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 0
17 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 1
89 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 10
25 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 2
2065 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 257
2481 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 309
265 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 32
3129 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 390
3209 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 400
3217 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 401
3273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 408
393 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 48
409 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 50
465 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 57
481 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 59
537 dr-xr-xr-x 2 root kmem 0 Sep 21 15:06 66
545 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 67
657 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 81
665 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 82
673 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 83
681 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 84
3273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 curproc
% ls -li /proc/curproc
total 792
135147 -r--r--r-- 1 jason staff 0 Aug 11 22:52 cmdline
135143 --w------- 1 jason staff 0 Aug 11 22:52 ctl
3860 -r-xr-xr-x 1 root bin 167936 Jul 30 14:23 file
135142 -rw------- 1 jason staff 108 Aug 11 22:52 fpregs
135140 -rw------- 1 jason staff 225280 Aug 11 22:52 mem
135145 --w------- 1 jason staff 0 Aug 11 22:52 note
135146 --w------- 1 jason staff 0 Aug 11 22:52 notepg
135141 -rw------- 1 jason staff 64 Aug 11 22:52 regs
135144 -r--r--r-- 1 jason staff 0 Aug 11 22:52 status
% df /proc/curproc /proc/curproc/file
Filesystem 512-blocks Used Avail Capacity Mounted on
proc 2 2 0 100% /proc
/dev/wd0a 16186 13548 1018 93% /
% cat /proc/curproc/status
cat 446 439 400 81 12,0 ctty 748620684 270000 0 0 0 20000 nochan 11 20 20 20 0 21 117
the basic sequence of commands written to "ctl" would be
attach - this stops the target process and
arranges for the sending process
to become the debug control process
wait - wait for the target process to come to
a steady state ready for debugging.
step - single step, with no signal delivery.
run - continue running, with no signal delivery,
until next trap or breakpoint.
<signame> - deliver signal <signame> and continue running.
detach - continue execution of the target process
and remove it from control by the debug process
Note that attach, wait, step, run and detach are not available if the
kernel is compiled without option PTRACE.
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). the parent should do a "wait" then an
"attach". as before, the child will hit a breakpoint on the first
instruction in any newly exec'd image.
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