/* $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. - deliver signal 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.