1/* $OpenBSD: README,v 1.6 2002/03/14 00:42:25 miod Exp $ */ 2/* $NetBSD: README,v 1.4 1994/06/29 06:34:43 cgd Exp $ */ 3 4saute procfs lyonnais 5 6procfs supports two levels of directory. the filesystem root 7directory contains a representation of the system process table. 8this consists of an entry for each active and zombie process, and 9an additional entry "curproc" which always represents the process 10making the lookup request. 11 12each of the sub-directories contains several files. these files 13are used to control and interrogate processes. the files implemented 14are: 15 16 file - xxx. the exec'ed file. 17 18 status - r/o. returns process status. 19 20 ctl - w/o. sends a control message to the process. 21 for example: 22 echo hup > /proc/curproc/note 23 will send a SIGHUP to the shell. 24 whereas 25 echo attach > /proc/1293/ctl 26 would set up process 1293 for debugging. 27 see below for more details. 28 29 mem - r/w. virtual memory image of the process. 30 parts of the address space are readable 31 only if they exist in the target process. 32 a more reasonable alternative might be 33 to return zero pages instead of an error. 34 comments? 35 36 note - w/o. writing a string here sends the 37 equivalent note to the process. 38 [ not implemented. ] 39 40 notepg - w/o. the same as note, but sends to all 41 members of the process group. 42 [ not implemented. ] 43 44 regs - r/w. process register set. this can be read 45 or written any time even if the process 46 is not stopped. since the bsd kernel 47 is single-processor, this implementation 48 will get the "right" register values. 49 a multi-proc kernel would need to do some 50 synchronisation. 51 52 fpregs - r/w. same as regs, but for floating point registers 53 when available. 54 55 cmdline - r/o. process command line parameters, separated 56 by NULs 57 58Note that regs and fpregs are not available if the kernel is compiled 59without option PTRACE. 60 61this then looks like: 62 63% ls -li /proc 64total 0 65 9 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 0 66 17 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 1 67 89 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 10 68 25 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 2 692065 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 257 702481 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 309 71 265 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 32 723129 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 390 733209 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 400 743217 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 401 753273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 408 76 393 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 48 77 409 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 50 78 465 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 57 79 481 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 59 80 537 dr-xr-xr-x 2 root kmem 0 Sep 21 15:06 66 81 545 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 67 82 657 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 81 83 665 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 82 84 673 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 83 85 681 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 84 863273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 curproc 87% ls -li /proc/curproc 88total 792 89135147 -r--r--r-- 1 jason staff 0 Aug 11 22:52 cmdline 90135143 --w------- 1 jason staff 0 Aug 11 22:52 ctl 91 3860 -r-xr-xr-x 1 root bin 167936 Jul 30 14:23 file 92135142 -rw------- 1 jason staff 108 Aug 11 22:52 fpregs 93135140 -rw------- 1 jason staff 225280 Aug 11 22:52 mem 94135145 --w------- 1 jason staff 0 Aug 11 22:52 note 95135146 --w------- 1 jason staff 0 Aug 11 22:52 notepg 96135141 -rw------- 1 jason staff 64 Aug 11 22:52 regs 97135144 -r--r--r-- 1 jason staff 0 Aug 11 22:52 status 98% df /proc/curproc /proc/curproc/file 99Filesystem 512-blocks Used Avail Capacity Mounted on 100proc 2 2 0 100% /proc 101/dev/wd0a 16186 13548 1018 93% / 102% cat /proc/curproc/status 103cat 446 439 400 81 12,0 ctty 748620684 270000 0 0 0 20000 nochan 11 20 20 20 0 21 117 104 105 106 107the basic sequence of commands written to "ctl" would be 108 109 attach - this stops the target process and 110 arranges for the sending process 111 to become the debug control process 112 wait - wait for the target process to come to 113 a steady state ready for debugging. 114 step - single step, with no signal delivery. 115 run - continue running, with no signal delivery, 116 until next trap or breakpoint. 117 <signame> - deliver signal <signame> and continue running. 118 detach - continue execution of the target process 119 and remove it from control by the debug process 120 121Note that attach, wait, step, run and detach are not available if the 122kernel is compiled without option PTRACE. 123 124in a normal debugging environment, where the target is fork/exec'd by 125the debugger, the debugger should fork and the child should stop itself 126(with a self-inflicted SIGSTOP). the parent should do a "wait" then an 127"attach". as before, the child will hit a breakpoint on the first 128instruction in any newly exec'd image. 129