1saute procfs lyonnais 2 3procfs supports two levels of directory. the filesystem root 4directory contains a representation of the system process table. 5this consists of an entry for each active and zombie process, and 6an additional entry "curproc" which always represents the process 7making the lookup request. 8 9each of the sub-directories contains several files. these files 10are used to control and interrogate processes. the files implemented 11are: 12 13 file - xxx. the exec'ed file. 14 15 status - r/o. returns process status. 16 17 ctl - w/o. sends a control message to the process. 18 for example: 19 echo hup > /proc/curproc/note 20 will send a SIGHUP to the shell. 21 whereas 22 echo attach > /proc/1293/ctl 23 would set up process 1293 for debugging. 24 see below for more details. 25 26 mem - r/w. virtual memory image of the process. 27 parts of the address space are readable 28 only if they exist in the target process. 29 a more reasonable alternative might be 30 to return zero pages instead of an error. 31 comments? 32 33 note - w/o. writing a string here sends the 34 equivalent note to the process. 35 [ not implemented. ] 36 37 notepg - w/o. the same as note, but sends to all 38 members of the process group. 39 [ not implemented. ] 40 41 regs - r/w. process register set. this can be read 42 or written any time even if the process 43 is not stopped. since the bsd kernel 44 is single-processor, this implementation 45 will get the "right" register values. 46 a multi-proc kernel would need to do some 47 synchronisation. 48 49this then looks like: 50 51% ls -li /proc 52total 0 53 9 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 0 54 17 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 1 55 89 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 10 56 25 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 2 572065 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 257 582481 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 309 59 265 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 32 603129 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 390 613209 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 400 623217 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 401 633273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 408 64 393 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 48 65 409 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 50 66 465 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 57 67 481 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 59 68 537 dr-xr-xr-x 2 root kmem 0 Sep 21 15:06 66 69 545 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 67 70 657 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 81 71 665 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 82 72 673 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 83 73 681 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 84 743273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 curproc 75% ls -li /proc/curproc 76total 408 773341 --w------- 1 jsp staff 0 Sep 21 15:06 ctl 781554 -r-xr-xr-x 1 bin bin 90112 Mar 29 04:52 file 793339 -rw------- 1 jsp staff 118784 Sep 21 15:06 mem 803343 --w------- 1 jsp staff 0 Sep 21 15:06 note 813344 --w------- 1 jsp staff 0 Sep 21 15:06 notepg 823340 -rw------- 1 jsp staff 0 Sep 21 15:06 regs 833342 -r--r--r-- 1 jsp staff 0 Sep 21 15:06 status 84% df /proc/curproc /proc/curproc/file 85Filesystem 512-blocks Used Avail Capacity Mounted on 86proc 4 4 0 100% /proc 87/dev/ad0s1a 254063 102444 131294 44% / 88% cat /proc/curproc/status 89cat 446 439 400 81 12,0 ctty 748620684 270000 0 0 0 20000 nochan 11 20 20 20 0 21 117 90 91 92 93the basic sequence of commands written to "ctl" would be 94 95 attach - this stops the target process and 96 arranges for the sending process 97 to become the debug control process 98 wait - wait for the target process to come to 99 a steady state ready for debugging. 100 step - single step, with no signal delivery. 101 run - continue running, with no signal delivery, 102 until next trap or breakpoint. 103 <signame> - deliver signal <signame> and continue running. 104 detach - continue execution of the target process 105 and remove it from control by the debug process 106 107in a normal debugging environment, where the target is fork/exec'd by 108the debugger, the debugger should fork and the child should stop itself 109(with a self-inflicted SIGSTOP). the parent should do a "wait" then an 110"attach". as before, the child will hit a breakpoint on the first 111instruction in any newly exec'd image. 112 113$FreeBSD: src/sys/miscfs/procfs/README,v 1.4 1999/08/28 00:46:53 peter Exp $ 114$DragonFly: src/sys/vfs/procfs/README,v 1.3 2005/02/26 12:00:55 swildner Exp $ 115