projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 2a37c4dc JSP |
1 | saute procfs lyonnais |
| 2 | ||
| 3 | procfs supports two levels of directory. the filesystem root | |
| 4 | directory contains a representation of the system process table. | |
| 5 | this consists of an entry for each active and zombie process, and | |
| 6 | an additional entry "curproc" which always represents the process | |
| 7 | making the lookup request. | |
| 8 | ||
| 9 | each of the sub-directories contains several files. these files | |
| 10 | are used to control and interrogate processes. the files implemented | |
| 11 | are: | |
| 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 | ||
| 49 | this then looks like: | |
| 50 | ||
| 51 | % ls -li /proc | |
| 52 | total 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 | |
| 57 | 2065 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 257 | |
| 58 | 2481 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 | |
| 60 | 3129 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 390 | |
| 61 | 3209 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 400 | |
| 62 | 3217 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 401 | |
| 63 | 3273 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 | |
| 74 | 3273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 curproc | |
| 75 | % ls -li /proc/curproc | |
| 76 | total 408 | |
| 77 | 3341 --w------- 1 jsp staff 0 Sep 21 15:06 ctl | |
| 78 | 1554 -r-xr-xr-x 1 bin bin 90112 Mar 29 04:52 file | |
| 79 | 3339 -rw------- 1 jsp staff 118784 Sep 21 15:06 mem | |
| 80 | 3343 --w------- 1 jsp staff 0 Sep 21 15:06 note | |
| 81 | 3344 --w------- 1 jsp staff 0 Sep 21 15:06 notepg | |
| 82 | 3340 -rw------- 1 jsp staff 0 Sep 21 15:06 regs | |
| 83 | 3342 -r--r--r-- 1 jsp staff 0 Sep 21 15:06 status | |
| 84 | % df /proc/curproc /proc/curproc/file | |
| 85 | Filesystem 512-blocks Used Avail Capacity Mounted on | |
| 86 | proc 2 2 0 100% /proc | |
| 87 | /dev/wd0a 16186 13548 1018 93% / | |
| 88 | % cat /proc/curproc/status | |
| 89 | cat 446 439 400 81 12,0 ctty 748620684 270000 0 0 0 20000 nochan 11 20 20 20 0 21 117 | |
| 90 | ||
| 91 | ||
| 92 | ||
| 93 | the 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 | ||
| 107 | in a normal debugging environment, where the target is fork/exec'd by | |
| 108 | the 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 | |
| 111 | instruction in any newly exec'd image. | |
| 112 | ||
| 113 | $Id: README,v 3.1 1993/12/15 09:40:17 jsp Exp $ |