Annotation of sys/miscfs/procfs/README, Revision 1.1.1.1
1.1 nbrk 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:
4: saute procfs lyonnais
5:
6: procfs supports two levels of directory. the filesystem root
7: directory contains a representation of the system process table.
8: this consists of an entry for each active and zombie process, and
9: an additional entry "curproc" which always represents the process
10: making the lookup request.
11:
12: each of the sub-directories contains several files. these files
13: are used to control and interrogate processes. the files implemented
14: are:
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:
58: Note that regs and fpregs are not available if the kernel is compiled
59: without option PTRACE.
60:
61: this then looks like:
62:
63: % ls -li /proc
64: total 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
69: 2065 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 257
70: 2481 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
72: 3129 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 390
73: 3209 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 400
74: 3217 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 401
75: 3273 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
86: 3273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 curproc
87: % ls -li /proc/curproc
88: total 792
89: 135147 -r--r--r-- 1 jason staff 0 Aug 11 22:52 cmdline
90: 135143 --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
92: 135142 -rw------- 1 jason staff 108 Aug 11 22:52 fpregs
93: 135140 -rw------- 1 jason staff 225280 Aug 11 22:52 mem
94: 135145 --w------- 1 jason staff 0 Aug 11 22:52 note
95: 135146 --w------- 1 jason staff 0 Aug 11 22:52 notepg
96: 135141 -rw------- 1 jason staff 64 Aug 11 22:52 regs
97: 135144 -r--r--r-- 1 jason staff 0 Aug 11 22:52 status
98: % df /proc/curproc /proc/curproc/file
99: Filesystem 512-blocks Used Avail Capacity Mounted on
100: proc 2 2 0 100% /proc
101: /dev/wd0a 16186 13548 1018 93% /
102: % cat /proc/curproc/status
103: cat 446 439 400 81 12,0 ctty 748620684 270000 0 0 0 20000 nochan 11 20 20 20 0 21 117
104:
105:
106:
107: the 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:
121: Note that attach, wait, step, run and detach are not available if the
122: kernel is compiled without option PTRACE.
123:
124: in a normal debugging environment, where the target is fork/exec'd by
125: the 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
128: instruction in any newly exec'd image.
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