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FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
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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. 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 408 3341 --w------- 1 jsp staff 0 Sep 21 15:06 ctl 1554 -r-xr-xr-x 1 bin bin 90112 Mar 29 04:52 file 3339 -rw------- 1 jsp staff 118784 Sep 21 15:06 mem 3343 --w------- 1 jsp staff 0 Sep 21 15:06 note 3344 --w------- 1 jsp staff 0 Sep 21 15:06 notepg 3340 -rw------- 1 jsp staff 0 Sep 21 15:06 regs 3342 -r--r--r-- 1 jsp staff 0 Sep 21 15:06 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. <signame> - deliver signal <signame> and continue running. detach - continue execution of the target process and remove it from control by the debug process 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. $FreeBSD: release/9.1.0/sys/fs/procfs/README 50477 1999-08-28 01:08:13Z peter $