1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
114 lines
4.2 KiB
Plaintext
114 lines
4.2 KiB
Plaintext
saute procfs lyonnais
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procfs supports two levels of directory. the filesystem root
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directory contains a representation of the system process table.
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this consists of an entry for each active and zombie process, and
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an additional entry "curproc" which always represents the process
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making the lookup request.
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each of the sub-directories contains several files. these files
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are used to control and interrogate processes. the files implemented
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are:
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file - xxx. the exec'ed file.
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status - r/o. returns process status.
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ctl - w/o. sends a control message to the process.
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for example:
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echo hup > /proc/curproc/note
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will send a SIGHUP to the shell.
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whereas
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echo attach > /proc/1293/ctl
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would set up process 1293 for debugging.
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see below for more details.
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mem - r/w. virtual memory image of the process.
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parts of the address space are readable
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only if they exist in the target process.
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a more reasonable alternative might be
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to return zero pages instead of an error.
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comments?
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note - w/o. writing a string here sends the
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equivalent note to the process.
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[ not implemented. ]
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notepg - w/o. the same as note, but sends to all
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members of the process group.
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[ not implemented. ]
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regs - r/w. process register set. this can be read
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or written any time even if the process
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is not stopped. since the bsd kernel
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is single-processor, this implementation
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will get the "right" register values.
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a multi-proc kernel would need to do some
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synchronisation.
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this then looks like:
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% ls -li /proc
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total 0
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9 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 0
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17 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 1
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89 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 10
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25 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 2
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2065 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 257
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2481 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 309
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265 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 32
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3129 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 390
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3209 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 400
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3217 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 401
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3273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 408
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393 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 48
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409 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 50
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465 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 57
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481 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 59
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537 dr-xr-xr-x 2 root kmem 0 Sep 21 15:06 66
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545 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 67
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657 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 81
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665 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 82
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673 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 83
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681 dr-xr-xr-x 2 root wheel 0 Sep 21 15:06 84
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3273 dr-xr-xr-x 2 jsp staff 0 Sep 21 15:06 curproc
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% ls -li /proc/curproc
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total 408
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3341 --w------- 1 jsp staff 0 Sep 21 15:06 ctl
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1554 -r-xr-xr-x 1 bin bin 90112 Mar 29 04:52 file
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3339 -rw------- 1 jsp staff 118784 Sep 21 15:06 mem
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3343 --w------- 1 jsp staff 0 Sep 21 15:06 note
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3344 --w------- 1 jsp staff 0 Sep 21 15:06 notepg
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3340 -rw------- 1 jsp staff 0 Sep 21 15:06 regs
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3342 -r--r--r-- 1 jsp staff 0 Sep 21 15:06 status
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% df /proc/curproc /proc/curproc/file
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Filesystem 512-blocks Used Avail Capacity Mounted on
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proc 2 2 0 100% /proc
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/dev/wd0a 16186 13548 1018 93% /
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% cat /proc/curproc/status
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cat 446 439 400 81 12,0 ctty 748620684 270000 0 0 0 20000 nochan 11 20 20 20 0 21 117
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the basic sequence of commands written to "ctl" would be
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attach - this stops the target process and
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arranges for the sending process
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to become the debug control process
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wait - wait for the target process to come to
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a steady state ready for debugging.
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step - single step, with no signal delivery.
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run - continue running, with no signal delivery,
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until next trap or breakpoint.
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<signame> - deliver signal <signame> and continue running.
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detach - continue execution of the target process
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and remove it from control by the debug process
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in a normal debugging environment, where the target is fork/exec'd by
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the debugger, the debugger should fork and the child should stop itself
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(with a self-inflicted SIGSTOP). the parent should do a "wait" then an
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"attach". as before, the child will hit a breakpoint on the first
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instruction in any newly exec'd image.
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$FreeBSD$
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