/proc/*/cmdline corrupted
Jon Clugston
jon.clugston@gmail.com
Mon Oct 17 00:17:00 GMT 2011
I've checked and on Linux (at least) xterm's command line is not
corrupted. From looking at the xterm code, it would appear that the X
libraries would have to be what is corrupting the command line. I
didn't look into the X library (XmParseCommand).
Jon
On Sun, Oct 16, 2011 at 5:31 PM, jan.kolar <kolar@math.cas.cz> wrote:
>
>> jc807j 2668 1 0 08:59 tty0 00:00:00 xterm -e ssh server
> 80x72+285+0 -e ssh server
>> jc807j 3004 1 0 08:59 tty0 00:00:00 xterm -e ssh server
>> 80x72-8+0 -e ssh server
>> jc807j 2928 5852 0 09:12 ? 00:00:00 xterm 20000 +tb
>
>> The actual command lines for the 3 xterm processes are:
>> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72+285+0 -e ssh server
>> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72-8+0 -e ssh server
>> C:\cygwin\bin\xterm.exe -sl 20000 +tb
>
> xterm calls XrmParseCommand() that
> "parses an (argc, argv) pair according to the specified option table ... and
> modifies the (argc, argv) pair to remove all recognized options."
>
> Therefore
> "-sl 20000 +tb -geometry 80x72+285+0"
> is properly removed
> and "-e ssh server" is moved to __argv[1 .. 3].
> Then __argv[4] (respectively __argv[1] for the shorter command) is assigned
> null pointer
> which results in the second "\0" in the od-output below.
>
>
> HOWEVER:
>
> Either XrmParseCommand() does not update argc
> or the change does not propagate (how would that be possible?) to __argc.
> Therefore the command lines appear corrupted this particular way.
>
>
> /proc/*/cmdline uses a copy of __argc named __argc_safe
> which is hardly to be updated anyway.
> " for (int i = 0; i < __argc_safe; i++) "
>
> Funny enough, /proc/self/cmdline is likely to contain shortened version of
> cmdline:
> " for (char **a = __argv; *a; a++) "
> [ pinfo.cc from cygwin 1.7.9-1 ]
>
>
>
>> I have verified that the "/proc/*/cmdline" is the source of the
>> corrupted information. "cmdline" from PID 2928 is:
>>
>> jc807j@~>od -c /proc/2928/cmdline
>> 0000000 x t e r m \0 \0 2 0 0 0 0 \0 + t b
>> 0000020 \0
>> 0000021
>
>
>
>
>
>
> ----
> What does xterm on different platforms ?
> While concept of modifying own cmdline (In fact, __argv[0]) is used very
> often to signal the process state down to the user,
> I was never thinking of modifying argc:
> main (int argc, char **argv)
> :-)
>
>
> JK
> --
> View this message in context: http://old.nabble.com/-proc-*-cmdline-corrupted-tp32639066p32663265.html
> Sent from the Cygwin list mailing list archive at Nabble.com.
>
>
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