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Re: /proc/*/cmdline corrupted
jan.kolar wrote:
>
> For example sendmail likes to do that (on Linux):
> root 3051 sendmail: accepting connections
> smmsp 3061 sendmail: Queue runner@00:01:00 for
> /var/spool/clientmqueue
> root 14631 sendmail: server [1.46.244.248] cmd read
> root 15254 sendmail: ./p9CDUban025571 mail3.cae3.com.: user
> open
> entries of sendmail are not nullterminated (!).
> Others have set (on Linux) a number of NULL pointers:
> 0000000 i n i t [ 3 ] \0 \0 \0 \0 \0 \0 \0 \0
> \0 \0
> 0000000 l p d W a i t i n g \0 \0 \0
>
This was on
Linux host.a.b.c. 2.6.18-194.26.1.el5-ipx #1 SMP Wed Dec 8 20:08:05 CET 2010
x86_64 x86_64 x86_64 GNU/Linux
Corinna Vinschen-2 wrote
> On Linux, /proc/$PID/cmdline always contains the full command line as
> it has been when the process got started, irrespectively of changes
> after process startup. It looks like the loader creates a copy of the
> argv array before calling main.
Yes, I agree. A simple C program behaves like that. I did not know how
exactly
sendmail, lpd, init and other achieve the change.
Also perl allows to set $0 with appropriate effect (but not $1).
So, Q: how they do that ? A:" It depends " :-)
See
http://cvs.rutgers.edu/cgi-bin/viewvc.cgi/tags/start/postman1.11/PsTitle.cc?revision=1806&view=markup
where (probably) cygwin is SPT_CHANGEARGV and Linux is SPT_REUSEARGV.
(And blind xterm modifies its command line in the case SPT_CHANGEARGV.
Do the same other programs using XmParseCommand(), or do they first
make a working copy of argv pointer array?)
This works on Linux to change /proc/<cmd>/cmdline:
main (int argc, char **argv)
{ int i;
argv[0][0]='A';
for (i=1; i<argc; i++) argv[i][0]= 'A'+i ; // ! bad for
"", much bad if last arg is ""
sleep(30); }
./a.out 1 2 3 4 5 &
ps -fC a.out
A/a.out B C D E F
Thanks for the timeout on proc-IPC !
JK
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