Greets,

        I wanted to get some process information, so I first wrote
a program just to test if I was doing things correctly.  The program
is below.  It takes one argument on the command line  (a process number)
and opens /proc/that-process-number, then does a PIOCPSINFO ioctl to
get some information.  Then I try to print that processes argv[].

        I am running Solaris 2.5 on a sparc 10 (dual cpu).  I'm using
gcc version 2.7.1.

        My test was to start a "sleep 10000" in the background, and then
use its process ID, to test.  My program is named 'testing'. i.e.,

FIRST TEST
                example% gcc -g testing.c -o testing
                example% sleep 10000 &
                [1] 1048
                example% ./testing 1048
                arglist: ./testing 1048
                example%

        I get the arglist of the executing program printed.  Then, I su
to root, and do it again:

SECOND TEST
                example# ./testing 1048
                Segmentation Fault (core dumped)
                example#

THIRD TEST (regular user, under gdb)
                example% gdb ./testing
                [GNU BABBLING MESSAGES REMOVED]
                (gdb) run 1048
                Starting program: /usr/local/home/andrew/c/proc/./testing 1048
                arglist: HZ=100 LD_LIBRARY_PATH=/usr/lib:/usr/openwin/lib

What gives?  I'm pretty certain I'm doing something very wrong, but
what is it?

Thanks,
Andrew Benson (and...@arbitrade.com)
--
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: Greets,
:
:       I wanted to get some process information, so I first wrote
: a program just to test if I was doing things correctly.  The program
: is below.  It takes one argument on the command line  (a process number)
: and opens /proc/that-process-number, then does a PIOCPSINFO ioctl to
: get some information.  Then I try to print that processes argv[].
: [...]

I forgot to include the program (Thanks Kevin Thomas for pointing
that out to me).  Here it is:

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/signal.h>
#include <sys/fault.h>
#include <sys/syscall.h>
#include <sys/procfs.h>
#include <sys/stat.h>
#include <fcntl.h>

int     main(int argc, char **argv)
{
        char            procname[1024];
        prpsinfo_t      p;
        int             fd;
        int             i;

        /* Open process */
        sprintf(procname, "/proc/%d", atol(argv[1]));

        if ((fd = open(procname, O_RDWR)) == -1) {
                perror(procname);
                exit(1);
        }

        /* Get process summary info */
        if (ioctl(fd, PIOCPSINFO, (void *)&p) == -1) {
                perror("PIOCPSINFO");
                exit(2);
        }

        /* Print argv[] of process */
        for(i=0; i < p.pr_argc; ++i)
                printf("%s%s%s", i ? " ": "arglist: ", p.pr_argv[i],
                         ((i+1) == p.pr_argc) ? "\n" : "" );

        close(fd);
        exit(0);

Style (and future portability nit): you're printing a long as an int.
Why not:

        sprintf(procname, "/proc/%s", argv[1]);

These pointers are relative to the traced processes address space.

You'll need to retrieve them with lseek/read from the fd you just
opened.  The pointers supplied just tell you where the arguments are
in the examined process.

Casper
--
Casper Dik - Sun Microsystems - via my guest account at the University
of Amsterdam.  My work e-mail address is: Casper....@Holland.Sun.COM
Statements on Sun products included here are not gospel and may
be fiction rather than truth.