Date: Sun, 9 Sep 2001 11:23:34 -0500 From: chrisw@Wicklein.ORG To: current@freebsd.org Cc: chrisw@wicklein.org Subject: problems with libkvm and sysctl Message-ID: <20010909162258.92A6F37B409@hub.freebsd.org>
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CONTEXT:
I'm writing a clone of pgrep(1) (part of Solaris) for FreeBSD
5.0-CURRENT. Similar to FreeBSD's killall, pgrep matches a pattern
against either the executable associated with each process or each
process's command line arguments. I have tried using both sysctl and
kvm to do this and have run into problems with each:
The snippet below works, except that for each non-zero kp[n].ki_args I
find that
ki_args is an invalid pointer and that dereferencing it to access
arguments to
process n results in a bus error.
size_t len;
int mib[3] = { CTL_KERN, KERN_PROC, KERN_PROC_ALL };
if( sysctl( mib, 3, NULL, &len, NULL, 0 ) < 0 )
{
perror( "sysctl failed" );
return( -1 );
}
assert( kp = malloc( len ) );
if( sysctl( mib, 3, kp, &len, NULL, 0 ) < 0 )
{
perror( "sysctl failed" );
return( -1 );
}
That failing, I fell back on libkvm using this snippet:
if( ( kern = kvm_open( NULL, NULL, NULL, O_RDONLY,
"kvm_open failed" ) ) == NULL )
{
exit( 1 );
}
and found that the resulting executable fails on kvm_open:
$ pgrep foo
kvm_open failed: /dev/mem: Invalid argument
The same open works on 4.1.1-STABLE with the same device file /dev/mem
present.
Am I doing something obviously wrong, or are these known limitations of
the proc info interfaces at this time?
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