semantic error: empty struct vfsmount

semantic error: empty struct vfsmount

[Robert Evans]

I am some what new to  SystemTap and am trying to gather some statistics about the VFS layer on RHEL4.

Short description of the problem.  When a struct is declared like the following

/*bar.h*/

struct foo;

struct bar {
    struct foo * foop;
}

/*foo.h*/

struct foo {
    int something;
}

The dwarf data for struct bar will point to an empty struct declaration for the type of foop.  When tapsets.cxx finds bar, and foop inside bar, it then finds an empty struct declaration for foo and outputs an error, if I try and look at anything inside foo.

I searched the archives of the mailing list and bugzilla.  I could not find anything describing this problem, the closest I found was BUG 3016, it outputs a different error message, but I don't really know how much it might have changed since that bug was filed.

DETAILS:

The following is an excerpt from the script

probe kernel.function("vfs_read").return
{
    if($return == 0)
    {
        devname = kernel_string($file->f_vfsmnt->mnt_devname);
        printf("DEV NAME %s\n",devname);
    }
}

I get the following error 

Pass 1: parsed user script and 37 library script(s) in 200usr/0sys/205real ms.
semantic error: empty struct vfsmount: identifier '$file' at ./fs_prof.stp:59:37


My version of stap is the following

$ stap -V
SystemTap translator/driver (version 0..6/Red Hat elfutils 0.125 built 2007-10-05)
Copyright (C) 2005-2007 Red Hat, Inc. and others
This is free software; see the source for copying conditions.

I grabbed a recent weekly snapshot.

I used
eu-readelf -w /usr/lib/debug/lib/modules/2.6.9-34.EL/vmlinux 
to verify that struct vfsmount is indeed described in the dwarf data in vmlinux

This is RHEL4 Update 4 x86_64.

Thanks,

Bobby Evans






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