[Crash-utility] [PATCH] Fix junk values when run crash on a .gz file

[Dave Anderson]

----- Original Message -----
> Hi Dave,
> 
> If a user by mistake issues the below command some junk characters are
> printed on the console. (crash vmlinux.gz or any .gz file) Please advise.
> 
> linux:/boot # crash vmlinux-3.0.10-0.7-default.gz
> 
> crash: ��{�UU����3ܣ@bjb
> R�I-& ��
>        
> �c�"O9�Y��X^f<3��86���v1RS�q��\`������#��^����k�s@��}���=�׳d��g_�^{���Z{�����O-
> F�-W|y�7���f9�k���g���: compressed file name does
> not start with "vmlinux"
>        Use "-f vmlinux-3.0.10-0.7-default.gz" on command line to
>        override.
> 
> crash: vmlinux-3.0.10-0.7-default.gz: not a supported file format

Hmmm, I'm not sure why that's happening, although the name string in the
header does get clipped.  The closest example I have on hand is this one,
where the pre-compressed filename was vmlinux-2.6.36-0.16.rc3.git0.fc15.x86_64,
and the .gz filename is vmlinux-2.6.36-0.16.rc3.git0.fc15.x86_64.gz, and 
which works fine.  And if I change its name to "vmlinux.gz", that still
works as expected.  So I don't know how to reproduce what you are seeing.

Anyway, the file command shows the (possibly clipped) string in the header
that is being looked at:

$ file vmlinux-2.6.36-0.16.rc3.git0.fc15.x86_64.gz
vmlinux-2.6.36-0.16.rc3.git0.fc15.x86_64.gz: gzip compressed data, was "vmlinux-2.6.36-0.16.rc3.git0.fc", from Unix, last modified: Tue Oct 12 14:43:02 2010
$ 

What does your .gz files show when you run "file" against them?
And is yours an x86_64 file?

Dave





> 
> Aruna
> 
> On Mon, 2011-12-05 at 08:28 -0500, Dave Anderson wrote:
> > The whole point of the "vmlinux" name check is to verify from
> > the compressed header itself whether it was generated from a file
> > that started with the name-string "vmlinux".  It's not interested
> > in whatever the .gz creator named the compressed file.  If you want
> > to work around that restriction, use "crash -f ...".
> > 
> > Dave
> > 
> > 
> > ----- Original Message -----
> > > Signed-off-by: Aruna Balakrishnaiah <aruna at linux.vnet.ibm.com>
> > > 
> > > ---
> > >  symbols.c |    4 ++--
> > >  1 files changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/symbols.c b/symbols.c
> > > index 0cd3a01..acd8ad5 100755
> > > --- a/symbols.c
> > > +++ b/symbols.c
> > > @@ -2995,10 +2995,10 @@ is_compressed_kernel(char *file, char
> > > **tmp)
> > >  	type = 0;
> > >  
> > >  	if ((header[0] == 0x1f) && (header[1] == 0x8b) && (header[2] ==
> > >  	8))
> > >  	{
> > > -		if (!STRNEQ((char *)&header[10], "vmlinux") &&
> > > +		if (!STRNEQ(basename(file), "vmlinux") &&
> > >  		    !(st->flags & FORCE_DEBUGINFO)) {
> > >  			error(INFO, "%s: compressed file name does not "
> > > -			    "start with \"vmlinux\"\n", &header[10]);
> > > +			    "start with \"vmlinux\"\n", file);
> > >  			error(CONT,
> > >  			    "Use \"-f %s\" on command line to override.\n\n",
> > >  				file);
> > > 
> > > 
> > 
> 
> 
>