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

[Dave Anderson]

----- Original Message -----
> On Mon, 2011-12-05 at 09:46 -0500, Dave Anderson wrote:
> > 
> > ----- 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
> 
> Yeah its an x86_64 file.
> 
> linux:/boot:file vmlinux-3.0.10-0.7-default.gz
> vmlinux-3.0.10-0.7-default.gz: gzip compressed data, from Unix, max compression

OK, so for whatever reason, it's not dumping the "was <filename>" part
of the header?

If I look at my sample's gzip header, it looks like:

$ od -c vmlinux-2.6.36-0.16.rc3.git0.fc15.x86_64.gz | head
0000000 037 213  \b  \b   6 254 264   L  \0 003   v   m   l   i   n   u
0000020   x   -   2   .   6   .   3   6   -   0   .   1   6   .   r   c
0000040   3   .   g   i   t   0   .   f   c   1   5   .   x   8   6   _
0000060   6   4  \0 354 375  \v   | 024 325 375 300 177   O   n   $   @
0000100   p 303 325 250 250   A 202   b 305   J 274 264   D   @ 263 232
0000120 350 254 335   (   ^   P 274   U   , 202   V 333 376 254 356 002
0000140   Z 251   Y 227   ( 343 262 224 326   K 351 035   + 266 264 372
0000160 253   x  \a   T   H 270   d 301   k   D   E 224   V   n  \n 023
0000200 203 212 250 341   * 373 377   ~ 317 354   - 200 332 377 345   y
0000220 376 257 327 363   | 336   /   % 273   s   f 346 234 231   9   s
$

where you can see the NULL-terminated filename string starting at
byte offset 10.  What does yours look like?

Dave
 
 
> and "by mistake" i meant if a user issues crash on a .gz file without
> using -f option.
> 
> Aruna.
> 
> > 
> > 
> > 
> > 
> > > 
> > > 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);
> > > > > 
> > > > > 
> > > > 
> > > 
> > > 
> > > 
> > 
> 
> 
> 
> 
>