[Crash-utility] [PATCH] ARM: corrupted pages tables vs unwind

[Dave Anderson]

----- Original Message -----
> On Sat, Jan 28, 2012 at 03:36:28PM +0530, Rabin Vincent wrote:
> > I have access to a system whose crashdump extraction mechanism
> > unfortunately trashes the first few hundred kilobytes of physical
> > memory,  which includes the page tables at swapper_pg_dir.
> > 
> > crash does chug along and remains quite useful without these page tables
> > since much of the interesting information is in the direct mapped
> > region, but it disables the use of the unwind tables because it
> > fails to read the module unwind tables, which are placed at a
> > non-direct-mapped address.
> > 
> > The patch below allows unwind tables to be used only for core kernel
> > addresses if the module tables are inaccessible.
> > 
> > Alternatively, we could perhaps not attempt to read the
> > module unwind tables when --no_modules is specified.
> 
> IMHO crash should at least try to allow user to perform analysis even if it
> cannot do V<->P translations via page tables. The patch looks good and makes
> ARM port of crash a bit more tolerant so,
> 
> Acked-by: Mika Westerberg <mika.westerberg at iki.fi>
> 
> Thanks!
> 

One small change required:

$ make warn
...
cc -c -g -DARM -m32 -D_FILE_OFFSET_BITS=64 -DGDB_7_3_1  unwind_arm.c -o unwind_arm.o -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector 
unwind_arm.c:219: warning: ‘free_kernel_unwind_table’ defined but not used
...

I'll remove the free_kernel_unwind_table() function since nobody
calls it anymore -- and then queue it for crash-6.0.3.

Dave

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