Instruction dump?

Can someone please explain the contents of the instruction dump in an
a Linux OOPS, or have a reference which does so?  How does one go
about using it in debugging?  For instance, I have the following
instruction dump:

Instruction dump:
7F850000 41BEFF7C 3860FFFF 4BFFFF78 9421FFE0 7C0802A6 BF61000C
7C9E2379
7C7C1B78 90010024 41820188 83BE034C <801D0034> 70090008 40820014
2F83001F

What can I do with this information?  I am running Linux 2.6.26 on a
powerpc.

On Sep 16, 11:45 am, Bill <jobhunt...@aol.com> wrote:
> Can someone please explain the contents of the instruction dump in an
> a Linux OOPS, or have a reference which does so?  How does one go
> about using it in debugging?  For instance, I have the following
> instruction dump:
>
> Instruction dump:
> 7F850000 41BEFF7C 3860FFFF 4BFFFF78 9421FFE0 7C0802A6 BF61000C
> 7C9E2379
> 7C7C1B78 90010024 41820188 83BE034C <801D0034> 70090008 40820014
> 2F83001F
>
> What can I do with this information?  I am running Linux 2.6.26 on a
> powerpc.

Usually you get a stackdump and often some messages that will tell you
what source file originated the code that was running at the time of
the oops.  If you get some addresses you can also manually convert
that
if you have the kernel symbols file for the kernel that crashed.
Generally try to figure out what went wrong.
Consider instrumenting suspect kernel code with additional printk's.
Also do web searches and see if
maybe the problem you found is known.

Oh, and is it repeatable?  How long and or how complicated external
conditions does it take to cause?

Bill <jobhunts02@aol.com> writes:

> Can someone please explain the contents of the instruction dump in an
> a Linux OOPS, or have a reference which does so?

Use the source Luke.

Specifically, show_instructions in arch/ppc64/kernel/process.c may
be a good start.

> How does one go about using it in debugging?

One becomes a kernel hacker :)

> For instance, I have the following
> instruction dump:
>
> Instruction dump:
> 7F850000 41BEFF7C 3860FFFF 4BFFFF78 9421FFE0 7C0802A6 BF61000C
> 7C9E2379
> 7C7C1B78 90010024 41820188 83BE034C <801D0034> 70090008 40820014
> 2F83001F
>
> What can I do with this information?

Write it to an assembly file, like this:

        .long 0x7F850000,0x41BEFF7C,0x3860FFFF,0x4BFFFF78,...

Compile and disasseble the result:

   0:   7f 85 00 00     cmpw    cr7,r5,r0
   4:   41 be ff 7c     beq-    cr7,0xffffffffffffff80
   8:   38 60 ff ff     li      r3,-1
   c:   4b ff ff 78     b       0xffffffffffffff84
  10:   94 21 ff e0     stwu    r1,-32(r1)
  14:   7c 08 02 a6     mflr    r0
  18:   bf 61 00 0c     stmw    r27,12(r1)
  1c:   7c 9e 23 79     mr.     r30,r4
  20:   7c 7c 1b 78     mr      r28,r3
  24:   90 01 00 24     stw     r0,36(r1)
  28:   41 82 01 88     beq-    0x1b0
  2c:   83 be 03 4c     lwz     r29,844(r30)
  30:   80 1d 00 34     lwz     r0,52(r29)    <<- crash here
  34:   70 09 00 08     andi.   r9,r0,8
  38:   40 82 00 14     bne-    0x4c
  3c:   2f 83 00 1f     cmpwi   cr7,r3,31

Cheers,
-- 
In order to understand recursion you must first understand recursion.
Remove /-nsp/ for email.

Bill <jobhunts02@aol.com> wrote:
>
>Can someone please explain the contents of the instruction dump in an
>a Linux OOPS, or have a reference which does so?  How does one go
>about using it in debugging?  For instance, I have the following
>instruction dump:
>
>Instruction dump:
>7F850000 41BEFF7C 3860FFFF 4BFFFF78 9421FFE0 7C0802A6 BF61000C
>7C9E2379
>7C7C1B78 90010024 41820188 83BE034C <801D0034> 70090008 40820014
>2F83001F
>
>What can I do with this information?  I am running Linux 2.6.26 on a
>powerpc.

You need a PowerPC disassembler.  I assume there must be one that can
disassemble raw dwords like this.  You could use objdump or gdb, with some
trickery.
-- 
Tim Roberts, timr@probo.com
Providenza & Boekelheide, Inc.