On Fri, 29 Sep 2006 17:29:04 -0400 (EDT)
Alan Stern <[EMAIL PROTECTED]> wrote:
> > But we have:
> >
> > 500894: 74 3f je 5008d5 <_end+0x2d>
> > 500896: 0f b6 46 20 movzbl 0x20(%rsi),%eax
> > 50089a: 8b 4e 20 mov 0x20(%rsi),%ecx
> > 50089d: ba .byte 0xba
> > 50089e: fe (bad)
> > 50089f: ff .byte 0xff
> >
> >
> > So "c7 04 24" turned into
> > "ba fe ff"
>
> What do you mean by "we have"? Where did your two disassembly listings
> come from? The values in the oops message above don't match either of
> your listings, at least not exactly.
Beacuse I'm an idiot :)
The first disassembed code comes from a 2.6.18 compiled with gcc 3.3.6
(but different config than Arkadiusz).
The second (and wrong one) comes from:
--- 1.c ---
char str[]={0x5c,0x89,0x57,0x2c,0x8b,0x40,0x44,0xc7,0x47,0x40,0x00,0x00,0x
00,0x00,0x89,0x47,0x3c,0x8b,0x45,0x00,0x8b,0x55,0x04,0x89,0x02,0x89,0x50,0
x04,0x89,0x6d,0x00,0x8d,0x47,0x18,0x89,0x6d,0x04,0x39,0x47,0x18,0x75,0x4b,
0x0f,0xb6,0x47,0x50,0xa8,0x02,0x88,0x44,0x24,0x08,0x74,0x3f,0x0f,0xb6,0x46
,0x20,0x8b,0x4e,0x20,0xba,0xfe,0xff};
void main(void){}
--------------
disassembled with "objdump -D".
The problem was that I'm on AMD64 and I've forgot to add "-m32" at gcc
options to produce a i386 executable ;)
This one should be correct:
00000000 <str>:
0: 5c pop %esp
1: 89 57 2c mov %edx,0x2c(%edi)
4: 8b 40 44 mov 0x44(%eax),%eax
7: c7 47 40 00 00 00 00 movl $0x0,0x40(%edi)
e: 89 47 3c mov %eax,0x3c(%edi)
11: 8b 45 00 mov 0x0(%ebp),%eax
14: 8b 55 04 mov 0x4(%ebp),%edx
17: 89 02 mov %eax,(%edx)
19: 89 50 04 mov %edx,0x4(%eax)
1c: 89 6d 00 mov %ebp,0x0(%ebp)
1f: 8d 47 18 lea 0x18(%edi),%eax
22: 89 6d 04 mov %ebp,0x4(%ebp)
25: 39 47 18 cmp %eax,0x18(%edi)
28: 75 4b jne 75 <main+0x75>
2a: 0f b6 47 50 movzbl 0x50(%edi),%eax
2e: a8 02 test $0x2,%al
30: 88 44 24 08 mov %al,0x8(%esp)
34: 74 3f je 75 <main+0x75>
36: 0f b6 46 20 movzbl 0x20(%esi),%eax <----- crash!
3a: 8b 4e 20 mov 0x20(%esi),%ecx
3d: ba .byte 0xba
3e: fe (bad)
3f: ff .byte 0xff
So now the problem is, as you pointed out, to discover why EIP is
pointing to "b6" intead of "0f".
--
Paolo Ornati
Linux 2.6.18 on x86_64
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