[Qemu-devel] qemu gdb issue

[Jacques]

Hi folks,

I'm busy with a small project and I'm running into problems debugging
qemu. I hope this is the right place to get help.

I'm running an application in qemu through the userspace qemu-i386 and
attaching to the process with gdb. I have pygdb scripts that then
interact with gdb.

The issue is that at some point I want to change $eip and redirect
instruction flow. I then set $eip to the value I need which gives me the
following:

Program received signal SIGSEGV, Segmentation fault.
0x46367046 in ?? ()
(gdb) i r
eax            0x4090ca0e       1083230734
ecx            0x0      0
edx            0x407fed20       1082125600
ebx            0x31704630       829441584
esp            0x407ffe40       0x407ffe40
ebp            0x35704634       0x35704634
esi            0x46327046       1177710662
edi            0x70463370       1883648880
eip            0x46367046       0x46367046
eflags         0x202    [ IF ]
cs             0x23     35
ss             0x2b     43
ds             0x2b     43
es             0x2b     43
fs             0x0      0
gs             0x33     51
(gdb) set $eip=0x08059924
Cannot access memory at address 0x35704638
(gdb) set $eip=0x08059924
(gdb) x/3i $eip
=> 0x8059924:   pop    %ebx
   0x8059925:   pop    %ebp
   0x8059926:   ret
(gdb) si

The si command never returns, I have no idea why this is not working.
Also no idea why the first set fails..

Any help would be massively appreciated!

Kind Regards,
J

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