Re: [Qemu-devel] out of bounds in set_cc_op()

[Laurent Vivier]

Le 21/12/2017 à 13:49, Thomas Huth a écrit :
> On 20.12.2017 22:56, Paolo Bonzini wrote:
>> On 20/12/2017 20:20, Peter Maydell wrote:
>>> On the x86/sanitizer build, new runtime errors:
>>>   GTESTER check-qtest-m68k
>>> /home/petmay01/linaro/qemu-for-merges/target/m68k/translate.c:230:12:
>>> runtime error: index -1 out of bounds for type 'const uint8_t [11]'
>>>
>>> ...and similar fails on one or two boards on most of the other
>>> guest architectures.
>>
>> These are preexisting bugs, now exposed by the boot-serial-test.
>> Thomas, can you identify the architectures that have a problem and
>> notify the maintainers?  In the meanwhile I'll keep the boot-serial-test
>> enhancements queued locally, and remove them from the pull request.
> 
>  Laurent, Richard,
> 
> looks like old_op is -1 when set_cc_op() is called here for the first
> time. The problem can be reproduced by running the mini-kernel directly.
> Just get http://people.redhat.com/~thuth/m68k-uart.bin and run QEMU like
> this:
> 
>  qemu-system-m68k -nographic -kernel  ~/tmp/m68k-uart.bin -serial none
> 
> That kernel only contains these few instructions:
> 
>   0x41, 0xf9, 0xfc, 0x06, 0x00, 0x00,     /* lea 0xfc060000,%a0 */
>   0x10, 0x3c, 0x00, 0x54,                 /* move.b #'T',%d0 */
>   0x11, 0x7c, 0x00, 0x04, 0x00, 0x08,     /* move.b #4,8(%a0) */
>   0x11, 0x40, 0x00, 0x0c,                 /* move.b %d0,12(%a0) */
>   0x60, 0xfa                              /* bra.s  loop */
> 
> The problem occurs during the second instruction (i.e. the first move.b).
> 
> Do you have any ideas where this -1 in s->cc_op could come from?

I think it comes from CCOp: it's the value of CC_OP_DYNAMIC.

We should not use it to access cc_op_live[].

I try to find a fix, but I think Richard knows this better than me.

Thanks,
Laurent