This is the mail archive of the mailing list for the GDB project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Bug in i386_process_record?

Hui Zhu wrote:
On Tue, Aug 11, 2009 at 05:57, Michael Snyder <> wrote:
Yes, this seems to be better.  It records only 4 bytes each time
it is called.

But there seems to be still an off-by-one error?  With the test
program that I provided, we call memset with an argument of
1024, but we actually record 1025 bytes... this code gets hit
257 times, with the last time recording only 1 byte.

Hi Michael,

This issue is because:

0xb7edf4e7 <memset+55>:	rep stos %eax,%es:(%edi)
0xb7edf4e9 <memset+57>:	mov    %edx,%ecx
0xb7edf4eb <memset+59>:	rep stos %al,%es:(%edi)
0xb7edf4ed <memset+61>:	mov    0x8(%esp),%eax
0xb7edf4f1 <memset+65>:	pop    %edi

If the memcpy size is not align with 4, it will handle by second rep stos.
Then rep stos will not execute if %ecx is 0.
i386_process_record doesn't check %ecx, so it get this error.

I make a new patch for it. Please help me review it.

This seems much better. Please give us a change log and post it for review.

By the way, I'm sorry, I only just realized that I posted two
completely different bug reports with the exact same subject line.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]