gdb reverse debugging fails with "Process record does not support instruction 0xf0d at address"

Question

i started to try reverse debugging with gdb 7, followin the tutorial:

http://www.sourceware.org/gdb/wiki/ProcessRecord/Tutorial

and I thought, great!

Then I started to debug a real program which gives an error at the end. So I run it with gdb, and I put a breakpoint just before the place I think the error appears. Then I type "record" in order to start to recrd actions for future reverse-debugging. But after some steps I get

Process record doesn't support instruction 0xf0d at address 0x2aaaab4c4b4e.
Process record: failed to record execution log.

Program received signal SIGTRAP, Trace/breakpoint trap.
0x00002aaaab4c4b4e in memcpy () from /lib64/libc.so.6
(gdb) n
Single stepping until exit from function memcpy,
which has no line number information.
Process record doesn't support instruction 0xf0d at address 0x2aaaab4c4b4e.
Process record: failed to record execution log.

Program received signal SIGABRT, Aborted.
0x00002aaaab4c4b4e in memcpy () from /lib64/libc.so.6

Before I look at in in detail, I wonder if this feature is still buggy, or if I should start to record from the beginning.

Where this "record" error happens, just an object is created as a copy of other.

Agricola

Answer 1

AVX is not supported as of GDB 7.11.1

Maybe this is the same problem as mentioned at:

• gdb reverse debugging avx2
• https://sourceware.org/ml/gdb/2016-08/msg00028.html

since your trace mentions memcpy, which uses AVX instructions in Ubuntu 16.04, but it is hard to be sure without a minimal example.

rr is an awesome working alternative: https://github.com/mozilla/rr Here is a minimal working example: Setting breakpoint in GDB where the function returns

Budgerigar

See https://mcmap.net/q/16415/-disable-avx-optimized-functions-in-glibc-ld_hwcap_mask-etc-ld-so-nohwcap-for-valgrind-amp-gdb-record for a solution and sourceware.org/bugzilla/show_bug.cgi?id=23188#c6 for the PR. – Desired

Answer 2

This is because this insn is still not support by prec.

It is fixed now. You can try the gdb-cvs-head.

Nonbeliever

thanks really, i hope not to get errors again and enjoy endlessly the reverse debugging – Agricola

Answer 3

Sounds like precord is still buggy.

Please make sure you are using the latest released GDB 7.1, and file a bug. Output from x/i 0x2aaaab4c4b4e will likely be helpful. So will be exact distribution and versions of GCC and libc.so.6

Gumboil