[PATCH] Unwinding CFI stop at the outermost clone()

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi,

currently (on x86_64) the gdb backtrace shows:

#2  0x0000000000400b65 in makeSyscall (ignored=0x0) at threadcrash.c:142
#3  0x00000036ddb0610a in start_thread () from /lib64/tls/libpthread.so.0
#4  0x00000036dd0c68c3 in clone () from /lib64/tls/libc.so.6
#5  0x0000000000000000 in ?? ()

Currently it relies only on clearing %rbp (0x0000000000000000 above is
unrelated to it, it got read from uninitialized memory).

http://sourceware.org/ml/gdb/2004-08/msg00060.html suggests 0x0 should be
enough for a debugger without CFI to stop unwinding, still it is a heuristic.

Provided proper CFI. GDB should also get fixed for the unCFIed functions.


Regards,
Jan

Attachment: glibc-clone-outermost.patch
Description: Text document