tree 616fc289b89945b8fb159e97dac1ddfded72bc2f
parent 77a7459536f38dd35364c24719ce5ca5cd6b76bc
author Denys Vlasenko <dvlasenk@redhat.com> 1314197963 +0200
committer Denys Vlasenko <dvlasenk@redhat.com> 1314197963 +0200

Speed up x86 by avoiding EAX read on syscall entry

on x86, EAX read on syscall entry is not necessary if we know
that post-execve SIGTRAP is disabled by PTRACE_O_TRACEEXEC ptrace option.
This patch (a) moves EAX retrieval from syscall_fixup
to get_scno_on_sysexit, and (b) perform EAX retrieval in syscall_fixup
only if we are in syscall entry and PTRACE_O_TRACEEXEC option is not on.

* syscall.c (get_scno_on_sysexit): On I386 and X86_64, read eax/rax
which contain syscall return value.
(syscall_fixup): On I386 and X86_64, read eax/rax only on syscall enter
and only if PTRACE_O_TRACEEXEC is not in effect.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>