[PATCH 4/5] On x86, EAX read on syscall entry is not necessary

Dmitry V. Levin ldv at altlinux.org
Tue Aug 23 19:18:53 UTC 2011

On Mon, Aug 22, 2011 at 12:28:59PM +0200, Denys Vlasenko wrote:
> On Mon, 2011-08-22 at 12:21 +0200, Denys Vlasenko wrote:
> > 4. Another speedup: on x86, EAX read on syscall entry is also 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.

If the sysexit part of this EAX retrieval code goes to
get_scno_on_sysexit(), why the sysenter part of it doesn't go to
get_scno_on_sysenter() as well?

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