x86/asm/entry/64: Use local label to skip around sycall dispatch
authorDenys Vlasenko <dvlasenk@redhat.com>
Tue, 31 Mar 2015 17:00:11 +0000 (19:00 +0200)
committerIngo Molnar <mingo@kernel.org>
Wed, 1 Apr 2015 11:17:39 +0000 (13:17 +0200)
commita6de5a21fb25cdbbdf3c3e9afd8481581c4f2464
tree7e9c124b37e7ef6f512ee9fbf7799bd9f3274a53
parenta734b4a23e4b5a5bba577d11b6e2ff21f6ca4fce
x86/asm/entry/64: Use local label to skip around sycall dispatch

Logically, we just want to jump around the following instruction
and its prologue/epilogue:

  call *sys_call_table(,%rax,8)

if the syscall number is too big - we do not specifically target
the "int_ret_from_sys_call" label.

Use a local, numerical label for this jump, for more clarity.

This also makes the code smaller:

 -ffffffff8187756b:      0f 87 0f 00 00 00       ja     ffffffff81877580 <int_ret_from_sys_call>
 +ffffffff8187756b:      77 0f                   ja     ffffffff8187757c <int_ret_from_sys_call>

because jumps to global labels are never translated to short jump
instructions by GAS.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-9-git-send-email-dvlasenk@redhat.com
[ Improved the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/kernel/entry_64.S