x86/entry: Do not special-case clone(2) in compat entry
authorDominik Brodowski <linux@dominikbrodowski.net>
Tue, 6 Mar 2018 21:18:08 +0000 (22:18 +0100)
committerIngo Molnar <mingo@kernel.org>
Wed, 7 Mar 2018 06:57:31 +0000 (07:57 +0100)
commitaf52201d991624d2d5adce2c123805b3d42a8d4d
tree6fcb0ec95c5ad0c7fff5dd51abb8df12c623dc53
parent4ddb45db30851b2269101ee8969f079b028dd257
x86/entry: Do not special-case clone(2) in compat entry

With the CPU renaming registers on its own, and all the overhead of the
syscall entry/exit, it is doubtful whether the compiled output of

mov %r8, %rax
mov %rcx, %r8
mov %rax, %rcx
jmpq sys_clone

is measurably slower than the hand-crafted version of

xchg %r8, %rcx

So get rid of this special case.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: luto@amacapital.net
Cc: viro@zeniv.linux.org.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/x86/entry/entry_64_compat.S
arch/x86/entry/syscalls/syscall_32.tbl
arch/x86/ia32/sys_ia32.c
arch/x86/include/asm/sys_ia32.h