x86/entry: Do not special-case clone(2) in compat entry

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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>

...

This commit is contained in:

Dominik Brodowski 2018-03-06 22:18:08 +01:00 • committed by Ingo Molnar

parent 4ddb45db30

commit af52201d99

4 changed files with 14 additions and 13 deletions

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12

arch/x86/entry/entry_64_compat.S

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2

arch/x86/entry/syscalls/syscall_32.tbl

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11

arch/x86/ia32/sys_ia32.c

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2

arch/x86/include/asm/sys_ia32.h

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