From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Date: Fri, 29 Sep 2017 14:15:36 +0000 (+0300)
Subject: x86/asm: Use register variable to get stack pointer value
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b34723841be5ceb3af07c8bd316337f9a79f26f;p=pandora-kernel.git

x86/asm: Use register variable to get stack pointer value

commit 196bd485ee4f03ce4c690bfcf38138abfcd0a4bc upstream.

Currently we use current_stack_pointer() function to get the value
of the stack pointer register. Since commit:

  f5caf621ee35 ("x86/asm: Fix inline asm call constraints for Clang")

... we have a stack register variable declared. It can be used instead of
current_stack_pointer() function which allows to optimize away some
excessive "mov %rsp, %<dst>" instructions:

 -mov    %rsp,%rdx
 -sub    %rdx,%rax
 -cmp    $0x3fff,%rax
 -ja     ffffffff810722fd <ist_begin_non_atomic+0x2d>

 +sub    %rsp,%rax
 +cmp    $0x3fff,%rax
 +ja     ffffffff810722fa <ist_begin_non_atomic+0x2a>

Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer
and use it instead of the removed function.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170929141537.29167-1-aryabinin@virtuozzo.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[dwmw2: We want ASM_CALL_CONSTRAINT for retpoline]
Signed-off-by: David Woodhouse <dwmw@amazon.co.ku>
Signed-off-by: Razvan Ghitulete <rga@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: current_stack_pointer was never changed to a function,
 but was only defined for x86_32]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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