linux-kernel - [tip:x86/asm] x86/entry/64: Use pop instead of movq in syscall_return_via

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Message-ID: <tip-4fbb39108f972437c44e5ffa781b56635d496826@git.kernel.org>
Date:   Thu, 2 Nov 2017 03:51:08 -0700
From:   tip-bot for Andy Lutomirski <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, brgerst@...il.com, torvalds@...ux-foundation.org,
        hpa@...or.com, luto@...nel.org, bpetkov@...e.de,
        linux-kernel@...r.kernel.org, peterz@...radead.org,
        dave.hansen@...el.com, tglx@...utronix.de, bp@...e.de
Subject: [tip:x86/asm] x86/entry/64: Use pop instead of movq in
 syscall_return_via_sysret

Commit-ID:  4fbb39108f972437c44e5ffa781b56635d496826
Gitweb:     https://git.kernel.org/tip/4fbb39108f972437c44e5ffa781b56635d496826
Author:     Andy Lutomirski <luto@...nel.org>
AuthorDate: Thu, 2 Nov 2017 00:59:03 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 2 Nov 2017 11:04:39 +0100

x86/entry/64: Use pop instead of movq in syscall_return_via_sysret

Saves 64 bytes.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Reviewed-by: Borislav Petkov <bp@...e.de>
Cc: Borislav Petkov <bpetkov@...e.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/6609b7f74ab31c36604ad746e019ea8495aec76c.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/entry_64.S | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 15539644..4f9b446 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -315,10 +315,18 @@ return_from_SYSCALL_64:
 	 */
 syscall_return_via_sysret:
 	/* rcx and r11 are already restored (see code above) */
-	RESTORE_EXTRA_REGS
-	RESTORE_C_REGS_EXCEPT_RCX_R11
-	movq	RSP(%rsp), %rsp
 	UNWIND_HINT_EMPTY
+	POP_EXTRA_REGS
+	popq	%rsi	/* skip r11 */
+	popq	%r10
+	popq	%r9
+	popq	%r8
+	popq	%rax
+	popq	%rsi	/* skip rcx */
+	popq	%rdx
+	popq	%rsi
+	popq	%rdi
+	movq	RSP-ORIG_RAX(%rsp), %rsp
 	USERGS_SYSRET64
 END(entry_SYSCALL_64)