linux-kernel - [tip:x86/pti] x86/entry/64: Simplify ENCODE_FRAME

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Date:   Wed, 21 Feb 2018 09:03:08 -0800
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org, tglx@...utronix.de,
        luto@...nel.org, torvalds@...ux-foundation.org, brgerst@...il.com,
        jpoimboe@...hat.com, linux@...inikbrodowski.net,
        dan.j.williams@...el.com, hpa@...or.com, peterz@...radead.org
Subject: [tip:x86/pti] x86/entry/64: Simplify ENCODE_FRAME_POINTER

Commit-ID:  0ca7d5baa1787e5f2a7abd6bfca3303b1bbb48ac
Gitweb:     https://git.kernel.org/tip/0ca7d5baa1787e5f2a7abd6bfca3303b1bbb48ac
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Tue, 20 Feb 2018 20:42:14 -0600
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 21 Feb 2018 16:54:07 +0100

x86/entry/64: Simplify ENCODE_FRAME_POINTER

On 64-bit, the stack pointer is always aligned on interrupt, so instead
of setting the LSB of the pt_regs address, we can just add 1 to it.

Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andrew Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Dominik Brodowski <linux@...inikbrodowski.net>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20180221024214.lhl5jfgw33c4vz3m@treble
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/calling.h | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 5d10b7a..be63330 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -181,12 +181,7 @@ For 32-bit we have the following conventions - kernel is built with
  */
 .macro ENCODE_FRAME_POINTER ptregs_offset=0
 #ifdef CONFIG_FRAME_POINTER
-	.if \ptregs_offset
-		leaq \ptregs_offset(%rsp), %rbp
-	.else
-		mov %rsp, %rbp
-	.endif
-	orq	$0x1, %rbp
+	leaq 1+\ptregs_offset(%rsp), %rbp
 #endif
 .endm