linux-kernel - [tip:x86/asm] x86/asm/entry/64: Fold the 'test_in

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Message-ID: <tip-0784b36448a2a85b95b6eb21a69b9045c896c065@git.kernel.org>
Date:	Thu, 2 Apr 2015 05:33:02 -0700
From:	tip-bot for Denys Vlasenko <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	bp@...e.de, rostedt@...dmis.org, dvlasenk@...hat.com,
	keescook@...omium.org, fweisbec@...il.com, ast@...mgrid.com,
	wad@...omium.org, luto@...capital.net, mingo@...nel.org,
	bp@...en8.de, linux-kernel@...r.kernel.org, hpa@...or.com,
	oleg@...hat.com, torvalds@...ux-foundation.org, tglx@...utronix.de
Subject: [tip:x86/asm] x86/asm/entry/64: Fold the 'test_in_nmi'
  macro into its only user

Commit-ID:  0784b36448a2a85b95b6eb21a69b9045c896c065
Gitweb:     http://git.kernel.org/tip/0784b36448a2a85b95b6eb21a69b9045c896c065
Author:     Denys Vlasenko <dvlasenk@...hat.com>
AuthorDate: Wed, 1 Apr 2015 16:50:57 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 2 Apr 2015 12:00:10 +0200

x86/asm/entry/64: Fold the 'test_in_nmi' macro into its only user

No code changes.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
Acked-by: Borislav Petkov <bp@...e.de>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Will Drewry <wad@...omium.org>
Link: http://lkml.kernel.org/r/1427899858-7165-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/entry_64.S | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 03c52e2..386375d 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1355,19 +1355,7 @@ ENTRY(error_exit)
 	CFI_ENDPROC
 END(error_exit)
 
-/*
- * Test if a given stack is an NMI stack or not.
- */
-	.macro test_in_nmi reg stack nmi_ret normal_ret
-	cmpq %\reg, \stack
-	ja \normal_ret
-	subq $EXCEPTION_STKSZ, %\reg
-	cmpq %\reg, \stack
-	jb \normal_ret
-	jmp \nmi_ret
-	.endm
-
-	/* runs on exception stack */
+/* Runs on exception stack */
 ENTRY(nmi)
 	INTR_FRAME
 	PARAVIRT_ADJUST_EXCEPTION_FRAME
@@ -1428,8 +1416,18 @@ ENTRY(nmi)
 	 * We check the variable because the first NMI could be in a
 	 * breakpoint routine using a breakpoint stack.
 	 */
-	lea 6*8(%rsp), %rdx
-	test_in_nmi rdx, 4*8(%rsp), nested_nmi, first_nmi
+	lea	6*8(%rsp), %rdx
+	/* Compare the NMI stack (rdx) with the stack we came from (4*8(%rsp)) */
+	cmpq	%rdx, 4*8(%rsp)
+	/* If the stack pointer is above the NMI stack, this is a normal NMI */
+	ja	first_nmi
+	subq	$EXCEPTION_STKSZ, %rdx
+	cmpq	%rdx, 4*8(%rsp)
+	/* If it is below the NMI stack, it is a normal NMI */
+	jb	first_nmi
+	/* Ah, it is within the NMI stack, treat it as nested */
+	jmp	nested_nmi
+
 	CFI_REMEMBER_STATE
 
 nested_nmi:
--
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