[PATCH 3.19.y-ckt 003/107] x86/asm/entry/64: Fold the 'test_in_nmi' macro into its only user

[Kamal Mostafa <kamal@canonical.com>]

3.19.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Denys Vlasenko <dvlasenk@redhat.com>

commit 0784b36448a2a85b95b6eb21a69b9045c896c065 upstream.

No code changes.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427899858-7165-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: John Johansen <john.johansen@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 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 4ee9a23..f02ba29 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1438,19 +1438,7 @@ 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
@@ -1511,8 +1499,18 @@ 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:
-- 
1.9.1