[PATCH] x86-64/asm: use negative immediates for stack adjustments

[PATCH] x86-64/asm: use negative immediates for stack adjustments

[Jan Beulich]

Doing so allows adjustments by 128 bytes (occurring for
REMOVE_PT_GPREGS_FROM_STACK 8 uses) to be expressed with a single byte
immediate.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
---
 arch/x86/include/asm/calling.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- 4.1-rc6/arch/x86/include/asm/calling.h
+++ 4.1-rc6-x86_64-invert-stack-adjust/arch/x86/include/asm/calling.h
@@ -91,7 +91,7 @@ For 32-bit we have the following convent
 #define SIZEOF_PTREGS	21*8
 
 	.macro ALLOC_PT_GPREGS_ON_STACK addskip=0
-	subq	$15*8+\addskip, %rsp
+	addq	$-(15*8+\addskip), %rsp
 	CFI_ADJUST_CFA_OFFSET 15*8+\addskip
 	.endm
 
@@ -204,7 +204,7 @@ For 32-bit we have the following convent
 	.endm
 
 	.macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
-	addq $15*8+\addskip, %rsp
+	subq $-(15*8+\addskip), %rsp
 	CFI_ADJUST_CFA_OFFSET -(15*8+\addskip)
 	.endm
 

[tip:x86/asm] x86/asm/entry/64: Use negative immediates for stack adjustments

[tip-bot for Jan Beulich]

Commit-ID:  2bf557ea3f49576fabe24cd5daf1a34e9ee22c3c
Gitweb:     http://git.kernel.org/tip/2bf557ea3f49576fabe24cd5daf1a34e9ee22c3c
Author:     Jan Beulich <JBeulich@suse.com>
AuthorDate: Mon, 1 Jun 2015 13:02:55 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 2 Jun 2015 10:10:09 +0200

x86/asm/entry/64: Use negative immediates for stack adjustments

Doing so allows adjustments by 128 bytes (occurring for
REMOVE_PT_GPREGS_FROM_STACK 8 uses) to be expressed with a
single byte immediate.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
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/556C660F020000780007FB60@mail.emea.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/calling.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/calling.h b/arch/x86/include/asm/calling.h
index 0d76acc..f4e6308 100644
--- a/arch/x86/include/asm/calling.h
+++ b/arch/x86/include/asm/calling.h
@@ -89,7 +89,7 @@ For 32-bit we have the following conventions - kernel is built with
 #define SIZEOF_PTREGS	21*8
 
 	.macro ALLOC_PT_GPREGS_ON_STACK addskip=0
-	subq	$15*8+\addskip, %rsp
+	addq	$-(15*8+\addskip), %rsp
 	.endm
 
 	.macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
@@ -201,7 +201,7 @@ For 32-bit we have the following conventions - kernel is built with
 	.endm
 
 	.macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
-	addq $15*8+\addskip, %rsp
+	subq $-(15*8+\addskip), %rsp
 	.endm
 
 	.macro icebp