Re: [PATCH 1/8] kasan,x86: Frob kasan_report() in an exception

From: Peter Zijlstra
Date: Thu Mar 07 2019 - 08:50:03 EST


On Wed, Mar 06, 2019 at 09:59:11AM -0800, Linus Torvalds wrote:
> Maybe we could just get rid of that oddity, and just make __ASM_CLAC
> be a string to begin with.

Seems to work.. I'll add it to the pile.

---
arch/x86/include/asm/smap.h | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

--- a/arch/x86/include/asm/smap.h
+++ b/arch/x86/include/asm/smap.h
@@ -13,13 +13,12 @@
#ifndef _ASM_X86_SMAP_H
#define _ASM_X86_SMAP_H

-#include <linux/stringify.h>
#include <asm/nops.h>
#include <asm/cpufeatures.h>

/* "Raw" instruction opcodes */
-#define __ASM_CLAC .byte 0x0f,0x01,0xca
-#define __ASM_STAC .byte 0x0f,0x01,0xcb
+#define __ASM_CLAC ".byte 0x0f,0x01,0xca"
+#define __ASM_STAC ".byte 0x0f,0x01,0xcb"

#ifdef __ASSEMBLY__

@@ -28,10 +27,10 @@
#ifdef CONFIG_X86_SMAP

#define ASM_CLAC \
- ALTERNATIVE "", __stringify(__ASM_CLAC), X86_FEATURE_SMAP
+ ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP

#define ASM_STAC \
- ALTERNATIVE "", __stringify(__ASM_STAC), X86_FEATURE_SMAP
+ ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP

#else /* CONFIG_X86_SMAP */

@@ -49,20 +48,20 @@
static __always_inline void clac(void)
{
/* Note: a barrier is implicit in alternative() */
- alternative("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP);
+ alternative("", __ASM_CLAC, X86_FEATURE_SMAP);
}

static __always_inline void stac(void)
{
/* Note: a barrier is implicit in alternative() */
- alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP);
+ alternative("", __ASM_STAC, X86_FEATURE_SMAP);
}

static __always_inline unsigned long smap_save(void)
{
unsigned long flags;

- asm volatile (ALTERNATIVE("", "pushf; pop %0; " __stringify(__ASM_CLAC),
+ asm volatile (ALTERNATIVE("", "pushf; pop %0; " __ASM_CLAC,
X86_FEATURE_SMAP)
: "=rm" (flags) : : "memory", "cc");

@@ -77,9 +76,9 @@ static __always_inline void smap_restore

/* These macros can be used in asm() statements */
#define ASM_CLAC \
- ALTERNATIVE("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
+ ALTERNATIVE("", __ASM_CLAC, X86_FEATURE_SMAP)
#define ASM_STAC \
- ALTERNATIVE("", __stringify(__ASM_STAC), X86_FEATURE_SMAP)
+ ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)

#else /* CONFIG_X86_SMAP */