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Message-ID: <20250418071437.4144391-1-ubizjak@gmail.com>
Date: Fri, 18 Apr 2025 09:13:50 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org,
linux-video@...ey.karlin.mff.cuni.cz,
xen-devel@...ts.xenproject.org,
linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>,
Martin Mares <mj@....cz>
Subject: [PATCH -tip v2 1/2] x86/boot: Remove semicolon from "rep" prefixes
Minimum version of binutils required to compile the kernel is 2.25.
This version correctly handles the "rep" prefixes, so it is possible
to remove the semicolon, which was used to support ancient versions
of GNU as.
Due to the semicolon, the compiler considers "rep; insn" (or its
alternate "rep\n\tinsn" form) as two separate instructions. Removing
the semicolon makes asm length calculations more accurate, consequently
making scheduling and inlining decisions of the compiler more accurate.
Removing the semicolon also enables assembler checks involving "rep"
prefixes. Trying to assemble e.g. "rep addl %eax, %ebx" results in:
Error: invalid instruction `add' after `rep'
Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Martin Mares <mj@....cz>
---
v2: Split the patch from the previous version.
---
arch/x86/boot/bioscall.S | 4 ++--
arch/x86/boot/boot.h | 4 ++--
arch/x86/boot/compressed/string.c | 8 ++++----
arch/x86/boot/copy.S | 8 ++++----
arch/x86/boot/header.S | 2 +-
arch/x86/boot/string.c | 2 +-
arch/x86/boot/video.c | 2 +-
7 files changed, 15 insertions(+), 15 deletions(-)
diff --git a/arch/x86/boot/bioscall.S b/arch/x86/boot/bioscall.S
index aa9b96457584..cf4a6155714e 100644
--- a/arch/x86/boot/bioscall.S
+++ b/arch/x86/boot/bioscall.S
@@ -32,7 +32,7 @@ intcall:
movw %dx, %si
movw %sp, %di
movw $11, %cx
- rep; movsl
+ rep movsl
/* Pop full state from the stack */
popal
@@ -67,7 +67,7 @@ intcall:
jz 4f
movw %sp, %si
movw $11, %cx
- rep; movsl
+ rep movsl
4: addw $44, %sp
/* Restore state and return */
diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
index 38f17a1e1e36..f3771a6373c7 100644
--- a/arch/x86/boot/boot.h
+++ b/arch/x86/boot/boot.h
@@ -155,14 +155,14 @@ static inline void wrgs32(u32 v, addr_t addr)
static inline bool memcmp_fs(const void *s1, addr_t s2, size_t len)
{
bool diff;
- asm volatile("fs; repe; cmpsb" CC_SET(nz)
+ asm volatile("fs repe cmpsb" CC_SET(nz)
: CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));
return diff;
}
static inline bool memcmp_gs(const void *s1, addr_t s2, size_t len)
{
bool diff;
- asm volatile("gs; repe; cmpsb" CC_SET(nz)
+ asm volatile("gs repe cmpsb" CC_SET(nz)
: CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));
return diff;
}
diff --git a/arch/x86/boot/compressed/string.c b/arch/x86/boot/compressed/string.c
index 81fc1eaa3229..9af19d9614cb 100644
--- a/arch/x86/boot/compressed/string.c
+++ b/arch/x86/boot/compressed/string.c
@@ -15,9 +15,9 @@ static void *____memcpy(void *dest, const void *src, size_t n)
{
int d0, d1, d2;
asm volatile(
- "rep ; movsl\n\t"
+ "rep movsl\n\t"
"movl %4,%%ecx\n\t"
- "rep ; movsb\n\t"
+ "rep movsb"
: "=&c" (d0), "=&D" (d1), "=&S" (d2)
: "0" (n >> 2), "g" (n & 3), "1" (dest), "2" (src)
: "memory");
@@ -29,9 +29,9 @@ static void *____memcpy(void *dest, const void *src, size_t n)
{
long d0, d1, d2;
asm volatile(
- "rep ; movsq\n\t"
+ "rep movsq\n\t"
"movq %4,%%rcx\n\t"
- "rep ; movsb\n\t"
+ "rep movsb"
: "=&c" (d0), "=&D" (d1), "=&S" (d2)
: "0" (n >> 3), "g" (n & 7), "1" (dest), "2" (src)
: "memory");
diff --git a/arch/x86/boot/copy.S b/arch/x86/boot/copy.S
index 6afd05e819d2..3973a67cd04e 100644
--- a/arch/x86/boot/copy.S
+++ b/arch/x86/boot/copy.S
@@ -22,10 +22,10 @@ SYM_FUNC_START_NOALIGN(memcpy)
movw %dx, %si
pushw %cx
shrw $2, %cx
- rep; movsl
+ rep movsl
popw %cx
andw $3, %cx
- rep; movsb
+ rep movsb
popw %di
popw %si
retl
@@ -38,10 +38,10 @@ SYM_FUNC_START_NOALIGN(memset)
imull $0x01010101,%eax
pushw %cx
shrw $2, %cx
- rep; stosl
+ rep stosl
popw %cx
andw $3, %cx
- rep; stosb
+ rep stosb
popw %di
retl
SYM_FUNC_END(memset)
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index b5c79f43359b..9cb91421b4e4 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -585,7 +585,7 @@ start_of_setup:
xorl %eax, %eax
subw %di, %cx
shrw $2, %cx
- rep; stosl
+ rep stosl
# Jump to C code (should not return)
calll main
diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
index 84f7a883ce1e..f35369bb14c5 100644
--- a/arch/x86/boot/string.c
+++ b/arch/x86/boot/string.c
@@ -32,7 +32,7 @@
int memcmp(const void *s1, const void *s2, size_t len)
{
bool diff;
- asm("repe; cmpsb" CC_SET(nz)
+ asm("repe cmpsb" CC_SET(nz)
: CC_OUT(nz) (diff), "+D" (s1), "+S" (s2), "+c" (len));
return diff;
}
diff --git a/arch/x86/boot/video.c b/arch/x86/boot/video.c
index f2e96905b3fe..0641c8c46aee 100644
--- a/arch/x86/boot/video.c
+++ b/arch/x86/boot/video.c
@@ -292,7 +292,7 @@ static void restore_screen(void)
"shrw %%cx ; "
"jnc 1f ; "
"stosw \n\t"
- "1: rep;stosl ; "
+ "1: rep stosl ; "
"popw %%es"
: "+D" (dst), "+c" (npad)
: "bdS" (video_segment),
--
2.49.0
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