x86/asm: 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@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@kernel.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20250418071437.4144391-2-ubizjak@gmail.com

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index e889c3bab5a245f3985290f9001b7446cd319280..ca309a3227c78bee2eafa2eecfb4b91f941072a8 100644 (file)
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -217,7 +217,7 @@ void memset_io(volatile void __iomem *, int, size_t);
 static inline void __iowrite32_copy(void __iomem *to, const void *from,
                                    size_t count)
 {
-       asm volatile("rep ; movsl"
+       asm volatile("rep movsl"
                     : "=&c"(count), "=&D"(to), "=&S"(from)
                     : "0"(count), "1"(to), "2"(from)
                     : "memory");
@@ -282,7 +282,7 @@ static inline void outs##bwl(u16 port, const void *addr, unsigned long count) \
                        count--;                                        \
                }                                                       \
        } else {                                                        \
-               asm volatile("rep; outs" #bwl                           \
+               asm volatile("rep outs" #bwl                            \
                             : "+S"(addr), "+c"(count)                  \
                             : "d"(port) : "memory");                   \
        }                                                               \
@@ -298,7 +298,7 @@ static inline void ins##bwl(u16 port, void *addr, unsigned long count)      \
                        count--;                                        \
                }                                                       \
        } else {                                                        \
-               asm volatile("rep; ins" #bwl                            \
+               asm volatile("rep ins" #bwl                             \
                             : "+D"(addr), "+c"(count)                  \
                             : "d"(port) : "memory");                   \
        }                                                               \

diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index 32c0d981a82ace5e4b86778c3f7d2822458a7959..e9cce169bb4cd1196897e90399afadd944947ac3 100644 (file)
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -33,11 +33,11 @@ extern size_t strlen(const char *s);
 static __always_inline void *__memcpy(void *to, const void *from, size_t n)
 {
        int d0, d1, d2;
-       asm volatile("rep ; movsl\n\t"
+       asm volatile("rep movsl\n\t"
                     "movl %4,%%ecx\n\t"
                     "andl $3,%%ecx\n\t"
                     "jz 1f\n\t"
-                    "rep ; movsb\n\t"
+                    "rep movsb\n\t"
                     "1:"
                     : "=&c" (d0), "=&D" (d1), "=&S" (d2)
                     : "0" (n / 4), "g" (n), "1" ((long)to), "2" ((long)from)
@@ -89,7 +89,7 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
        if (n >= 5 * 4) {
                /* large block: use rep prefix */
                int ecx;
-               asm volatile("rep ; movsl"
+               asm volatile("rep movsl"
                             : "=&c" (ecx), "=&D" (edi), "=&S" (esi)
                             : "0" (n / 4), "1" (edi), "2" (esi)
                             : "memory"
@@ -165,8 +165,7 @@ extern void *memchr(const void *cs, int c, size_t count);
 static inline void *__memset_generic(void *s, char c, size_t count)
 {
        int d0, d1;
-       asm volatile("rep\n\t"
-                    "stosb"
+       asm volatile("rep stosb"
                     : "=&c" (d0), "=&D" (d1)
                     : "a" (c), "1" (s), "0" (count)
                     : "memory");
@@ -199,8 +198,7 @@ extern void *memset(void *, int, size_t);
 static inline void *memset16(uint16_t *s, uint16_t v, size_t n)
 {
        int d0, d1;
-       asm volatile("rep\n\t"
-                    "stosw"
+       asm volatile("rep stosw"
                     : "=&c" (d0), "=&D" (d1)
                     : "a" (v), "1" (s), "0" (n)
                     : "memory");
@@ -211,8 +209,7 @@ static inline void *memset16(uint16_t *s, uint16_t v, size_t n)
 static inline void *memset32(uint32_t *s, uint32_t v, size_t n)
 {
        int d0, d1;
-       asm volatile("rep\n\t"
-                    "stosl"
+       asm volatile("rep stosl"
                     : "=&c" (d0), "=&D" (d1)
                     : "a" (v), "1" (s), "0" (n)
                     : "memory");

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 2e42056d230630369f69659893f9a21ac753560b..76743dfad6ab9d2c49b8e71dcef0813bc63aa14b 100644 (file)
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -86,7 +86,7 @@ SYM_CODE_START(startup_32)
        movl $pa(__bss_stop),%ecx
        subl %edi,%ecx
        shrl $2,%ecx
-       rep ; stosl
+       rep stosl
 /*
  * Copy bootup parameters out of the way.
  * Note: %esi still has the pointer to the real-mode data.
@@ -98,15 +98,13 @@ SYM_CODE_START(startup_32)
        movl $pa(boot_params),%edi
        movl $(PARAM_SIZE/4),%ecx
        cld
-       rep
-       movsl
+       rep movsl
        movl pa(boot_params) + NEW_CL_POINTER,%esi
        andl %esi,%esi
        jz 1f                   # No command line
        movl $pa(boot_command_line),%edi
        movl $(COMMAND_LINE_SIZE/4),%ecx
-       rep
-       movsl
+       rep movsl
 1:
 
 #ifdef CONFIG_OLPC

diff --git a/arch/x86/kernel/relocate_kernel_32.S b/arch/x86/kernel/relocate_kernel_32.S
index c7c4b1917336d1d95b5b998b0b065a89513287cd..57276f134d12a94ebb04aee096ac507c01735629 100644 (file)
--- a/arch/x86/kernel/relocate_kernel_32.S
+++ b/arch/x86/kernel/relocate_kernel_32.S
@@ -263,17 +263,17 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
 
        movl    %edx, %edi
        movl    $1024, %ecx
-       rep ; movsl
+       rep movsl
 
        movl    %ebp, %edi
        movl    %eax, %esi
        movl    $1024, %ecx
-       rep ; movsl
+       rep movsl
 
        movl    %eax, %edi
        movl    %edx, %esi
        movl    $1024, %ecx
-       rep ; movsl
+       rep movsl
 
        lea     PAGE_SIZE(%ebp), %esi
        jmp     0b

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 3062cb3efc443516c83ff16b7d8f3d122216c995..1d6355227bf60d13d8d3313702bfedbe3e06114f 100644 (file)
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -363,20 +363,20 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
        /* copy source page to swap page */
        movq    kexec_pa_swap_page(%rip), %rdi
        movl    $512, %ecx
-       rep ; movsq
+       rep movsq
 
        /* copy destination page to source page */
        movq    %rax, %rdi
        movq    %rdx, %rsi
        movl    $512, %ecx
-       rep ; movsq
+       rep movsq
 
        /* copy swap page to destination page */
        movq    %rdx, %rdi
        movq    kexec_pa_swap_page(%rip), %rsi
 .Lnoswap:
        movl    $512, %ecx
-       rep ; movsq
+       rep movsq
 
        lea     PAGE_SIZE(%rax), %rsi
        jmp     .Lloop

diff --git a/arch/x86/lib/iomem.c b/arch/x86/lib/iomem.c
index 5eecb45d05d5daf6b8c219473900919de711c66e..c20e04764edc8df460266b2827b2653278cacb50 100644 (file)
--- a/arch/x86/lib/iomem.c
+++ b/arch/x86/lib/iomem.c
@@ -10,7 +10,7 @@
 static __always_inline void rep_movs(void *to, const void *from, size_t n)
 {
        unsigned long d0, d1, d2;
-       asm volatile("rep ; movsl\n\t"
+       asm volatile("rep movsl\n\t"
                     "testb $2,%b4\n\t"
                     "je 1f\n\t"
                     "movsw\n"

diff --git a/arch/x86/lib/string_32.c b/arch/x86/lib/string_32.c
index 53b3f202267c274d9f217afc1858ba944ade73ad..f87ec24fa5790d799059b05bdd12ec6704c06da2 100644 (file)
--- a/arch/x86/lib/string_32.c
+++ b/arch/x86/lib/string_32.c
@@ -40,8 +40,7 @@ char *strncpy(char *dest, const char *src, size_t count)
                "stosb\n\t"
                "testb %%al,%%al\n\t"
                "jne 1b\n\t"
-               "rep\n\t"
-               "stosb\n"
+               "rep stosb\n"
                "2:"
                : "=&S" (d0), "=&D" (d1), "=&c" (d2), "=&a" (d3)
                : "0" (src), "1" (dest), "2" (count) : "memory");
@@ -54,8 +53,7 @@ EXPORT_SYMBOL(strncpy);
 char *strcat(char *dest, const char *src)
 {
        int d0, d1, d2, d3;
-       asm volatile("repne\n\t"
-               "scasb\n\t"
+       asm volatile("repne scasb\n\t"
                "decl %1\n"
                "1:\tlodsb\n\t"
                "stosb\n\t"
@@ -72,8 +70,7 @@ EXPORT_SYMBOL(strcat);
 char *strncat(char *dest, const char *src, size_t count)
 {
        int d0, d1, d2, d3;
-       asm volatile("repne\n\t"
-               "scasb\n\t"
+       asm volatile("repne scasb\n\t"
                "decl %1\n\t"
                "movl %8,%3\n"
                "1:\tdecl %3\n\t"
@@ -167,8 +164,7 @@ size_t strlen(const char *s)
 {
        int d0;
        size_t res;
-       asm volatile("repne\n\t"
-               "scasb"
+       asm volatile("repne scasb"
                : "=c" (res), "=&D" (d0)
                : "1" (s), "a" (0), "0" (0xffffffffu)
                : "memory");
@@ -184,8 +180,7 @@ void *memchr(const void *cs, int c, size_t count)
        void *res;
        if (!count)
                return NULL;
-       asm volatile("repne\n\t"
-               "scasb\n\t"
+       asm volatile("repne scasb\n\t"
                "je 1f\n\t"
                "movl $1,%0\n"
                "1:\tdecl %0"
@@ -202,7 +197,7 @@ void *memscan(void *addr, int c, size_t size)
 {
        if (!size)
                return addr;
-       asm volatile("repnz; scasb\n\t"
+       asm volatile("repnz scasb\n\t"
            "jnz 1f\n\t"
            "dec %%edi\n"
            "1:"

diff --git a/arch/x86/lib/strstr_32.c b/arch/x86/lib/strstr_32.c
index 38f37df056f72ea6f93c0c11d15bc8c80103c785..28267985e85f4a42763aeb874ddaed6f7dcd32ba 100644 (file)
--- a/arch/x86/lib/strstr_32.c
+++ b/arch/x86/lib/strstr_32.c
@@ -8,16 +8,14 @@ int   d0, d1;
 register char *__res;
 __asm__ __volatile__(
        "movl %6,%%edi\n\t"
-       "repne\n\t"
-       "scasb\n\t"
+       "repne scasb\n\t"
        "notl %%ecx\n\t"
        "decl %%ecx\n\t"        /* NOTE! This also sets Z if searchstring='' */
        "movl %%ecx,%%edx\n"
        "1:\tmovl %6,%%edi\n\t"
        "movl %%esi,%%eax\n\t"
        "movl %%edx,%%ecx\n\t"
-       "repe\n\t"
-       "cmpsb\n\t"
+       "repe cmpsb\n\t"
        "je 2f\n\t"             /* also works for empty string, see above */
        "xchgl %%eax,%%esi\n\t"
        "incl %%esi\n\t"

diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 422257c350c68d566032e657c156ab193804f8ae..f6f436f1d57375534b05b948c2c336feffff3c7d 100644 (file)
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -38,9 +38,9 @@ do {                                                                  \
        might_fault();                                                  \
        __asm__ __volatile__(                                           \
                ASM_STAC "\n"                                           \
-               "0:     rep; stosl\n"                                   \
+               "0:     rep stosl\n"                                    \
                "       movl %2,%0\n"                                   \
-               "1:     rep; stosb\n"                                   \
+               "1:     rep stosb\n"                                    \
                "2: " ASM_CLAC "\n"                                     \
                _ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN4, %2)   \
                _ASM_EXTABLE_UA(1b, 2b)                                 \
@@ -140,9 +140,9 @@ __copy_user_intel(void __user *to, const void *from, unsigned long size)
                       "       shrl  $2, %0\n"
                       "       andl  $3, %%eax\n"
                       "       cld\n"
-                      "99:    rep; movsl\n"
+                      "99:    rep movsl\n"
                       "36:    movl %%eax, %0\n"
-                      "37:    rep; movsb\n"
+                      "37:    rep movsb\n"
                       "100:\n"
                       _ASM_EXTABLE_UA(1b, 100b)
                       _ASM_EXTABLE_UA(2b, 100b)
@@ -242,9 +242,9 @@ static unsigned long __copy_user_intel_nocache(void *to,
               "        shrl  $2, %0\n"
               "        andl $3, %%eax\n"
               "        cld\n"
-              "6:      rep; movsl\n"
+              "6:      rep movsl\n"
               "        movl %%eax,%0\n"
-              "7:      rep; movsb\n"
+              "7:      rep movsb\n"
               "8:\n"
               _ASM_EXTABLE_UA(0b, 8b)
               _ASM_EXTABLE_UA(1b, 8b)
@@ -293,14 +293,14 @@ do {                                                                      \
                "       negl %0\n"                                      \
                "       andl $7,%0\n"                                   \
                "       subl %0,%3\n"                                   \
-               "4:     rep; movsb\n"                                   \
+               "4:     rep movsb\n"                                    \
                "       movl %3,%0\n"                                   \
                "       shrl $2,%0\n"                                   \
                "       andl $3,%3\n"                                   \
                "       .align 2,0x90\n"                                \
-               "0:     rep; movsl\n"                                   \
+               "0:     rep movsl\n"                                    \
                "       movl %3,%0\n"                                   \
-               "1:     rep; movsb\n"                                   \
+               "1:     rep movsb\n"                                    \
                "2:\n"                                                  \
                _ASM_EXTABLE_TYPE_REG(4b, 2b, EX_TYPE_UCOPY_LEN1, %3)   \
                _ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN4, %3)   \

diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index cfa18ec7d55f19ba15e1665b393d080ebbe059aa..1d78e5631bb81c7bd118b6aefd5d5f7de8c57b22 100644 (file)
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -87,8 +87,7 @@ SYM_CODE_START(pvh_start_xen)
        mov %ebx, %esi
        movl rva(pvh_start_info_sz)(%ebp), %ecx
        shr $2,%ecx
-       rep
-       movsl
+       rep movsl
 
        leal rva(early_stack_end)(%ebp), %esp
 

diff --git a/arch/x86/power/hibernate_asm_32.S b/arch/x86/power/hibernate_asm_32.S
index 5606a15cf9a173b39dba6dbbdd8409dd822bdb00..fb910d9f847123c35ff371723ad56865f17c5b7f 100644 (file)
--- a/arch/x86/power/hibernate_asm_32.S
+++ b/arch/x86/power/hibernate_asm_32.S
@@ -69,8 +69,7 @@ copy_loop:
        movl    pbe_orig_address(%edx), %edi
 
        movl    $(PAGE_SIZE >> 2), %ecx
-       rep
-       movsl
+       rep movsl
 
        movl    pbe_next(%edx), %edx
        jmp     copy_loop

diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
index 8c534c36adfa2865349f1d4c202345abdc721a7e..f5bda01904c7d90e320149ccb7be5e131d6eb862 100644 (file)
--- a/arch/x86/power/hibernate_asm_64.S
+++ b/arch/x86/power/hibernate_asm_64.S
@@ -138,8 +138,7 @@ SYM_FUNC_START(core_restore_code)
        movq    pbe_address(%rdx), %rsi
        movq    pbe_orig_address(%rdx), %rdi
        movq    $(PAGE_SIZE >> 3), %rcx
-       rep
-       movsq
+       rep movsq
 
        /* progress to the next pbe */
        movq    pbe_next(%rdx), %rdx