linux-kernel - [PATCH 3/3] tools/nolibc: x86_64: wrap asm functions in functions

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Message-Id: <20240810-nolibc-lto-v1-3-a86e514c7fc1@weissschuh.net>
Date: Sat, 10 Aug 2024 12:54:46 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>
Cc: Ammar Faizi <ammarfaizi2@...weeb.org>, linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 3/3] tools/nolibc: x86_64: wrap asm functions in functions

The bare asm usage does not work well together with LTO.
It leads to errors:

  /tmp/ccIHTYT6.s: Assembler messages:
  /tmp/ccIHTYT6.s:36: Error: symbol `memmove' is already defined
  /tmp/ccIHTYT6.s:37: Error: symbol `memcpy' is already defined
  /tmp/ccIHTYT6.s:46: Error: symbol `.Lbackward_copy' is already defined
  /tmp/ccIHTYT6.s:54: Error: symbol `memset' is already defined

Wrap the asm in naked functions, which leads to the same object code but
avoids the errors.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 tools/include/nolibc/arch-x86_64.h | 80 +++++++++++++++++++++-----------------
 1 file changed, 44 insertions(+), 36 deletions(-)

diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h
index 3c3b703d9b0c..efbea173fb74 100644
--- a/tools/include/nolibc/arch-x86_64.h
+++ b/tools/include/nolibc/arch-x86_64.h
@@ -174,45 +174,53 @@ void __attribute__((weak, noreturn)) __nolibc_naked __no_stack_protector _start(
 }
 
 #define NOLIBC_ARCH_HAS_MEMMOVE
-void *memmove(void *dst, const void *src, size_t len);
+__attribute__((weak,unused,section(".text.nolibc_memmove")))
+__nolibc_naked __no_stack_protector
+void *memmove(void *dst __attribute__((unused)),
+	      const void *src __attribute__((unused)),
+	      size_t len __attribute__((unused)))
+{
+	__asm__ volatile (
+		"movq %rdx, %rcx\n\t"
+		"movq %rdi, %rax\n\t"
+		"movq %rdi, %rdx\n\t"
+		"subq %rsi, %rdx\n\t"
+		"cmpq %rcx, %rdx\n\t"
+		"jb   .Lbackward_copy\n\t"
+		"rep movsb\n\t"
+		"retq\n"
+		".Lbackward_copy:"
+		"leaq -1(%rdi, %rcx, 1), %rdi\n\t"
+		"leaq -1(%rsi, %rcx, 1), %rsi\n\t"
+		"std\n\t"
+		"rep movsb\n\t"
+		"cld\n\t"
+		"retq\n"
+	);
+	__nolibc_naked_epilogue();
+}
 
 #define NOLIBC_ARCH_HAS_MEMCPY
-void *memcpy(void *dst, const void *src, size_t len);
+static __inline__ void *memcpy(void *dst, const void *src, size_t len)
+{
+	return memmove(dst, src, len);
+}
 
 #define NOLIBC_ARCH_HAS_MEMSET
-void *memset(void *dst, int c, size_t len);
-
-__asm__ (
-".section .text.nolibc_memmove_memcpy\n"
-".weak memmove\n"
-".weak memcpy\n"
-"memmove:\n"
-"memcpy:\n"
-	"movq %rdx, %rcx\n\t"
-	"movq %rdi, %rax\n\t"
-	"movq %rdi, %rdx\n\t"
-	"subq %rsi, %rdx\n\t"
-	"cmpq %rcx, %rdx\n\t"
-	"jb   .Lbackward_copy\n\t"
-	"rep movsb\n\t"
-	"retq\n"
-".Lbackward_copy:"
-	"leaq -1(%rdi, %rcx, 1), %rdi\n\t"
-	"leaq -1(%rsi, %rcx, 1), %rsi\n\t"
-	"std\n\t"
-	"rep movsb\n\t"
-	"cld\n\t"
-	"retq\n"
-
-".section .text.nolibc_memset\n"
-".weak memset\n"
-"memset:\n"
-	"xchgl %eax, %esi\n\t"
-	"movq  %rdx, %rcx\n\t"
-	"pushq %rdi\n\t"
-	"rep stosb\n\t"
-	"popq  %rax\n\t"
-	"retq\n"
-);
+__attribute__((weak,unused,section(".text.nolibc_memset")))
+__nolibc_naked __no_stack_protector
+void *memset(void *dst __attribute__((unused)), int c __attribute__((unused)),
+	     size_t len __attribute__((unused)))
+{
+	__asm__ volatile (
+		"xchgl %eax, %esi\n\t"
+		"movq  %rdx, %rcx\n\t"
+		"pushq %rdi\n\t"
+		"rep stosb\n\t"
+		"popq  %rax\n\t"
+		"retq\n"
+	);
+	__nolibc_naked_epilogue();
+}
 
 #endif /* _NOLIBC_ARCH_X86_64_H */

-- 
2.46.0