linux-kernel - [PATCH] perf bench: Update arch/x86/lib/mem{cpy,set}

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Date:   Tue,  3 Nov 2020 16:56:09 -0800
From:   Fangrui Song <maskray@...gle.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com,
        Ian Rogers <irogers@...gle.com>,
        Fangrui Song <maskray@...gle.com>
Subject: [PATCH] perf bench: Update arch/x86/lib/mem{cpy,set}_64.S

In memset_64.S, the macros expand to `.weak MEMSET ... .globl MEMSET`
which will produce a STB_WEAK MEMSET with GNU as but STB_GLOBAL MEMSET
with LLVM's integrated assembler before LLVM 12. LLVM 12 (since
https://reviews.llvm.org/D90108) will error on such an overridden symbol
binding. memcpy_64.S is similar.

Port http://lore.kernel.org/r/20201103012358.168682-1-maskray@google.com
("x86_64: Change .weak to SYM_FUNC_START_WEAK for arch/x86/lib/mem*_64.S")
to fix the issue. Additionally, port SYM_L_WEAK and SYM_FUNC_START_WEAK
from include/linux/linkage.h to tools/perf/util/include/linux/linkage.h

Fixes: 7d7d1bf1d1da ("perf bench: Copy kernel files needed to build mem{cpy,set} x86_64 benchmarks")
Link: https://lore.kernel.org/r/20201103012358.168682-1-maskray@google.com
Signed-off-by: Fangrui Song <maskray@...gle.com>
---
 tools/arch/x86/lib/memcpy_64.S          | 4 +---
 tools/arch/x86/lib/memset_64.S          | 4 +---
 tools/perf/util/include/linux/linkage.h | 7 +++++++
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/tools/arch/x86/lib/memcpy_64.S b/tools/arch/x86/lib/memcpy_64.S
index 0b5b8ae56bd9..9428f251df0f 100644
--- a/tools/arch/x86/lib/memcpy_64.S
+++ b/tools/arch/x86/lib/memcpy_64.S
@@ -16,8 +16,6 @@
  * to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
  */
 
-.weak memcpy
-
 /*
  * memcpy - Copy a memory block.
  *
@@ -30,7 +28,7 @@
  * rax original destination
  */
 SYM_FUNC_START_ALIAS(__memcpy)
-SYM_FUNC_START_LOCAL(memcpy)
+SYM_FUNC_START_WEAK(memcpy)
 	ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
 		      "jmp memcpy_erms", X86_FEATURE_ERMS
 
diff --git a/tools/arch/x86/lib/memset_64.S b/tools/arch/x86/lib/memset_64.S
index fd5d25a474b7..1f9b11f9244d 100644
--- a/tools/arch/x86/lib/memset_64.S
+++ b/tools/arch/x86/lib/memset_64.S
@@ -5,8 +5,6 @@
 #include <asm/cpufeatures.h>
 #include <asm/alternative-asm.h>
 
-.weak memset
-
 /*
  * ISO C memset - set a memory block to a byte value. This function uses fast
  * string to get better performance than the original function. The code is
@@ -18,7 +16,7 @@
  *
  * rax   original destination
  */
-SYM_FUNC_START_ALIAS(memset)
+SYM_FUNC_START_WEAK(memset)
 SYM_FUNC_START(__memset)
 	/*
 	 * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
diff --git a/tools/perf/util/include/linux/linkage.h b/tools/perf/util/include/linux/linkage.h
index b8a5159361b4..0e493bf3151b 100644
--- a/tools/perf/util/include/linux/linkage.h
+++ b/tools/perf/util/include/linux/linkage.h
@@ -25,6 +25,7 @@
 
 /* SYM_L_* -- linkage of symbols */
 #define SYM_L_GLOBAL(name)			.globl name
+#define SYM_L_WEAK(name)			.weak name
 #define SYM_L_LOCAL(name)			/* nothing */
 
 #define ALIGN __ALIGN
@@ -78,6 +79,12 @@
 	SYM_START(name, SYM_L_LOCAL, SYM_A_ALIGN)
 #endif
 
+/* SYM_FUNC_START_WEAK -- use for weak functions */
+#ifndef SYM_FUNC_START_WEAK
+#define SYM_FUNC_START_WEAK(name)			\
+	SYM_START(name, SYM_L_WEAK, SYM_A_ALIGN)
+#endif
+
 /* SYM_FUNC_END_ALIAS -- the end of LOCAL_ALIASed or ALIASed function */
 #ifndef SYM_FUNC_END_ALIAS
 #define SYM_FUNC_END_ALIAS(name)			\
-- 
2.29.1.341.ge80a0c044ae-goog