Dear stable kernel maintainers,
Please consider accepting the following backport to 5.4 and 4.19 of
commit 4d6ffa27b8e5 ("x86/lib: Change .weak to SYM_FUNC_START_WEAK for
arch/x86/lib/mem*_64.S"), attached.
The patch to 5.4 had a conflict due to 5.4 missing upstream commit
e9b9d020c487 ("x86/asm: Annotate aliases") which first landed in
v5.5-rc1.
The patch to 4.19 had a conflict due to 4.19 missing the above commit
and ffedeeb780dc ("linkage: Introduce new macros for assembler
symbols") which also first landed in v5.5-rc1 but was backported to
linux-5.4.y as commit 840d8c9b3e5f ("linkage: Introduce new macros for
assembler symbols") which shipped in v5.4.76.
This patch fixes a build error from clang's assembler when building
with Clang-12, which now errors when symbols are redeclared with
different bindings. We're using clang's assembler in Android and
ChromeOS for 4.19+.
Jiri, would you mind reviewing the 4.19 patch (or both)? It simply
open codes what the upstream macros would expand to; this can be and
was observed from running:
$ make ... arch/x86/lib/memmove_64.s
(ie. lowercase s, to invoke the C preprocessor on the uppercase .S file)
See also: https://github.com/ClangBuiltLinux/linux/issues/1190.
--
Thanks,
~Nick Desaulniers
From fecddb0ab4ab58b69e29cb936b05336574cb029f Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@xxxxxxxxxx>
Date: Mon, 2 Nov 2020 17:23:58 -0800
Subject: [PATCH] x86/lib: Change .weak to SYM_FUNC_START_WEAK for
arch/x86/lib/mem*_64.S
commit 4d6ffa27b8e5116c0abb318790fd01d4e12d75e6 upstream.
Commit
393f203f5fd5 ("x86_64: kasan: add interceptors for memset/memmove/memcpy functions")
added .weak directives to arch/x86/lib/mem*_64.S instead of changing the
existing ENTRY macros to WEAK. This can lead to the assembly snippet
.weak memcpy
...
.globl memcpy
which will produce a STB_WEAK memcpy with GNU as but STB_GLOBAL memcpy
with LLVM's integrated assembler before LLVM 12. LLVM 12 (since
https://reviews.llvm.org/D90108) will error on such an overridden symbol
binding.
Commit
ef1e03152cb0 ("x86/asm: Make some functions local")
changed ENTRY in arch/x86/lib/memcpy_64.S to SYM_FUNC_START_LOCAL, which
was ineffective due to the preceding .weak directive.
Use the appropriate SYM_FUNC_START_WEAK instead.
Fixes: 393f203f5fd5 ("x86_64: kasan: add interceptors for memset/memmove/memcpy functions")
Fixes: ef1e03152cb0 ("x86/asm: Make some functions local")
Reported-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Signed-off-by: Fangrui Song <maskray@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20201103012358.168682-1-maskray@xxxxxxxxxx
[nd: backport due to missing commit e9b9d020c487 ("x86/asm: Annotate aliases")]
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
arch/x86/lib/memcpy_64.S | 6 ++----
arch/x86/lib/memmove_64.S | 6 ++----
arch/x86/lib/memset_64.S | 6 ++----
3 files changed, 6 insertions(+), 12 deletions(-)
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 92748660ba51..29f1eecffdfd 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -15,8 +15,6 @@
* to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
*/
-.weak memcpy
-
/*
* memcpy - Copy a memory block.
*
@@ -28,8 +26,8 @@
* Output:
* rax original destination
*/
-ENTRY(__memcpy)
-ENTRY(memcpy)
+SYM_FUNC_START_ALIAS(__memcpy)
+SYM_FUNC_START_WEAK(memcpy)
ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
"jmp memcpy_erms", X86_FEATURE_ERMS
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index bbec69d8223b..f8deefb5a994 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -24,10 +24,8 @@
* Output:
* rax: dest
*/
-.weak memmove
-
-ENTRY(memmove)
-ENTRY(__memmove)
+SYM_FUNC_START_WEAK(memmove)
+SYM_FUNC_START(__memmove)
/* Handle more 32 bytes in loop */
mov %rdi, %rax
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 9bc861c71e75..65837f7eeb32 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -6,8 +6,6 @@
#include <asm/alternative-asm.h>
#include <asm/export.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
@@ -19,8 +17,8 @@
*
* rax original destination
*/
-ENTRY(memset)
-ENTRY(__memset)
+SYM_FUNC_START_WEAK(memset)
+SYM_FUNC_START(__memset)
/*
* Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
* to use it when possible. If not available, use fast string instructions.
--
2.29.2.576.ga3fc446d84-goog
From f30647cb41dee6a219609b3f7f5552ba576e4807 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@xxxxxxxxxx>
Date: Mon, 2 Nov 2020 17:23:58 -0800
Subject: [PATCH] x86/lib: Change .weak to SYM_FUNC_START_WEAK for
arch/x86/lib/mem*_64.S
commit 4d6ffa27b8e5116c0abb318790fd01d4e12d75e6 upstream.
Commit
393f203f5fd5 ("x86_64: kasan: add interceptors for memset/memmove/memcpy functions")
added .weak directives to arch/x86/lib/mem*_64.S instead of changing the
existing ENTRY macros to WEAK. This can lead to the assembly snippet
.weak memcpy
...
.globl memcpy
which will produce a STB_WEAK memcpy with GNU as but STB_GLOBAL memcpy
with LLVM's integrated assembler before LLVM 12. LLVM 12 (since
https://reviews.llvm.org/D90108) will error on such an overridden symbol
binding.
Commit
ef1e03152cb0 ("x86/asm: Make some functions local")
changed ENTRY in arch/x86/lib/memcpy_64.S to SYM_FUNC_START_LOCAL, which
was ineffective due to the preceding .weak directive.
Use the appropriate SYM_FUNC_START_WEAK instead.
Fixes: 393f203f5fd5 ("x86_64: kasan: add interceptors for memset/memmove/memcpy functions")
Fixes: ef1e03152cb0 ("x86/asm: Make some functions local")
Reported-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
Signed-off-by: Fangrui Song <maskray@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Tested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20201103012358.168682-1-maskray@xxxxxxxxxx
[nd: backport due to missing
commit e9b9d020c487 ("x86/asm: Annotate aliases")
commit ffedeeb780dc ("linkage: Introduce new macros for assembler symbols")]
Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
arch/x86/lib/memcpy_64.S | 10 ++++++----
arch/x86/lib/memmove_64.S | 8 +++++---
arch/x86/lib/memset_64.S | 10 ++++++----
3 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 9d05572370ed..5e9fec9052ae 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -14,8 +14,6 @@
* to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
*/
-.weak memcpy
-
/*
* memcpy - Copy a memory block.
*
@@ -27,8 +25,12 @@
* Output:
* rax original destination
*/
-ENTRY(__memcpy)
-ENTRY(memcpy)
+.globl __memcpy
+.p2align 4, 0x90
+__memcpy:
+.weak memcpy
+.p2align 4, 0x90
+memcpy:
ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
"jmp memcpy_erms", X86_FEATURE_ERMS
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index bbec69d8223b..00c1f4fe3c02 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -25,9 +25,11 @@
* rax: dest
*/
.weak memmove
-
-ENTRY(memmove)
-ENTRY(__memmove)
+.p2align 4, 0x90
+memmove:
+.globl __memmove
+.p2align 4, 0x90
+__memmove:
/* Handle more 32 bytes in loop */
mov %rdi, %rax
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 9bc861c71e75..116750bb555d 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -6,8 +6,6 @@
#include <asm/alternative-asm.h>
#include <asm/export.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
@@ -19,8 +17,12 @@
*
* rax original destination
*/
-ENTRY(memset)
-ENTRY(__memset)
+.weak memset
+.p2align 4, 0x90
+memset:
+.globl __memset
+.p2align 4, 0x90
+__memset:
/*
* Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
* to use it when possible. If not available, use fast string instructions.
--
2.29.2.576.ga3fc446d84-goog
