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* 5.4 and 4.19 fix for LLVM_IAS/clang-12
@ 2020-12-09  0:12 Nick Desaulniers
  2020-12-09  7:20 ` Jiri Slaby
  0 siblings, 1 reply; 5+ messages in thread
From: Nick Desaulniers @ 2020-12-09  0:12 UTC (permalink / raw)
  To: Greg KH, Sasha Levin, Jiri Slaby
  Cc: stable, Jian Cai, Fangrui Song, Sami Tolvanen, Borislav Petkov,
	Nathan Chancellor, clang-built-linux

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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

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From fecddb0ab4ab58b69e29cb936b05336574cb029f Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
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@google.com>
Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201103012358.168682-1-maskray@google.com
[nd: backport due to missing commit e9b9d020c487 ("x86/asm: Annotate aliases")]
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 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


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From f30647cb41dee6a219609b3f7f5552ba576e4807 Mon Sep 17 00:00:00 2001
From: Fangrui Song <maskray@google.com>
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@google.com>
Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201103012358.168682-1-maskray@google.com
[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@google.com>
---
 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


^ permalink raw reply related	[flat|nested] 5+ messages in thread
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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-12-09  0:12 5.4 and 4.19 fix for LLVM_IAS/clang-12 Nick Desaulniers
2020-12-09  7:20 ` Jiri Slaby
2020-12-09  7:21   ` Jiri Slaby
2020-12-10 21:15     ` Nick Desaulniers
2020-12-11 14:41       ` Greg KH

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