+ LKML so I can find this easier to fetch via b4
On Mon, Nov 2, 2020 at 5:46 PM Nathan Chancellor natechancellor@gmail.com wrote:
On Mon, Nov 02, 2020 at 05:23:58PM -0800, 'Fangrui Song' via Clang Built Linux wrote:
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 Cc: stable@vger.kernel.org
This resolves the build error I see with LLVM_IAS=1 and ToT LLVM.
Tested-by: Nathan Chancellor natechancellor@gmail.com
Reviewed-by: Nick Desaulniers ndesaulniers@google.com Tested-by: Nick Desaulniers ndesaulniers@google.com
Changes in v2
- Correct the message: SYM_FUNC_START_WEAK was not available at commit 393f203f5fd5.
- Mention Fixes: ef1e03152cb0
arch/x86/lib/memcpy_64.S | 4 +--- arch/x86/lib/memmove_64.S | 4 +--- arch/x86/lib/memset_64.S | 4 +--- 3 files changed, 3 insertions(+), 9 deletions(-)
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S index 037faac46b0c..1e299ac73c86 100644 --- a/arch/x86/lib/memcpy_64.S +++ b/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/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S index 7ff00ea64e4f..41902fe8b859 100644 --- a/arch/x86/lib/memmove_64.S +++ b/arch/x86/lib/memmove_64.S @@ -24,9 +24,7 @@
- Output:
- rax: dest
*/ -.weak memmove
-SYM_FUNC_START_ALIAS(memmove) +SYM_FUNC_START_WEAK(memmove) SYM_FUNC_START(__memmove)
mov %rdi, %raxdiff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S index 9ff15ee404a4..0bfd26e4ca9e 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
@@ -19,7 +17,7 @@
- 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 --