On Fri, Oct 30, 2020 at 2:48 AM Jiri Slaby <jirislaby@xxxxxxxxxx> wrote:
>
> On 29. 10. 20, 19:05, Fangrui Song 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 SYM_FUNC_START_*
> > macros.
>
> There were no SYM_FUNC_START_* macros in 2015.
include/linux/linkage.h had WEAK in 2015 and WEAK should have been
used instead. Do I just need to fix the description?
> > This can lead to the assembly snippet `.weak memcpy ... .globl
> > memcpy`
>
> SYM_FUNC_START_LOCAL(memcpy)
> does not add .globl, so I don't understand the rationale.
There is no problem using
.weak
SYM_FUNC_START_LOCAL
just looks suspicious so I changed it, too.
> > 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.
> >
> > Use the appropriate SYM_FUNC_START_WEAK instead.
> >
> > Fixes: 393f203f5fd5 ("x86_64: kasan: add interceptors for memset/memmove/memcpy functions")
> > Reported-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> > Signed-off-by: Fangrui Song <maskray@xxxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > ---
> > 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, %rax
> > diff --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
> >
>
>
> --
> js
> suse labs
--
宋方睿
