2020-10-01 21:01:14

by Gabriel Krisman Bertazi

Subject: [PATCH v2 4/9] x86: elf: Use e_machine to choose DLINFO in compat

Since TIF_X32 is going away, avoid using it to find the ELF type on
ARCH_DLINFO.

According to SysV AMD64 ABI Draft, an AMD64 ELF object using ILP32 must
have ELFCLASS32 with (E_MACHINE == EM_X86_64), so use that ELF field to
differentiate a x32 object from a IA32 object when loading ARCH_DLINFO
in compat mode.

Signed-off-by: Gabriel Krisman Bertazi <[email protected]>
---
arch/x86/include/asm/elf.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index b9a5d488f1a5..9220efc65d78 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -361,7 +361,7 @@ do { \
#define AT_SYSINFO 32

#define COMPAT_ARCH_DLINFO \
-if (test_thread_flag(TIF_X32)) \
+if (exec->e_machine == EM_X86_64) \
ARCH_DLINFO_X32; \
else \
ARCH_DLINFO_IA32
--
2.28.0

2020-10-01 21:48:10

by Andy Lutomirski

Subject: Re: [PATCH v2 4/9] x86: elf: Use e_machine to choose DLINFO in compat

On Thu, Oct 1, 2020 at 1:59 PM Gabriel Krisman Bertazi
<[email protected]> wrote:
>
> Since TIF_X32 is going away, avoid using it to find the ELF type on
> ARCH_DLINFO.
>
> According to SysV AMD64 ABI Draft, an AMD64 ELF object using ILP32 must
> have ELFCLASS32 with (E_MACHINE == EM_X86_64), so use that ELF field to
> differentiate a x32 object from a IA32 object when loading ARCH_DLINFO
> in compat mode.
>

Reviewed-by: Andy Lutomirski <[email protected]>

> Signed-off-by: Gabriel Krisman Bertazi <[email protected]>