linux-kernel - [PATCH v3 04/10] x86: elf: Use e_machine to choose DLINFO in compat

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Message-Id: <20201004032536.1229030-5-krisman@collabora.com>
Date:   Sat,  3 Oct 2020 23:25:30 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     luto@...nel.org, tglx@...utronix.de
Cc:     hch@....de, hpa@...or.com, bp@...en8.de, rric@...nel.org,
        peterz@...radead.org, mingo@...hat.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, dave.hansen@...ux.intel.com,
        sean.j.christopherson@...el.com,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH v3 04/10] 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 <krisman@...labora.com>
Reviewed-by: Andy Lutomirski <luto@...nel.org>
---
 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