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x86/elf: Use e_machine to select start_thread for x32

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Since TIF_X32 is going away, avoid using it to find the ELF type in
compat_start_thread.

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 executing start_thread()
in compat mode.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201004032536.1229030-7-krisman@collabora.com
This commit is contained in:
Gabriel Krisman Bertazi 2020-10-03 23:25:32 -04:00 committed by Thomas Gleixner
parent bc3d7bf61a
commit 2424b14605
2 changed files with 5 additions and 5 deletions
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5
arch/x86/include/asm/elf.h
View File

@ -186,8 +186,9 @@ static inline void elf_common_init(struct thread_struct *t,
#define COMPAT_ELF_PLAT_INIT(regs, load_addr) \
elf_common_init(&current->thread, regs, __USER_DS)
void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp);
#define compat_start_thread compat_start_thread
void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp, bool x32);
#define COMPAT_START_THREAD(ex, regs, new_ip, new_sp) \
compat_start_thread(regs, new_ip, new_sp, ex->e_machine == EM_X86_64)
void set_personality_ia32(bool);
#define COMPAT_SET_PERSONALITY(ex) \

5
arch/x86/kernel/process_64.c
View File

@ -511,11 +511,10 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
EXPORT_SYMBOL_GPL(start_thread);
#ifdef CONFIG_COMPAT
void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp)
void compat_start_thread(struct pt_regs *regs, u32 new_ip, u32 new_sp, bool x32)
{
start_thread_common(regs, new_ip, new_sp,
test_thread_flag(TIF_X32)
? __USER_CS : __USER32_CS,
x32 ? __USER_CS : __USER32_CS,
__USER_DS, __USER_DS);
}
#endif