Commit 2424b146 authored by Gabriel Krisman Bertazi's avatar Gabriel Krisman Bertazi Committed by Thomas Gleixner
Browse files

x86/elf: Use e_machine to select start_thread for x32 



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: default avatarGabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAndy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201004032536.1229030-7-krisman@collabora.com
parent bc3d7bf6

arch/x86/include/asm/elf.h

+3 −2
Original line number Diff line number Diff line
@@ -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)			\

arch/x86/kernel/process_64.c

+2 −3
Original line number Diff line number Diff line
@@ -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