x86/arch_prctl: Simplify sys_arch_prctl()

Use in_ia32_syscall() instead of a compat syscall entry.

No change in functionality intended.

Signed-off-by: Brian Gerst <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Cc: "H. Peter Anvin" <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/entry/syscalls/syscall_32.tbl

···
 381	i386	pkey_alloc		sys_pkey_alloc
 382	i386	pkey_free		sys_pkey_free
 383	i386	statx			sys_statx
-384	i386	arch_prctl		sys_arch_prctl			compat_sys_arch_prctl
+384	i386	arch_prctl		sys_arch_prctl
 385	i386	io_pgetevents		sys_io_pgetevents_time32	compat_sys_io_pgetevents
 386	i386	rseq			sys_rseq
 393	i386	semget			sys_semget

arch/x86/include/asm/proto.h

···
 void entry_SYSCALL_64_safe_stack(void);
 void entry_SYSRETQ_unsafe_stack(void);
 void entry_SYSRETQ_end(void);
-long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2);
 #endif
 
 #ifdef CONFIG_X86_32
···
 
 extern int reboot_force;
 
-long do_arch_prctl_common(int option, unsigned long arg2);
+long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2);
 
 #endif /* _ASM_X86_PROTO_H */

arch/x86/kernel/process.c

···
 	return addr;
 }
 
-long do_arch_prctl_common(int option, unsigned long arg2)
+SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
 {
 	switch (option) {
 	case ARCH_GET_CPUID:
···
 	case ARCH_REQ_XCOMP_GUEST_PERM:
 		return fpu_xstate_prctl(option, arg2);
 	}
+
+	if (!in_ia32_syscall())
+		return do_arch_prctl_64(current, option, arg2);
 
 	return -EINVAL;
 }

arch/x86/kernel/process_32.c

···
 
 	return prev_p;
 }
-
-SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
-{
-	return do_arch_prctl_common(option, arg2);
-}

arch/x86/kernel/process_64.c

···
 	return ret;
 }
 
-SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
-{
-	long ret;
-
-	ret = do_arch_prctl_64(current, option, arg2);
-	if (ret == -EINVAL)
-		ret = do_arch_prctl_common(option, arg2);
-
-	return ret;
-}
-
-#ifdef CONFIG_IA32_EMULATION
-COMPAT_SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
-{
-	return do_arch_prctl_common(option, arg2);
-}
-#endif
-
 unsigned long KSTK_ESP(struct task_struct *task)
 {
 	return task_pt_regs(task)->sp;