x86/entry/64: Use syscall wrappers for x32_rt_sigreturn

Add missing syscall wrapper for x32_rt_sigreturn().
Signed-off-by: NBrian Gerst <brgerst@gmail.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NDominik Brodowski <linux@dominikbrodowski.net>
Reviewed-by: NAndy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200313195144.164260-6-brgerst@gmail.com

arch/x86/entry/syscalls/syscall_64.tbl

@@ -367,7 +367,7 @@
 # is defined.
 #
 512	x32	rt_sigaction		__x32_compat_sys_rt_sigaction
-513	x32	rt_sigreturn		sys32_x32_rt_sigreturn
+513	x32	rt_sigreturn		__x32_compat_sys_x32_rt_sigreturn
 514	x32	ioctl			__x32_compat_sys_ioctl
 515	x32	readv			__x32_compat_sys_readv
 516	x32	writev			__x32_compat_sys_writev

arch/x86/include/asm/sighandling.h

@@ -17,9 +17,4 @@ void signal_fault(struct pt_regs *regs, void __user *frame, char *where);
 int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 		     struct pt_regs *regs, unsigned long mask);
 
-
-#ifdef CONFIG_X86_X32_ABI
-asmlinkage long sys32_x32_rt_sigreturn(void);
-#endif
-
 #endif /* _ASM_X86_SIGHANDLING_H */

arch/x86/kernel/signal.c

@@ -859,7 +859,7 @@ void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 }
 
 #ifdef CONFIG_X86_X32_ABI
-asmlinkage long sys32_x32_rt_sigreturn(void)
+COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
 {
 	struct pt_regs *regs = current_pt_regs();
 	struct rt_sigframe_x32 __user *frame;