ARC: sigaction: fold default sigrestorer into "C"

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

libc/sysdeps/linux/arc/Makefile.arch

@@ -7,5 +7,4 @@
 
 CSRC-y := syscall.c sigaction.c __syscall_error.c cacheflush.c
 
-SSRC-y := sigrestorer.S __longjmp.S setjmp.S bsd-setjmp.S bsd-_setjmp.S \
-	vfork.S clone.S
+SSRC-y := __longjmp.S setjmp.S bsd-setjmp.S bsd-_setjmp.S vfork.S clone.S

libc/sysdeps/linux/arc/sigaction.c

@@ -10,8 +10,13 @@
 #include <sys/syscall.h>
 #include <bits/kernel_sigaction.h>
 
-extern void __default_rt_sa_restorer(void);
-//libc_hidden_proto(__default_rt_sa_restorer);
+/*
+ * Default sigretrun stub if user doesn't specify SA_RESTORER
+ */
+static void __default_rt_sa_restorer(void)
+{
+	INTERNAL_SYSCALL_NCS(__NR_rt_sigreturn, , 0);
+}
 
 #define SA_RESTORER	0x04000000
 
@@ -25,11 +30,6 @@ __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
 	/*
 	 * SA_RESTORER is only relevant for act != NULL case
 	 * (!act means caller only wants to know @oact)
-	 *
-	 * For the normal/default cases (user not providing SA_RESTORER) use
-	 * a real sigreturn stub to avoid kernel synthesizing one on user stack
-	 * at runtime, which needs PTE permissions update (hence TLB entry
-	 * update) and costly cache line flushes for code modification
 	 */
 	if (act && !(act->sa_flags & SA_RESTORER)) {
 		kact.sa_restorer = __default_rt_sa_restorer;

libc/sysdeps/linux/arc/sigrestorer.S

@@ -1,21 +0,0 @@
-/*
- * Copyright (C) 2013 Synopsys, Inc. (www.synopsys.com)
- *
- * Licensed under the LGPL v2.1 or later, see the file COPYING.LIB in this tarball.
- */
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/*
- * Provide a real sigreturn stub to avoid kernel synthesizing one
- * on user stack at runtime, which needs PTE permissions update
- * (hence TLB entry update) and costly cache line flushes for
- * code modification
- */
-
-ENTRY(__default_rt_sa_restorer)
-    mov r8, __NR_rt_sigreturn
-    ARC_TRAP_INSN
-END(__default_rt_sa_restorer)
-libc_hidden_def(__default_rt_sa_restorer)