sigreturn: make use of RVAL_DECODED

* sigreturn.c (arch_sigreturn): New function.
(sys_sigreturn): Use it.  Return RVAL_DECODED.
* linux/alpha/arch_sigreturn.c: Update.
* linux/crisv10/arch_sigreturn.c: Likewise.
* linux/m68k/arch_sigreturn.c: Likewise.
* linux/microblaze/arch_sigreturn.c: Likewise.
* linux/x86_64/arch_sigreturn.c: Likewise.

linux/alpha/arch_sigreturn.c

@@ -1,7 +1,7 @@
 long addr;
 
 if (upeek(tcp->pid, REG_FP, &addr) < 0)
-	return 0;
+	return;
 addr += offsetof(struct sigcontext, sc_mask);
 
 tprints("{mask=");

linux/crisv10/arch_sigreturn.c

@@ -2,7 +2,7 @@ long regs[PT_MAX + 1];
 
 if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, (long)regs) < 0) {
 	perror_msg("sigreturn: PTRACE_GETREGS");
-	return 0;
+	return;
 }
 const long addr = regs[PT_USP] + offsetof(struct sigcontext, oldmask);
 

linux/m68k/arch_sigreturn.c

@@ -1,20 +1,20 @@
 long addr;
 
 if (upeek(tcp->pid, 4*PT_USP, &addr) < 0)
-	return 0;
+	return;
 /* Fetch pointer to struct sigcontext.  */
 if (umove(tcp, addr + 2 * sizeof(int), &addr) < 0)
-	return 0;
+	return;
 
 unsigned long mask[NSIG / 8 / sizeof(long)];
 /* Fetch first word of signal mask.  */
 if (umove(tcp, addr, &mask[0]) < 0)
-	return 0;
+	return;
 
 /* Fetch remaining words of signal mask, located immediately before.  */
 addr -= sizeof(mask) - sizeof(long);
 if (umoven(tcp, addr, sizeof(mask) - sizeof(long), &mask[1]) < 0)
-	return 0;
+	return;
 
 tprintsigmask_addr("{mask=", mask);
 tprints("}");

linux/microblaze/arch_sigreturn.c

@@ -4,7 +4,7 @@ long addr;
 
 /* Read r1, the stack pointer.  */
 if (upeek(tcp->pid, 1 * 4, &addr) < 0)
-	return 0;
+	return;
 addr += offsetof(struct sigcontext, oldmask);
 
 tprints("{mask=");

linux/x86_64/arch_sigreturn.c

@@ -5,6 +5,6 @@ if (current_personality != 1) {
 	tprints("{mask=");
 	print_sigset_addr_len(tcp, addr, NSIG / 8);
 	tprints("}");
-	return 0;
+	return;
 }
 #include "i386/arch_sigreturn.c"

sigreturn.c

@@ -14,10 +14,15 @@
 # error NSIG < 32
 #endif
 
+static void
+arch_sigreturn(struct tcb *tcp)
+{
+#include "arch_sigreturn.c"
+}
+
 SYS_FUNC(sigreturn)
 {
-	if (entering(tcp)) {
-#include "arch_sigreturn.c"
-	}
-	return 0;
+	arch_sigreturn(tcp);
+
+	return RVAL_DECODED;
 }