arm: new way of handling ERESTART_RESTARTBLOCK

new "syscall start" flag; handled in syscall_trace() by switching
syscall number to that of syscall_restart(2).  Restarts of that
kind (ERESTART_RESTARTBLOCK) are handled by setting that bit;
syscall number is not modified until the actual call.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 9650c14..d407ebf 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -24,6 +24,7 @@
 #include <linux/hw_breakpoint.h>
 #include <linux/regset.h>
 #include <linux/audit.h>
+#include <linux/unistd.h>
 
 #include <asm/pgtable.h>
 #include <asm/traps.h>
@@ -916,6 +917,8 @@
 		audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0,
 				    regs->ARM_r1, regs->ARM_r2, regs->ARM_r3);
 
+	if (why == 0 && test_and_clear_thread_flag(TIF_SYSCALL_RESTARTSYS))
+		scno = __NR_restart_syscall - __NR_SYSCALL_BASE;
 	if (!test_thread_flag(TIF_SYSCALL_TRACE))
 		return scno;
 	if (!(current->ptrace & PT_PTRACED))
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 6b37d4d..75c70d1 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -624,12 +624,10 @@
 		case -ERESTARTNOHAND:
 		case -ERESTARTSYS:
 		case -ERESTARTNOINTR:
+		case -ERESTART_RESTARTBLOCK:
 			regs->ARM_r0 = regs->ARM_ORIG_r0;
 			regs->ARM_pc = restart_addr;
 			break;
-		case -ERESTART_RESTARTBLOCK:
-			regs->ARM_r0 = -EINTR;
-			break;
 		}
 	}
 
@@ -647,12 +645,14 @@
 		 * debugger has chosen to restart at a different PC.
 		 */
 		if (regs->ARM_pc == restart_addr) {
-			if (retval == -ERESTARTNOHAND
+			if (retval == -ERESTARTNOHAND ||
+			    retval == -ERESTART_RESTARTBLOCK
 			    || (retval == -ERESTARTSYS
 				&& !(ka.sa.sa_flags & SA_RESTART))) {
 				regs->ARM_r0 = -EINTR;
 				regs->ARM_pc = continue_addr;
 			}
+			clear_thread_flag(TIF_SYSCALL_RESTARTSYS);
 		}
 
 		if (test_thread_flag(TIF_RESTORE_SIGMASK))
@@ -679,29 +679,8 @@
 		 * ignore the restart.
 		 */
 		if (retval == -ERESTART_RESTARTBLOCK
-		    && regs->ARM_pc == continue_addr) {
-			if (thumb_mode(regs)) {
-				regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
-				regs->ARM_pc -= 2;
-			} else {
-#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT)
-				regs->ARM_r7 = __NR_restart_syscall;
-				regs->ARM_pc -= 4;
-#else
-				u32 __user *usp;
-
-				regs->ARM_sp -= 4;
-				usp = (u32 __user *)regs->ARM_sp;
-
-				if (put_user(regs->ARM_pc, usp) == 0) {
-					regs->ARM_pc = KERN_RESTART_CODE;
-				} else {
-					regs->ARM_sp += 4;
-					force_sigsegv(0, current);
-				}
-#endif
-			}
-		}
+		    && regs->ARM_pc == restart_addr)
+			set_thread_flag(TIF_SYSCALL_RESTARTSYS);
 	}
 
 	/* If there's no signal to deliver, we just put the saved sigmask