ARM: 7470/1: Revert "7443/1: Revert "new way of handling ERESTART_RESTARTBLOCK""

This reverts commit 433e2f30.

Conflicts:

	arch/arm/kernel/ptrace.c

Reintroduce the new syscall restart handling in preparation for further
patches from Al Viro.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/thread_info.h

@@ -148,6 +148,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define TIF_NOTIFY_RESUME	2	/* callback before returning to user */
 #define TIF_SYSCALL_TRACE	8
 #define TIF_SYSCALL_AUDIT	9
+#define TIF_SYSCALL_RESTARTSYS	10
 #define TIF_POLLING_NRFLAG	16
 #define TIF_USING_IWMMXT	17
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
@@ -163,9 +164,11 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_USING_IWMMXT	(1 << TIF_USING_IWMMXT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_SYSCALL_RESTARTSYS	(1 << TIF_SYSCALL_RESTARTSYS)
 
 /* Checks for any syscall work in entry-common.S */
-#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT)
+#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+			   _TIF_SYSCALL_RESTARTSYS)
 
 /*
  * Change these and you break ASM code in entry-common.S

arch/arm/kernel/ptrace.c

@@ -25,6 +25,7 @@
 #include <linux/regset.h>
 #include <linux/audit.h>
 #include <linux/tracehook.h>
+#include <linux/unistd.h>
 
 #include <asm/pgtable.h>
 #include <asm/traps.h>
@@ -940,7 +941,12 @@ static int ptrace_syscall_trace(struct pt_regs *regs, int scno,
 
 asmlinkage int syscall_trace_enter(struct pt_regs *regs, int scno)
 {
-	int ret = ptrace_syscall_trace(regs, scno, PTRACE_SYSCALL_ENTER);
+	int ret;
+
+	if (test_and_clear_thread_flag(TIF_SYSCALL_RESTARTSYS))
+		scno = __NR_restart_syscall - __NR_SYSCALL_BASE;
+
+	ret = ptrace_syscall_trace(regs, scno, PTRACE_SYSCALL_ENTER);
 	audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0, regs->ARM_r1,
 			    regs->ARM_r2, regs->ARM_r3);
 	return ret;

arch/arm/kernel/signal.c

@@ -605,12 +605,10 @@ static void do_signal(struct pt_regs *regs, int syscall)
 		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;
 		}
 	}
 
@@ -626,12 +624,14 @@ static void do_signal(struct pt_regs *regs, int syscall)
 		 * 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);
 		}
 
 		handle_signal(signr, &ka, &info, regs);
@@ -645,29 +645,8 @@ static void do_signal(struct pt_regs *regs, int syscall)
 		 * 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);
 	}
 
 	restore_saved_sigmask();