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

This reverts commit 433e2f307beff8adba241646ce9108544e0c5a03.

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>

2 files changed, 13 insertions, 28 deletions

diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index dab711e6e1ca..efd25d65ae13 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/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;
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 536c5d6b340b..6d3bce5bd7bc 100644
--- a/arch/arm/kernel/signal.c
+++ b/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();