ARM: 7473/1: deal with handlerless restarts without leaving the kernel

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 29 insertions, 21 deletions

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 8756e5dcd377..99851cb9591d 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -569,12 +569,13 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
  * the kernel can handle, and then we build all the user-level signal handling
  * stack-frames in one go after that.
  */
-static void do_signal(struct pt_regs *regs, int syscall)
+static int do_signal(struct pt_regs *regs, int syscall)
 {
         unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
         struct k_sigaction ka;
         siginfo_t info;
         int signr;
+        int restart = 0;
 
         /*
          * If we were from a system call, check for system call restarting...
@@ -589,10 +590,12 @@ static void do_signal(struct pt_regs *regs, int syscall)
                  * debugger will see the already changed PSW.
                  */
                 switch (retval) {
+                case -ERESTART_RESTARTBLOCK:
+                        restart++;
                 case -ERESTARTNOHAND:
                 case -ERESTARTSYS:
                 case -ERESTARTNOINTR:
-                case -ERESTART_RESTARTBLOCK:
+                        restart++;
                         regs->ARM_r0 = regs->ARM_ORIG_r0;
                         regs->ARM_pc = restart_addr;
                         break;
@@ -604,13 +607,15 @@ static void do_signal(struct pt_regs *regs, int syscall)
          * point the debugger may change all our registers ...
          */
         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
+        /*
+         * Depending on the signal settings we may need to revert the
+         * decision to restart the system call.  But skip this if a
+         * debugger has chosen to restart at a different PC.
+         */
+        if (regs->ARM_pc != restart_addr)
+                restart = 0;
         if (signr > 0) {
-                /*
-                 * Depending on the signal settings we may need to revert the
-                 * decision to restart the system call.  But skip this if a
-                 * debugger has chosen to restart at a different PC.
-                 */
-                if (regs->ARM_pc == restart_addr) {
+                if (unlikely(restart)) {
                         if (retval == -ERESTARTNOHAND ||
                             retval == -ERESTART_RESTARTBLOCK
                             || (retval == -ERESTARTSYS
@@ -618,28 +623,23 @@ static void do_signal(struct pt_regs *regs, int syscall)
                                 regs->ARM_r0 = -EINTR;
                                 regs->ARM_pc = continue_addr;
                         }
-                        clear_thread_flag(TIF_SYSCALL_RESTARTSYS);
                 }
 
                 handle_signal(signr, &ka, &info, regs);
-                return;
+                return 0;
         }
 
-        if (syscall) {
-                /*
-                 * Handle restarting a different system call.  As above,
-                 * if a debugger has chosen to restart at a different PC,
-                 * ignore the restart.
-                 */
-                if (retval == -ERESTART_RESTARTBLOCK
-                    && regs->ARM_pc == restart_addr)
+        if (unlikely(restart)) {
+                if (restart > 1)
                         set_thread_flag(TIF_SYSCALL_RESTARTSYS);
+                regs->ARM_pc = continue_addr;
         }
 
         restore_saved_sigmask();
+        return restart;
 }
 
-asmlinkage void
+asmlinkage int
 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 {
         do {
@@ -647,10 +647,17 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
                         schedule();
                 } else {
                         if (unlikely(!user_mode(regs)))
-                                return;
+                                return 0;
                         local_irq_enable();
                         if (thread_flags & _TIF_SIGPENDING) {
-                                do_signal(regs, syscall);
+                                if (unlikely(do_signal(regs, syscall))) {
+                                        /*
+                                         * Restart without handlers.
+                                         * Deal with it without leaving
+                                         * the kernel space.
+                                         */
+                                        return 1;
+                                }
                                 syscall = 0;
                         } else {
                                 clear_thread_flag(TIF_NOTIFY_RESUME);
@@ -660,4 +667,5 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
                 local_irq_disable();
                 thread_flags = current_thread_info()->flags;
         } while (thread_flags & _TIF_WORK_MASK);
+        return 0;
 }