CRISv32: handle multiple signals

Al Viro noted that CRIS fails to handle multiple signals.

This fixes the problem for CRISv32 by making it use a C work_pending
handling loop similar to the ARM implementation in 0a267fa6a15d41c
("ARM: 7472/1: pull all work_pending logics into C function").

This also happens to fixes the warnings which currently trigger on
CRISv32 due to do_signal() being called with interrupts disabled.

Test case (should die of the SIGSEGV which gets raised when setting up
the stack for SIGALRM, but instead reaches and executes the _exit(1)):

  #include <unistd.h>
  #include <signal.h>
  #include <sys/time.h>
  #include <err.h>

  static void handler(int sig) { }

  int main(int argc, char *argv[])
  {
  	int ret;
  	struct itimerval t1 = { .it_value = {1} };
  	stack_t ss = {
  		.ss_sp = NULL,
  		.ss_size = SIGSTKSZ,
  	};
  	struct sigaction action = {
  		.sa_handler = handler,
  		.sa_flags = SA_ONSTACK,
  	};

  	ret = sigaltstack(&ss, NULL);
  	if (ret < 0)
  		err(1, "sigaltstack");

  	sigaction(SIGALRM, &action, NULL);
   	setitimer(ITIMER_REAL, &t1, NULL);

  	pause();

  	_exit(1);

  	return 0;
  }

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Link: http://lkml.kernel.org/r/20121208074429.GC4939@ZenIV.linux.org.uk
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Jesper Nilsson <jespern@axis.com>

arch/cris/arch-v32/kernel/entry.S

@@ -280,44 +280,15 @@ _syscall_exit_work:
 
 	.type	_work_pending,@function
 _work_pending:
-	addoq	+TI_flags, $r0, $acr
-	move.d	[$acr], $r10
-	btstq	TIF_NEED_RESCHED, $r10	; Need resched?
-	bpl	_work_notifysig		; No, must be signal/notify.
-	nop
-	.size	_work_pending, . - _work_pending
-
-	.type	_work_resched,@function
-_work_resched:
-	move.d	$r9, $r1		; Preserve R9.
-	jsr	schedule
-	nop
-	move.d	$r1, $r9
-	di
-
-	addoq	+TI_flags, $r0, $acr
-	move.d	[$acr], $r1
-	and.d	_TIF_WORK_MASK, $r1	; Ignore sycall trace counter.
-	beq	_Rexit
-	nop
-	btstq	TIF_NEED_RESCHED, $r1
-	bmi	_work_resched		; current->work.need_resched.
-	nop
-	.size	_work_resched, . - _work_resched
-
-	.type	_work_notifysig,@function
-_work_notifysig:
-	;; Deal with pending signals and notify-resume requests.
-
 	addoq	+TI_flags, $r0, $acr
 	move.d	[$acr], $r12		; The thread_info_flags parameter.
 	move.d	$sp, $r11		; The regs param.
-	jsr	do_notify_resume
-	move.d	$r9, $r10		; do_notify_resume syscall/irq param.
+	jsr	do_work_pending
+	move.d	$r9, $r10		; The syscall/irq param.
 
 	ba _Rexit
 	nop
-	.size	_work_notifysig, . - _work_notifysig
+	.size	_work_pending, . - _work_pending
 
 	;; We get here as a sidetrack when we've entered a syscall with the
 	;; trace-bit set. We need to call do_syscall_trace and then continue

arch/cris/kernel/ptrace.c

@@ -42,3 +42,26 @@ void do_notify_resume(int canrestart, struct pt_regs *regs,
 		tracehook_notify_resume(regs);
 	}
 }
+
+void do_work_pending(int syscall, struct pt_regs *regs,
+		     unsigned int thread_flags)
+{
+	do {
+		if (likely(thread_flags & _TIF_NEED_RESCHED)) {
+			schedule();
+		} else {
+			if (unlikely(!user_mode(regs)))
+				return;
+			local_irq_enable();
+			if (thread_flags & _TIF_SIGPENDING) {
+				do_signal(syscall, regs);
+				syscall = 0;
+			} else {
+				clear_thread_flag(TIF_NOTIFY_RESUME);
+				tracehook_notify_resume(regs);
+			}
+		}
+		local_irq_disable();
+		thread_flags = current_thread_info()->flags;
+	} while (thread_flags & _TIF_WORK_MASK);
+}