CRIS: Add config for pausing a seg-faulting process

Put it on a wait queue, so we can attach gdb to the process
to debug it instead of just killing it.

Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>

arch/cris/Kconfig.debug

@@ -32,4 +32,10 @@ config DEBUG_NMI_OOPS
 	  If the system locks up without any debug information you can say Y
 	  here to make it possible to dump an OOPS with an external NMI.
 
+config NO_SEGFAULT_TERMINATION
+	bool "Keep segfaulting processes"
+	help
+	  Place segfaulting user mode processes on a wait queue instead of
+	  delivering a terminating SIGSEGV to allow debugging with gdb.
+
 endmenu

arch/cris/mm/fault.c

@@ -7,6 +7,7 @@
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
+#include <linux/wait.h>
 #include <asm/uaccess.h>
 
 extern int find_fixup_code(struct pt_regs *);
@@ -190,14 +191,20 @@ do_page_fault(unsigned long address, struct pt_regs *regs,
 	/* User mode accesses just cause a SIGSEGV */
 
 	if (user_mode(regs)) {
+		printk(KERN_NOTICE "%s (pid %d) segfaults for page "
+			"address %08lx at pc %08lx\n",
+			tsk->comm, tsk->pid,
+			address, instruction_pointer(regs));
+#ifdef CONFIG_NO_SEGFAULT_TERMINATION
+		DECLARE_WAIT_QUEUE_HEAD(wq);
+		wait_event_interruptible(wq, 0 == 1);
+#else
 		info.si_signo = SIGSEGV;
 		info.si_errno = 0;
 		/* info.si_code has been set above */
 		info.si_addr = (void *)address;
 		force_sig_info(SIGSEGV, &info, tsk);
-		printk(KERN_NOTICE "%s (pid %d) segfaults for page "
-		       "address %08lx at pc %08lx\n",
-		       tsk->comm, tsk->pid, address, instruction_pointer(regs));
+#endif
 		return;
 	}