x86, dumpstack: let signr=0 signal no do_exit

Change oops_end such that signr=0 signals that do_exit
is not to be called.

Currently, each use of __die is soon followed by a call
to oops_end and 'regs' is set to NULL if oops_end is expected
not to call do_exit. Change all such pairs to set signr=0
instead. On x86_64 oops_end is used 'bare' in die_nmi; use
signr=0 instead of regs=NULL there, too.

Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/dumpstack_32.c

@@ -318,7 +318,7 @@ void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 	__raw_spin_unlock(&die_lock);
 	raw_local_irq_restore(flags);
 
-	if (!regs)
+	if (!signr)
 		return;
 
 	if (in_interrupt())
@@ -371,17 +371,18 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
 void die(const char *str, struct pt_regs *regs, long err)
 {
 	unsigned long flags = oops_begin();
+	int sig = SIGSEGV;
 
 	if (die_nest_count < 3) {
 		report_bug(regs->ip, regs);
 
 		if (__die(str, regs, err))
-			regs = NULL;
+			sig = 0;
 	} else {
 		printk(KERN_EMERG "Recursive die() failure, output suppressed\n");
 	}
 
-	oops_end(flags, regs, SIGSEGV);
+	oops_end(flags, regs, sig);
 }
 
 static DEFINE_SPINLOCK(nmi_print_lock);

arch/x86/kernel/dumpstack_64.c

@@ -465,7 +465,7 @@ void __kprobes oops_end(unsigned long flags, struct pt_regs *regs, int signr)
 		/* Nest count reaches zero, release the lock. */
 		__raw_spin_unlock(&die_lock);
 	raw_local_irq_restore(flags);
-	if (!regs) {
+	if (!signr) {
 		oops_exit();
 		return;
 	}
@@ -509,13 +509,14 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
 void die(const char *str, struct pt_regs *regs, long err)
 {
 	unsigned long flags = oops_begin();
+	int sig = SIGSEGV;
 
 	if (!user_mode(regs))
 		report_bug(regs->ip, regs);
 
 	if (__die(str, regs, err))
-		regs = NULL;
-	oops_end(flags, regs, SIGSEGV);
+		sig = 0;
+	oops_end(flags, regs, sig);
 }
 
 notrace __kprobes void
@@ -539,7 +540,7 @@ die_nmi(char *str, struct pt_regs *regs, int do_panic)
 		crash_kexec(regs);
 	if (do_panic || panic_on_oops)
 		panic("Non maskable interrupt");
-	oops_end(flags, NULL, SIGBUS);
+	oops_end(flags, regs, 0);
 	nmi_exit();
 	local_irq_enable();
 	do_exit(SIGBUS);

arch/x86/mm/fault.c

@@ -413,6 +413,7 @@ static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
 				 unsigned long error_code)
 {
 	unsigned long flags = oops_begin();
+	int sig = SIGKILL;
 	struct task_struct *tsk;
 
 	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
@@ -423,8 +424,8 @@ static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
 	tsk->thread.trap_no = 14;
 	tsk->thread.error_code = error_code;
 	if (__die("Bad pagetable", regs, error_code))
-		regs = NULL;
-	oops_end(flags, regs, SIGKILL);
+		sig = 0;
+	oops_end(flags, regs, sig);
 }
 #endif
 
@@ -590,6 +591,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	int fault;
 #ifdef CONFIG_X86_64
 	unsigned long flags;
+	int sig;
 #endif
 
 	tsk = current;
@@ -849,11 +851,12 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 	bust_spinlocks(0);
 	do_exit(SIGKILL);
 #else
+	sig = SIGKILL;
 	if (__die("Oops", regs, error_code))
-		regs = NULL;
+		sig = 0;
 	/* Executive summary in case the body of the oops scrolled away */
 	printk(KERN_EMERG "CR2: %016lx\n", address);
-	oops_end(flags, regs, SIGKILL);
+	oops_end(flags, regs, sig);
 #endif
 
 /*