---

yaml
---
r: 23080
b: refs/heads/master
c: dd28779
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 41c28ff1635e71af072c4711ff5fadd5855d48e7
+refs/heads/master: dd287796d608fcdc3fe5e8fdb5bf762a8f1bc32a

trunk/Documentation/kernel-parameters.txt

@@ -1126,6 +1126,11 @@ running once the system is up.
 	pas16=		[HW,SCSI]
 			See header of drivers/scsi/pas16.c.
 
+	pause_on_oops=
+			Halt all CPUs after the first oops has been printed for
+			the specified number of seconds.  This is to be used if
+			your oopses keep scrolling off the screen.
+
 	pcbit=		[HW,ISDN]
 
 	pcd.		[PARIDE]

trunk/arch/i386/kernel/traps.c

@@ -352,6 +352,8 @@ void die(const char * str, struct pt_regs * regs, long err)
 	static int die_counter;
 	unsigned long flags;
 
+	oops_enter();
+
 	if (die.lock_owner != raw_smp_processor_id()) {
 		console_verbose();
 		spin_lock_irqsave(&die.lock, flags);
@@ -404,6 +406,7 @@ void die(const char * str, struct pt_regs * regs, long err)
 		ssleep(5);
 		panic("Fatal exception");
 	}
+	oops_exit();
 	do_exit(SIGSEGV);
 }
 

trunk/arch/i386/mm/fault.c

@@ -509,32 +509,39 @@ fastcall void __kprobes do_page_fault(struct pt_regs *regs,
 
 	bust_spinlocks(1);
 
-#ifdef CONFIG_X86_PAE
-	if (error_code & 16) {
-		pte_t *pte = lookup_address(address);
-
-		if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
-			printk(KERN_CRIT "kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n", current->uid);
+	if (oops_may_print()) {
+	#ifdef CONFIG_X86_PAE
+		if (error_code & 16) {
+			pte_t *pte = lookup_address(address);
+
+			if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
+				printk(KERN_CRIT "kernel tried to execute "
+					"NX-protected page - exploit attempt? "
+					"(uid: %d)\n", current->uid);
+		}
+	#endif
+		if (address < PAGE_SIZE)
+			printk(KERN_ALERT "BUG: unable to handle kernel NULL "
+					"pointer dereference");
+		else
+			printk(KERN_ALERT "BUG: unable to handle kernel paging"
+					" request");
+		printk(" at virtual address %08lx\n",address);
+		printk(KERN_ALERT " printing eip:\n");
+		printk("%08lx\n", regs->eip);
 	}
-#endif
-	if (address < PAGE_SIZE)
-		printk(KERN_ALERT "BUG: unable to handle kernel NULL pointer dereference");
-	else
-		printk(KERN_ALERT "BUG: unable to handle kernel paging request");
-	printk(" at virtual address %08lx\n",address);
-	printk(KERN_ALERT " printing eip:\n");
-	printk("%08lx\n", regs->eip);
 	page = read_cr3();
 	page = ((unsigned long *) __va(page))[address >> 22];
-	printk(KERN_ALERT "*pde = %08lx\n", page);
+	if (oops_may_print())
+		printk(KERN_ALERT "*pde = %08lx\n", page);
 	/*
 	 * We must not directly access the pte in the highpte
 	 * case, the page table might be allocated in highmem.
 	 * And lets rather not kmap-atomic the pte, just in case
 	 * it's allocated already.
 	 */
 #ifndef CONFIG_HIGHPTE
-	if (page & 1) {
+	if ((page & 1) && oops_may_print()) {
 		page &= PAGE_MASK;
 		address &= 0x003ff000;
 		page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];

trunk/include/linux/kernel.h

@@ -91,6 +91,9 @@ extern struct notifier_block *panic_notifier_list;
 extern long (*panic_blink)(long time);
 NORET_TYPE void panic(const char * fmt, ...)
 	__attribute__ ((NORET_AND format (printf, 1, 2)));
+extern void oops_enter(void);
+extern void oops_exit(void);
+extern int oops_may_print(void);
 fastcall NORET_TYPE void do_exit(long error_code)
 	ATTRIB_NORET;
 NORET_TYPE void complete_and_exit(struct completion *, long)

trunk/kernel/panic.c

@@ -20,10 +20,13 @@
 #include <linux/nmi.h>
 #include <linux/kexec.h>
 
-int panic_timeout;
 int panic_on_oops;
 int tainted;
+static int pause_on_oops;
+static int pause_on_oops_flag;
+static DEFINE_SPINLOCK(pause_on_oops_lock);
 
+int panic_timeout;
 EXPORT_SYMBOL(panic_timeout);
 
 struct notifier_block *panic_notifier_list;
@@ -174,3 +177,95 @@ void add_taint(unsigned flag)
 	tainted |= flag;
 }
 EXPORT_SYMBOL(add_taint);
+
+static int __init pause_on_oops_setup(char *str)
+{
+	pause_on_oops = simple_strtoul(str, NULL, 0);
+	return 1;
+}
+__setup("pause_on_oops=", pause_on_oops_setup);
+
+static void spin_msec(int msecs)
+{
+	int i;
+
+	for (i = 0; i < msecs; i++) {
+		touch_nmi_watchdog();
+		mdelay(1);
+	}
+}
+
+/*
+ * It just happens that oops_enter() and oops_exit() are identically
+ * implemented...
+ */
+static void do_oops_enter_exit(void)
+{
+	unsigned long flags;
+	static int spin_counter;
+
+	if (!pause_on_oops)
+		return;
+
+	spin_lock_irqsave(&pause_on_oops_lock, flags);
+	if (pause_on_oops_flag == 0) {
+		/* This CPU may now print the oops message */
+		pause_on_oops_flag = 1;
+	} else {
+		/* We need to stall this CPU */
+		if (!spin_counter) {
+			/* This CPU gets to do the counting */
+			spin_counter = pause_on_oops;
+			do {
+				spin_unlock(&pause_on_oops_lock);
+				spin_msec(MSEC_PER_SEC);
+				spin_lock(&pause_on_oops_lock);
+			} while (--spin_counter);
+			pause_on_oops_flag = 0;
+		} else {
+			/* This CPU waits for a different one */
+			while (spin_counter) {
+				spin_unlock(&pause_on_oops_lock);
+				spin_msec(1);
+				spin_lock(&pause_on_oops_lock);
+			}
+		}
+	}
+	spin_unlock_irqrestore(&pause_on_oops_lock, flags);
+}
+
+/*
+ * Return true if the calling CPU is allowed to print oops-related info.  This
+ * is a bit racy..
+ */
+int oops_may_print(void)
+{
+	return pause_on_oops_flag == 0;
+}
+
+/*
+ * Called when the architecture enters its oops handler, before it prints
+ * anything.  If this is the first CPU to oops, and it's oopsing the first time
+ * then let it proceed.
+ *
+ * This is all enabled by the pause_on_oops kernel boot option.  We do all this
+ * to ensure that oopses don't scroll off the screen.  It has the side-effect
+ * of preventing later-oopsing CPUs from mucking up the display, too.
+ *
+ * It turns out that the CPU which is allowed to print ends up pausing for the
+ * right duration, whereas all the other CPUs pause for twice as long: once in
+ * oops_enter(), once in oops_exit().
+ */
+void oops_enter(void)
+{
+	do_oops_enter_exit();
+}
+
+/*
+ * Called when the architecture exits its oops handler, after printing
+ * everything.
+ */
+void oops_exit(void)
+{
+	do_oops_enter_exit();
+}