1 files changed, 116 insertions, 49 deletions

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 5a5311d3de0..b1249774d1e 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -76,13 +76,13 @@ int register_die_notifier(struct notifier_block *nb)
 	vmalloc_sync_all();
 	return atomic_notifier_chain_register(&die_chain, nb);
 }
-EXPORT_SYMBOL(register_die_notifier);
+EXPORT_SYMBOL(register_die_notifier); /* used modular by kdb */
 
 int unregister_die_notifier(struct notifier_block *nb)
 {
 	return atomic_notifier_chain_unregister(&die_chain, nb);
 }
-EXPORT_SYMBOL(unregister_die_notifier);
+EXPORT_SYMBOL(unregister_die_notifier); /* used modular by kdb */
 
 static inline void conditional_sti(struct pt_regs *regs)
 {
@@ -107,31 +107,38 @@ static inline void preempt_conditional_cli(struct pt_regs *regs)
 }
 
 static int kstack_depth_to_print = 12;
+#ifdef CONFIG_STACK_UNWIND
 static int call_trace = 1;
+#else
+#define call_trace (-1)
+#endif
 
 #ifdef CONFIG_KALLSYMS
-#include <linux/kallsyms.h> 
-int printk_address(unsigned long address)
-{ 
+# include <linux/kallsyms.h>
+void printk_address(unsigned long address)
+{
 	unsigned long offset = 0, symsize;
 	const char *symname;
 	char *modname;
-	char *delim = ":"; 
+	char *delim = ":";
 	char namebuf[128];
 
-	symname = kallsyms_lookup(address, &symsize, &offset, &modname, namebuf); 
-	if (!symname) 
-		return printk("[<%016lx>]", address);
-	if (!modname) 
+	symname = kallsyms_lookup(address, &symsize, &offset,
+					&modname, namebuf);
+	if (!symname) {
+		printk(" [<%016lx>]\n", address);
+		return;
+	}
+	if (!modname)
 		modname = delim = ""; 		
-        return printk("<%016lx>{%s%s%s%s%+ld}",
-		      address, delim, modname, delim, symname, offset); 
-} 
+	printk(" [<%016lx>] %s%s%s%s+0x%lx/0x%lx\n",
+		address, delim, modname, delim, symname, offset, symsize);
+}
 #else
-int printk_address(unsigned long address)
-{ 
-	return printk("[<%016lx>]", address);
-} 
+void printk_address(unsigned long address)
+{
+	printk(" [<%016lx>]\n", address);
+}
 #endif
 
 static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
@@ -149,32 +156,68 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
 	};
 	unsigned k;
 
+	/*
+	 * Iterate over all exception stacks, and figure out whether
+	 * 'stack' is in one of them:
+	 */
 	for (k = 0; k < N_EXCEPTION_STACKS; k++) {
 		unsigned long end;
 
+		/*
+		 * set 'end' to the end of the exception stack.
+		 */
 		switch (k + 1) {
+		/*
+		 * TODO: this block is not needed i think, because
+		 * setup64.c:cpu_init() sets up t->ist[DEBUG_STACK]
+		 * properly too.
+		 */
 #if DEBUG_STKSZ > EXCEPTION_STKSZ
 		case DEBUG_STACK:
 			end = cpu_pda(cpu)->debugstack + DEBUG_STKSZ;
 			break;
 #endif
 		default:
-			end = per_cpu(init_tss, cpu).ist[k];
+			end = per_cpu(orig_ist, cpu).ist[k];
 			break;
 		}
+		/*
+		 * Is 'stack' above this exception frame's end?
+		 * If yes then skip to the next frame.
+		 */
 		if (stack >= end)
 			continue;
+		/*
+		 * Is 'stack' above this exception frame's start address?
+		 * If yes then we found the right frame.
+		 */
 		if (stack >= end - EXCEPTION_STKSZ) {
+			/*
+			 * Make sure we only iterate through an exception
+			 * stack once. If it comes up for the second time
+			 * then there's something wrong going on - just
+			 * break out and return NULL:
+			 */
 			if (*usedp & (1U << k))
 				break;
 			*usedp |= 1U << k;
 			*idp = ids[k];
 			return (unsigned long *)end;
 		}
+		/*
+		 * If this is a debug stack, and if it has a larger size than
+		 * the usual exception stacks, then 'stack' might still
+		 * be within the lower portion of the debug stack:
+		 */
 #if DEBUG_STKSZ > EXCEPTION_STKSZ
 		if (k == DEBUG_STACK - 1 && stack >= end - DEBUG_STKSZ) {
 			unsigned j = N_EXCEPTION_STACKS - 1;
 
+			/*
+			 * Black magic. A large debug stack is composed of
+			 * multiple exception stack entries, which we
+			 * iterate through now. Dont look:
+			 */
 			do {
 				++j;
 				end -= EXCEPTION_STKSZ;
@@ -193,20 +236,14 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
 
 static int show_trace_unwind(struct unwind_frame_info *info, void *context)
 {
-	int i = 11, n = 0;
+	int n = 0;
 
 	while (unwind(info) == 0 && UNW_PC(info)) {
-		++n;
-		if (i > 50) {
-			printk("\n       ");
-			i = 7;
-		} else
-			i += printk(" ");
-		i += printk_address(UNW_PC(info));
+		n++;
+		printk_address(UNW_PC(info));
 		if (arch_unw_user_mode(info))
 			break;
 	}
-	printk("\n");
 	return n;
 }
 
@@ -221,10 +258,9 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 {
 	const unsigned cpu = safe_smp_processor_id();
 	unsigned long *irqstack_end = (unsigned long *)cpu_pda(cpu)->irqstackptr;
-	int i = 11;
 	unsigned used = 0;
 
-	printk("\nCall Trace:");
+	printk("\nCall Trace:\n");
 
 	if (!tsk)
 		tsk = current;
@@ -243,23 +279,31 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 				unw_ret = show_trace_unwind(&info, NULL);
 		}
 		if (unw_ret > 0) {
-			if (call_trace > 0)
+			if (call_trace == 1 && !arch_unw_user_mode(&info)) {
+				print_symbol("DWARF2 unwinder stuck at %s\n",
+					     UNW_PC(&info));
+				if ((long)UNW_SP(&info) < 0) {
+					printk("Leftover inexact backtrace:\n");
+					stack = (unsigned long *)UNW_SP(&info);
+				} else
+					printk("Full inexact backtrace again:\n");
+			} else if (call_trace >= 1)
 				return;
-			printk("Legacy call trace:");
-			i = 18;
-		}
+			else
+				printk("Full inexact backtrace again:\n");
+		} else
+			printk("Inexact backtrace:\n");
 	}
 
+	/*
+	 * Print function call entries within a stack. 'cond' is the
+	 * "end of stackframe" condition, that the 'stack++'
+	 * iteration will eventually trigger.
+	 */
 #define HANDLE_STACK(cond) \
 	do while (cond) { \
 		unsigned long addr = *stack++; \
 		if (kernel_text_address(addr)) { \
-			if (i > 50) { \
-				printk("\n       "); \
-				i = 0; \
-			} \
-			else \
-				i += printk(" "); \
 			/* \
 			 * If the address is either in the text segment of the \
 			 * kernel, or in the region which contains vmalloc'ed \
@@ -268,20 +312,30 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 			 * down the cause of the crash will be able to figure \
 			 * out the call path that was taken. \
 			 */ \
-			i += printk_address(addr); \
+			printk_address(addr); \
 		} \
 	} while (0)
 
-	for(; ; ) {
+	/*
+	 * Print function call entries in all stacks, starting at the
+	 * current stack address. If the stacks consist of nested
+	 * exceptions
+	 */
+	for ( ; ; ) {
 		const char *id;
 		unsigned long *estack_end;
 		estack_end = in_exception_stack(cpu, (unsigned long)stack,
 						&used, &id);
 
 		if (estack_end) {
-			i += printk(" <%s>", id);
+			printk(" <%s>", id);
 			HANDLE_STACK (stack < estack_end);
-			i += printk(" <EOE>");
+			printk(" <EOE>");
+			/*
+			 * We link to the next stack via the
+			 * second-to-last pointer (index -2 to end) in the
+			 * exception stack:
+			 */
 			stack = (unsigned long *) estack_end[-2];
 			continue;
 		}
@@ -291,19 +345,28 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 				(IRQSTACKSIZE - 64) / sizeof(*irqstack);
 
 			if (stack >= irqstack && stack < irqstack_end) {
-				i += printk(" <IRQ>");
+				printk(" <IRQ>");
 				HANDLE_STACK (stack < irqstack_end);
+				/*
+				 * We link to the next stack (which would be
+				 * the process stack normally) the last
+				 * pointer (index -1 to end) in the IRQ stack:
+				 */
 				stack = (unsigned long *) (irqstack_end[-1]);
 				irqstack_end = NULL;
-				i += printk(" <EOI>");
+				printk(" <EOI>");
 				continue;
 			}
 		}
 		break;
 	}
 
+	/*
+	 * This prints the process stack:
+	 */
 	HANDLE_STACK (((long) stack & (THREAD_SIZE-1)) != 0);
 #undef HANDLE_STACK
+
 	printk("\n");
 }
 
@@ -337,8 +400,8 @@ static void _show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned
 			break;
 		}
 		if (i && ((i % 4) == 0))
-			printk("\n       ");
-		printk("%016lx ", *stack++);
+			printk("\n");
+		printk(" %016lx", *stack++);
 		touch_nmi_watchdog();
 	}
 	show_trace(tsk, regs, rsp);
@@ -470,7 +533,7 @@ void __kprobes oops_end(unsigned long flags)
 		/* Nest count reaches zero, release the lock. */
 		spin_unlock_irqrestore(&die_lock, flags);
 	if (panic_on_oops)
-		panic("Oops");
+		panic("Fatal exception");
 }
 
 void __kprobes __die(const char * str, struct pt_regs * regs, long err)
@@ -1061,14 +1124,18 @@ static int __init kstack_setup(char *s)
 }
 __setup("kstack=", kstack_setup);
 
+#ifdef CONFIG_STACK_UNWIND
 static int __init call_trace_setup(char *s)
 {
 	if (strcmp(s, "old") == 0)
 		call_trace = -1;
 	else if (strcmp(s, "both") == 0)
 		call_trace = 0;
-	else if (strcmp(s, "new") == 0)
+	else if (strcmp(s, "newfallback") == 0)
 		call_trace = 1;
+	else if (strcmp(s, "new") == 0)
+		call_trace = 2;
 	return 1;
 }
 __setup("call_trace=", call_trace_setup);
+#endif