[PATCH] Merge stacktrace and show_trace

This unifies the standard backtracer and the new stacktrace
in memory backtracer. The standard one is converted to use callbacks
and then reimplement stacktrace using new callbacks.

The main advantage is that stacktrace can now use the new dwarf2 unwinder
and avoid false positives in many cases.

I kept it simple to make sure the standard backtracer stays reliable.

Cc: mingo@elte.hu

Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 76 insertions, 23 deletions

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 9ec2b1d5893..4ac18b02ead 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -45,6 +45,7 @@
 #include <asm/pda.h>
 #include <asm/proto.h>
 #include <asm/nmi.h>
+#include <asm/stacktrace.h>
 
 asmlinkage void divide_error(void);
 asmlinkage void debug(void);
@@ -142,7 +143,7 @@ void printk_address(unsigned long address)
 #endif
 
 static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
-					unsigned *usedp, const char **idp)
+					unsigned *usedp, char **idp)
 {
 	static char ids[][8] = {
 		[DEBUG_STACK - 1] = "#DB",
@@ -234,13 +235,19 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
 	return NULL;
 }
 
-static int show_trace_unwind(struct unwind_frame_info *info, void *context)
+struct ops_and_data {
+	struct stacktrace_ops *ops;
+	void *data;
+};
+
+static int dump_trace_unwind(struct unwind_frame_info *info, void *context)
 {
+	struct ops_and_data *oad = (struct ops_and_data *)context;
 	int n = 0;
 
 	while (unwind(info) == 0 && UNW_PC(info)) {
 		n++;
-		printk_address(UNW_PC(info));
+		oad->ops->address(oad->data, UNW_PC(info));
 		if (arch_unw_user_mode(info))
 			break;
 	}
@@ -254,45 +261,51 @@ static int show_trace_unwind(struct unwind_frame_info *info, void *context)
  * severe exception (double fault, nmi, stack fault, debug, mce) hardware stack
  */
 
-void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * stack)
+void dump_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * stack,
+		struct stacktrace_ops *ops, void *data)
 {
 	const unsigned cpu = safe_smp_processor_id();
 	unsigned long *irqstack_end = (unsigned long *)cpu_pda(cpu)->irqstackptr;
 	unsigned used = 0;
 
-	printk("\nCall Trace:\n");
-
 	if (!tsk)
 		tsk = current;
 
 	if (call_trace >= 0) {
 		int unw_ret = 0;
 		struct unwind_frame_info info;
+		struct ops_and_data oad = { .ops = ops, .data = data };
 
 		if (regs) {
 			if (unwind_init_frame_info(&info, tsk, regs) == 0)
-				unw_ret = show_trace_unwind(&info, NULL);
+				unw_ret = dump_trace_unwind(&info, &oad);
 		} else if (tsk == current)
-			unw_ret = unwind_init_running(&info, show_trace_unwind, NULL);
+			unw_ret = unwind_init_running(&info, dump_trace_unwind, &oad);
 		else {
 			if (unwind_init_blocked(&info, tsk) == 0)
-				unw_ret = show_trace_unwind(&info, NULL);
+				unw_ret = dump_trace_unwind(&info, &oad);
 		}
 		if (unw_ret > 0) {
 			if (call_trace == 1 && !arch_unw_user_mode(&info)) {
-				print_symbol("DWARF2 unwinder stuck at %s\n",
+				ops->warning_symbol(data, "DWARF2 unwinder stuck at %s\n",
 					     UNW_PC(&info));
 				if ((long)UNW_SP(&info) < 0) {
-					printk("Leftover inexact backtrace:\n");
+					ops->warning(data, "Leftover inexact backtrace:\n");
 					stack = (unsigned long *)UNW_SP(&info);
 				} else
-					printk("Full inexact backtrace again:\n");
+					ops->warning(data, "Full inexact backtrace again:\n");
 			} else if (call_trace >= 1)
 				return;
 			else
-				printk("Full inexact backtrace again:\n");
+				ops->warning(data, "Full inexact backtrace again:\n");
 		} else
-			printk("Inexact backtrace:\n");
+			ops->warning(data, "Inexact backtrace:\n");
+	}
+	if (!stack) {
+		unsigned long dummy;
+		stack = &dummy;
+		if (tsk && tsk != current)
+			stack = (unsigned long *)tsk->thread.rsp;
 	}
 
 	/*
@@ -312,7 +325,7 @@ 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. \
 			 */ \
-			printk_address(addr); \
+			ops->address(data, addr);   \
 		} \
 	} while (0)
 
@@ -321,16 +334,17 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 	 * current stack address. If the stacks consist of nested
 	 * exceptions
 	 */
-	for ( ; ; ) {
-		const char *id;
+	for (;;) {
+		char *id;
 		unsigned long *estack_end;
 		estack_end = in_exception_stack(cpu, (unsigned long)stack,
 						&used, &id);
 
 		if (estack_end) {
-			printk(" <%s>", id);
+			if (ops->stack(data, id) < 0)
+				break;
 			HANDLE_STACK (stack < estack_end);
-			printk(" <EOE>");
+			ops->stack(data, "<EOE>");
 			/*
 			 * We link to the next stack via the
 			 * second-to-last pointer (index -2 to end) in the
@@ -345,7 +359,8 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 				(IRQSTACKSIZE - 64) / sizeof(*irqstack);
 
 			if (stack >= irqstack && stack < irqstack_end) {
-				printk(" <IRQ>");
+				if (ops->stack(data, "IRQ") < 0)
+					break;
 				HANDLE_STACK (stack < irqstack_end);
 				/*
 				 * We link to the next stack (which would be
@@ -354,7 +369,7 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 				 */
 				stack = (unsigned long *) (irqstack_end[-1]);
 				irqstack_end = NULL;
-				printk(" <EOI>");
+				ops->stack(data, "EOI");
 				continue;
 			}
 		}
@@ -362,15 +377,53 @@ void show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long * s
 	}
 
 	/*
-	 * This prints the process stack:
+	 * This handles the process stack:
 	 */
 	HANDLE_STACK (((long) stack & (THREAD_SIZE-1)) != 0);
 #undef HANDLE_STACK
+}
+EXPORT_SYMBOL(dump_trace);
 
+static void
+print_trace_warning_symbol(void *data, char *msg, unsigned long symbol)
+{
+	print_symbol(msg, symbol);
+	printk("\n");
+}
+
+static void print_trace_warning(void *data, char *msg)
+{
+	printk("%s\n", msg);
+}
+
+static int print_trace_stack(void *data, char *name)
+{
+	printk(" <%s> ", name);
+	return 0;
+}
+
+static void print_trace_address(void *data, unsigned long addr)
+{
+	printk_address(addr);
+}
+
+static struct stacktrace_ops print_trace_ops = {
+	.warning = print_trace_warning,
+	.warning_symbol = print_trace_warning_symbol,
+	.stack = print_trace_stack,
+	.address = print_trace_address,
+};
+
+void
+show_trace(struct task_struct *tsk, struct pt_regs *regs, unsigned long *stack)
+{
+	printk("\nCall Trace:\n");
+	dump_trace(tsk, regs, stack, &print_trace_ops, NULL);
 	printk("\n");
 }
 
-static void _show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned long * rsp)
+static void
+_show_stack(struct task_struct *tsk, struct pt_regs *regs, unsigned long *rsp)
 {
 	unsigned long *stack;
 	int i;