[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, 26 insertions, 188 deletions

diff --git a/arch/x86_64/kernel/stacktrace.c b/arch/x86_64/kernel/stacktrace.c
index 1c022af8fe1e..6026b31d037e 100644
--- a/arch/x86_64/kernel/stacktrace.c
+++ b/arch/x86_64/kernel/stacktrace.c
@@ -7,211 +7,49 @@
  */
 #include <linux/sched.h>
 #include <linux/stacktrace.h>
+#include <linux/module.h>
+#include <asm/stacktrace.h>
 
-#include <asm/smp.h>
-
-static inline int
-in_range(unsigned long start, unsigned long addr, unsigned long end)
+static void save_stack_warning(void *data, char *msg)
 {
-	return addr >= start && addr <= end;
 }
 
-static unsigned long
-get_stack_end(struct task_struct *task, unsigned long stack)
+static void
+save_stack_warning_symbol(void *data, char *msg, unsigned long symbol)
 {
-	unsigned long stack_start, stack_end, flags;
-	int i, cpu;
-
-	/*
-	 * The most common case is that we are in the task stack:
-	 */
-	stack_start = (unsigned long)task->thread_info;
-	stack_end = stack_start + THREAD_SIZE;
-
-	if (in_range(stack_start, stack, stack_end))
-		return stack_end;
-
-	/*
-	 * We are in an interrupt if irqstackptr is set:
-	 */
-	raw_local_irq_save(flags);
-	cpu = safe_smp_processor_id();
-	stack_end = (unsigned long)cpu_pda(cpu)->irqstackptr;
-
-	if (stack_end) {
-		stack_start = stack_end & ~(IRQSTACKSIZE-1);
-		if (in_range(stack_start, stack, stack_end))
-			goto out_restore;
-		/*
-		 * We get here if we are in an IRQ context but we
-		 * are also in an exception stack.
-		 */
-	}
-
-	/*
-	 * Iterate over all exception stacks, and figure out whether
-	 * 'stack' is in one of them:
-	 */
-	for (i = 0; i < N_EXCEPTION_STACKS; i++) {
-		/*
-		 * set 'end' to the end of the exception stack.
-		 */
-		stack_end = per_cpu(init_tss, cpu).ist[i];
-		stack_start = stack_end - EXCEPTION_STKSZ;
-
-		/*
-		 * Is 'stack' above this exception frame's end?
-		 * If yes then skip to the next frame.
-		 */
-		if (stack >= stack_end)
-			continue;
-		/*
-		 * Is 'stack' above this exception frame's start address?
-		 * If yes then we found the right frame.
-		 */
-		if (stack >= stack_start)
-			goto out_restore;
-
-		/*
-		 * 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 (i == DEBUG_STACK - 1 && stack >= stack_end - DEBUG_STKSZ) {
-			/*
-			 * Black magic. A large debug stack is composed of
-			 * multiple exception stack entries, which we
-			 * iterate through now. Dont look:
-			 */
-			do {
-				stack_end -= EXCEPTION_STKSZ;
-				stack_start -= EXCEPTION_STKSZ;
-			} while (stack < stack_start);
-
-			goto out_restore;
-		}
-#endif
-	}
-	/*
-	 * Ok, 'stack' is not pointing to any of the system stacks.
-	 */
-	stack_end = 0;
-
-out_restore:
-	raw_local_irq_restore(flags);
-
-	return stack_end;
 }
 
-
-/*
- * Save stack-backtrace addresses into a stack_trace buffer:
- */
-static inline unsigned long
-save_context_stack(struct stack_trace *trace,
-		   unsigned long stack, unsigned long stack_end)
+static int save_stack_stack(void *data, char *name)
 {
-	int skip = trace->skip;
-	unsigned long addr;
-
-#ifdef CONFIG_FRAME_POINTER
-	unsigned long prev_stack = 0;
+	struct stack_trace *trace = (struct stack_trace *)data;
+	return trace->all_contexts ? 0 : -1;
+}
 
-	while (in_range(prev_stack, stack, stack_end)) {
-		pr_debug("stack:          %p\n", (void *)stack);
-		addr = (unsigned long)(((unsigned long *)stack)[1]);
-		pr_debug("addr:           %p\n", (void *)addr);
-		if (!skip)
-			trace->entries[trace->nr_entries++] = addr-1;
-		else
-			skip--;
-		if (trace->nr_entries >= trace->max_entries)
-			break;
-		if (!addr)
-			return 0;
-		/*
-		 * Stack frames must go forwards (otherwise a loop could
-		 * happen if the stackframe is corrupted), so we move
-		 * prev_stack forwards:
-		 */
-		prev_stack = stack;
-		stack = (unsigned long)(((unsigned long *)stack)[0]);
-	}
-	pr_debug("invalid:        %p\n", (void *)stack);
-#else
-	while (stack < stack_end) {
-		addr = ((unsigned long *)stack)[0];
-		stack += sizeof(long);
-		if (__kernel_text_address(addr)) {
-			if (!skip)
-				trace->entries[trace->nr_entries++] = addr-1;
-			else
-				skip--;
-			if (trace->nr_entries >= trace->max_entries)
-				break;
-		}
+static void save_stack_address(void *data, unsigned long addr)
+{
+	struct stack_trace *trace = (struct stack_trace *)data;
+	if (trace->skip > 0) {
+		trace->skip--;
+		return;
 	}
-#endif
-	return stack;
+	if (trace->nr_entries < trace->max_entries - 1)
+		trace->entries[trace->nr_entries++] = addr;
 }
 
-#define MAX_STACKS 10
+static struct stacktrace_ops save_stack_ops = {
+	.warning = save_stack_warning,
+	.warning_symbol = save_stack_warning_symbol,
+	.stack = save_stack_stack,
+	.address = save_stack_address,
+};
 
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
  */
 void save_stack_trace(struct stack_trace *trace, struct task_struct *task)
 {
-	unsigned long stack = (unsigned long)&stack;
-	int i, nr_stacks = 0, stacks_done[MAX_STACKS];
-
-	WARN_ON(trace->nr_entries || !trace->max_entries);
-
-	if (!task)
-		task = current;
-
-	pr_debug("task: %p, ti: %p\n", task, task->thread_info);
-
-	if (!task || task == current) {
-		/* Grab rbp right from our regs: */
-		asm ("mov %%rbp, %0" : "=r" (stack));
-		pr_debug("rbp:            %p\n", (void *)stack);
-	} else {
-		/* rbp is the last reg pushed by switch_to(): */
-		stack = task->thread.rsp;
-		pr_debug("other task rsp: %p\n", (void *)stack);
-		stack = (unsigned long)(((unsigned long *)stack)[0]);
-		pr_debug("other task rbp: %p\n", (void *)stack);
-	}
-
-	while (1) {
-		unsigned long stack_end = get_stack_end(task, stack);
-
-		pr_debug("stack:          %p\n", (void *)stack);
-		pr_debug("stack end:      %p\n", (void *)stack_end);
-
-		/*
-		 * Invalid stack addres?
-		 */
-		if (!stack_end)
-			return;
-		/*
-		 * Were we in this stack already? (recursion)
-		 */
-		for (i = 0; i < nr_stacks; i++)
-			if (stacks_done[i] == stack_end)
-				return;
-		stacks_done[nr_stacks] = stack_end;
-
-		stack = save_context_stack(trace, stack, stack_end);
-		if (!stack || trace->nr_entries >= trace->max_entries)
-			return;
-		trace->entries[trace->nr_entries++] = ULONG_MAX;
-		if (trace->nr_entries >= trace->max_entries)
-			return;
-		if (++nr_stacks >= MAX_STACKS)
-			return;
-	}
+	dump_trace(task, NULL, NULL, &save_stack_ops, trace);
+	trace->entries[trace->nr_entries++] = ULONG_MAX;
 }
+EXPORT_SYMBOL(save_stack_trace);