stacktrace.c

/*
 * Stack trace management functions
 *
 *  Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 */
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <asm/stacktrace.h>

static void save_stack_warning(void *data, char *msg)
{
}

static void
save_stack_warning_symbol(void *data, char *msg, unsigned long symbol)
{
}

static int save_stack_stack(void *data, char *name)
{
	return 0;
}

static void save_stack_address(void *data, unsigned long addr, int reliable)
{
	struct stack_trace *trace = data;
	if (!reliable)
		return;
	if (trace->skip > 0) {
		trace->skip--;
		return;
	}
	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = addr;
}

static void
save_stack_address_nosched(void *data, unsigned long addr, int reliable)
{
	struct stack_trace *trace = (struct stack_trace *)data;
	if (!reliable)
		return;
	if (in_sched_functions(addr))
		return;
	if (trace->skip > 0) {
		trace->skip--;
		return;
	}
	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = addr;
}

static const struct stacktrace_ops save_stack_ops = {
	.warning = save_stack_warning,
	.warning_symbol = save_stack_warning_symbol,
	.stack = save_stack_stack,
	.address = save_stack_address,
};

static const struct stacktrace_ops save_stack_ops_nosched = {
	.warning = save_stack_warning,
	.warning_symbol = save_stack_warning_symbol,
	.stack = save_stack_stack,
	.address = save_stack_address_nosched,
};

/*
 * Save stack-backtrace addresses into a stack_trace buffer.
 */
void save_stack_trace(struct stack_trace *trace)
{
	dump_trace(current, NULL, NULL, 0, &save_stack_ops, trace);
	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = ULONG_MAX;
}
EXPORT_SYMBOL_GPL(save_stack_trace);

void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
	dump_trace(tsk, NULL, NULL, 0, &save_stack_ops_nosched, trace);
	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = ULONG_MAX;
}
EXPORT_SYMBOL_GPL(save_stack_trace_tsk);

/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */

struct stack_frame {
	const void __user	*next_fp;
	unsigned long		ret_addr;
};

static int copy_stack_frame(const void __user *fp, struct stack_frame *frame)
{
	int ret;

	if (!access_ok(VERIFY_READ, fp, sizeof(*frame)))
		return 0;

	ret = 1;
	pagefault_disable();
	if (__copy_from_user_inatomic(frame, fp, sizeof(*frame)))
		ret = 0;
	pagefault_enable();

	return ret;
}

static inline void __save_stack_trace_user(struct stack_trace *trace)
{
	const struct pt_regs *regs = task_pt_regs(current);
	const void __user *fp = (const void __user *)regs->bp;

	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = regs->ip;

	while (trace->nr_entries < trace->max_entries) {
		struct stack_frame frame;

		frame.next_fp = NULL;
		frame.ret_addr = 0;
		if (!copy_stack_frame(fp, &frame))
			break;
		if ((unsigned long)fp < regs->sp)
			break;
		if (frame.ret_addr) {
			trace->entries[trace->nr_entries++] =
				frame.ret_addr;
		}
		if (fp == frame.next_fp)
			break;
		fp = frame.next_fp;
	}
}

void save_stack_trace_user(struct stack_trace *trace)
{
	/*
	 * Trace user stack if we are not a kernel thread
	 */
	if (current->mm) {
		__save_stack_trace_user(trace);
	}
	if (trace->nr_entries < trace->max_entries)
		trace->entries[trace->nr_entries++] = ULONG_MAX;
}