oprofile, x86: Fix race in nmi handler while starting counters

[deliverable/linux.git] / arch / x86 / oprofile / backtrace.c

/**
 * @file backtrace.c
 *
 * @remark Copyright 2002 OProfile authors
 * @remark Read the file COPYING
 *
 * @author John Levon
 * @author David Smith
 */

#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/ptrace.h>
#include <asm/uaccess.h>
#include <asm/stacktrace.h>
#include <linux/compat.h>

static int backtrace_stack(void *data, char *name)
{
	/* Yes, we want all stacks */
	return 0;
}

static void backtrace_address(void *data, unsigned long addr, int reliable)
{
	unsigned int *depth = data;

	if ((*depth)--)
		oprofile_add_trace(addr);
}

static struct stacktrace_ops backtrace_ops = {
	.stack		= backtrace_stack,
	.address	= backtrace_address,
	.walk_stack	= print_context_stack,
};

#ifdef CONFIG_COMPAT
static struct stack_frame_ia32 *
dump_user_backtrace_32(struct stack_frame_ia32 *head)
{
	struct stack_frame_ia32 bufhead[2];
	struct stack_frame_ia32 *fp;

	/* Also check accessibility of one struct frame_head beyond */
	if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
		return NULL;
	if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
		return NULL;

	fp = (struct stack_frame_ia32 *) compat_ptr(bufhead[0].next_frame);

	oprofile_add_trace(bufhead[0].return_address);

	/* frame pointers should strictly progress back up the stack
	* (towards higher addresses) */
	if (head >= fp)
		return NULL;

	return fp;
}

static inline int
x86_backtrace_32(struct pt_regs * const regs, unsigned int depth)
{
	struct stack_frame_ia32 *head;

	/* User process is 32-bit */
	if (!current || !test_thread_flag(TIF_IA32))
		return 0;

	head = (struct stack_frame_ia32 *) regs->bp;
	while (depth-- && head)
		head = dump_user_backtrace_32(head);

	return 1;
}

#else
static inline int
x86_backtrace_32(struct pt_regs * const regs, unsigned int depth)
{
	return 0;
}
#endif /* CONFIG_COMPAT */

static struct stack_frame *dump_user_backtrace(struct stack_frame *head)
{
	struct stack_frame bufhead[2];

	/* Also check accessibility of one struct stack_frame beyond */
	if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
		return NULL;
	if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
		return NULL;

	oprofile_add_trace(bufhead[0].return_address);

	/* frame pointers should strictly progress back up the stack
	 * (towards higher addresses) */
	if (head >= bufhead[0].next_frame)
		return NULL;

	return bufhead[0].next_frame;
}

void
x86_backtrace(struct pt_regs * const regs, unsigned int depth)
{
	struct stack_frame *head = (struct stack_frame *)frame_pointer(regs);

	if (!user_mode_vm(regs)) {
		unsigned long stack = kernel_stack_pointer(regs);
		if (depth)
			dump_trace(NULL, regs, (unsigned long *)stack, 0,
				   &backtrace_ops, &depth);
		return;
	}

	if (x86_backtrace_32(regs, depth))
		return;

	while (depth-- && head)
		head = dump_user_backtrace(head);
}