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Commit e9d4efdd authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Ingo Molnar
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x86: improve the 32 bit Frame Pointer backtracer to also use the traditional backtrace 



The 32 bit Frame Pointer backtracer code checks if the EBP is valid
to do a backtrace; however currently on a failure it just gives up
and prints nothing. That's not very nice; we can do better and still
print a decent backtrace.

This patch changes the backtracer to use the regular backtracing algorithm
at the same time as the EBP backtracer; the EBP backtracer is basically
used to figure out which part of the backtrace are reliable vs those
which are likely to be noise.

Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent bc850d6b

arch/x86/kernel/traps_32.c

+20 −24
Original line number Diff line number Diff line
@@ -118,36 +118,32 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo, 
				unsigned long *stack, unsigned long bp,

				const struct stacktrace_ops *ops, void *data)

{

#ifdef	CONFIG_FRAME_POINTER

	struct stack_frame *frame = (struct stack_frame *)bp;

	while (valid_stack_ptr(tinfo, frame, sizeof(*frame))) {

		struct stack_frame *next;

		unsigned long addr;



		addr = frame->return_address;

		if (__kernel_text_address(addr))

			ops->address(data, addr, 1);

	/*

		 * break out of recursive entries (such as

		 * end_of_stack_stop_unwind_function). Also,

		 * we can never allow a frame pointer to

		 * move downwards!

	 * if EBP is "deeper" into the stack than the actual stack pointer,

	 * we need to rewind the stack pointer a little to start at the

	 * first stack frame, but only if EBP is in this stack frame.

	 */

		next = frame->next_frame;

		bp = (unsigned long) next;

		if (next <= frame)

			break;

		frame = next;

	}

#else

	if (stack > (unsigned long *) bp

			&& valid_stack_ptr(tinfo, frame, sizeof(*frame)))

		stack = (unsigned long *) bp;



	while (valid_stack_ptr(tinfo, stack, sizeof(*stack))) {

		unsigned long addr;



		addr = *stack++;

		if (__kernel_text_address(addr))

		addr = *stack;

		if (__kernel_text_address(addr)) {

			if ((unsigned long) stack == bp + 4) {

				ops->address(data, addr, 1);

				frame = frame->next_frame;

				bp = (unsigned long) frame;

			} else {

				ops->address(data, addr, 0);

			}

		}

		stack++;

	}

#endif

	return bp;

}