Commit 9e09d445 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon
Browse files

arm64: stacktrace: recover return address for first entry 



The function which calls the top-level backtracing function may have
been instrumented with ftrace and/or kprobes, and hence the first return
address may have been rewritten.

Factor out the existing fgraph / kretprobes address recovery, and use
this for the first address. As the comment for the fgraph case isn't all
that helpful, I've also dropped that.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarKalesh Singh <kaleshsingh@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Madhavan T. Venkataraman <madvenka@linux.microsoft.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230411162943.203199-2-mark.rutland@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent e8d018dd

arch/arm64/kernel/stacktrace.c

+30 −23
Original line number Diff line number Diff line
@@ -69,6 +69,32 @@ static __always_inline void unwind_init_from_task(struct unwind_state *state, 
	state->pc = thread_saved_pc(task);

}



static __always_inline int

unwind_recover_return_address(struct unwind_state *state)

{

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	if (state->task->ret_stack &&

	    (state->pc == (unsigned long)return_to_handler)) {

		unsigned long orig_pc;

		orig_pc = ftrace_graph_ret_addr(state->task, NULL, state->pc,

						(void *)state->fp);

		if (WARN_ON_ONCE(state->pc == orig_pc))

			return -EINVAL;

		state->pc = orig_pc;

	}

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */



#ifdef CONFIG_KRETPROBES

	if (is_kretprobe_trampoline(state->pc)) {

		state->pc = kretprobe_find_ret_addr(state->task,

						    (void *)state->fp,

						    &state->kr_cur);

	}

#endif /* CONFIG_KRETPROBES */



	return 0;

}



/*

 * Unwind from one frame record (A) to the next frame record (B).

 *
@@ -92,35 +118,16 @@ static int notrace unwind_next(struct unwind_state *state) 


	state->pc = ptrauth_strip_insn_pac(state->pc);



#ifdef CONFIG_FUNCTION_GRAPH_TRACER

	if (tsk->ret_stack &&

		(state->pc == (unsigned long)return_to_handler)) {

		unsigned long orig_pc;

		/*

		 * This is a case where function graph tracer has

		 * modified a return address (LR) in a stack frame

		 * to hook a function return.

		 * So replace it to an original value.

		 */

		orig_pc = ftrace_graph_ret_addr(tsk, NULL, state->pc,

						(void *)state->fp);

		if (WARN_ON_ONCE(state->pc == orig_pc))

			return -EINVAL;

		state->pc = orig_pc;

	}

#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

#ifdef CONFIG_KRETPROBES

	if (is_kretprobe_trampoline(state->pc))

		state->pc = kretprobe_find_ret_addr(tsk, (void *)state->fp, &state->kr_cur);

#endif



	return 0;

	return unwind_recover_return_address(state);

}

NOKPROBE_SYMBOL(unwind_next);



static void notrace unwind(struct unwind_state *state,

			   stack_trace_consume_fn consume_entry, void *cookie)

{

	if (unwind_recover_return_address(state))

		return;



	while (1) {

		int ret;