arm64: stacktrace: WARN_ON(state->common.pc == orig_pc) in kunwind_recover_return_address()
Oleg Nesterov
oleg at redhat.com
Mon Sep 16 03:38:11 PDT 2024
Ah, sorry for the noise, I looked into the wrong tree, missed the recent
c060f93253ca ("arm64: stacktrace: fix the usage of ftrace_graph_ret_addr()")
On 09/16, Oleg Nesterov wrote:
>
> I don't know the details but people report that
> kunwind_recover_return_address() hits this warning.
>
> I know absolutely nothing about arm64 or kernel/trace/fgraph.c, but at
> first glance this code looks broken:
>
> kunwind_recover_return_address:
>
> ...
>
> orig_pc = ftrace_graph_ret_addr(state->task, NULL,
> state->common.pc,
> (void *)state->common.fp);
> if (WARN_ON_ONCE(state->common.pc == orig_pc))
>
> ftrace_graph_ret_addr:
>
> ...
>
> if (!idx)
> return ret;
>
>
> given that kunwind_recover_return_address() passes idx == NULL to
> ftrace_graph_ret_addr(), it should always return ret == state->common.pc ?
>
>
> Perhaps this connects to 29c1c24a27 ("function_graph: Fix up ftrace_graph_ret_addr()")
> and I have no idea if something like the patch below makes any sense.
>
> Oleg.
>
> --- a/arch/arm64/kernel/stacktrace.c
> +++ b/arch/arm64/kernel/stacktrace.c
> @@ -106,7 +106,8 @@ kunwind_recover_return_address(struct kunwind_state *state)
> if (state->task->ret_stack &&
> (state->common.pc == (unsigned long)return_to_handler)) {
> unsigned long orig_pc;
> - orig_pc = ftrace_graph_ret_addr(state->task, NULL,
> + orig_pc = ftrace_graph_ret_addr(state->task,
> + &state->task->curr_ret_stack,
> state->common.pc,
> (void *)state->common.fp);
> if (WARN_ON_ONCE(state->common.pc == orig_pc))
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