On Tue, Aug 31, 2021 at 05:02:15PM +0200, Marco Elver wrote: > 2. stack_trace_save() is subtly broken on s390: it starts the trace in > stack_trace_save() itself. This is incorrect, as the trace should > start with the caller. We reported something similar to arm64, also > because one of our sanitizer tests failed: > https://lkml.kernel.org/r/20210319184106.5688-1-mark.rutland@xxxxxxx Thanks a lot for looking into it and debugging it! > Fix it by skipping the initial entry in s390's arch_stack_walk(). ... > diff --git a/arch/s390/kernel/stacktrace.c b/arch/s390/kernel/stacktrace.c > index 101477b3e263..47d1841af03e 100644 > --- a/arch/s390/kernel/stacktrace.c > +++ b/arch/s390/kernel/stacktrace.c > @@ -16,11 +16,16 @@ void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, > { > struct unwind_state state; > unsigned long addr; > + bool init = true; > > unwind_for_each_frame(&state, task, regs, 0) { > addr = unwind_get_return_address(&state); > - if (!addr || !consume_entry(cookie, addr)) > + if (!addr) > + break; > + > + if (!init && !consume_entry(cookie, addr)) > break; > + init = false; > } I believe we don't need to skip the first unwinder result if task != current or regs != NULL. Same for arch_stack_walk_reliable. But after you pinpointed the problem I see that the actual difference with x86 implementation comes from get_stack_pointer(). I'll send a patch as reply.
