On Mon, Oct 02, 2017 at 01:09:31PM -0700, Linus Torvalds wrote: > Bringing in Josh on this, because the merge commit gets fingered > because it seems to be an interaction between the new code from the > merge and the ORC unwinder changes. It's probably some almost trivial > code difference that just causes some code generation to change. > > And because Josh wasn't implicated in the merge, he didn't get cc'd by > the kernel test robot. > > Of course, the stack trace itself seems to be pretty useless, since > that randconfig doesn't have KALLSYMS enabled, so it's just random hex > numbers. > > Josh, original email on lkml and a few other mailing lists, see for example: > > https://www.spinics.net/lists/devicetree/msg196692.html > > Any ideas? The bisect is pointing to a commit which is almost 5 months old, so this is pre-ORC. Kallsyms *is* enabled, but the unwinder dump isn't smart enough to realize it's dumping misaligned stack addresses: [ 110.399425] WARNING: kernel stack regs at bd92bc2e in 01-cpu-hotplug:3811 has bad 'bp' value 000001be [ 110.399428] unwind stack type:0 next_sp: (null) mask:0x2 graph_idx:0 [ 110.399431] bd92bc2e: 92bc7f00 (0x92bc7f00) [ 110.399433] bd92bc32: c27041bd (0xc27041bd) So kallsyms doesn't help if I'm dumping bad data. Oops. I tried to recreate it with the reproducer script and a similar GCC version, but no luck. Fengguang, assuming it's reliably recreatable, any chance you could recreate with the following patch? diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index 82c6d7f1fd73..64282ec73eb8 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -42,7 +42,7 @@ static void unwind_dump(struct unwind_state *state) state->stack_info.type, state->stack_info.next_sp, state->stack_mask, state->graph_idx); - for (sp = state->orig_sp; sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { + for (sp = PTR_ALIGN(state->orig_sp); sp; sp = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { if (get_stack_info(sp, state->task, &stack_info, &visit_mask)) break; -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
