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SubjectRe: [PATCH] x86/orc: Don't bail on stack overflow

* Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> On Mon, Nov 27, 2017 at 10:38:42AM +0100, Ingo Molnar wrote:
> >
> > * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > > On Sat, Nov 25, 2017 at 04:16:23PM -0800, Andy Lutomirski wrote:
> > > > Can you send me whatever config and exact commit hash generated this?
> > > > I can try to figure out why it failed.
> > >
> > > Sorry, I've been traveling. I just got some time to take a look at
> > > this. I think there are at least two unwinder issues here:
> > >
> > > - It doesn't deal gracefully with the case where the stack overflows and
> > > the stack pointer itself isn't on a valid stack but the
> > > to-be-dereferenced data *is*.
> > >
> > > - The oops dump code doesn't know how to print partial pt_regs, for the
> > > case where if we get an interrupt/exception in *early* entry code
> > > before the full pt_regs have been saved.
> > >
> > > (Andy, I'm not quite sure about your patch, and whether it's still
> > > needed after these patches. I'll need to look at it later when I have
> > > more time.)
> > >
> > > I attempted to fix both of the issues with the below patch. Thomas or
> > > Ingo, can you test to see if this gets rid of the question marks?
> > >
> > > I can split it up into proper patches next week. I'm assuming this
> > > isn't holding up the KAISER merge?
> >
> > It's not holding up the Kaiser merge, but good debuggability of weird crashes is a
> > really good thing, so I constructed a changelog and picked up this patch as a
> > single commit, and added your Signed-off-by, if that's OK with you.
> >
> > Will only push it out if it passes testing.
>
> The commit log looks good, though there's a CONFIG_FRAME_POINTER build
> failure. Can you fold in this fix?
>
> diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c
> index 7dd0d2a0d142..77835bc021c7 100644
> --- a/arch/x86/kernel/stacktrace.c
> +++ b/arch/x86/kernel/stacktrace.c
> @@ -102,7 +102,7 @@ __save_stack_trace_reliable(struct stack_trace *trace,
> for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state);
> unwind_next_frame(&state)) {
>
> - regs = unwind_get_entry_regs(&state, NULL);
> + regs = unwind_get_entry_regs(&state);
> if (regs) {
> /*
> * Kernel mode registers on the stack indicate an

Done, thanks!

Ingo

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