Messages in this thread | | | From | Sami Tolvanen <> | Date | Mon, 4 Nov 2019 13:35:28 -0800 | Subject | Re: [PATCH v4 07/17] scs: add support for stack usage debugging |
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On Mon, Nov 4, 2019 at 4:40 AM Mark Rutland <mark.rutland@arm.com> wrote: > > +#ifdef CONFIG_DEBUG_STACK_USAGE > > +static inline unsigned long scs_used(struct task_struct *tsk) > > +{ > > + unsigned long *p = __scs_base(tsk); > > + unsigned long *end = scs_magic(tsk); > > + uintptr_t s = (uintptr_t)p; > > As previously, please use unsigned long for consistency.
Ack.
> > + while (p < end && *p) > > + p++; > > I think this is the only place where we legtimately access the shadow > call stack directly.
There's also scs_corrupted, which checks that the end magic is intact.
> When using SCS and KASAN, are the > compiler-generated accesses to the SCS instrumented? > > If not, it might make sense to make this: > > while (p < end && READ_ONCE_NOCKECK(*p)) > > ... and poison the allocation from KASAN's PoV, so that we can find > unintentional accesses more easily.
Sure, that makes sense. I can poison the allocation for the non-vmalloc case, I'll just need to refactor scs_set_magic to happen before the poisoning.
Sami
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