Messages in this thread | | | From | Sami Tolvanen <> | Date | Fri, 18 Oct 2019 10:35:49 -0700 | Subject | Re: [PATCH 18/18] arm64: implement Shadow Call Stack |
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On Fri, Oct 18, 2019 at 10:23 AM Mark Rutland <mark.rutland@arm.com> wrote: > I think scs_save() would better live in assembly in cpu_switch_to(), > where we switch the stack and current. It shouldn't matter whether > scs_load() is inlined or not, since the x18 value _should_ be invariant > from the PoV of the task.
Note that there's also a call to scs_save in cpu_die, because the current task's shadow stack pointer is only stored in x18 and we don't want to lose it.
> We just need to add a TSK_TI_SCS to asm-offsets.c, and then insert a > single LDR at the end: > > mov sp, x9 > msr sp_el0, x1 > #ifdef CONFIG_SHADOW_CALL_STACK > ldr x18, [x1, TSK_TI_SCS] > #endif > ret
TSK_TI_SCS is already defined, so yes, we could move this to cpu_switch_to. I would still prefer to have the overflow check that's in scs_thread_switch though.
Sami
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