Re: [PATCH 1/3] linux-user/aarch64: Add ESR signal frame for SIGSEGV, SIGBUS

[Richard Henderson]

On 8/29/23 07:35, Peter Maydell wrote:
> > +    /* See arch/arm64/mm/fault.c, set_thread_esr. */
> > +    if (sig == TARGET_SIGSEGV || sig == TARGET_SIGBUS) {
> > +        return true;
> > +    }
>
> It's possible to get here without env->exception.syndrome
> being set correctly, I think, if we take a host
> SIGSEGV or SIGBUS and host_signal_handler() calls either
> cpu_loop_exit_sigsegv() or cpu_loop_exit_sigbus(). Can also
> happen for other places that call one of those two functions,
> like allocation_tag_mem(). At least, I can't see where we
> would be setting syndrome in that code path.

cpu_loop_exit_sig* go through arm_cpu_record_sigsegv and arm_cpu_record_sigbus, which use 
the normal fault processing paths to populate FAR_EL1 and ESR_EL1.

> Maybe we should do the "sanitize ESR for fault addresses in
> the upper half of guest address space" logic that the kernel
> set_thread_esr() does?

I guess we could, though I'm not sure how such an address could occur.


r~