[PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation

Mark Rutland
2016-04-25T11:04:55Z

On Mon, Apr 25, 2016 at 11:51:53AM +0100, Matt Fleming wrote:
> On Mon, 25 Apr, at 11:40:09AM, Mark Rutland wrote:
> >
> > It looks like irqs_disabled_flags() will do what you expect, and ignore
> > everything but the interrupt flag.
> >
> > However, for ARM that will ignore the other exceptions we've seen FW
> > erroneously unmask (e.g. FIQ), which is unfortunate, as fiddling with
> > those is just as disastrous.
>
> Bah, right.
>
> > Would you be happy with an arch_efi_call_check_flags(before, after),
> > instead? That way we can make the flags we check arch-specific.
>
> Could we just make the flag mask arch-specific instead of the call
> since the rest of efi_call_virt_check_flags() is good?

Yup, I meant that arch_efi_call_check_flags would only do the flag
comparison, only replacing the bit currently in the WARN_ON_ONCE().

> Something like this (uncompiled, untested, half-baked),
>
> ---
>
> diff --git a/drivers/firmware/efi/runtime-wrappers.c b/drivers/firmware/efi/runtime-wrappers.c
> index c38b1cfc26e2..057d00bee7d6 100644
> --- a/drivers/firmware/efi/runtime-wrappers.c
> +++ b/drivers/firmware/efi/runtime-wrappers.c
> @@ -25,9 +25,12 @@
> static void efi_call_virt_check_flags(unsigned long flags, const char *call)
> {
> unsigned long cur_flags;
> + bool mismatch;
>
> local_save_flags(cur_flags);
> - if (!WARN_ON_ONCE(cur_flags != flags))
> +
> + mismatch = (cur_flags ^ flags) & ARCH_EFI_IRQ_FLAGS_MASK;
> + if (!WARN_ON_ONCE(mismatch))
> return;

This style also works for me.

Should I respin patch 6 as a series doing the above?

I assume that the first 5 patches are fine as-is.

Thanks,
Mark.