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

Matt Fleming
2016-04-25T10:51:53Z

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?

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;

add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_NOW_UNRELIABLE);