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

From	Matt Fleming <matt@codeblueprint.co.uk>
Newsgroups	linux.kernel
Subject	Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation
Date	2016-04-25 13:00 +0200
Message-ID	<rrMpe-4ls-49@gated-at.bofh.it> (permalink)
References	(2 earlier) <rrzLk-2IO-13@gated-at.bofh.it> <rrLMv-406-25@gated-at.bofh.it> <rrLWb-46w-41@gated-at.bofh.it> <rrLWb-46w-39@gated-at.bofh.it> <rrMfv-4fB-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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);

Thread

[PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Mark Rutland <mark.rutland@arm.com> - 2016-04-22 16:00 +0200
  [PATCHv2 3/6] arm/efi: move to generic {__,}efi_call_virt Mark Rutland <mark.rutland@arm.com> - 2016-04-22 16:00 +0200
  [PATCHv2 6/6] efi/runtime-wrappers: detect FW irq flag corruption Mark Rutland <mark.rutland@arm.com> - 2016-04-22 16:00 +0200
    Re: [PATCHv2 6/6] efi/runtime-wrappers: detect FW irq flag corruption Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-24 23:20 +0200
  [PATCHv2 2/6] arm64/efi: move to generic {__,}efi_call_virt Mark Rutland <mark.rutland@arm.com> - 2016-04-22 16:00 +0200
  [PATCHv2 1/6] efi/runtime-wrappers: add {__,}efi_call_virt templates Mark Rutland <mark.rutland@arm.com> - 2016-04-22 16:00 +0200
    Re: [PATCHv2 1/6] efi/runtime-wrappers: add {__,}efi_call_virt  templates Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-24 23:20 +0200
  Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-04-22 16:20 +0200
    Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-24 23:30 +0200
      Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-25 12:20 +0200
        Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-04-25 12:30 +0200
          Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-25 12:30 +0200
            Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Mark Rutland <mark.rutland@arm.com> - 2016-04-25 12:50 +0200
              Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-25 13:00 +0200
                Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Mark Rutland <mark.rutland@arm.com> - 2016-04-25 13:10 +0200
                Re: [PATCHv2 0/6] efi: detect erroneous firmware IRQ manipulation Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-25 13:20 +0200

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