linux-kernel - Re: [PATCHv3 0/5] efi: detect erroneous firmware IRQ manipulation

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Date:	Mon, 25 Apr 2016 17:03:09 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Mark Rutland <mark.rutland@....com>
Cc:	linux-efi@...r.kernel.org, ard.biesheuvel@...aro.org,
	catalin.marinas@....com, hpa@...or.com, leif.lindholm@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
	will.deacon@....com, Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCHv3 0/5] efi: detect erroneous firmware IRQ manipulation

On Mon, 25 Apr, at 02:46:29PM, Mark Rutland wrote:
> Note: this is largely a rework of the final patch from v2 [2], which now has a
> per-arch component (and hence additional patches). The rest of v2 has already
> been picked up, and hence dropped from this posting.
> 
> Some firmware erroneously unmask IRQs (and potentially other architecture
> specific exceptions) during runtime services functions, in violation of both
> common sense and the UEFI specification. This can result in a number of issues
> if said exceptions are taken when they are expected to be masked, and
> additionally can confuse IRQ tracing if the original mask state is not
> restored prior to returning from firmware.
> 
> In practice it's difficult to check that firmware never unmasks exceptions, but
> we can at least check that the IRQ flags are at least consistent upon entry to
> and return from a runtime services function call. This series implements said
> check in the shared EFI runtime wrappers code, after an initial round of
> refactoring (patches 1-5 of [2]).
> 
> I have left ia64 as-is, without this check, as ia64 doesn't currently use the
> generic runtime wrappers, has many special cases for the runtime calls which
> don't fit well with the generic code, and I don't expect a new, buggy ia64
> firmware to appear soon.
> 
> The first time corruption of the IRQ flags is detected, we dump a stack trace,
> and set TAINT_FIRMWARE_WORKAROUND. Additionally, and in all subsequent cases,
> we log (with ratelimiting) the specific corruption of the flags, and restore
> the expected flags to avoid redundant warnings elsewhere.

Thanks Mark. I've picked up the series and applied it to the v4.7
queue.