From: Jeffrey Hugo <jhugo@codeaurora.org>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
leif.lindholm@linaro.org, mark.rutland@arm.com,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
"H . Peter Anvin" <hpa@zytor.com>
Cc: linux-arm-kernel@lists.infradead.org, riku.voipio@linaro.org,
matt@codeblueprint.co.uk, linux-kernel@vger.kernel.org,
linux-efi@vger.kernel.org
Subject: Re: [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices()
Date: Wed, 1 Feb 2017 14:08:23 -0700 [thread overview]
Message-ID: <ac1bad94-ffa3-4acf-a719-a8e8f4c7a283@codeaurora.org> (raw)
In-Reply-To: <1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org>
On 2/1/2017 10:45 AM, Ard Biesheuvel wrote:
> Some AArch64 UEFI implementations disable the MMU in ExitBootServices(),
> after which unaligned accesses to RAM are no longer supported.
>
> Commit abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the
> kernel") fixed an issue in the memory map handling of the stub FDT code,
> but inadvertently created an issue with such firmwares, by moving some
> of the FDT manipulation to after the invocation of ExitBootServices().
> Given that the stub's libfdt implementation uses the ordinary, accelerated
> string functions, which rely on hardware handling of unaligned accesses,
> manipulating the FDT with the MMU off may result in alignment faults.
>
> So fix the situation by moving the update_fdt_memmap() call into the
> callback function invoked by efi_exit_boot_services() right before it
> calls the ExitBootServices() UEFI service (which is arguably a better
> place for it anyway)
>
> Note that disabling the MMU in ExitBootServices() is not compliant with
> the UEFI spec, and carries great risk due to the fact that switching from
> cached to uncached memory accesses halfway through compiler generated code
> (i.e., involving a stack) can never be done in a way that is architecturally
> safe.
>
> Cc: <stable@vger.kernel.org>
> Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel")
> Tested-by: Riku Voipio <riku.voipio@linaro.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
NACK, please. This causes a regression on my platform, in the form of
an assert in UEFI once ExitBootServices() is called, per initial
testing. I'll do more testing to determine why.
--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
WARNING: multiple messages have this Message-ID (diff)
From: Jeffrey Hugo <jhugo-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>
To: Ard Biesheuvel
<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org,
mark.rutland-5wv7dgnIgG8@public.gmane.org,
Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>,
"H . Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Cc: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
riku.voipio-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org,
matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices()
Date: Wed, 1 Feb 2017 14:08:23 -0700 [thread overview]
Message-ID: <ac1bad94-ffa3-4acf-a719-a8e8f4c7a283@codeaurora.org> (raw)
In-Reply-To: <1485971102-23330-2-git-send-email-ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
On 2/1/2017 10:45 AM, Ard Biesheuvel wrote:
> Some AArch64 UEFI implementations disable the MMU in ExitBootServices(),
> after which unaligned accesses to RAM are no longer supported.
>
> Commit abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the
> kernel") fixed an issue in the memory map handling of the stub FDT code,
> but inadvertently created an issue with such firmwares, by moving some
> of the FDT manipulation to after the invocation of ExitBootServices().
> Given that the stub's libfdt implementation uses the ordinary, accelerated
> string functions, which rely on hardware handling of unaligned accesses,
> manipulating the FDT with the MMU off may result in alignment faults.
>
> So fix the situation by moving the update_fdt_memmap() call into the
> callback function invoked by efi_exit_boot_services() right before it
> calls the ExitBootServices() UEFI service (which is arguably a better
> place for it anyway)
>
> Note that disabling the MMU in ExitBootServices() is not compliant with
> the UEFI spec, and carries great risk due to the fact that switching from
> cached to uncached memory accesses halfway through compiler generated code
> (i.e., involving a stack) can never be done in a way that is architecturally
> safe.
>
> Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
> Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel")
> Tested-by: Riku Voipio <riku.voipio-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
NACK, please. This causes a regression on my platform, in the form of
an assert in UEFI once ExitBootServices() is called, per initial
testing. I'll do more testing to determine why.
--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
WARNING: multiple messages have this Message-ID (diff)
From: jhugo@codeaurora.org (Jeffrey Hugo)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices()
Date: Wed, 1 Feb 2017 14:08:23 -0700 [thread overview]
Message-ID: <ac1bad94-ffa3-4acf-a719-a8e8f4c7a283@codeaurora.org> (raw)
In-Reply-To: <1485971102-23330-2-git-send-email-ard.biesheuvel@linaro.org>
On 2/1/2017 10:45 AM, Ard Biesheuvel wrote:
> Some AArch64 UEFI implementations disable the MMU in ExitBootServices(),
> after which unaligned accesses to RAM are no longer supported.
>
> Commit abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the
> kernel") fixed an issue in the memory map handling of the stub FDT code,
> but inadvertently created an issue with such firmwares, by moving some
> of the FDT manipulation to after the invocation of ExitBootServices().
> Given that the stub's libfdt implementation uses the ordinary, accelerated
> string functions, which rely on hardware handling of unaligned accesses,
> manipulating the FDT with the MMU off may result in alignment faults.
>
> So fix the situation by moving the update_fdt_memmap() call into the
> callback function invoked by efi_exit_boot_services() right before it
> calls the ExitBootServices() UEFI service (which is arguably a better
> place for it anyway)
>
> Note that disabling the MMU in ExitBootServices() is not compliant with
> the UEFI spec, and carries great risk due to the fact that switching from
> cached to uncached memory accesses halfway through compiler generated code
> (i.e., involving a stack) can never be done in a way that is architecturally
> safe.
>
> Cc: <stable@vger.kernel.org>
> Fixes: abfb7b686a3e ("efi/libstub/arm*: Pass latest memory map to the kernel")
> Tested-by: Riku Voipio <riku.voipio@linaro.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
NACK, please. This causes a regression on my platform, in the form of
an assert in UEFI once ExitBootServices() is called, per initial
testing. I'll do more testing to determine why.
--
Jeffrey Hugo
Qualcomm Datacenter Technologies as an affiliate of Qualcomm
Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2017-02-01 21:08 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-01 17:45 [GIT PULL] EFI urgent fix for v4.10 Ard Biesheuvel
2017-02-01 17:45 ` Ard Biesheuvel
2017-02-01 17:45 ` [PATCH] efi: fdt: avoid FDT manipulation after ExitBootServices() Ard Biesheuvel
2017-02-01 17:45 ` Ard Biesheuvel
2017-02-01 17:49 ` Leif Lindholm
2017-02-01 17:49 ` Leif Lindholm
2017-02-01 19:03 ` Ingo Molnar
2017-02-01 19:03 ` Ingo Molnar
2017-02-01 19:03 ` Ingo Molnar
2017-02-01 19:28 ` Ard Biesheuvel
2017-02-01 19:28 ` Ard Biesheuvel
2017-02-01 19:28 ` Ard Biesheuvel
2017-02-01 20:16 ` Ingo Molnar
2017-02-01 20:16 ` Ingo Molnar
2017-02-01 20:16 ` Ingo Molnar
2017-02-01 21:08 ` Jeffrey Hugo [this message]
2017-02-01 21:08 ` Jeffrey Hugo
2017-02-01 21:08 ` Jeffrey Hugo
2017-02-01 22:59 ` Jeffrey Hugo
2017-02-01 22:59 ` Jeffrey Hugo
2017-02-01 22:59 ` Jeffrey Hugo
2017-02-02 16:14 ` Ard Biesheuvel
2017-02-02 16:14 ` Ard Biesheuvel
2017-02-02 16:14 ` Ard Biesheuvel
2017-02-02 1:31 ` [tip:efi/urgent] efi/fdt: Avoid " tip-bot for Ard Biesheuvel
-- strict thread matches above, loose matches on Subject: below --
2017-02-01 13:11 [PATCH] efi: fdt: avoid " Ard Biesheuvel
2017-02-01 13:11 ` Ard Biesheuvel
[not found] ` <1485954693-25750-1-git-send-email-ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2017-02-01 13:39 ` Leif Lindholm
2017-02-01 13:39 ` Leif Lindholm
[not found] ` <CAF7UmSyYvmo8k910mJEAYhaOJy9j_bpXw6f+Cj=cS_m_iYiCCQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-02-01 13:41 ` Ard Biesheuvel
2017-02-01 13:41 ` Ard Biesheuvel
2017-02-01 14:08 ` Mark Rutland
2017-02-01 14:08 ` Mark Rutland
2017-02-01 14:46 ` Riku Voipio
2017-02-01 14:46 ` Riku Voipio
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