linux-kernel - Re: [tip:efi/core] efi/libstub: Make efi_random

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Date:   Sun, 4 Dec 2016 14:31:23 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Matt Fleming <matt@...eblueprint.co.uk>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hpa@...or.com" <hpa@...or.com>, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:efi/core] efi/libstub: Make efi_random_alloc() allocate
 below 4 GB on 32-bit

On 4 December 2016 at 14:17, Matt Fleming <matt@...eblueprint.co.uk> wrote:
> On Thu, 24 Nov, at 10:47:15PM, tip-bot for Ard Biesheuvel wrote:
>> Commit-ID:  018edcfac4c3b140366ad51b0907f3becb5bb624
>> Gitweb:     http://git.kernel.org/tip/018edcfac4c3b140366ad51b0907f3becb5bb624
>> Author:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
>> AuthorDate: Thu, 24 Nov 2016 18:02:23 +0000
>> Committer:  Ingo Molnar <mingo@...nel.org>
>> CommitDate: Fri, 25 Nov 2016 07:15:23 +0100
>>
>> efi/libstub: Make efi_random_alloc() allocate below 4 GB on 32-bit
>>
>> The UEFI stub executes in the context of the firmware, which identity
>> maps the available system RAM, which implies that only memory below
>> 4 GB can be used for allocations on 32-bit architectures, even on [L]PAE
>> capable hardware.
>>
>> So ignore any reported memory above 4 GB in efi_random_alloc(). This
>> also fixes a reported build problem on ARM under -Os, where the 64-bit
>> logical shift relies on a software routine that the ARM decompressor does
>> not provide.
>>
>> A second [minor] issue is also fixed, where the '+ 1' is moved out of
>> the shift, where it belongs: the reason for its presence is that a
>> memory region where start == end should count as a single slot, given
>> that 'end' takes the desired size and alignment of the allocation into
>> account.
>>
>> To clarify the code in this regard, rename start/end to 'first_slot' and
>> 'last_slot', respectively, and introduce 'region_end' to describe the
>> last usable address of the current region.
>>
>> Reported-by: Arnd Bergmann <arnd@...db.de>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>> Cc: Matt Fleming <matt@...eblueprint.co.uk>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: linux-efi@...r.kernel.org
>> Link: http://lkml.kernel.org/r/1480010543-25709-2-git-send-email-ard.biesheuvel@linaro.org
>> Signed-off-by: Ingo Molnar <mingo@...nel.org>
>> ---
>>  drivers/firmware/efi/libstub/random.c | 13 +++++++------
>>  1 file changed, 7 insertions(+), 6 deletions(-)
>
> Ard, was this picked up for the correct tip branch? If it fixes a
> build failure it should have gone into tip/efi/urgent, right?

The failure was in -next, with a patch queued up for v4.10, so that is
where the fix went as well.