Re: [PATCH v1 0/3] Import Arm Optimized Routines str{n}cmp functions

From: Mark Rutland <mark.rutland@arm.com>
To: Joey Gouly <joey.gouly@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, nd@arm.com,
	catalin.marinas@arm.com, robin.murphy@arm.com, will@kernel.org
Subject: Re: [PATCH v1 0/3] Import Arm Optimized Routines str{n}cmp functions
Date: Wed, 16 Feb 2022 16:30:26 +0000	[thread overview]
Message-ID: <Yg0mouX04hSRt/r4@lakrids> (raw)
In-Reply-To: <20220215170723.21266-1-joey.gouly@arm.com>

On Tue, Feb 15, 2022 at 05:07:20PM +0000, Joey Gouly wrote:
> Hi all,

Hi,

> The previous str{n}cmp routines were not MTE safe, so were disabled in:
>   59a68d413808 ("arm64: Mitigate MTE issues with str{n}cmp()")
> 
> The Arm Optimized Routines repository recently merged [1] their strcmp.S and
> strcmp-mte.S files into a single file that is MTE safe.
> 
> Therefore we can import these new MTE safe functions and remove the workaround.
> 
> I did some light boot tests using QEMU.

Nice!

As as minor thing, on the two import patches, I think we should be more
explicit about what's going on with licensing, so that it's clear the
license change relative to upstream is intended and legitimate.

For example, in commit:

  758602c04409d8c5 ("arm64: Import latest version of Cortex Strings' strcmp")

We had a note in the commit message:

| Note that for simplicity Arm have chosen to contribute this code
| to Linux under GPLv2 rather than the original MIT license.

... and I reckon it's worth being slightly more explicit, e.g.

| Note that for simplicity Arm have chosen to contribute this code
| to Linux under GPLv2 rather than the original MIT license. Arm is the
| sole copyright holder for this code.

That was previously confirmed at: 

  https://lore.kernel.org/linux-arm-kernel/20210526101723.GA3806@C02TD0UTHF1T.local/

So with that latter wording added to the import patches:

Acked-by: Mark Rutland <mark.rutland@arm.com>

As a heads-up, I believe this will conflict with changes I'm making to
the way symbol aliasing works:

  https://lore.kernel.org/lkml/20220216162229.1076788-1-mark.rutland@arm.com/

... and I reckon we need to fix that conflict in the arm64 tree, either
as a merge resolution or rebasing this atop my series.

Thanks,
Mark.

> 
> Thanks,
> Joey
> 
> [1] https://github.com/ARM-software/optimized-routines/commit/7b91c3cdb12b023004cb4dda30a1aa3424329ce6
> 
> Joey Gouly (3):
>   arm64: lib:  Import latest version of Arm Optimized Routines' strcmp
>   arm64: lib:  Import latest version of Arm Optimized Routines' strncmp
>   Revert "arm64: Mitigate MTE issues with str{n}cmp()"
> 
>  arch/arm64/include/asm/assembler.h |   5 -
>  arch/arm64/include/asm/string.h    |   2 -
>  arch/arm64/lib/strcmp.S            | 240 +++++++++++++++--------------
>  arch/arm64/lib/strncmp.S           | 236 +++++++++++++++++-----------
>  4 files changed, 269 insertions(+), 214 deletions(-)
> 
> -- 
> 2.17.1
> 

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