From: "Arnd Bergmann" <arnd@arndb.de>
To: "Karl Mehltretter" <kmehltretter@gmail.com>
Cc: "Catalin Marinas" <catalin.marinas@arm.com>,
"Will Deacon" <will@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: compat: Keep alignment address arithmetic 32-bit
Date: Tue, 18 Aug 2026 09:31:14 +0200 [thread overview]
Message-ID: <e3c463a1-81ae-4bef-b65b-fea1a4eda5bc@app.fastmail.com> (raw)
In-Reply-To: <aoPKzPb9YUVULlXG@gmail.com>
On Tue, Aug 18, 2026, at 05:22, Karl Mehltretter wrote:
> On Mon, Aug 17, 2026 at 11:15:33AM +0100, Arnd Bergmann wrote:
<
> The 4 GiB wraparound case is possible with a rather unusual arm64
> kernel configuration, and correctly handling an individual word
> crossing the boundary would require byte accesses. That seems too
> contrived to justify the extra complexity here.
I don't understand, what is special about the configuration?
Isn't this exactly the case you were trying to address with
the compat_ptr() hack?
> Just to be sure by "both instances" do you mean the nr_regs
> declarations in both arch/arm64/kernel/compat_alignment.c and
> arch/arm/mm/alignment.c?
Yes
> Changing nr_regs in arm32 alignment.c would not change the generated
> code and I guess probably not be backported, so that would create a
> divergence with stable kernels.
>
> Would you prefer changing both files, or only the arm64 implementation?
I would suggest doing only a small change to arm64.
Arnd
next prev parent reply other threads:[~2026-08-18 7:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-17 0:02 [PATCH] arm64: compat: Keep alignment address arithmetic 32-bit Karl Mehltretter
2026-08-17 9:15 ` Arnd Bergmann
2026-08-18 3:22 ` Karl Mehltretter
2026-08-18 7:31 ` Arnd Bergmann [this message]
2026-08-19 4:56 ` Karl Mehltretter
2026-08-19 11:19 ` Arnd Bergmann
2026-08-19 18:55 ` Karl Mehltretter
2026-08-19 20:27 ` Arnd Bergmann
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