linux-kernel - Re: [PATCH 3/3] riscv: fix __user annotation for __copy

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Message-ID: <CAMHZB6E3Jcvni=nsxvOB-+g8sDGCvEV2G2q2+3XrJJy7f__-eg@mail.gmail.com>
Date:   Tue, 12 Jun 2018 20:19:57 +0200
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Atish Patra <atish.patra@....com>, linux-riscv@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Albert Ou <albert@...ive.com>
Subject: Re: [PATCH 3/3] riscv: fix __user annotation for __copy_user()

On Tue, Jun 12, 2018 at 7:12 PM, Palmer Dabbelt <palmer@...ive.com> wrote:
> On Mon, 11 Jun 2018 20:00:08 PDT (-0700), luc.vanoostenryck@...il.com wrote:
>> On Mon, Jun 11, 2018 at 12:01:37PM -0700, Palmer Dabbelt wrote:
>>>
>>> OK, I'll try and figure out what's going on.  We've had a handful of
>>> headaches trying to get things like '.align 2; .align 2' to actually
>>> produce
>>> no NOPs for the second alignment directive, which is surprisingly
>>> complicated due to the aggressive linker relaxation we do.
>>
>>
>> OK. I imagine indeed but note that no linker is involved here so,
>> if the problem is still present, it must already be in the assembler.
>
>
> Ah, OK -- in that case then it's just not a bug.  In RISC-V land we handle
> alignment as part of relaxation in the linker, so if you're looking at the
> output of the assembler then you'll always see a bunch of NOPs for every
> alignment directive.  If you 'objdump -dr' you should be able to see the
> relocations that get emitted, there should be a R_RISCV_ALIGN that points to
> the run of NOPs.

Ah OK. Indeed I see the R_RISCV_ALIGN.
Thanks for the explanation.

-- Luc