linux-kernel - Re: [PATCH] crypto: wp512: disable kmsan checks in wp512_process

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Message-Id: <aa26bed0-dd8e-4fac-9606-91769eee96b8@app.fastmail.com>
Date:   Fri, 16 Dec 2022 19:29:53 +0100
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Alexander Potapenko" <glider@...gle.com>,
        "Arnd Bergmann" <arnd@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        "Herbert Xu" <herbert@...dor.apana.org.au>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: wp512: disable kmsan checks in wp512_process_buffer()

On Fri, Dec 16, 2022, at 17:08, Alexander Potapenko wrote:
>> The memory sanitizer causes excessive register spills in this function:
>
>> crypto/wp512.c:782:13: error: stack frame size (2104) exceeds limit (2048) in 'wp512_process_buffer' [-Werror,-Wframe-larger-than]
>
>> Assume that this one is safe, and mark it as needing no checks to
>> get the stack usage back down to the normal level.
>
> KMSAN indeed bloats the stack frames heavily.
> Wouldn't it be more preferable to further increase KMSAN's 
> -Wframe-larger-than limit instead?
> It is not intended for production anyway, and detecting a runtime stack 
> overflow in the debug mode should not be a problem.

I don't actually see a lot of compiler warnings with KMSAN
hitting the limit, I think we can deal with them individually.

I'd rather not raise the limit more, as that makes it harder
to identify functions that use more stack than they should.

    Arnd