linux-kernel - Re: [PATCH v1 3/3] x86: call instrumentation hooks from copy

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Message-ID: <f9a8a442-0ff2-4da9-af4d-3d0e2805c4a7@I-love.SAKURA.ne.jp>
Date: Wed, 20 Mar 2024 12:54:25 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Alexander Potapenko <glider@...gle.com>, akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kasan-dev@...glegroups.com, tglx@...utronix.de, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Dmitry Vyukov <dvyukov@...gle.com>, Marco Elver <elver@...gle.com>
Subject: Re: [PATCH v1 3/3] x86: call instrumentation hooks from copy_mc.c

On 2024/03/20 1:36, Alexander Potapenko wrote:
> @@ -61,10 +62,20 @@ unsigned long copy_mc_enhanced_fast_string(void *dst, const void *src, unsigned
>   */
>  unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigned len)
>  {
> -	if (copy_mc_fragile_enabled)
> -		return copy_mc_fragile(dst, src, len);
> -	if (static_cpu_has(X86_FEATURE_ERMS))
> -		return copy_mc_enhanced_fast_string(dst, src, len);
> +	unsigned long ret;
> +
> +	if (copy_mc_fragile_enabled) {
> +		instrument_memcpy_before(dst, src, len);

I feel that instrument_memcpy_before() needs to be called *after*
copy_mc_fragile() etc. , for we can't predict how many bytes will
copy_mc_fragile() etc. actually copy.

> +		ret = copy_mc_fragile(dst, src, len);
> +		instrument_memcpy_after(dst, src, len, ret);
> +		return ret;
> +	}