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Date: Mon, 12 Feb 2024 16:29:48 -0800
From: Kees Cook <keescook@chromium.org>
To: Suren Baghdasaryan <surenb@google.com>
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Subject: Re: [PATCH v3 00/35] Memory allocation profiling
Message-ID: <202402121602.CC62228@keescook>
References: <20240212213922.783301-1-surenb@google.com>
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In-Reply-To: <20240212213922.783301-1-surenb@google.com>

On Mon, Feb 12, 2024 at 01:38:46PM -0800, Suren Baghdasaryan wrote:
> Low overhead [1] per-callsite memory allocation profiling. Not just for debug
> kernels, overhead low enough to be deployed in production.

What's the plan for things like devm_kmalloc() and similar relatively
simple wrappers? I was thinking it would be possible to reimplement at
least devm_kmalloc() with size and flags changing helper a while back:

https://lore.kernel.org/all/202309111428.6F36672F57@keescook/

I suspect it could be possible to adapt the alloc_hooks wrapper in this
series similarly:

#define alloc_hooks_prep(_do_alloc, _do_prepare, _do_finish,		\
			  ctx, size, flags)				\
({									\
	typeof(_do_alloc) _res;						\
	DEFINE_ALLOC_TAG(_alloc_tag, _old);				\
	ssize_t _size = (size);						\
	size_t _usable = _size;						\
	gfp_t _flags = (flags);						\
									\
	_res = _do_prepare(ctx, &_size, &_flags);			\
	if (!IS_ERR_OR_NULL(_res)					\
		_res = _do_alloc(_size, _flags);			\
	if (!IS_ERR_OR_NULL(_res)					\
		_res = _do_finish(ctx, _usable, _size, _flags, _res);	\
	_res;								\
})

#define devm_kmalloc(dev, size, flags)					\
	alloc_hooks_prep(kmalloc, devm_alloc_prep, devm_alloc_finish,	\
			 dev, size, flags)

And devm_alloc_prep() and devm_alloc_finish() adapted from the URL
above.

And _do_finish instances could be marked with __realloc_size(2)

-Kees

-- 
Kees Cook