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From: Suren Baghdasaryan <surenb@google.com>
Date: Mon, 12 Feb 2024 16:47:05 -0800
Message-ID: <CAJuCfpF677Fu152GQAgD-GW=eFPsRMXfXzyXtnc5p6kPsxeQJA@mail.gmail.com>
Subject: Re: [PATCH v3 00/35] Memory allocation profiling
To: Kees Cook <keescook@chromium.org>
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On Mon, Feb 12, 2024 at 4:29=E2=80=AFPM Kees Cook <keescook@chromium.org> w=
rote:
>
> 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 =3D (size);                                        =
 \
>         size_t _usable =3D _size;                                        =
 \
>         gfp_t _flags =3D (flags);                                        =
 \
>                                                                         \
>         _res =3D _do_prepare(ctx, &_size, &_flags);                      =
 \
>         if (!IS_ERR_OR_NULL(_res)                                       \
>                 _res =3D _do_alloc(_size, _flags);                       =
 \
>         if (!IS_ERR_OR_NULL(_res)                                       \
>                 _res =3D _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)

devm_kmalloc() is definitely a great candidate to account separately.
Looks like it's currently using
alloc_dr()->kmalloc_node_track_caller(), so this series will account
the internal kmalloc_node_track_caller() allocation. We can easily
apply alloc_hook to devm_kmalloc() and friends and replace the
kmalloc_node_track_caller() call inside alloc_dr() with
kmalloc_node_track_caller_noprof(). That will move accounting directly
to devm_kmalloc().

>
> -Kees
>
> --
> Kees Cook