linux-kernel - Re: [PATCH v4 1/2] bpf: add __weak hook for allocating executable memory

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Date:   Wed, 5 Dec 2018 15:37:48 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jessica Yu <jeyu@...nel.org>, Jann Horn <jannh@...gle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Network Development <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v4 1/2] bpf: add __weak hook for allocating executable memory

On Mon, Nov 26, 2018 at 9:02 AM Edgecombe, Rick P
<rick.p.edgecombe@...el.com> wrote:
>
> On Fri, 2018-11-23 at 23:18 +0100, Ard Biesheuvel wrote:
> > By default, BPF uses module_alloc() to allocate executable memory,
> > but this is not necessary on all arches and potentially undesirable
> > on some of them.
> >
> > So break out the module_alloc() and module_memfree() calls into __weak
> > functions to allow them to be overridden in arch code.
> >
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > ---
>
> It looks like some of the architectures call module_alloc directly in their
> bpf_jit_compile implementations as well.

Ew, good catch. :P

-- 
Kees Cook