linux-kernel - Re: [PATCH 0/4] bpf: permit JIT allocations to be served outside the module region

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Message-ID: <CAH3MdRX5MYv-QQGj25APd4-17syF3Vc_f0AWpEgUoL46qbHrGQ@mail.gmail.com>
Date:   Sun, 18 Nov 2018 07:48:59 +0000
From:   Y Song <ys114321@...il.com>
To:     ard.biesheuvel@...aro.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        rick.p.edgecombe@...el.com, eric.dumazet@...il.com,
        jannh@...gle.com, Kees Cook <keescook@...omium.org>,
        jeyu@...nel.org, arnd@...db.de, catalin.marinas@....com,
        will.deacon@....com, mark.rutland@....com, ralf@...ux-mips.org,
        paul.burton@...s.com, jhogan@...nel.org, benh@...nel.crashing.org,
        paulus@...ba.org, mpe@...erman.id.au,
        David Miller <davem@...emloft.net>,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH 0/4] bpf: permit JIT allocations to be served outside the
 module region

On Sat, Nov 17, 2018 at 6:58 PM Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
>
> On arm64, modules are allocated from a 128 MB window which is close to
> the core kernel, so that relative direct branches are guaranteed to be
> in range (except in some KASLR configurations). Also, module_alloc()
> is in charge of allocating KASAN shadow memory when running with KASAN
> enabled.
>
> This means that the way BPF reuses module_alloc()/module_memfree() is
> undesirable on arm64 (and potentially other architectures as well),
> and so this series refactors BPF's use of those functions to permit
> architectures to change this behavior.
>
> Patch #1 fixes a bug introduced during the merge window, where the new
> alloc/free tracking does not account for memory that is freed by some
> arch code.
>
> Patch #2 refactors the freeing path so that architectures can switch to
> something other than module_memfree().
>
> Patch #3 does the same for module_alloc().
>
> Patch #4 implements the new alloc/free overrides for arm64

Except a minor comment, the whole patch set looks good to me.
Acked-by: Yonghong Song <yhs@...com>

>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Jann Horn <jannh@...gle.com>
> Cc: Kees Cook <keescook@...omium.org>
>
> Cc: Jessica Yu <jeyu@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: Paul Burton <paul.burton@...s.com>
> Cc: James Hogan <jhogan@...nel.org>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Cc: linux-mips@...ux-mips.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Cc: sparclinux@...r.kernel.org
> Cc: netdev@...r.kernel.org
>
> Ard Biesheuvel (4):
>   bpf: account for freed JIT allocations in arch code
>   net/bpf: refactor freeing of executable allocations
>   bpf: add __weak hook for allocating executable memory
>   arm64/bpf: don't allocate BPF JIT programs in module memory
>
>  arch/arm64/net/bpf_jit_comp.c     | 11 ++++++++++
>  arch/mips/net/bpf_jit.c           |  7 ++-----
>  arch/powerpc/net/bpf_jit_comp.c   |  7 ++-----
>  arch/powerpc/net/bpf_jit_comp64.c | 12 +++--------
>  arch/sparc/net/bpf_jit_comp_32.c  |  7 ++-----
>  kernel/bpf/core.c                 | 22 ++++++++++----------
>  6 files changed, 31 insertions(+), 35 deletions(-)
>
> --
> 2.17.1
>