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

[Y Song <ys114321@gmail.com>]

On Sat, Nov 17, 2018 at 6:58 PM Ard Biesheuvel
<ard.biesheuvel@linaro.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@fb.com>

>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
> Cc: Jann Horn <jannh@google.com>
> Cc: Kees Cook <keescook@chromium.org>
>
> Cc: Jessica Yu <jeyu@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Paul Burton <paul.burton@mips.com>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-mips@linux-mips.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: sparclinux@vger.kernel.org
> Cc: netdev@vger.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
>