[PATCH v2 0/2] bpf: permit JIT allocations to be served outside the module region

[Ard Biesheuvel]

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 breaks out the module_alloc() and module_memfree() calls into
__weak functions so they can be overridden.

Patch #4 implements the new alloc/free overrides for arm64

Changes since v1:
- Drop misguided attempt to 'fix' and refactor the free path. Instead,
  just add another __weak wrapper for the invocation of module_memfree()

Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>

Cc: Jessica Yu <jeyu@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx

Ard Biesheuvel (2):
  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 | 10 ++++++++++
 kernel/bpf/core.c             | 14 ++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

-- 
2.17.1