[RFC,bpf,0/2] bpf: kernel CO-RE relocation

Message

Matteo Croce Sept. 9, 2021, 1:31 p.m. UTC

From: Matteo Croce <[e-mail]>

This series is a preliminary work to move the CO-RE relocations in the kernel.
This is the first step to have signed BPF files, since userspace instruction
patching makes any verification ineffective.

The first patch just copies the relocation code from tools/lib/bpf/,
the second one refactors the whole code so to build it in kernel.
It builds with a single warning, which can be suppressed by switching to
dynamic allocation:

  kernel/bpf/relo_core.c: In function 'bpf_core_apply_relo_insn':
  kernel/bpf/relo_core.c:1457:1: warning: the frame size of 2776 bytes is larger than 1024 bytes [-Wframe-larger-than=]

To really use this code and do the the relocations done in kernel, we will
need an API to pass the relocation informations along the BPF file, so don't
consider this patches for inclusion, but just as a first step toward the
full work.

Matteo Croce (2):
  btf: copy relo_core from tools to kernel
  btf: adapt relo_core for kernel compilation

 include/linux/btf.h    |   65 ++
 kernel/bpf/Makefile    |    1 +
 kernel/bpf/btf.c       |   45 +-
 kernel/bpf/relo_core.c | 1457 ++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/relo_core.h |  100 +++
 5 files changed, 1630 insertions(+), 38 deletions(-)
 create mode 100644 kernel/bpf/relo_core.c
 create mode 100644 kernel/bpf/relo_core.h