[PATCH v2 0/3] libbpf/bpftool: support merging split BTFs

[Josef Bacik <josef@toxicpanda.com>]

v1: https://lore.kernel.org/bpf/cover.1771605821.git.josef@toxicpanda.com/

v1->v2:
- Added a btf__dedup() call to btf__add_btf() to ensure that we don't have
  duplicate types in the merged BTF.

--- Original email ---

Hello,

I'm extending systing to do introspection on vfio devices, which requires having
the structs I need from the kernel available in userspace. Normally these are
loadable modules, but in the case of vfio there's multiple structs across
multiple modules. Normally you'd do the following to generate your vmlinux.h
with a module

bpftool btf dump file /sys/kernel/btf/<module> format c \
	--base /sys/kernel/btf/vmlinux > vmlinux.h

but if you need multiple modules you have to hack together multiple dumps and
merge them together. This patch series adds support for merging multiple BTF
sources together, so you can do

bpftool btf dump file /sys/kernel/btf/<module1> \
	file /sys/kernel/btf/<module2> format c \
	--base /sys/kernel/btf/vmlinux > vmlinux.h

I tested this with my usecase and it works. Thanks,

Josef

Josef Bacik (3):
  libbpf: support appending split BTF in btf__add_btf()
  bpftool: support merging multiple module BTFs in btf dump
  selftests/bpf: add test for btf__add_btf() with split BTF sources

 tools/bpf/bpftool/btf.c                       | 135 ++++++++++++++++--
 tools/lib/bpf/btf.c                           |  38 +++--
 .../selftests/bpf/prog_tests/btf_write.c      |  89 ++++++++++++
 3 files changed, 241 insertions(+), 21 deletions(-)

-- 
2.53.0