This patch series extends the previously added __ksym externs with btf support.
Right now the __ksym externs are treated as pure 64-bit scalar value. Libbpf replaces ld_imm64 insn of __ksym by its kernel address at load time. This patch series extend those externs with their btf info. Note that btf support for __ksym must come with the kernel btf that has VARs encoded to work properly. The corresponding chagnes in pahole is available at [1].
The first 5 patches in this series add support for general kernel global variables, which includes verifier checking (01/08), libbpf type checking (03/08) and btf_id resolving (04/08).
The last 3 patches extends that capability further by introducing a helper bpf_per_cpu_ptr(), which allows accessing kernel percpu vars correctly (06/08).
The tests of this feature were performed against the extended pahole. For kernel btf that does not have VARs encoded, the selftests will be skipped.
[1] https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=f3d9054ba8...
rfc -> v1: - Encode VAR's btf_id for PSEUDO_BTF_ID. - More checks in verifier. Checking the btf_id passed as PSEUDO_BTF_ID is valid VAR, its name and type. - Checks in libbpf on type compatibility of ksyms. - Add bpf_per_cpu_ptr() to access kernel percpu vars. Introduced new ARG and RET types for this helper.
Hao Luo (8): bpf: Introduce pseudo_btf_id bpf: Propagate BPF_PSEUDO_BTF_ID to uapi headers in /tools bpf: Introduce help function to validate ksym's type. bpf/libbpf: BTF support for typed ksyms bpf/selftests: ksyms_btf to test typed ksyms bpf: Introduce bpf_per_cpu_ptr() bpf: Propagate bpf_per_cpu_ptr() to /tools bpf/selftests: Test for bpf_per_cpu_ptr()
include/linux/bpf.h | 3 + include/linux/btf.h | 26 +++ include/uapi/linux/bpf.h | 52 +++++- kernel/bpf/btf.c | 25 --- kernel/bpf/verifier.c | 128 ++++++++++++- kernel/trace/bpf_trace.c | 18 ++ tools/include/uapi/linux/bpf.h | 53 +++++- tools/lib/bpf/btf.c | 171 ++++++++++++++++++ tools/lib/bpf/btf.h | 2 + tools/lib/bpf/libbpf.c | 130 +++++++++++-- .../selftests/bpf/prog_tests/ksyms_btf.c | 81 +++++++++ .../selftests/bpf/progs/test_ksyms_btf.c | 36 ++++ 12 files changed, 665 insertions(+), 60 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_btf.c create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_btf.c