This set enables kernel module function calls, and also modifies verifier logic to permit invalid kernel function calls as long as they are pruned as part of dead code elimination. This is done to provide better runtime portability for BPF objects, which can conditionally disable parts of code that are pruned later by the verifier (e.g. const volatile vars, kconfig options). libbpf modifications are made along with kernel changes to support module function calls. The set includes gen_loader support for emitting kfunc relocations. It also converts TCP congestion control objects to use the module kfunc support instead of relying on IS_BUILTIN ifdef. Changelog: ---------- RFC v1 -> v2 v1: https://lore.kernel.org/bpf/20210830173424.1385796-1-memxor@xxxxxxxxx * Address comments from Alexei * Reuse fd_array instead of introducing kfunc_btf_fds array * Take btf and module reference as needed, instead of preloading * Add BTF_KIND_FUNC relocation support to gen_loader infrastructure * Address comments from Andrii * Drop hashmap in libbpf for finding index of existing BTF in fd_array * Preserve invalid kfunc calls only when the symbol is weak * Adjust verifier selftests Kumar Kartikeya Dwivedi (10): bpf: Introduce BPF support for kernel module function calls bpf: Be conservative while processing invalid kfunc calls bpf: btf: Introduce helpers for dynamic BTF set registration tools: Allow specifying base BTF file in resolve_btfids bpf: Enable TCP congestion control kfunc from modules bpf: Bump MAX_BPF_STACK size to 768 bytes libbpf: Support kernel module function calls libbpf: Resolve invalid weak kfunc calls with imm = 0, off = 0 libbpf: Update gen_loader to emit BTF_KIND_FUNC relocations bpf, selftests: Add basic test for module kfunc call include/linux/bpf.h | 8 +- include/linux/bpf_verifier.h | 2 + include/linux/bpfptr.h | 1 + include/linux/btf.h | 38 ++++ include/linux/filter.h | 4 +- kernel/bpf/btf.c | 56 +++++ kernel/bpf/core.c | 2 + kernel/bpf/verifier.c | 200 ++++++++++++++++-- kernel/trace/bpf_trace.c | 1 + net/bpf/test_run.c | 2 +- net/ipv4/bpf_tcp_ca.c | 36 +--- net/ipv4/tcp_bbr.c | 28 ++- net/ipv4/tcp_cubic.c | 26 ++- net/ipv4/tcp_dctcp.c | 26 ++- scripts/Makefile.modfinal | 1 + tools/bpf/resolve_btfids/main.c | 19 +- tools/lib/bpf/bpf.c | 1 + tools/lib/bpf/bpf_gen_internal.h | 12 +- tools/lib/bpf/gen_loader.c | 93 +++++++- tools/lib/bpf/libbpf.c | 81 +++++-- tools/lib/bpf/libbpf_internal.h | 1 + tools/testing/selftests/bpf/Makefile | 1 + .../selftests/bpf/bpf_testmod/bpf_testmod.c | 23 +- .../selftests/bpf/prog_tests/ksyms_module.c | 13 +- .../bpf/prog_tests/ksyms_module_libbpf.c | 18 ++ .../selftests/bpf/progs/test_ksyms_module.c | 9 + .../bpf/progs/test_ksyms_module_libbpf.c | 35 +++ tools/testing/selftests/bpf/verifier/calls.c | 22 +- .../selftests/bpf/verifier/raw_stack.c | 4 +- .../selftests/bpf/verifier/stack_ptr.c | 6 +- .../testing/selftests/bpf/verifier/var_off.c | 4 +- 31 files changed, 661 insertions(+), 112 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c create mode 100644 tools/testing/selftests/bpf/progs/test_ksyms_module_libbpf.c -- 2.33.0
