On Fri, May 7, 2021 at 8:49 PM Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > From: Alexei Starovoitov <ast@xxxxxxxxxx> > > The BPF program loading process performed by libbpf is quite complex > and consists of the following steps: > "open" phase: > - parse elf file and remember relocations, sections > - collect externs and ksyms including their btf_ids in prog's BTF > - patch BTF datasec (since llvm couldn't do it) > - init maps (old style map_def, BTF based, global data map, kconfig map) > - collect relocations against progs and maps > "load" phase: > - probe kernel features > - load vmlinux BTF > - resolve externs (kconfig and ksym) > - load program BTF > - init struct_ops > - create maps > - apply CO-RE relocations > - patch ld_imm64 insns with src_reg=PSEUDO_MAP, PSEUDO_MAP_VALUE, PSEUDO_BTF_ID > - reposition subprograms and adjust call insns > - sanitize and load progs > > During this process libbpf does sys_bpf() calls to load BTF, create maps, > populate maps and finally load programs. > Instead of actually doing the syscalls generate a trace of what libbpf > would have done and represent it as the "loader program". > The "loader program" consists of single map with: > - union bpf_attr(s) > - BTF bytes > - map value bytes > - insns bytes > and single bpf program that passes bpf_attr(s) and data into bpf_sys_bpf() helper. > Executing such "loader program" via bpf_prog_test_run() command will > replay the sequence of syscalls that libbpf would have done which will result > the same maps created and programs loaded as specified in the elf file. > The "loader program" removes libelf and majority of libbpf dependency from > program loading process. > > kconfig, typeless ksym, struct_ops and CO-RE are not supported yet. > > The order of relocate_data and relocate_calls had to change, so that > bpf_gen__prog_load() can see all relocations for a given program with > correct insn_idx-es. > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > --- LGTM. Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx> > tools/lib/bpf/Build | 2 +- > tools/lib/bpf/bpf_gen_internal.h | 40 ++ > tools/lib/bpf/gen_loader.c | 657 +++++++++++++++++++++++++++++++ > tools/lib/bpf/libbpf.c | 224 +++++++++-- > tools/lib/bpf/libbpf.h | 12 + > tools/lib/bpf/libbpf.map | 1 + > tools/lib/bpf/libbpf_internal.h | 2 + > tools/lib/bpf/skel_internal.h | 116 ++++++ > 8 files changed, 1022 insertions(+), 32 deletions(-) > create mode 100644 tools/lib/bpf/bpf_gen_internal.h > create mode 100644 tools/lib/bpf/gen_loader.c > create mode 100644 tools/lib/bpf/skel_internal.h > [...]
