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  6. 05 Dec, 2021 1 commit
    • Alexei Starovoitov's avatar
      bpftool: Add debug mode for gen_loader. · 942df4dc
      Alexei Starovoitov authored
      Make -d flag functional for gen_loader style program loading.
      
      For example:
      $ bpftool prog load -L -d test_d_path.o
      ... // will print:
      libbpf: loading ./test_d_path.o
      libbpf: elf: section(3) fentry/security_inode_getattr, size 280, link 0, flags 6, type=1
      ...
      libbpf: prog 'prog_close': found data map 0 (test_d_p.bss, sec 7, off 0) for insn 30
      libbpf: gen: load_btf: size 5376
      libbpf: gen: map_create: test_d_p.bss idx 0 type 2 value_type_id 118
      libbpf: map 'test_d_p.bss': created successfully, fd=0
      libbpf: gen: map_update_elem: idx 0
      libbpf: sec 'fentry/filp_close': found 1 CO-RE relocations
      libbpf: record_relo_core: prog 1 insn[15] struct file 0:1 final insn_idx 15
      libbpf: gen: prog_load: type 26 insns_cnt 35 progi_idx 0
      libbpf: gen: find_attach_tgt security_inode_getattr 12
      libbpf: gen: prog_load: type 26 insns_cnt 37 progi_idx 1
      libbpf: gen: find_attach_tgt filp_close 12
      libbpf: gen: finish 0
      ... // at this point libbpf finished generating loader program
         0: (bf) r6 = r1
         1: (bf) r1 = r10
         2: (07) r1 += -136
         3: (b7) r2 = 136
         4: (b7) r3 = 0
         5: (85) call bpf_probe_read_kernel#113
         6: (05) goto pc+104
      ... // this is the assembly dump of the loader program
       390: (63) *(u32 *)(r6 +44) = r0
       391: (18) r1 = map[idx:0]+5584
       393: (61) r0 = *(u32 *)(r1 +0)
       394: (63) *(u32 *)(r6 +24) = r0
       395: (b7) r0 = 0
       396: (95) exit
      err 0  // the loader program was loaded and executed successfully
      (null)
      func#0 @0
      ...  // CO-RE in the kernel logs:
      CO-RE relocating STRUCT file: found target candidate [500]
      prog '': relo #0: kind <byte_off> (0), spec is [8] STRUCT file.f_path (0:1 @ offset 16)
      prog '': relo #0: matching candidate #0 [500] STRUCT file.f_path (0:1 @ offset 16)
      prog '': relo #0: patched insn #15 (ALU/ALU64) imm 16 -> 16
      vmlinux_cand_cache:[11]file(500),
      module_cand_cache:
      ... // verifier logs when it was checking test_d_path.o program:
      R1 type=ctx expected=fp
      0: R1=ctx(id=0,off=0,imm=0) R10=fp0
      ; int BPF_PROG(prog_close, struct file *file, void *id)
      0: (79) r6 = *(u64 *)(r1 +0)
      func 'filp_close' arg0 has btf_id 500 type STRUCT 'file'
      1: R1=ctx(id=0,off=0,imm=0) R6_w=ptr_file(id=0,off=0,imm=0) R10=fp0
      ; pid_t pid = bpf_get_current_pid_tgid() >> 32;
      1: (85) call bpf_get_current_pid_tgid#14
      
      ... // if there are multiple programs being loaded by the loader program
      ... // only the last program in the elf file will be printed, since
      ... // the same verifier log_buf is used for all PROG_LOAD commands.
      Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
      Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
      Link: https://lore.kernel.org/bpf/20211204194623.27779-1-alexei.starovoitov@gmail.com
      942df4dc
  7. 04 Dec, 2021 1 commit
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