focal (8) bpftool-btf.8.gz

Provided by: linux-nvidia-tegra-5.15-tools-common_5.15.0-1027.27~20.04.1_all bug

NAME

       bpftool-btf - tool for inspection of BTF data

SYNOPSIS

          bpftool [OPTIONS] btf COMMAND

          OPTIONS := { { -j | --json } [{ -p | --pretty }] | {-d | --debug } | { -B | --base-btf } }

          COMMANDS := { dump | help }

BTF COMMANDS

       bpftool btf { show | list } [id BTF_ID]
       bpftool btf dump BTF_SRC [format FORMAT]
       bpftool btf help

       BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }
       FORMAT := { raw | c }
       MAP := { id MAP_ID | pinned FILE }
       PROG := { id PROG_ID | pinned FILE | tag PROG_TAG }

DESCRIPTION

          bpftool btf { show | list } [id BTF_ID]
                 Show  information  about  loaded  BTF  objects. If a BTF ID is specified, show information only
                 about given BTF object, otherwise list all BTF objects currently loaded on the system.

                 Since Linux 5.8 bpftool is able to discover information about processes  that  hold  open  file
                 descriptors  (FDs)  against  BTF  objects. On such kernels bpftool will automatically emit this
                 information as well.

          bpftool btf dump BTF_SRC
                 Dump BTF entries from a given BTF_SRC.

                 When id is specified, BTF object with that ID will be loaded and all its BTF types emitted.

                 When map is provided, it's  expected  that  map  has  associated  BTF  object  with  BTF  types
                 describing  key  and value. It's possible to select whether to dump only BTF type(s) associated
                 with key (key), value (value), both key and value (kv), or all BTF types present in  associated
                 BTF object (all). If not specified, kv is assumed.

                 When prog is provided, it's expected that program has associated BTF object with BTF types.

                 When  specifying  FILE,  an ELF file is expected, containing .BTF section with well-defined BTF
                 binary format data, typically produced by clang or pahole.

                 format option can be used to override default (raw) output format. Raw (raw)  or  C-syntax  (c)
                 output formats are supported.

          bpftool btf help
                 Print short help message.

OPTIONS

          -h, --help
                 Print short help message (similar to bpftool help).

          -V, --version
                 Print  version  number  (similar  to bpftool version), and optional features that were included
                 when bpftool was compiled. Optional features include linking  against  libbfd  to  provide  the
                 disassembler  for  JIT-ted  programs (bpftool prog dump jited) and usage of BPF skeletons (some
                 features like bpftool prog profile or showing pids associated to BPF objects may rely on it).

          -j, --json
                 Generate JSON output. For commands that cannot produce JSON, this option has no effect.

          -p, --pretty
                 Generate human-readable JSON output. Implies -j.

          -d, --debug
                 Print all logs available, even debug-level information. This includes logs from libbpf as  well
                 as from the verifier, when attempting to load programs.

          -B, --base-btf FILE
                 Pass  a  base  BTF  object.  Base  BTF  objects  are typically used with BTF objects for kernel
                 modules. To avoid duplicating all kernel symbols required by modules, BTF objects  for  modules
                 are  "split",  they  are  built incrementally on top of the kernel (vmlinux) BTF object. So the
                 base BTF reference should usually point to the kernel BTF.

                 When the main BTF object to process (for example, the module BTF to dump) is passed as a  FILE,
                 bpftool  attempts  to  autodetect  the  path  for  the  base object, and passing this option is
                 optional. When the main BTF object  is  passed  through  other  handles,  this  option  becomes
                 necessary.

EXAMPLES

       # bpftool btf dump id 1226

          [1] PTR '(anon)' type_id=2
          [2] STRUCT 'dummy_tracepoint_args' size=16 vlen=2
                  'pad' type_id=3 bits_offset=0
                  'sock' type_id=4 bits_offset=64
          [3] INT 'long long unsigned int' size=8 bits_offset=0 nr_bits=64 encoding=(none)
          [4] PTR '(anon)' type_id=5
          [5] FWD 'sock' fwd_kind=union

       This gives an example of default output for all supported BTF kinds.

       $ cat prog.c

          struct fwd_struct;

          enum my_enum {
                  VAL1 = 3,
                  VAL2 = 7,
          };

          typedef struct my_struct my_struct_t;

          struct my_struct {
                  const unsigned int const_int_field;
                  int bitfield_field: 4;
                  char arr_field[16];
                  const struct fwd_struct *restrict fwd_field;
                  enum my_enum enum_field;
                  volatile my_struct_t *typedef_ptr_field;
          };

          union my_union {
                  int a;
                  struct my_struct b;
          };

          struct my_struct struct_global_var __attribute__((section("data_sec"))) = {
                  .bitfield_field = 3,
                  .enum_field = VAL1,
          };
          int global_var __attribute__((section("data_sec"))) = 7;

          __attribute__((noinline))
          int my_func(union my_union *arg1, int arg2)
          {
                  static int static_var __attribute__((section("data_sec"))) = 123;
                  static_var++;
                  return static_var;
          }

       $ bpftool btf dump file prog.o

          [1] PTR '(anon)' type_id=2
          [2] UNION 'my_union' size=48 vlen=2
                  'a' type_id=3 bits_offset=0
                  'b' type_id=4 bits_offset=0
          [3] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED
          [4] STRUCT 'my_struct' size=48 vlen=6
                  'const_int_field' type_id=5 bits_offset=0
                  'bitfield_field' type_id=3 bits_offset=32 bitfield_size=4
                  'arr_field' type_id=8 bits_offset=40
                  'fwd_field' type_id=10 bits_offset=192
                  'enum_field' type_id=14 bits_offset=256
                  'typedef_ptr_field' type_id=15 bits_offset=320
          [5] CONST '(anon)' type_id=6
          [6] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none)
          [7] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED
          [8] ARRAY '(anon)' type_id=7 index_type_id=9 nr_elems=16
          [9] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
          [10] RESTRICT '(anon)' type_id=11
          [11] PTR '(anon)' type_id=12
          [12] CONST '(anon)' type_id=13
          [13] FWD 'fwd_struct' fwd_kind=union
          [14] ENUM 'my_enum' size=4 vlen=2
                  'VAL1' val=3
                  'VAL2' val=7
          [15] PTR '(anon)' type_id=16
          [16] VOLATILE '(anon)' type_id=17
          [17] TYPEDEF 'my_struct_t' type_id=4
          [18] FUNC_PROTO '(anon)' ret_type_id=3 vlen=2
                  'arg1' type_id=1
                  'arg2' type_id=3
          [19] FUNC 'my_func' type_id=18
          [20] VAR 'struct_global_var' type_id=4, linkage=global-alloc
          [21] VAR 'global_var' type_id=3, linkage=global-alloc
          [22] VAR 'my_func.static_var' type_id=3, linkage=static
          [23] DATASEC 'data_sec' size=0 vlen=3
                  type_id=20 offset=0 size=48
                  type_id=21 offset=0 size=4
                  type_id=22 offset=52 size=4

       The  following  commands  print BTF types associated with specified map's key, value, both key and value,
       and all BTF types, respectively. By default, both key and value types will be printed.

       # bpftool btf dump map id 123 key

          [39] TYPEDEF 'u32' type_id=37

       # bpftool btf dump map id 123 value

          [86] PTR '(anon)' type_id=87

       # bpftool btf dump map id 123 kv

          [39] TYPEDEF 'u32' type_id=37
          [86] PTR '(anon)' type_id=87

       # bpftool btf dump map id 123 all

          [1] PTR '(anon)' type_id=0
          .
          .
          .
          [2866] ARRAY '(anon)' type_id=52 index_type_id=51 nr_elems=4

       All the standard ways to specify map or program are supported:

       # bpftool btf dump map id 123

       # bpftool btf dump map pinned /sys/fs/bpf/map_name

       # bpftool btf dump prog id 456

       # bpftool btf dump prog tag b88e0a09b1d9759d

       # bpftool btf dump prog pinned /sys/fs/bpf/prog_name

       # bpftool btf dump file /sys/kernel/btf/i2c_smbus
       (or)
       # I2C_SMBUS_ID=$(bpftool btf show -p | jq '.[] | select(.name=="i2c_smbus").id')
       # bpftool btf dump id ${I2C_SMBUS_ID} -B /sys/kernel/btf/vmlinux

          [104848] STRUCT 'i2c_smbus_alert' size=40 vlen=2
                  'alert' type_id=393 bits_offset=0
                  'ara' type_id=56050 bits_offset=256
          [104849] STRUCT 'alert_data' size=12 vlen=3
                  'addr' type_id=16 bits_offset=0
                  'type' type_id=56053 bits_offset=32
                  'data' type_id=7 bits_offset=64
          [104850] PTR '(anon)' type_id=104848
          [104851] PTR '(anon)' type_id=104849
          [104852] FUNC 'i2c_register_spd' type_id=84745 linkage=static
          [104853] FUNC 'smbalert_driver_init' type_id=1213 linkage=static
          [104854] FUNC_PROTO '(anon)' ret_type_id=18 vlen=1
                  'ara' type_id=56050
          [104855] FUNC 'i2c_handle_smbus_alert' type_id=104854 linkage=static
          [104856] FUNC 'smbalert_remove' type_id=104854 linkage=static
          [104857] FUNC_PROTO '(anon)' ret_type_id=18 vlen=2
                  'ara' type_id=56050
                  'id' type_id=56056
          [104858] FUNC 'smbalert_probe' type_id=104857 linkage=static
          [104859] FUNC 'smbalert_work' type_id=9695 linkage=static
          [104860] FUNC 'smbus_alert' type_id=71367 linkage=static
          [104861] FUNC 'smbus_do_alert' type_id=84827 linkage=static

SEE ALSO

          bpf(2),   bpf-helpers(7),   bpftool(8),   bpftool-cgroup(8),    bpftool-feature(8),    bpftool-gen(8),
          bpftool-iter(8),  bpftool-link(8),  bpftool-map(8),  bpftool-net(8), bpftool-perf(8), bpftool-prog(8),
          bpftool-struct_ops(8)

                                                                                                  BPFTOOL-BTF(8)