This consumes functionality exported in the previous patch. It does the main job of printing with BTF data. This is used in the following patch to provide a more readable output of a map's dump. It relies on json_writer to do json printing. Below is sample output where map keys are ints and values are of type struct A: typedef int int_type; enum E { E0, E1, }; struct B { int x; int y; }; struct A { int m; unsigned long long n; char o; int p[8]; int q[4][8]; enum E r; void *s; struct B t; const int u; int_type v; unsigned int w1: 3; unsigned int w2: 3; }; $ sudo bpftool map dump id 14 [{ "key": 0, "value": { "m": 1, "n": 2, "o": "c", "p": [15,16,17,18,15,16,17,18 ], "q": [[25,26,27,28,25,26,27,28 ],[35,36,37,38,35,36,37,38 ],[45,46,47,48,45,46,47,48 ],[55,56,57,58,55,56,57,58 ] ], "r": 1, "s": 0x7ffd80531cf8, "t": { "x": 5, "y": 10 }, "u": 100, "v": 20, "w1": 0x7, "w2": 0x3 } } ] This patch uses json's {} and [] to imply struct/union and array. More explicit information can be added later. For example, a command line option can be introduced to print whether a key or value is struct or union, name of a struct etc. This will however come at the expense of duplicating info when, for example, printing an array of structs. enums are printed as ints without their names. Signed-off-by: Okash Khawaja --- tools/bpf/bpftool/btf_dumper.c | 248 +++++++++++++++++++++++++++++++++++++++++ tools/bpf/bpftool/main.h | 15 ++ 2 files changed, 263 insertions(+) --- /dev/null +++ b/tools/bpf/bpftool/btf_dumper.c @@ -0,0 +1,248 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2018 Facebook */ + +#include +#include +#include /* for (FILE *) used by json_writer */ +#include +#include +#include + +#include "btf.h" +#include "json_writer.h" +#include "main.h" + +#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1) +#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK) +#define BITS_ROUNDDOWN_BYTES(bits) ((bits) >> 3) +#define BITS_ROUNDUP_BYTES(bits) \ + (BITS_ROUNDDOWN_BYTES(bits) + !!BITS_PER_BYTE_MASKED(bits)) + +static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id, + __u8 bit_offset, const void *data); + +static void btf_dumper_ptr(const void *data, json_writer_t *jw, + bool is_plain_text) +{ + if (is_plain_text) + jsonw_printf(jw, "%p", *((unsigned long *)data)); + else + jsonw_printf(jw, "%u", *((unsigned long *)data)); +} + +static int btf_dumper_modifier(const struct btf_dumper *d, __u32 type_id, + const void *data) +{ + int actual_type_id; + + actual_type_id = btf__resolve_type(d->btf, type_id); + if (actual_type_id < 0) + return actual_type_id; + + return btf_dumper_do_type(d, actual_type_id, 0, data); +} + +static void btf_dumper_enum(const void *data, json_writer_t *jw) +{ + jsonw_printf(jw, "%d", *(int *)data); +} + +static int btf_dumper_array(const struct btf_dumper *d, __u32 type_id, + const void *data) +{ + const struct btf_type *t = btf__type_by_id(d->btf, type_id); + struct btf_array *arr = (struct btf_array *)(t + 1); + long long elem_size; + int ret = 0; + __u32 i; + + elem_size = btf__resolve_size(d->btf, arr->type); + if (elem_size < 0) + return elem_size; + + jsonw_start_array(d->jw); + for (i = 0; i < arr->nelems; i++) { + ret = btf_dumper_do_type(d, arr->type, 0, + data + i * elem_size); + if (ret) + break; + } + + jsonw_end_array(d->jw); + return ret; +} + +static void btf_dumper_int_bits(__u32 int_type, __u8 bit_offset, + const void *data, json_writer_t *jw, + bool is_plain_text) +{ + int left_shift_bits, right_shift_bits; + int nr_bits = BTF_INT_BITS(int_type); + int total_bits_offset; + int bytes_to_copy; + int bits_to_copy; + __u64 print_num; + + total_bits_offset = bit_offset + BTF_INT_OFFSET(int_type); + data += BITS_ROUNDDOWN_BYTES(total_bits_offset); + bit_offset = BITS_PER_BYTE_MASKED(total_bits_offset); + bits_to_copy = bit_offset + nr_bits; + bytes_to_copy = BITS_ROUNDUP_BYTES(bits_to_copy); + + print_num = 0; + memcpy(&print_num, data, bytes_to_copy); +#ifdef __BIG_ENDIAN_BITFIELD + left_shift_bits = bit_offset; +#else + left_shift_bits = 64 - bits_to_copy; +#endif + right_shift_bits = 64 - nr_bits; + + print_num <<= left_shift_bits; + print_num >>= right_shift_bits; + if (is_plain_text) + jsonw_printf(jw, "0x%llx", print_num); + else + jsonw_printf(jw, "%llu", print_num); +} + +static int btf_dumper_int(const struct btf_type *t, __u8 bit_offset, + const void *data, json_writer_t *jw, + bool is_plain_text) +{ + __u32 *int_type; + __u32 nr_bits; + + int_type = (__u32 *)(t + 1); + nr_bits = BTF_INT_BITS(*int_type); + /* if this is bit field */ + if (bit_offset || BTF_INT_OFFSET(*int_type) || + BITS_PER_BYTE_MASKED(nr_bits)) { + btf_dumper_int_bits(*int_type, bit_offset, data, jw, + is_plain_text); + return 0; + } + + switch (BTF_INT_ENCODING(*int_type)) { + case 0: + if (BTF_INT_BITS(*int_type) == 64) + jsonw_printf(jw, "%lu", *(__u64 *)data); + else if (BTF_INT_BITS(*int_type) == 32) + jsonw_printf(jw, "%u", *(__u32 *)data); + else if (BTF_INT_BITS(*int_type) == 16) + jsonw_printf(jw, "%hu", *(__u16 *)data); + else if (BTF_INT_BITS(*int_type) == 8) + jsonw_printf(jw, "%hhu", *(__u8 *)data); + else + btf_dumper_int_bits(*int_type, bit_offset, data, jw, + is_plain_text); + break; + case BTF_INT_SIGNED: + if (BTF_INT_BITS(*int_type) == 64) + jsonw_printf(jw, "%ld", *(long long *)data); + else if (BTF_INT_BITS(*int_type) == 32) + jsonw_printf(jw, "%d", *(int *)data); + else if (BTF_INT_BITS(*int_type) == 16) + jsonw_printf(jw, "%hd", *(short *)data); + else if (BTF_INT_BITS(*int_type) == 8) + jsonw_printf(jw, "%hhd", *(char *)data); + else + btf_dumper_int_bits(*int_type, bit_offset, data, jw, + is_plain_text); + break; + case BTF_INT_CHAR: + if (isprint(*(char *)data)) + jsonw_printf(jw, "\"%c\"", *(char *)data); + else + if (is_plain_text) + jsonw_printf(jw, "0x%hhx", *(char *)data); + else + jsonw_printf(jw, "\"\\u00%02hhx\"", + *(char *)data); + break; + case BTF_INT_BOOL: + jsonw_bool(jw, *(int *)data); + break; + default: + /* shouldn't happen */ + return -EINVAL; + } + + return 0; +} + +static int btf_dumper_struct(const struct btf_dumper *d, __u32 type_id, + const void *data) +{ + const struct btf_type *t; + struct btf_member *m; + const void *data_off; + int ret = 0; + int i, vlen; + + t = btf__type_by_id(d->btf, type_id); + if (!t) + return -EINVAL; + + vlen = BTF_INFO_VLEN(t->info); + jsonw_start_object(d->jw); + m = (struct btf_member *)(t + 1); + + for (i = 0; i < vlen; i++) { + data_off = data + BITS_ROUNDDOWN_BYTES(m[i].offset); + jsonw_name(d->jw, btf__name_by_offset(d->btf, m[i].name_off)); + ret = btf_dumper_do_type(d, m[i].type, + BITS_PER_BYTE_MASKED(m[i].offset), + data_off); + if (ret) + break; + } + + jsonw_end_object(d->jw); + + return ret; +} + +static int btf_dumper_do_type(const struct btf_dumper *d, __u32 type_id, + __u8 bit_offset, const void *data) +{ + const struct btf_type *t = btf__type_by_id(d->btf, type_id); + + switch (BTF_INFO_KIND(t->info)) { + case BTF_KIND_INT: + return btf_dumper_int(t, bit_offset, data, d->jw, + d->is_plain_text); + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + return btf_dumper_struct(d, type_id, data); + case BTF_KIND_ARRAY: + return btf_dumper_array(d, type_id, data); + case BTF_KIND_ENUM: + btf_dumper_enum(data, d->jw); + return 0; + case BTF_KIND_PTR: + btf_dumper_ptr(data, d->jw, d->is_plain_text); + return 0; + case BTF_KIND_UNKN: + jsonw_printf(d->jw, "(unknown)"); + return 0; + case BTF_KIND_FWD: + /* map key or value can't be forward */ + jsonw_printf(d->jw, "(fwd-kind-invalid)"); + return -EINVAL; + case BTF_KIND_TYPEDEF: + case BTF_KIND_VOLATILE: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + return btf_dumper_modifier(d, type_id, data); + default: + jsonw_printf(d->jw, "(unsupported-kind"); + return -EINVAL; + } +} + +int btf_dumper_type(const struct btf_dumper *d, __u32 type_id, + const void *data) +{ + return btf_dumper_do_type(d, type_id, 0, data); +} --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -131,4 +131,19 @@ unsigned int get_page_size(void); unsigned int get_possible_cpus(void); const char *ifindex_to_bfd_name_ns(__u32 ifindex, __u64 ns_dev, __u64 ns_ino); +struct btf_dumper { + const struct btf *btf; + json_writer_t *jw; + bool is_plain_text; +}; + +/* btf_dumper_type - print data along with type information + * @d: an instance containing context for dumping types + * @type_id: index in btf->types array. this points to the type to be dumped + * @data: pointer the actual data, i.e. the values to be printed + * + * Returns zero on success and negative error code otherwise + */ +int btf_dumper_type(const struct btf_dumper *d, __u32 type_id, + const void *data); #endif