Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH bpf-next 2/3] bpf: btf: add btf json print functionality | Date | Wed, 20 Jun 2018 23:14:33 +0000 |
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> On Jun 20, 2018, at 1:30 PM, Okash Khawaja <osk@fb.com> wrote: > > 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 -p 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": 0x7ffff6f70568, > "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 <osk@fb.com> > Acked-by: Martin KaFai Lau <kafai@fb.com> > > --- > tools/bpf/bpftool/btf_dumper.c | 247 +++++++++++++++++++++++++++++++++++++++++ > tools/bpf/bpftool/btf_dumper.h | 18 ++ > 2 files changed, 265 insertions(+) > > --- /dev/null > +++ b/tools/bpf/bpftool/btf_dumper.c > @@ -0,0 +1,247 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* Copyright (c) 2018 Facebook */ > + > +#include <linux/btf.h> > +#include <linux/err.h> > +#include <stdio.h> /* for (FILE *) used by json_writer */ > +#include <linux/bitops.h> > +#include <string.h> > +#include <ctype.h> > + > +#include "btf.h" > +#include "json_writer.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 *btf, uint32_t type_id, > + uint8_t bit_offset, const void *data, json_writer_t *jw); > + > +static void btf_dumper_ptr(const void *data, json_writer_t *jw) > +{ > + jsonw_printf(jw, "%p", *((uintptr_t *)data)); > +} > + > +static int btf_dumper_modifier(const struct btf *btf, uint32_t type_id, > + const void *data, json_writer_t *jw) > +{ > + int32_t actual_type_id = btf__resolve_type(btf, type_id); > + int ret; > + > + if (actual_type_id < 0) > + return actual_type_id; > + > + ret = btf_dumper_do_type(btf, actual_type_id, 0, data, jw); > + > + return ret; > +} > + > +static void btf_dumper_enum(const void *data, json_writer_t *jw) > +{ > + jsonw_printf(jw, "%d", *((int32_t *)data)); > +} > + > +static int btf_dumper_array(const struct btf *btf, uint32_t type_id, > + const void *data, json_writer_t *jw) > +{ > + const struct btf_type *t = btf__type_by_id(btf, type_id); > + struct btf_array *arr = (struct btf_array *)(t + 1); > + int64_t elem_size; > + uint32_t i; > + int ret; > + > + elem_size = btf__resolve_size(btf, arr->type); > + if (elem_size < 0) > + return elem_size; > + > + jsonw_start_array(jw); > + for (i = 0; i < arr->nelems; i++) { > + ret = btf_dumper_do_type(btf, arr->type, 0, > + data + (i * elem_size), jw); > + if (ret) > + return ret;
Shall we call jsonw_end_array() before return here?
> + } > + > + jsonw_end_array(jw); > + > + return 0; > +} > + > +static void btf_dumper_int_bits(uint32_t int_type, uint8_t bit_offset, > + const void *data, json_writer_t *jw) > +{ > + uint16_t total_bits_offset; > + uint32_t bits = BTF_INT_BITS(int_type); > + uint16_t bytes_to_copy; > + uint16_t bits_to_copy; > + uint8_t upper_bits; > + union { > + uint64_t u64_num; > + uint8_t u8_nums[8]; > + } 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 = bits + bit_offset; > + bytes_to_copy = BITS_ROUNDUP_BYTES(bits_to_copy); > + > + print_num.u64_num = 0; > + memcpy(&print_num.u64_num, data, bytes_to_copy); > + > + upper_bits = BITS_PER_BYTE_MASKED(bits_to_copy); > + if (upper_bits) { > + uint8_t mask = (1 << upper_bits) - 1; > + > + print_num.u8_nums[bytes_to_copy - 1] &= mask; > + } > + > + print_num.u64_num >>= bit_offset; > + > + jsonw_printf(jw, "0x%llx", print_num.u64_num); > +} > + > +static int btf_dumper_int(const struct btf_type *t, uint8_t bit_offset, > + const void *data, json_writer_t *jw) > +{ > + uint32_t *int_type = (uint32_t *)(t + 1); > + uint32_t bits = BTF_INT_BITS(*int_type); > + int ret = 0; > + > + /* if this is bit field */ > + if (bit_offset || BTF_INT_OFFSET(*int_type) || > + BITS_PER_BYTE_MASKED(bits)) { > + btf_dumper_int_bits(*int_type, bit_offset, data, jw); > + return ret; > + } > + > + switch (BTF_INT_ENCODING(*int_type)) { > + case 0: > + if (BTF_INT_BITS(*int_type) == 64) > + jsonw_printf(jw, "%lu", *((uint64_t *)data)); > + else if (BTF_INT_BITS(*int_type) == 32) > + jsonw_printf(jw, "%u", *((uint32_t *)data)); > + else if (BTF_INT_BITS(*int_type) == 16) > + jsonw_printf(jw, "%hu", *((uint16_t *)data)); > + else if (BTF_INT_BITS(*int_type) == 8) > + jsonw_printf(jw, "%hhu", *((uint8_t *)data)); > + else > + btf_dumper_int_bits(*int_type, bit_offset, data, jw); > + break; > + case BTF_INT_SIGNED: > + if (BTF_INT_BITS(*int_type) == 64) > + jsonw_printf(jw, "%ld", *((int64_t *)data)); > + else if (BTF_INT_BITS(*int_type) == 32) > + jsonw_printf(jw, "%d", *((int32_t *)data)); > + else if (BTF_INT_BITS(*int_type) == 16) > + jsonw_printf(jw, "%hd", *((int16_t *)data)); > + else if (BTF_INT_BITS(*int_type) == 8) > + jsonw_printf(jw, "%hhd", *((int8_t *)data)); > + else > + btf_dumper_int_bits(*int_type, bit_offset, data, jw); > + break; > + case BTF_INT_CHAR: > + if (*((char *)data) == '\0') > + jsonw_null(jw); > + else if (isprint(*((char *)data))) > + jsonw_printf(jw, "\"%c\"", *((char *)data)); > + else > + jsonw_printf(jw, "%hhx", *((char *)data)); > + break; > + case BTF_INT_BOOL: > + jsonw_bool(jw, *((int *)data)); > + break; > + default: > + /* shouldn't happen */ > + ret = -EINVAL; > + break; > + } > + > + return ret; > +} > + > +static int btf_dumper_struct(const struct btf *btf, uint32_t type_id, > + const void *data, json_writer_t *jw) > +{ > + const struct btf_type *t = btf__type_by_id(btf, type_id); > + struct btf_member *m; > + int ret = 0; > + int i, vlen; > + > + if (t == NULL) > + return -EINVAL; > + > + vlen = BTF_INFO_VLEN(t->info); > + jsonw_start_object(jw); > + m = (struct btf_member *)(t + 1); > + > + for (i = 0; i < vlen; i++) { > + jsonw_name(jw, btf__name_by_offset(btf, m[i].name_off)); > + ret = btf_dumper_do_type(btf, m[i].type, > + BITS_PER_BYTE_MASKED(m[i].offset), > + data + BITS_ROUNDDOWN_BYTES(m[i].offset), jw); > + if (ret) > + return ret;
Shall we call jsonw_end_object() before return here?
> + } > + > + jsonw_end_object(jw); > + > + return 0; > +} > + > +static int btf_dumper_do_type(const struct btf *btf, uint32_t type_id, > + uint8_t bit_offset, const void *data, json_writer_t *jw) > +{ > + const struct btf_type *t = btf__type_by_id(btf, type_id); > + int ret = 0; > + > + switch (BTF_INFO_KIND(t->info)) { > + case BTF_KIND_INT: > + ret = btf_dumper_int(t, bit_offset, data, jw); > + break; > + case BTF_KIND_STRUCT: > + case BTF_KIND_UNION: > + ret = btf_dumper_struct(btf, type_id, data, jw); > + break; > + case BTF_KIND_ARRAY: > + ret = btf_dumper_array(btf, type_id, data, jw); > + break; > + case BTF_KIND_ENUM: > + btf_dumper_enum(data, jw); > + break; > + case BTF_KIND_PTR: > + btf_dumper_ptr(data, jw); > + break; > + case BTF_KIND_UNKN: > + jsonw_printf(jw, "(unknown)"); > + break; > + case BTF_KIND_FWD: > + /* map key or value can't be forward */ > + ret = -EINVAL; > + break; > + case BTF_KIND_TYPEDEF: > + case BTF_KIND_VOLATILE: > + case BTF_KIND_CONST: > + case BTF_KIND_RESTRICT: > + ret = btf_dumper_modifier(btf, type_id, data, jw); > + break; > + default: > + jsonw_printf(jw, "(unsupported-kind");
"(unsupported-kind)" (missing ')').
> + ret = -EINVAL; > + break; > + } > + > + return ret; > +} > + > +int32_t btf_dumper_type(const struct btf *btf, json_writer_t *jw, > + uint32_t type_id, const void *data) > +{ > + if (!jw) > + return -EINVAL; > + > + return btf_dumper_do_type(btf, type_id, 0, data, jw); nit: btf_dumper_do_type() returns int, while btf_dumper_type() returns int32_t. This should not matter though.
> +} > --- /dev/null > +++ b/tools/bpf/bpftool/btf_dumper.h > @@ -0,0 +1,18 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* Copyright (c) 2018 Facebook */ > + > +#ifndef BTF_DUMPER_H > +#define BTF_DUMPER_H > + > +/* btf_dumper_type - json print data along with type information > + * @btf: btf instance initialised via btf__new() > + * @jw: json writer used for printing > + * @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 > + */ > +int32_t btf_dumper_type(const struct btf *btf, json_writer_t *jw, > + uint32_t type_id, void *data); > + > +#endif >
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