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bpf: btf: add btf print functionality

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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 <osk@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Okash Khawaja 2018-07-13 21:57:03 -07:00 committed by Daniel Borkmann
parent 92b57121ca
commit b12d6ec097
2 changed files with 266 additions and 0 deletions
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251
tools/bpf/bpftool/btf_dumper.c Normal file
View File

@ -0,0 +1,251 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018 Facebook */
#include <ctype.h>
#include <stdio.h> /* for (FILE *) used by json_writer */
#include <string.h>
#include <asm/byteorder.h>
#include <linux/bitops.h>
#include <linux/btf.h>
#include <linux/err.h>
#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);
#if defined(__BIG_ENDIAN_BITFIELD)
left_shift_bits = bit_offset;
#elif defined(__LITTLE_ENDIAN_BITFIELD)
left_shift_bits = 64 - bits_to_copy;
#else
#error neither big nor little endian
#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);
}

15
tools/bpf/bpftool/main.h
View File

@ -150,4 +150,19 @@ 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