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28b93c6449
linux/tools/lib/bpf/btf.c
Andrii Nakryiko 28b93c6449 libbpf: Clean up and improve CO-RE reloc logging 
Add logging of local/target type kind (struct/union/typedef/etc). Preserve
unresolved root type ID (for cases of typedef). Improve the format of CO-RE
reloc spec output format to contain only relevant and succinct info.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200818223921.2911963-3-andriin@fb.com
2020-08-18 18:12:45 -07:00

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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/* Copyright (c) 2018 Facebook */
#include <endian.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/utsname.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/btf.h>
#include <gelf.h>
#include "btf.h"
#include "bpf.h"
#include "libbpf.h"
#include "libbpf_internal.h"
#include "hashmap.h"
/* make sure libbpf doesn't use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
#define BTF_MAX_NR_TYPES 0x7fffffffU
#define BTF_MAX_STR_OFFSET 0x7fffffffU
static struct btf_type btf_void;
struct btf {
union {
struct btf_header *hdr;
void *data;
};
struct btf_type **types;
const char *strings;
void *nohdr_data;
__u32 nr_types;
__u32 types_size;
__u32 data_size;
int fd;
int ptr_sz;
};
static inline __u64 ptr_to_u64(const void *ptr)
{
return (__u64) (unsigned long) ptr;
}
static int btf_add_type(struct btf *btf, struct btf_type *t)
{
if (btf->types_size - btf->nr_types < 2) {
struct btf_type **new_types;
__u32 expand_by, new_size;
if (btf->types_size == BTF_MAX_NR_TYPES)
return -E2BIG;
expand_by = max(btf->types_size >> 2, 16U);
new_size = min(BTF_MAX_NR_TYPES, btf->types_size + expand_by);
new_types = realloc(btf->types, sizeof(*new_types) * new_size);
if (!new_types)
return -ENOMEM;
if (btf->nr_types == 0)
new_types[0] = &btf_void;
btf->types = new_types;
btf->types_size = new_size;
}
btf->types[++(btf->nr_types)] = t;
return 0;
}
static int btf_parse_hdr(struct btf *btf)
{
const struct btf_header *hdr = btf->hdr;
__u32 meta_left;
if (btf->data_size < sizeof(struct btf_header)) {
pr_debug("BTF header not found\n");
return -EINVAL;
}
if (hdr->magic != BTF_MAGIC) {
pr_debug("Invalid BTF magic:%x\n", hdr->magic);
return -EINVAL;
}
if (hdr->version != BTF_VERSION) {
pr_debug("Unsupported BTF version:%u\n", hdr->version);
return -ENOTSUP;
}
if (hdr->flags) {
pr_debug("Unsupported BTF flags:%x\n", hdr->flags);
return -ENOTSUP;
}
meta_left = btf->data_size - sizeof(*hdr);
if (!meta_left) {
pr_debug("BTF has no data\n");
return -EINVAL;
}
if (meta_left < hdr->type_off) {
pr_debug("Invalid BTF type section offset:%u\n", hdr->type_off);
return -EINVAL;
}
if (meta_left < hdr->str_off) {
pr_debug("Invalid BTF string section offset:%u\n", hdr->str_off);
return -EINVAL;
}
if (hdr->type_off >= hdr->str_off) {
pr_debug("BTF type section offset >= string section offset. No type?\n");
return -EINVAL;
}
if (hdr->type_off & 0x02) {
pr_debug("BTF type section is not aligned to 4 bytes\n");
return -EINVAL;
}
btf->nohdr_data = btf->hdr + 1;
return 0;
}
static int btf_parse_str_sec(struct btf *btf)
{
const struct btf_header *hdr = btf->hdr;
const char *start = btf->nohdr_data + hdr->str_off;
const char *end = start + btf->hdr->str_len;
if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_STR_OFFSET ||
start[0] || end[-1]) {
pr_debug("Invalid BTF string section\n");
return -EINVAL;
}
btf->strings = start;
return 0;
}
static int btf_type_size(struct btf_type *t)
{
int base_size = sizeof(struct btf_type);
__u16 vlen = btf_vlen(t);
switch (btf_kind(t)) {
case BTF_KIND_FWD:
case BTF_KIND_CONST:
case BTF_KIND_VOLATILE:
case BTF_KIND_RESTRICT:
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
return base_size;
case BTF_KIND_INT:
return base_size + sizeof(__u32);
case BTF_KIND_ENUM:
return base_size + vlen * sizeof(struct btf_enum);
case BTF_KIND_ARRAY:
return base_size + sizeof(struct btf_array);
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
return base_size + vlen * sizeof(struct btf_member);
case BTF_KIND_FUNC_PROTO:
return base_size + vlen * sizeof(struct btf_param);
case BTF_KIND_VAR:
return base_size + sizeof(struct btf_var);
case BTF_KIND_DATASEC:
return base_size + vlen * sizeof(struct btf_var_secinfo);
default:
pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));
return -EINVAL;
}
}
static int btf_parse_type_sec(struct btf *btf)
{
struct btf_header *hdr = btf->hdr;
void *nohdr_data = btf->nohdr_data;
void *next_type = nohdr_data + hdr->type_off;
void *end_type = nohdr_data + hdr->str_off;
while (next_type < end_type) {
struct btf_type *t = next_type;
int type_size;
int err;
type_size = btf_type_size(t);
if (type_size < 0)
return type_size;
next_type += type_size;
err = btf_add_type(btf, t);
if (err)
return err;
}
return 0;
}
__u32 btf__get_nr_types(const struct btf *btf)
{
return btf->nr_types;
}
const struct btf_type *btf__type_by_id(const struct btf *btf, __u32 type_id)
{
if (type_id > btf->nr_types)
return NULL;
return btf->types[type_id];
}
static int determine_ptr_size(const struct btf *btf)
{
const struct btf_type *t;
const char *name;
int i;
for (i = 1; i <= btf->nr_types; i++) {
t = btf__type_by_id(btf, i);
if (!btf_is_int(t))
continue;
name = btf__name_by_offset(btf, t->name_off);
if (!name)
continue;
if (strcmp(name, "long int") == 0 ||
strcmp(name, "long unsigned int") == 0) {
if (t->size != 4 && t->size != 8)
continue;
return t->size;
}
}
return -1;
}
static size_t btf_ptr_sz(const struct btf *btf)
{
if (!btf->ptr_sz)
((struct btf *)btf)->ptr_sz = determine_ptr_size(btf);
return btf->ptr_sz < 0 ? sizeof(void *) : btf->ptr_sz;
}
/* Return pointer size this BTF instance assumes. The size is heuristically
* determined by looking for 'long' or 'unsigned long' integer type and
* recording its size in bytes. If BTF type information doesn't have any such
* type, this function returns 0. In the latter case, native architecture's
* pointer size is assumed, so will be either 4 or 8, depending on
* architecture that libbpf was compiled for. It's possible to override
* guessed value by using btf__set_pointer_size() API.
*/
size_t btf__pointer_size(const struct btf *btf)
{
if (!btf->ptr_sz)
((struct btf *)btf)->ptr_sz = determine_ptr_size(btf);
if (btf->ptr_sz < 0)
/* not enough BTF type info to guess */
return 0;
return btf->ptr_sz;
}
/* Override or set pointer size in bytes. Only values of 4 and 8 are
* supported.
*/
int btf__set_pointer_size(struct btf *btf, size_t ptr_sz)
{
if (ptr_sz != 4 && ptr_sz != 8)
return -EINVAL;
btf->ptr_sz = ptr_sz;
return 0;
}
static bool btf_type_is_void(const struct btf_type *t)
{
return t == &btf_void || btf_is_fwd(t);
}
static bool btf_type_is_void_or_null(const struct btf_type *t)
{
return !t || btf_type_is_void(t);
}
#define MAX_RESOLVE_DEPTH 32
__s64 btf__resolve_size(const struct btf *btf, __u32 type_id)
{
const struct btf_array *array;
const struct btf_type *t;
__u32 nelems = 1;
__s64 size = -1;
int i;
t = btf__type_by_id(btf, type_id);
for (i = 0; i < MAX_RESOLVE_DEPTH && !btf_type_is_void_or_null(t);
i++) {
switch (btf_kind(t)) {
case BTF_KIND_INT:
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
case BTF_KIND_ENUM:
case BTF_KIND_DATASEC:
size = t->size;
goto done;
case BTF_KIND_PTR:
size = btf_ptr_sz(btf);
goto done;
case BTF_KIND_TYPEDEF:
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
case BTF_KIND_VAR:
type_id = t->type;
break;
case BTF_KIND_ARRAY:
array = btf_array(t);
if (nelems && array->nelems > UINT32_MAX / nelems)
return -E2BIG;
nelems *= array->nelems;
type_id = array->type;
break;
default:
return -EINVAL;
}
t = btf__type_by_id(btf, type_id);
}
done:
if (size < 0)
return -EINVAL;
if (nelems && size > UINT32_MAX / nelems)
return -E2BIG;
return nelems * size;
}
int btf__align_of(const struct btf *btf, __u32 id)
{
const struct btf_type *t = btf__type_by_id(btf, id);
__u16 kind = btf_kind(t);
switch (kind) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
return min(btf_ptr_sz(btf), (size_t)t->size);
case BTF_KIND_PTR:
return btf_ptr_sz(btf);
case BTF_KIND_TYPEDEF:
case BTF_KIND_VOLATILE:
case BTF_KIND_CONST:
case BTF_KIND_RESTRICT:
return btf__align_of(btf, t->type);
case BTF_KIND_ARRAY:
return btf__align_of(btf, btf_array(t)->type);
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
const struct btf_member *m = btf_members(t);
__u16 vlen = btf_vlen(t);
int i, max_align = 1, align;
for (i = 0; i < vlen; i++, m++) {
align = btf__align_of(btf, m->type);
if (align <= 0)
return align;
max_align = max(max_align, align);
}
return max_align;
}
default:
pr_warn("unsupported BTF_KIND:%u\n", btf_kind(t));
return 0;
}
}
int btf__resolve_type(const struct btf *btf, __u32 type_id)
{
const struct btf_type *t;
int depth = 0;
t = btf__type_by_id(btf, type_id);
while (depth < MAX_RESOLVE_DEPTH &&
!btf_type_is_void_or_null(t) &&
(btf_is_mod(t) || btf_is_typedef(t) || btf_is_var(t))) {
type_id = t->type;
t = btf__type_by_id(btf, type_id);
depth++;
}
if (depth == MAX_RESOLVE_DEPTH || btf_type_is_void_or_null(t))
return -EINVAL;
return type_id;
}
__s32 btf__find_by_name(const struct btf *btf, const char *type_name)
{
__u32 i;
if (!strcmp(type_name, "void"))
return 0;
for (i = 1; i <= btf->nr_types; i++) {
const struct btf_type *t = btf->types[i];
const char *name = btf__name_by_offset(btf, t->name_off);
if (name && !strcmp(type_name, name))
return i;
}
return -ENOENT;
}
__s32 btf__find_by_name_kind(const struct btf *btf, const char *type_name,
__u32 kind)
{
__u32 i;
if (kind == BTF_KIND_UNKN || !strcmp(type_name, "void"))
return 0;
for (i = 1; i <= btf->nr_types; i++) {
const struct btf_type *t = btf->types[i];
const char *name;
if (btf_kind(t) != kind)
continue;
name = btf__name_by_offset(btf, t->name_off);
if (name && !strcmp(type_name, name))
return i;
}
return -ENOENT;
}
void btf__free(struct btf *btf)
{
if (IS_ERR_OR_NULL(btf))
return;
if (btf->fd >= 0)
close(btf->fd);
free(btf->data);
free(btf->types);
free(btf);
}
struct btf *btf__new(const void *data, __u32 size)
{
struct btf *btf;
int err;
btf = calloc(1, sizeof(struct btf));
if (!btf)
return ERR_PTR(-ENOMEM);
btf->fd = -1;
btf->data = malloc(size);
if (!btf->data) {
err = -ENOMEM;
goto done;
}
memcpy(btf->data, data, size);
btf->data_size = size;
err = btf_parse_hdr(btf);
if (err)
goto done;
err = btf_parse_str_sec(btf);
if (err)
goto done;
err = btf_parse_type_sec(btf);
done:
if (err) {
btf__free(btf);
return ERR_PTR(err);
}
return btf;
}
static bool btf_check_endianness(const GElf_Ehdr *ehdr)
{
#if __BYTE_ORDER == __LITTLE_ENDIAN
return ehdr->e_ident[EI_DATA] == ELFDATA2LSB;
#elif __BYTE_ORDER == __BIG_ENDIAN
return ehdr->e_ident[EI_DATA] == ELFDATA2MSB;
#else
# error "Unrecognized __BYTE_ORDER__"
#endif
}
struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext)
{
Elf_Data *btf_data = NULL, *btf_ext_data = NULL;
int err = 0, fd = -1, idx = 0;
struct btf *btf = NULL;
Elf_Scn *scn = NULL;
Elf *elf = NULL;
GElf_Ehdr ehdr;
if (elf_version(EV_CURRENT) == EV_NONE) {
pr_warn("failed to init libelf for %s\n", path);
return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
}
fd = open(path, O_RDONLY);
if (fd < 0) {
err = -errno;
pr_warn("failed to open %s: %s\n", path, strerror(errno));
return ERR_PTR(err);
}
err = -LIBBPF_ERRNO__FORMAT;
elf = elf_begin(fd, ELF_C_READ, NULL);
if (!elf) {
pr_warn("failed to open %s as ELF file\n", path);
goto done;
}
if (!gelf_getehdr(elf, &ehdr)) {
pr_warn("failed to get EHDR from %s\n", path);
goto done;
}
if (!btf_check_endianness(&ehdr)) {
pr_warn("non-native ELF endianness is not supported\n");
goto done;
}
if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
pr_warn("failed to get e_shstrndx from %s\n", path);
goto done;
}
while ((scn = elf_nextscn(elf, scn)) != NULL) {
GElf_Shdr sh;
char *name;
idx++;
if (gelf_getshdr(scn, &sh) != &sh) {
pr_warn("failed to get section(%d) header from %s\n",
idx, path);
goto done;
}
name = elf_strptr(elf, ehdr.e_shstrndx, sh.sh_name);
if (!name) {
pr_warn("failed to get section(%d) name from %s\n",
idx, path);
goto done;
}
if (strcmp(name, BTF_ELF_SEC) == 0) {
btf_data = elf_getdata(scn, 0);
if (!btf_data) {
pr_warn("failed to get section(%d, %s) data from %s\n",
idx, name, path);
goto done;
}
continue;
} else if (btf_ext && strcmp(name, BTF_EXT_ELF_SEC) == 0) {
btf_ext_data = elf_getdata(scn, 0);
if (!btf_ext_data) {
pr_warn("failed to get section(%d, %s) data from %s\n",
idx, name, path);
goto done;
}
continue;
}
}
err = 0;
if (!btf_data) {
err = -ENOENT;
goto done;
}
btf = btf__new(btf_data->d_buf, btf_data->d_size);
if (IS_ERR(btf))
goto done;
switch (gelf_getclass(elf)) {
case ELFCLASS32:
btf__set_pointer_size(btf, 4);
break;
case ELFCLASS64:
btf__set_pointer_size(btf, 8);
break;
default:
pr_warn("failed to get ELF class (bitness) for %s\n", path);
break;
}
if (btf_ext && btf_ext_data) {
*btf_ext = btf_ext__new(btf_ext_data->d_buf,
btf_ext_data->d_size);
if (IS_ERR(*btf_ext))
goto done;
} else if (btf_ext) {
*btf_ext = NULL;
}
done:
if (elf)
elf_end(elf);
close(fd);
if (err)
return ERR_PTR(err);
/*
* btf is always parsed before btf_ext, so no need to clean up
* btf_ext, if btf loading failed
*/
if (IS_ERR(btf))
return btf;
if (btf_ext && IS_ERR(*btf_ext)) {
btf__free(btf);
err = PTR_ERR(*btf_ext);
return ERR_PTR(err);
}
return btf;
}
struct btf *btf__parse_raw(const char *path)
{
struct btf *btf = NULL;
void *data = NULL;
FILE *f = NULL;
__u16 magic;
int err = 0;
long sz;
f = fopen(path, "rb");
if (!f) {
err = -errno;
goto err_out;
}
/* check BTF magic */
if (fread(&magic, 1, sizeof(magic), f) < sizeof(magic)) {
err = -EIO;
goto err_out;
}
if (magic != BTF_MAGIC) {
/* definitely not a raw BTF */
err = -EPROTO;
goto err_out;
}
/* get file size */
if (fseek(f, 0, SEEK_END)) {
err = -errno;
goto err_out;
}
sz = ftell(f);
if (sz < 0) {
err = -errno;
goto err_out;
}
/* rewind to the start */
if (fseek(f, 0, SEEK_SET)) {
err = -errno;
goto err_out;
}
/* pre-alloc memory and read all of BTF data */
data = malloc(sz);
if (!data) {
err = -ENOMEM;
goto err_out;
}
if (fread(data, 1, sz, f) < sz) {
err = -EIO;
goto err_out;
}
/* finally parse BTF data */
btf = btf__new(data, sz);
err_out:
free(data);
if (f)
fclose(f);
return err ? ERR_PTR(err) : btf;
}
struct btf *btf__parse(const char *path, struct btf_ext **btf_ext)
{
struct btf *btf;
if (btf_ext)
*btf_ext = NULL;
btf = btf__parse_raw(path);
if (!IS_ERR(btf) || PTR_ERR(btf) != -EPROTO)
return btf;
return btf__parse_elf(path, btf_ext);
}
static int compare_vsi_off(const void *_a, const void *_b)
{
const struct btf_var_secinfo *a = _a;
const struct btf_var_secinfo *b = _b;
return a->offset - b->offset;
}
static int btf_fixup_datasec(struct bpf_object *obj, struct btf *btf,
struct btf_type *t)
{
__u32 size = 0, off = 0, i, vars = btf_vlen(t);
const char *name = btf__name_by_offset(btf, t->name_off);
const struct btf_type *t_var;
struct btf_var_secinfo *vsi;
const struct btf_var *var;
int ret;
if (!name) {
pr_debug("No name found in string section for DATASEC kind.\n");
return -ENOENT;
}
/* .extern datasec size and var offsets were set correctly during
* extern collection step, so just skip straight to sorting variables
*/
if (t->size)
goto sort_vars;
ret = bpf_object__section_size(obj, name, &size);
if (ret || !size || (t->size && t->size != size)) {
pr_debug("Invalid size for section %s: %u bytes\n", name, size);
return -ENOENT;
}
t->size = size;
for (i = 0, vsi = btf_var_secinfos(t); i < vars; i++, vsi++) {
t_var = btf__type_by_id(btf, vsi->type);
var = btf_var(t_var);
if (!btf_is_var(t_var)) {
pr_debug("Non-VAR type seen in section %s\n", name);
return -EINVAL;
}
if (var->linkage == BTF_VAR_STATIC)
continue;
name = btf__name_by_offset(btf, t_var->name_off);
if (!name) {
pr_debug("No name found in string section for VAR kind\n");
return -ENOENT;
}
ret = bpf_object__variable_offset(obj, name, &off);
if (ret) {
pr_debug("No offset found in symbol table for VAR %s\n",
name);
return -ENOENT;
}
vsi->offset = off;
}
sort_vars:
qsort(btf_var_secinfos(t), vars, sizeof(*vsi), compare_vsi_off);
return 0;
}
int btf__finalize_data(struct bpf_object *obj, struct btf *btf)
{
int err = 0;
__u32 i;
for (i = 1; i <= btf->nr_types; i++) {
struct btf_type *t = btf->types[i];
/* Loader needs to fix up some of the things compiler
* couldn't get its hands on while emitting BTF. This
* is section size and global variable offset. We use
* the info from the ELF itself for this purpose.
*/
if (btf_is_datasec(t)) {
err = btf_fixup_datasec(obj, btf, t);
if (err)
break;
}
}
return err;
}
int btf__load(struct btf *btf)
{
__u32 log_buf_size = 0;
char *log_buf = NULL;
int err = 0;
if (btf->fd >= 0)
return -EEXIST;
retry_load:
if (log_buf_size) {
log_buf = malloc(log_buf_size);
if (!log_buf)
return -ENOMEM;
*log_buf = 0;
}
btf->fd = bpf_load_btf(btf->data, btf->data_size,
log_buf, log_buf_size, false);
if (btf->fd < 0) {
if (!log_buf || errno == ENOSPC) {
log_buf_size = max((__u32)BPF_LOG_BUF_SIZE,
log_buf_size << 1);
free(log_buf);
goto retry_load;
}
err = -errno;
pr_warn("Error loading BTF: %s(%d)\n", strerror(errno), errno);
if (*log_buf)
pr_warn("%s\n", log_buf);
goto done;
}
done:
free(log_buf);
return err;
}
int btf__fd(const struct btf *btf)
{
return btf->fd;
}
void btf__set_fd(struct btf *btf, int fd)
{
btf->fd = fd;
}
const void *btf__get_raw_data(const struct btf *btf, __u32 *size)
{
*size = btf->data_size;
return btf->data;
}
const char *btf__name_by_offset(const struct btf *btf, __u32 offset)
{
if (offset < btf->hdr->str_len)
return &btf->strings[offset];
else
return NULL;
}
int btf__get_from_id(__u32 id, struct btf **btf)
{
struct bpf_btf_info btf_info = { 0 };
__u32 len = sizeof(btf_info);
__u32 last_size;
int btf_fd;
void *ptr;
int err;
err = 0;
*btf = NULL;
btf_fd = bpf_btf_get_fd_by_id(id);
if (btf_fd < 0)
return 0;
/* we won't know btf_size until we call bpf_obj_get_info_by_fd(). so
* let's start with a sane default - 4KiB here - and resize it only if
* bpf_obj_get_info_by_fd() needs a bigger buffer.
*/
btf_info.btf_size = 4096;
last_size = btf_info.btf_size;
ptr = malloc(last_size);
if (!ptr) {
err = -ENOMEM;
goto exit_free;
}
memset(ptr, 0, last_size);
btf_info.btf = ptr_to_u64(ptr);
err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);
if (!err && btf_info.btf_size > last_size) {
void *temp_ptr;
last_size = btf_info.btf_size;
temp_ptr = realloc(ptr, last_size);
if (!temp_ptr) {
err = -ENOMEM;
goto exit_free;
}
ptr = temp_ptr;
memset(ptr, 0, last_size);
btf_info.btf = ptr_to_u64(ptr);
err = bpf_obj_get_info_by_fd(btf_fd, &btf_info, &len);
}
if (err || btf_info.btf_size > last_size) {
err = errno;
goto exit_free;
}
*btf = btf__new((__u8 *)(long)btf_info.btf, btf_info.btf_size);
if (IS_ERR(*btf)) {
err = PTR_ERR(*btf);
*btf = NULL;
}
exit_free:
close(btf_fd);
free(ptr);
return err;
}
int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
__u32 expected_key_size, __u32 expected_value_size,
__u32 *key_type_id, __u32 *value_type_id)
{
const struct btf_type *container_type;
const struct btf_member *key, *value;
const size_t max_name = 256;
char container_name[max_name];
__s64 key_size, value_size;
__s32 container_id;
if (snprintf(container_name, max_name, "____btf_map_%s", map_name) ==
max_name) {
pr_warn("map:%s length of '____btf_map_%s' is too long\n",
map_name, map_name);
return -EINVAL;
}
container_id = btf__find_by_name(btf, container_name);
if (container_id < 0) {
pr_debug("map:%s container_name:%s cannot be found in BTF. Missing BPF_ANNOTATE_KV_PAIR?\n",
map_name, container_name);
return container_id;
}
container_type = btf__type_by_id(btf, container_id);
if (!container_type) {
pr_warn("map:%s cannot find BTF type for container_id:%u\n",
map_name, container_id);
return -EINVAL;
}
if (!btf_is_struct(container_type) || btf_vlen(container_type) < 2) {
pr_warn("map:%s container_name:%s is an invalid container struct\n",
map_name, container_name);
return -EINVAL;
}
key = btf_members(container_type);
value = key + 1;
key_size = btf__resolve_size(btf, key->type);
if (key_size < 0) {
pr_warn("map:%s invalid BTF key_type_size\n", map_name);
return key_size;
}
if (expected_key_size != key_size) {
pr_warn("map:%s btf_key_type_size:%u != map_def_key_size:%u\n",
map_name, (__u32)key_size, expected_key_size);
return -EINVAL;
}
value_size = btf__resolve_size(btf, value->type);
if (value_size < 0) {
pr_warn("map:%s invalid BTF value_type_size\n", map_name);
return value_size;
}
if (expected_value_size != value_size) {
pr_warn("map:%s btf_value_type_size:%u != map_def_value_size:%u\n",
map_name, (__u32)value_size, expected_value_size);
return -EINVAL;
}
*key_type_id = key->type;
*value_type_id = value->type;
return 0;
}
struct btf_ext_sec_setup_param {
__u32 off;
__u32 len;
__u32 min_rec_size;
struct btf_ext_info *ext_info;
const char *desc;
};
static int btf_ext_setup_info(struct btf_ext *btf_ext,
struct btf_ext_sec_setup_param *ext_sec)
{
const struct btf_ext_info_sec *sinfo;
struct btf_ext_info *ext_info;
__u32 info_left, record_size;
/* The start of the info sec (including the __u32 record_size). */
void *info;
if (ext_sec->len == 0)
return 0;
if (ext_sec->off & 0x03) {
pr_debug(".BTF.ext %s section is not aligned to 4 bytes\n",
ext_sec->desc);
return -EINVAL;
}
info = btf_ext->data + btf_ext->hdr->hdr_len + ext_sec->off;
info_left = ext_sec->len;
if (btf_ext->data + btf_ext->data_size < info + ext_sec->len) {
pr_debug("%s section (off:%u len:%u) is beyond the end of the ELF section .BTF.ext\n",
ext_sec->desc, ext_sec->off, ext_sec->len);
return -EINVAL;
}
/* At least a record size */
if (info_left < sizeof(__u32)) {
pr_debug(".BTF.ext %s record size not found\n", ext_sec->desc);
return -EINVAL;
}
/* The record size needs to meet the minimum standard */
record_size = *(__u32 *)info;
if (record_size < ext_sec->min_rec_size ||
record_size & 0x03) {
pr_debug("%s section in .BTF.ext has invalid record size %u\n",
ext_sec->desc, record_size);
return -EINVAL;
}
sinfo = info + sizeof(__u32);
info_left -= sizeof(__u32);
/* If no records, return failure now so .BTF.ext won't be used. */
if (!info_left) {
pr_debug("%s section in .BTF.ext has no records", ext_sec->desc);
return -EINVAL;
}
while (info_left) {
unsigned int sec_hdrlen = sizeof(struct btf_ext_info_sec);
__u64 total_record_size;
__u32 num_records;
if (info_left < sec_hdrlen) {
pr_debug("%s section header is not found in .BTF.ext\n",
ext_sec->desc);
return -EINVAL;
}
num_records = sinfo->num_info;
if (num_records == 0) {
pr_debug("%s section has incorrect num_records in .BTF.ext\n",
ext_sec->desc);
return -EINVAL;
}
total_record_size = sec_hdrlen +
(__u64)num_records * record_size;
if (info_left < total_record_size) {
pr_debug("%s section has incorrect num_records in .BTF.ext\n",
ext_sec->desc);
return -EINVAL;
}
info_left -= total_record_size;
sinfo = (void *)sinfo + total_record_size;
}
ext_info = ext_sec->ext_info;
ext_info->len = ext_sec->len - sizeof(__u32);
ext_info->rec_size = record_size;
ext_info->info = info + sizeof(__u32);
return 0;
}
static int btf_ext_setup_func_info(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
.off = btf_ext->hdr->func_info_off,
.len = btf_ext->hdr->func_info_len,
.min_rec_size = sizeof(struct bpf_func_info_min),
.ext_info = &btf_ext->func_info,
.desc = "func_info"
};
return btf_ext_setup_info(btf_ext, &param);
}
static int btf_ext_setup_line_info(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
.off = btf_ext->hdr->line_info_off,
.len = btf_ext->hdr->line_info_len,
.min_rec_size = sizeof(struct bpf_line_info_min),
.ext_info = &btf_ext->line_info,
.desc = "line_info",
};
return btf_ext_setup_info(btf_ext, &param);
}
static int btf_ext_setup_core_relos(struct btf_ext *btf_ext)
{
struct btf_ext_sec_setup_param param = {
.off = btf_ext->hdr->core_relo_off,
.len = btf_ext->hdr->core_relo_len,
.min_rec_size = sizeof(struct bpf_core_relo),
.ext_info = &btf_ext->core_relo_info,
.desc = "core_relo",
};
return btf_ext_setup_info(btf_ext, &param);
}
static int btf_ext_parse_hdr(__u8 *data, __u32 data_size)
{
const struct btf_ext_header *hdr = (struct btf_ext_header *)data;
if (data_size < offsetofend(struct btf_ext_header, hdr_len) ||
data_size < hdr->hdr_len) {
pr_debug("BTF.ext header not found");
return -EINVAL;
}
if (hdr->magic != BTF_MAGIC) {
pr_debug("Invalid BTF.ext magic:%x\n", hdr->magic);
return -EINVAL;
}
if (hdr->version != BTF_VERSION) {
pr_debug("Unsupported BTF.ext version:%u\n", hdr->version);
return -ENOTSUP;
}
if (hdr->flags) {
pr_debug("Unsupported BTF.ext flags:%x\n", hdr->flags);
return -ENOTSUP;
}
if (data_size == hdr->hdr_len) {
pr_debug("BTF.ext has no data\n");
return -EINVAL;
}
return 0;
}
void btf_ext__free(struct btf_ext *btf_ext)
{
if (IS_ERR_OR_NULL(btf_ext))
return;
free(btf_ext->data);
free(btf_ext);
}
struct btf_ext *btf_ext__new(__u8 *data, __u32 size)
{
struct btf_ext *btf_ext;
int err;
err = btf_ext_parse_hdr(data, size);
if (err)
return ERR_PTR(err);
btf_ext = calloc(1, sizeof(struct btf_ext));
if (!btf_ext)
return ERR_PTR(-ENOMEM);
btf_ext->data_size = size;
btf_ext->data = malloc(size);
if (!btf_ext->data) {
err = -ENOMEM;
goto done;
}
memcpy(btf_ext->data, data, size);
if (btf_ext->hdr->hdr_len <
offsetofend(struct btf_ext_header, line_info_len))
goto done;
err = btf_ext_setup_func_info(btf_ext);
if (err)
goto done;
err = btf_ext_setup_line_info(btf_ext);
if (err)
goto done;
if (btf_ext->hdr->hdr_len < offsetofend(struct btf_ext_header, core_relo_len))
goto done;
err = btf_ext_setup_core_relos(btf_ext);
if (err)
goto done;
done:
if (err) {
btf_ext__free(btf_ext);
return ERR_PTR(err);
}
return btf_ext;
}
const void *btf_ext__get_raw_data(const struct btf_ext *btf_ext, __u32 *size)
{
*size = btf_ext->data_size;
return btf_ext->data;
}
static int btf_ext_reloc_info(const struct btf *btf,
const struct btf_ext_info *ext_info,
const char *sec_name, __u32 insns_cnt,
void **info, __u32 *cnt)
{
__u32 sec_hdrlen = sizeof(struct btf_ext_info_sec);
__u32 i, record_size, existing_len, records_len;
struct btf_ext_info_sec *sinfo;
const char *info_sec_name;
__u64 remain_len;
void *data;
record_size = ext_info->rec_size;
sinfo = ext_info->info;
remain_len = ext_info->len;
while (remain_len > 0) {
records_len = sinfo->num_info * record_size;
info_sec_name = btf__name_by_offset(btf, sinfo->sec_name_off);
if (strcmp(info_sec_name, sec_name)) {
remain_len -= sec_hdrlen + records_len;
sinfo = (void *)sinfo + sec_hdrlen + records_len;
continue;
}
existing_len = (*cnt) * record_size;
data = realloc(*info, existing_len + records_len);
if (!data)
return -ENOMEM;
memcpy(data + existing_len, sinfo->data, records_len);
/* adjust insn_off only, the rest data will be passed
* to the kernel.
*/
for (i = 0; i < sinfo->num_info; i++) {
__u32 *insn_off;
insn_off = data + existing_len + (i * record_size);
*insn_off = *insn_off / sizeof(struct bpf_insn) +
insns_cnt;
}
*info = data;
*cnt += sinfo->num_info;
return 0;
}
return -ENOENT;
}
int btf_ext__reloc_func_info(const struct btf *btf,
const struct btf_ext *btf_ext,
const char *sec_name, __u32 insns_cnt,
void **func_info, __u32 *cnt)
{
return btf_ext_reloc_info(btf, &btf_ext->func_info, sec_name,
insns_cnt, func_info, cnt);
}
int btf_ext__reloc_line_info(const struct btf *btf,
const struct btf_ext *btf_ext,
const char *sec_name, __u32 insns_cnt,
void **line_info, __u32 *cnt)
{
return btf_ext_reloc_info(btf, &btf_ext->line_info, sec_name,
insns_cnt, line_info, cnt);
}
__u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext)
{
return btf_ext->func_info.rec_size;
}
__u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext)
{
return btf_ext->line_info.rec_size;
}
struct btf_dedup;
static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
const struct btf_dedup_opts *opts);
static void btf_dedup_free(struct btf_dedup *d);
static int btf_dedup_strings(struct btf_dedup *d);
static int btf_dedup_prim_types(struct btf_dedup *d);
static int btf_dedup_struct_types(struct btf_dedup *d);
static int btf_dedup_ref_types(struct btf_dedup *d);
static int btf_dedup_compact_types(struct btf_dedup *d);
static int btf_dedup_remap_types(struct btf_dedup *d);
/*
* Deduplicate BTF types and strings.
*
* BTF dedup algorithm takes as an input `struct btf` representing `.BTF` ELF
* section with all BTF type descriptors and string data. It overwrites that
* memory in-place with deduplicated types and strings without any loss of
* information. If optional `struct btf_ext` representing '.BTF.ext' ELF section
* is provided, all the strings referenced from .BTF.ext section are honored
* and updated to point to the right offsets after deduplication.
*
* If function returns with error, type/string data might be garbled and should
* be discarded.
*
* More verbose and detailed description of both problem btf_dedup is solving,
* as well as solution could be found at:
* https://facebookmicrosites.github.io/bpf/blog/2018/11/14/btf-enhancement.html
*
* Problem description and justification
* =====================================
*
* BTF type information is typically emitted either as a result of conversion
* from DWARF to BTF or directly by compiler. In both cases, each compilation
* unit contains information about a subset of all the types that are used
* in an application. These subsets are frequently overlapping and contain a lot
* of duplicated information when later concatenated together into a single
* binary. This algorithm ensures that each unique type is represented by single
* BTF type descriptor, greatly reducing resulting size of BTF data.
*
* Compilation unit isolation and subsequent duplication of data is not the only
* problem. The same type hierarchy (e.g., struct and all the type that struct
* references) in different compilation units can be represented in BTF to
* various degrees of completeness (or, rather, incompleteness) due to
* struct/union forward declarations.
*
* Let's take a look at an example, that we'll use to better understand the
* problem (and solution). Suppose we have two compilation units, each using
* same `struct S`, but each of them having incomplete type information about
* struct's fields:
*
* // CU #1:
* struct S;
* struct A {
* int a;
* struct A* self;
* struct S* parent;
* };
* struct B;
* struct S {
* struct A* a_ptr;
* struct B* b_ptr;
* };
*
* // CU #2:
* struct S;
* struct A;
* struct B {
* int b;
* struct B* self;
* struct S* parent;
* };
* struct S {
* struct A* a_ptr;
* struct B* b_ptr;
* };
*
* In case of CU #1, BTF data will know only that `struct B` exist (but no
* more), but will know the complete type information about `struct A`. While
* for CU #2, it will know full type information about `struct B`, but will
* only know about forward declaration of `struct A` (in BTF terms, it will
* have `BTF_KIND_FWD` type descriptor with name `B`).
*
* This compilation unit isolation means that it's possible that there is no
* single CU with complete type information describing structs `S`, `A`, and
* `B`. Also, we might get tons of duplicated and redundant type information.
*
* Additional complication we need to keep in mind comes from the fact that
* types, in general, can form graphs containing cycles, not just DAGs.
*
* While algorithm does deduplication, it also merges and resolves type
* information (unless disabled throught `struct btf_opts`), whenever possible.
* E.g., in the example above with two compilation units having partial type
* information for structs `A` and `B`, the output of algorithm will emit
* a single copy of each BTF type that describes structs `A`, `B`, and `S`
* (as well as type information for `int` and pointers), as if they were defined
* in a single compilation unit as:
*
* struct A {
* int a;
* struct A* self;
* struct S* parent;
* };
* struct B {
* int b;
* struct B* self;
* struct S* parent;
* };
* struct S {
* struct A* a_ptr;
* struct B* b_ptr;
* };
*
* Algorithm summary
* =================
*
* Algorithm completes its work in 6 separate passes:
*
* 1. Strings deduplication.
* 2. Primitive types deduplication (int, enum, fwd).
* 3. Struct/union types deduplication.
* 4. Reference types deduplication (pointers, typedefs, arrays, funcs, func
* protos, and const/volatile/restrict modifiers).
* 5. Types compaction.
* 6. Types remapping.
*
* Algorithm determines canonical type descriptor, which is a single
* representative type for each truly unique type. This canonical type is the
* one that will go into final deduplicated BTF type information. For
* struct/unions, it is also the type that algorithm will merge additional type
* information into (while resolving FWDs), as it discovers it from data in
* other CUs. Each input BTF type eventually gets either mapped to itself, if
* that type is canonical, or to some other type, if that type is equivalent
* and was chosen as canonical representative. This mapping is stored in
* `btf_dedup->map` array. This map is also used to record STRUCT/UNION that
* FWD type got resolved to.
*
* To facilitate fast discovery of canonical types, we also maintain canonical
* index (`btf_dedup->dedup_table`), which maps type descriptor's signature hash
* (i.e., hashed kind, name, size, fields, etc) into a list of canonical types
* that match that signature. With sufficiently good choice of type signature
* hashing function, we can limit number of canonical types for each unique type
* signature to a very small number, allowing to find canonical type for any
* duplicated type very quickly.
*
* Struct/union deduplication is the most critical part and algorithm for
* deduplicating structs/unions is described in greater details in comments for
* `btf_dedup_is_equiv` function.
*/
int btf__dedup(struct btf *btf, struct btf_ext *btf_ext,
const struct btf_dedup_opts *opts)
{
struct btf_dedup *d = btf_dedup_new(btf, btf_ext, opts);
int err;
if (IS_ERR(d)) {
pr_debug("btf_dedup_new failed: %ld", PTR_ERR(d));
return -EINVAL;
}
err = btf_dedup_strings(d);
if (err < 0) {
pr_debug("btf_dedup_strings failed:%d\n", err);
goto done;
}
err = btf_dedup_prim_types(d);
if (err < 0) {
pr_debug("btf_dedup_prim_types failed:%d\n", err);
goto done;
}
err = btf_dedup_struct_types(d);
if (err < 0) {
pr_debug("btf_dedup_struct_types failed:%d\n", err);
goto done;
}
err = btf_dedup_ref_types(d);
if (err < 0) {
pr_debug("btf_dedup_ref_types failed:%d\n", err);
goto done;
}
err = btf_dedup_compact_types(d);
if (err < 0) {
pr_debug("btf_dedup_compact_types failed:%d\n", err);
goto done;
}
err = btf_dedup_remap_types(d);
if (err < 0) {
pr_debug("btf_dedup_remap_types failed:%d\n", err);
goto done;
}
done:
btf_dedup_free(d);
return err;
}
#define BTF_UNPROCESSED_ID ((__u32)-1)
#define BTF_IN_PROGRESS_ID ((__u32)-2)
struct btf_dedup {
/* .BTF section to be deduped in-place */
struct btf *btf;
/*
* Optional .BTF.ext section. When provided, any strings referenced
* from it will be taken into account when deduping strings
*/
struct btf_ext *btf_ext;
/*
* This is a map from any type's signature hash to a list of possible
* canonical representative type candidates. Hash collisions are
* ignored, so even types of various kinds can share same list of
* candidates, which is fine because we rely on subsequent
* btf_xxx_equal() checks to authoritatively verify type equality.
*/
struct hashmap *dedup_table;
/* Canonical types map */
__u32 *map;
/* Hypothetical mapping, used during type graph equivalence checks */
__u32 *hypot_map;
__u32 *hypot_list;
size_t hypot_cnt;
size_t hypot_cap;
/* Various option modifying behavior of algorithm */
struct btf_dedup_opts opts;
};
struct btf_str_ptr {
const char *str;
__u32 new_off;
bool used;
};
struct btf_str_ptrs {
struct btf_str_ptr *ptrs;
const char *data;
__u32 cnt;
__u32 cap;
};
static long hash_combine(long h, long value)
{
return h * 31 + value;
}
#define for_each_dedup_cand(d, node, hash) \
hashmap__for_each_key_entry(d->dedup_table, node, (void *)hash)
static int btf_dedup_table_add(struct btf_dedup *d, long hash, __u32 type_id)
{
return hashmap__append(d->dedup_table,
(void *)hash, (void *)(long)type_id);
}
static int btf_dedup_hypot_map_add(struct btf_dedup *d,
__u32 from_id, __u32 to_id)
{
if (d->hypot_cnt == d->hypot_cap) {
__u32 *new_list;
d->hypot_cap += max((size_t)16, d->hypot_cap / 2);
new_list = realloc(d->hypot_list, sizeof(__u32) * d->hypot_cap);
if (!new_list)
return -ENOMEM;
d->hypot_list = new_list;
}
d->hypot_list[d->hypot_cnt++] = from_id;
d->hypot_map[from_id] = to_id;
return 0;
}
static void btf_dedup_clear_hypot_map(struct btf_dedup *d)
{
int i;
for (i = 0; i < d->hypot_cnt; i++)
d->hypot_map[d->hypot_list[i]] = BTF_UNPROCESSED_ID;
d->hypot_cnt = 0;
}
static void btf_dedup_free(struct btf_dedup *d)
{
hashmap__free(d->dedup_table);
d->dedup_table = NULL;
free(d->map);
d->map = NULL;
free(d->hypot_map);
d->hypot_map = NULL;
free(d->hypot_list);
d->hypot_list = NULL;
free(d);
}
static size_t btf_dedup_identity_hash_fn(const void *key, void *ctx)
{
return (size_t)key;
}
static size_t btf_dedup_collision_hash_fn(const void *key, void *ctx)
{
return 0;
}
static bool btf_dedup_equal_fn(const void *k1, const void *k2, void *ctx)
{
return k1 == k2;
}
static struct btf_dedup *btf_dedup_new(struct btf *btf, struct btf_ext *btf_ext,
const struct btf_dedup_opts *opts)
{
struct btf_dedup *d = calloc(1, sizeof(struct btf_dedup));
hashmap_hash_fn hash_fn = btf_dedup_identity_hash_fn;
int i, err = 0;
if (!d)
return ERR_PTR(-ENOMEM);
d->opts.dont_resolve_fwds = opts && opts->dont_resolve_fwds;
/* dedup_table_size is now used only to force collisions in tests */
if (opts && opts->dedup_table_size == 1)
hash_fn = btf_dedup_collision_hash_fn;
d->btf = btf;
d->btf_ext = btf_ext;
d->dedup_table = hashmap__new(hash_fn, btf_dedup_equal_fn, NULL);
if (IS_ERR(d->dedup_table)) {
err = PTR_ERR(d->dedup_table);
d->dedup_table = NULL;
goto done;
}
d->map = malloc(sizeof(__u32) * (1 + btf->nr_types));
if (!d->map) {
err = -ENOMEM;
goto done;
}
/* special BTF "void" type is made canonical immediately */
d->map[0] = 0;
for (i = 1; i <= btf->nr_types; i++) {
struct btf_type *t = d->btf->types[i];
/* VAR and DATASEC are never deduped and are self-canonical */
if (btf_is_var(t) || btf_is_datasec(t))
d->map[i] = i;
else
d->map[i] = BTF_UNPROCESSED_ID;
}
d->hypot_map = malloc(sizeof(__u32) * (1 + btf->nr_types));
if (!d->hypot_map) {
err = -ENOMEM;
goto done;
}
for (i = 0; i <= btf->nr_types; i++)
d->hypot_map[i] = BTF_UNPROCESSED_ID;
done:
if (err) {
btf_dedup_free(d);
return ERR_PTR(err);
}
return d;
}
typedef int (*str_off_fn_t)(__u32 *str_off_ptr, void *ctx);
/*
* Iterate over all possible places in .BTF and .BTF.ext that can reference
* string and pass pointer to it to a provided callback `fn`.
*/
static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx)
{
void *line_data_cur, *line_data_end;
int i, j, r, rec_size;
struct btf_type *t;
for (i = 1; i <= d->btf->nr_types; i++) {
t = d->btf->types[i];
r = fn(&t->name_off, ctx);
if (r)
return r;
switch (btf_kind(t)) {
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
struct btf_member *m = btf_members(t);
__u16 vlen = btf_vlen(t);
for (j = 0; j < vlen; j++) {
r = fn(&m->name_off, ctx);
if (r)
return r;
m++;
}
break;
}
case BTF_KIND_ENUM: {
struct btf_enum *m = btf_enum(t);
__u16 vlen = btf_vlen(t);
for (j = 0; j < vlen; j++) {
r = fn(&m->name_off, ctx);
if (r)
return r;
m++;
}
break;
}
case BTF_KIND_FUNC_PROTO: {
struct btf_param *m = btf_params(t);
__u16 vlen = btf_vlen(t);
for (j = 0; j < vlen; j++) {
r = fn(&m->name_off, ctx);
if (r)
return r;
m++;
}
break;
}
default:
break;
}
}
if (!d->btf_ext)
return 0;
line_data_cur = d->btf_ext->line_info.info;
line_data_end = d->btf_ext->line_info.info + d->btf_ext->line_info.len;
rec_size = d->btf_ext->line_info.rec_size;
while (line_data_cur < line_data_end) {
struct btf_ext_info_sec *sec = line_data_cur;
struct bpf_line_info_min *line_info;
__u32 num_info = sec->num_info;
r = fn(&sec->sec_name_off, ctx);
if (r)
return r;
line_data_cur += sizeof(struct btf_ext_info_sec);
for (i = 0; i < num_info; i++) {
line_info = line_data_cur;
r = fn(&line_info->file_name_off, ctx);
if (r)
return r;
r = fn(&line_info->line_off, ctx);
if (r)
return r;
line_data_cur += rec_size;
}
}
return 0;
}
static int str_sort_by_content(const void *a1, const void *a2)
{
const struct btf_str_ptr *p1 = a1;
const struct btf_str_ptr *p2 = a2;
return strcmp(p1->str, p2->str);
}
static int str_sort_by_offset(const void *a1, const void *a2)
{
const struct btf_str_ptr *p1 = a1;
const struct btf_str_ptr *p2 = a2;
if (p1->str != p2->str)
return p1->str < p2->str ? -1 : 1;
return 0;
}
static int btf_dedup_str_ptr_cmp(const void *str_ptr, const void *pelem)
{
const struct btf_str_ptr *p = pelem;
if (str_ptr != p->str)
return (const char *)str_ptr < p->str ? -1 : 1;
return 0;
}
static int btf_str_mark_as_used(__u32 *str_off_ptr, void *ctx)
{
struct btf_str_ptrs *strs;
struct btf_str_ptr *s;
if (*str_off_ptr == 0)
return 0;
strs = ctx;
s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt,
sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp);
if (!s)
return -EINVAL;
s->used = true;
return 0;
}
static int btf_str_remap_offset(__u32 *str_off_ptr, void *ctx)
{
struct btf_str_ptrs *strs;
struct btf_str_ptr *s;
if (*str_off_ptr == 0)
return 0;
strs = ctx;
s = bsearch(strs->data + *str_off_ptr, strs->ptrs, strs->cnt,
sizeof(struct btf_str_ptr), btf_dedup_str_ptr_cmp);
if (!s)
return -EINVAL;
*str_off_ptr = s->new_off;
return 0;
}
/*
* Dedup string and filter out those that are not referenced from either .BTF
* or .BTF.ext (if provided) sections.
*
* This is done by building index of all strings in BTF's string section,
* then iterating over all entities that can reference strings (e.g., type
* names, struct field names, .BTF.ext line info, etc) and marking corresponding
* strings as used. After that all used strings are deduped and compacted into
* sequential blob of memory and new offsets are calculated. Then all the string
* references are iterated again and rewritten using new offsets.
*/
static int btf_dedup_strings(struct btf_dedup *d)
{
const struct btf_header *hdr = d->btf->hdr;
char *start = (char *)d->btf->nohdr_data + hdr->str_off;
char *end = start + d->btf->hdr->str_len;
char *p = start, *tmp_strs = NULL;
struct btf_str_ptrs strs = {
.cnt = 0,
.cap = 0,
.ptrs = NULL,
.data = start,
};
int i, j, err = 0, grp_idx;
bool grp_used;
/* build index of all strings */
while (p < end) {
if (strs.cnt + 1 > strs.cap) {
struct btf_str_ptr *new_ptrs;
strs.cap += max(strs.cnt / 2, 16U);
new_ptrs = realloc(strs.ptrs,
sizeof(strs.ptrs[0]) * strs.cap);
if (!new_ptrs) {
err = -ENOMEM;
goto done;
}
strs.ptrs = new_ptrs;
}
strs.ptrs[strs.cnt].str = p;
strs.ptrs[strs.cnt].used = false;
p += strlen(p) + 1;
strs.cnt++;
}
/* temporary storage for deduplicated strings */
tmp_strs = malloc(d->btf->hdr->str_len);
if (!tmp_strs) {
err = -ENOMEM;
goto done;
}
/* mark all used strings */
strs.ptrs[0].used = true;
err = btf_for_each_str_off(d, btf_str_mark_as_used, &strs);
if (err)
goto done;
/* sort strings by context, so that we can identify duplicates */
qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_content);
/*
* iterate groups of equal strings and if any instance in a group was
* referenced, emit single instance and remember new offset
*/
p = tmp_strs;
grp_idx = 0;
grp_used = strs.ptrs[0].used;
/* iterate past end to avoid code duplication after loop */
for (i = 1; i <= strs.cnt; i++) {
/*
* when i == strs.cnt, we want to skip string comparison and go
* straight to handling last group of strings (otherwise we'd
* need to handle last group after the loop w/ duplicated code)
*/
if (i < strs.cnt &&
!strcmp(strs.ptrs[i].str, strs.ptrs[grp_idx].str)) {
grp_used = grp_used || strs.ptrs[i].used;
continue;
}
/*
* this check would have been required after the loop to handle
* last group of strings, but due to <= condition in a loop
* we avoid that duplication
*/
if (grp_used) {
int new_off = p - tmp_strs;
__u32 len = strlen(strs.ptrs[grp_idx].str);
memmove(p, strs.ptrs[grp_idx].str, len + 1);
for (j = grp_idx; j < i; j++)
strs.ptrs[j].new_off = new_off;
p += len + 1;
}
if (i < strs.cnt) {
grp_idx = i;
grp_used = strs.ptrs[i].used;
}
}
/* replace original strings with deduped ones */
d->btf->hdr->str_len = p - tmp_strs;
memmove(start, tmp_strs, d->btf->hdr->str_len);
end = start + d->btf->hdr->str_len;
/* restore original order for further binary search lookups */
qsort(strs.ptrs, strs.cnt, sizeof(strs.ptrs[0]), str_sort_by_offset);
/* remap string offsets */
err = btf_for_each_str_off(d, btf_str_remap_offset, &strs);
if (err)
goto done;
d->btf->hdr->str_len = end - start;
done:
free(tmp_strs);
free(strs.ptrs);
return err;
}
static long btf_hash_common(struct btf_type *t)
{
long h;
h = hash_combine(0, t->name_off);
h = hash_combine(h, t->info);
h = hash_combine(h, t->size);
return h;
}
static bool btf_equal_common(struct btf_type *t1, struct btf_type *t2)
{
return t1->name_off == t2->name_off &&
t1->info == t2->info &&
t1->size == t2->size;
}
/* Calculate type signature hash of INT. */
static long btf_hash_int(struct btf_type *t)
{
__u32 info = *(__u32 *)(t + 1);
long h;
h = btf_hash_common(t);
h = hash_combine(h, info);
return h;
}
/* Check structural equality of two INTs. */
static bool btf_equal_int(struct btf_type *t1, struct btf_type *t2)
{
__u32 info1, info2;
if (!btf_equal_common(t1, t2))
return false;
info1 = *(__u32 *)(t1 + 1);
info2 = *(__u32 *)(t2 + 1);
return info1 == info2;
}
/* Calculate type signature hash of ENUM. */
static long btf_hash_enum(struct btf_type *t)
{
long h;
/* don't hash vlen and enum members to support enum fwd resolving */
h = hash_combine(0, t->name_off);
h = hash_combine(h, t->info & ~0xffff);
h = hash_combine(h, t->size);
return h;
}
/* Check structural equality of two ENUMs. */
static bool btf_equal_enum(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_enum *m1, *m2;
__u16 vlen;
int i;
if (!btf_equal_common(t1, t2))
return false;
vlen = btf_vlen(t1);
m1 = btf_enum(t1);
m2 = btf_enum(t2);
for (i = 0; i < vlen; i++) {
if (m1->name_off != m2->name_off || m1->val != m2->val)
return false;
m1++;
m2++;
}
return true;
}
static inline bool btf_is_enum_fwd(struct btf_type *t)
{
return btf_is_enum(t) && btf_vlen(t) == 0;
}
static bool btf_compat_enum(struct btf_type *t1, struct btf_type *t2)
{
if (!btf_is_enum_fwd(t1) && !btf_is_enum_fwd(t2))
return btf_equal_enum(t1, t2);
/* ignore vlen when comparing */
return t1->name_off == t2->name_off &&
(t1->info & ~0xffff) == (t2->info & ~0xffff) &&
t1->size == t2->size;
}
/*
* Calculate type signature hash of STRUCT/UNION, ignoring referenced type IDs,
* as referenced type IDs equivalence is established separately during type
* graph equivalence check algorithm.
*/
static long btf_hash_struct(struct btf_type *t)
{
const struct btf_member *member = btf_members(t);
__u32 vlen = btf_vlen(t);
long h = btf_hash_common(t);
int i;
for (i = 0; i < vlen; i++) {
h = hash_combine(h, member->name_off);
h = hash_combine(h, member->offset);
/* no hashing of referenced type ID, it can be unresolved yet */
member++;
}
return h;
}
/*
* Check structural compatibility of two FUNC_PROTOs, ignoring referenced type
* IDs. This check is performed during type graph equivalence check and
* referenced types equivalence is checked separately.
*/
static bool btf_shallow_equal_struct(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_member *m1, *m2;
__u16 vlen;
int i;
if (!btf_equal_common(t1, t2))
return false;
vlen = btf_vlen(t1);
m1 = btf_members(t1);
m2 = btf_members(t2);
for (i = 0; i < vlen; i++) {
if (m1->name_off != m2->name_off || m1->offset != m2->offset)
return false;
m1++;
m2++;
}
return true;
}
/*
* Calculate type signature hash of ARRAY, including referenced type IDs,
* under assumption that they were already resolved to canonical type IDs and
* are not going to change.
*/
static long btf_hash_array(struct btf_type *t)
{
const struct btf_array *info = btf_array(t);
long h = btf_hash_common(t);
h = hash_combine(h, info->type);
h = hash_combine(h, info->index_type);
h = hash_combine(h, info->nelems);
return h;
}
/*
* Check exact equality of two ARRAYs, taking into account referenced
* type IDs, under assumption that they were already resolved to canonical
* type IDs and are not going to change.
* This function is called during reference types deduplication to compare
* ARRAY to potential canonical representative.
*/
static bool btf_equal_array(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_array *info1, *info2;
if (!btf_equal_common(t1, t2))
return false;
info1 = btf_array(t1);
info2 = btf_array(t2);
return info1->type == info2->type &&
info1->index_type == info2->index_type &&
info1->nelems == info2->nelems;
}
/*
* Check structural compatibility of two ARRAYs, ignoring referenced type
* IDs. This check is performed during type graph equivalence check and
* referenced types equivalence is checked separately.
*/
static bool btf_compat_array(struct btf_type *t1, struct btf_type *t2)
{
if (!btf_equal_common(t1, t2))
return false;
return btf_array(t1)->nelems == btf_array(t2)->nelems;
}
/*
* Calculate type signature hash of FUNC_PROTO, including referenced type IDs,
* under assumption that they were already resolved to canonical type IDs and
* are not going to change.
*/
static long btf_hash_fnproto(struct btf_type *t)
{
const struct btf_param *member = btf_params(t);
__u16 vlen = btf_vlen(t);
long h = btf_hash_common(t);
int i;
for (i = 0; i < vlen; i++) {
h = hash_combine(h, member->name_off);
h = hash_combine(h, member->type);
member++;
}
return h;
}
/*
* Check exact equality of two FUNC_PROTOs, taking into account referenced
* type IDs, under assumption that they were already resolved to canonical
* type IDs and are not going to change.
* This function is called during reference types deduplication to compare
* FUNC_PROTO to potential canonical representative.
*/
static bool btf_equal_fnproto(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_param *m1, *m2;
__u16 vlen;
int i;
if (!btf_equal_common(t1, t2))
return false;
vlen = btf_vlen(t1);
m1 = btf_params(t1);
m2 = btf_params(t2);
for (i = 0; i < vlen; i++) {
if (m1->name_off != m2->name_off || m1->type != m2->type)
return false;
m1++;
m2++;
}
return true;
}
/*
* Check structural compatibility of two FUNC_PROTOs, ignoring referenced type
* IDs. This check is performed during type graph equivalence check and
* referenced types equivalence is checked separately.
*/
static bool btf_compat_fnproto(struct btf_type *t1, struct btf_type *t2)
{
const struct btf_param *m1, *m2;
__u16 vlen;
int i;
/* skip return type ID */
if (t1->name_off != t2->name_off || t1->info != t2->info)
return false;
vlen = btf_vlen(t1);
m1 = btf_params(t1);
m2 = btf_params(t2);
for (i = 0; i < vlen; i++) {
if (m1->name_off != m2->name_off)
return false;
m1++;
m2++;
}
return true;
}
/*
* Deduplicate primitive types, that can't reference other types, by calculating
* their type signature hash and comparing them with any possible canonical
* candidate. If no canonical candidate matches, type itself is marked as
* canonical and is added into `btf_dedup->dedup_table` as another candidate.
*/
static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id)
{
struct btf_type *t = d->btf->types[type_id];
struct hashmap_entry *hash_entry;
struct btf_type *cand;
/* if we don't find equivalent type, then we are canonical */
__u32 new_id = type_id;
__u32 cand_id;
long h;
switch (btf_kind(t)) {
case BTF_KIND_CONST:
case BTF_KIND_VOLATILE:
case BTF_KIND_RESTRICT:
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_ARRAY:
case BTF_KIND_STRUCT:
case BTF_KIND_UNION:
case BTF_KIND_FUNC:
case BTF_KIND_FUNC_PROTO:
case BTF_KIND_VAR:
case BTF_KIND_DATASEC:
return 0;
case BTF_KIND_INT:
h = btf_hash_int(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = d->btf->types[cand_id];
if (btf_equal_int(t, cand)) {
new_id = cand_id;
break;
}
}
break;
case BTF_KIND_ENUM:
h = btf_hash_enum(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = d->btf->types[cand_id];
if (btf_equal_enum(t, cand)) {
new_id = cand_id;
break;
}
if (d->opts.dont_resolve_fwds)
continue;
if (btf_compat_enum(t, cand)) {
if (btf_is_enum_fwd(t)) {
/* resolve fwd to full enum */
new_id = cand_id;
break;
}
/* resolve canonical enum fwd to full enum */
d->map[cand_id] = type_id;
}
}
break;
case BTF_KIND_FWD:
h = btf_hash_common(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = d->btf->types[cand_id];
if (btf_equal_common(t, cand)) {
new_id = cand_id;
break;
}
}
break;
default:
return -EINVAL;
}
d->map[type_id] = new_id;
if (type_id == new_id && btf_dedup_table_add(d, h, type_id))
return -ENOMEM;
return 0;
}
static int btf_dedup_prim_types(struct btf_dedup *d)
{
int i, err;
for (i = 1; i <= d->btf->nr_types; i++) {
err = btf_dedup_prim_type(d, i);
if (err)
return err;
}
return 0;
}
/*
* Check whether type is already mapped into canonical one (could be to itself).
*/
static inline bool is_type_mapped(struct btf_dedup *d, uint32_t type_id)
{
return d->map[type_id] <= BTF_MAX_NR_TYPES;
}
/*
* Resolve type ID into its canonical type ID, if any; otherwise return original
* type ID. If type is FWD and is resolved into STRUCT/UNION already, follow
* STRUCT/UNION link and resolve it into canonical type ID as well.
*/
static inline __u32 resolve_type_id(struct btf_dedup *d, __u32 type_id)
{
while (is_type_mapped(d, type_id) && d->map[type_id] != type_id)
type_id = d->map[type_id];
return type_id;
}
/*
* Resolve FWD to underlying STRUCT/UNION, if any; otherwise return original
* type ID.
*/
static uint32_t resolve_fwd_id(struct btf_dedup *d, uint32_t type_id)
{
__u32 orig_type_id = type_id;
if (!btf_is_fwd(d->btf->types[type_id]))
return type_id;
while (is_type_mapped(d, type_id) && d->map[type_id] != type_id)
type_id = d->map[type_id];
if (!btf_is_fwd(d->btf->types[type_id]))
return type_id;
return orig_type_id;
}
static inline __u16 btf_fwd_kind(struct btf_type *t)
{
return btf_kflag(t) ? BTF_KIND_UNION : BTF_KIND_STRUCT;
}
/*
* Check equivalence of BTF type graph formed by candidate struct/union (we'll
* call it "candidate graph" in this description for brevity) to a type graph
* formed by (potential) canonical struct/union ("canonical graph" for brevity
* here, though keep in mind that not all types in canonical graph are
* necessarily canonical representatives themselves, some of them might be
* duplicates or its uniqueness might not have been established yet).
* Returns:
* - >0, if type graphs are equivalent;
* - 0, if not equivalent;
* - <0, on error.
*
* Algorithm performs side-by-side DFS traversal of both type graphs and checks
* equivalence of BTF types at each step. If at any point BTF types in candidate
* and canonical graphs are not compatible structurally, whole graphs are
* incompatible. If types are structurally equivalent (i.e., all information
* except referenced type IDs is exactly the same), a mapping from `canon_id` to
* a `cand_id` is recored in hypothetical mapping (`btf_dedup->hypot_map`).
* If a type references other types, then those referenced types are checked
* for equivalence recursively.
*
* During DFS traversal, if we find that for current `canon_id` type we
* already have some mapping in hypothetical map, we check for two possible
* situations:
* - `canon_id` is mapped to exactly the same type as `cand_id`. This will
* happen when type graphs have cycles. In this case we assume those two
* types are equivalent.
* - `canon_id` is mapped to different type. This is contradiction in our
* hypothetical mapping, because same graph in canonical graph corresponds
* to two different types in candidate graph, which for equivalent type
* graphs shouldn't happen. This condition terminates equivalence check
* with negative result.
*
* If type graphs traversal exhausts types to check and find no contradiction,
* then type graphs are equivalent.
*
* When checking types for equivalence, there is one special case: FWD types.
* If FWD type resolution is allowed and one of the types (either from canonical
* or candidate graph) is FWD and other is STRUCT/UNION (depending on FWD's kind
* flag) and their names match, hypothetical mapping is updated to point from
* FWD to STRUCT/UNION. If graphs will be determined as equivalent successfully,
* this mapping will be used to record FWD -> STRUCT/UNION mapping permanently.
*
* Technically, this could lead to incorrect FWD to STRUCT/UNION resolution,
* if there are two exactly named (or anonymous) structs/unions that are
* compatible structurally, one of which has FWD field, while other is concrete
* STRUCT/UNION, but according to C sources they are different structs/unions
* that are referencing different types with the same name. This is extremely
* unlikely to happen, but btf_dedup API allows to disable FWD resolution if
* this logic is causing problems.
*
* Doing FWD resolution means that both candidate and/or canonical graphs can
* consists of portions of the graph that come from multiple compilation units.
* This is due to the fact that types within single compilation unit are always
* deduplicated and FWDs are already resolved, if referenced struct/union
* definiton is available. So, if we had unresolved FWD and found corresponding
* STRUCT/UNION, they will be from different compilation units. This
* consequently means that when we "link" FWD to corresponding STRUCT/UNION,
* type graph will likely have at least two different BTF types that describe
* same type (e.g., most probably there will be two different BTF types for the
* same 'int' primitive type) and could even have "overlapping" parts of type
* graph that describe same subset of types.
*
* This in turn means that our assumption that each type in canonical graph
* must correspond to exactly one type in candidate graph might not hold
* anymore and will make it harder to detect contradictions using hypothetical
* map. To handle this problem, we allow to follow FWD -> STRUCT/UNION
* resolution only in canonical graph. FWDs in candidate graphs are never
* resolved. To see why it's OK, let's check all possible situations w.r.t. FWDs
* that can occur:
* - Both types in canonical and candidate graphs are FWDs. If they are
* structurally equivalent, then they can either be both resolved to the
* same STRUCT/UNION or not resolved at all. In both cases they are
* equivalent and there is no need to resolve FWD on candidate side.
* - Both types in canonical and candidate graphs are concrete STRUCT/UNION,
* so nothing to resolve as well, algorithm will check equivalence anyway.
* - Type in canonical graph is FWD, while type in candidate is concrete
* STRUCT/UNION. In this case candidate graph comes from single compilation
* unit, so there is exactly one BTF type for each unique C type. After
* resolving FWD into STRUCT/UNION, there might be more than one BTF type
* in canonical graph mapping to single BTF type in candidate graph, but
* because hypothetical mapping maps from canonical to candidate types, it's
* alright, and we still maintain the property of having single `canon_id`
* mapping to single `cand_id` (there could be two different `canon_id`
* mapped to the same `cand_id`, but it's not contradictory).
* - Type in canonical graph is concrete STRUCT/UNION, while type in candidate
* graph is FWD. In this case we are just going to check compatibility of
* STRUCT/UNION and corresponding FWD, and if they are compatible, we'll
* assume that whatever STRUCT/UNION FWD resolves to must be equivalent to
* a concrete STRUCT/UNION from canonical graph. If the rest of type graphs
* turn out equivalent, we'll re-resolve FWD to concrete STRUCT/UNION from
* canonical graph.
*/
static int btf_dedup_is_equiv(struct btf_dedup *d, __u32 cand_id,
__u32 canon_id)
{
struct btf_type *cand_type;
struct btf_type *canon_type;
__u32 hypot_type_id;
__u16 cand_kind;
__u16 canon_kind;
int i, eq;
/* if both resolve to the same canonical, they must be equivalent */
if (resolve_type_id(d, cand_id) == resolve_type_id(d, canon_id))
return 1;
canon_id = resolve_fwd_id(d, canon_id);
hypot_type_id = d->hypot_map[canon_id];
if (hypot_type_id <= BTF_MAX_NR_TYPES)
return hypot_type_id == cand_id;
if (btf_dedup_hypot_map_add(d, canon_id, cand_id))
return -ENOMEM;
cand_type = d->btf->types[cand_id];
canon_type = d->btf->types[canon_id];
cand_kind = btf_kind(cand_type);
canon_kind = btf_kind(canon_type);
if (cand_type->name_off != canon_type->name_off)
return 0;
/* FWD <--> STRUCT/UNION equivalence check, if enabled */
if (!d->opts.dont_resolve_fwds
&& (cand_kind == BTF_KIND_FWD || canon_kind == BTF_KIND_FWD)
&& cand_kind != canon_kind) {
__u16 real_kind;
__u16 fwd_kind;
if (cand_kind == BTF_KIND_FWD) {
real_kind = canon_kind;
fwd_kind = btf_fwd_kind(cand_type);
} else {
real_kind = cand_kind;
fwd_kind = btf_fwd_kind(canon_type);
}
return fwd_kind == real_kind;
}
if (cand_kind != canon_kind)
return 0;
switch (cand_kind) {
case BTF_KIND_INT:
return btf_equal_int(cand_type, canon_type);
case BTF_KIND_ENUM:
if (d->opts.dont_resolve_fwds)
return btf_equal_enum(cand_type, canon_type);
else
return btf_compat_enum(cand_type, canon_type);
case BTF_KIND_FWD:
return btf_equal_common(cand_type, canon_type);
case BTF_KIND_CONST:
case BTF_KIND_VOLATILE:
case BTF_KIND_RESTRICT:
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
if (cand_type->info != canon_type->info)
return 0;
return btf_dedup_is_equiv(d, cand_type->type, canon_type->type);
case BTF_KIND_ARRAY: {
const struct btf_array *cand_arr, *canon_arr;
if (!btf_compat_array(cand_type, canon_type))
return 0;
cand_arr = btf_array(cand_type);
canon_arr = btf_array(canon_type);
eq = btf_dedup_is_equiv(d,
cand_arr->index_type, canon_arr->index_type);
if (eq <= 0)
return eq;
return btf_dedup_is_equiv(d, cand_arr->type, canon_arr->type);
}
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
const struct btf_member *cand_m, *canon_m;
__u16 vlen;
if (!btf_shallow_equal_struct(cand_type, canon_type))
return 0;
vlen = btf_vlen(cand_type);
cand_m = btf_members(cand_type);
canon_m = btf_members(canon_type);
for (i = 0; i < vlen; i++) {
eq = btf_dedup_is_equiv(d, cand_m->type, canon_m->type);
if (eq <= 0)
return eq;
cand_m++;
canon_m++;
}
return 1;
}
case BTF_KIND_FUNC_PROTO: {
const struct btf_param *cand_p, *canon_p;
__u16 vlen;
if (!btf_compat_fnproto(cand_type, canon_type))
return 0;
eq = btf_dedup_is_equiv(d, cand_type->type, canon_type->type);
if (eq <= 0)
return eq;
vlen = btf_vlen(cand_type);
cand_p = btf_params(cand_type);
canon_p = btf_params(canon_type);
for (i = 0; i < vlen; i++) {
eq = btf_dedup_is_equiv(d, cand_p->type, canon_p->type);
if (eq <= 0)
return eq;
cand_p++;
canon_p++;
}
return 1;
}
default:
return -EINVAL;
}
return 0;
}
/*
* Use hypothetical mapping, produced by successful type graph equivalence
* check, to augment existing struct/union canonical mapping, where possible.
*
* If BTF_KIND_FWD resolution is allowed, this mapping is also used to record
* FWD -> STRUCT/UNION correspondence as well. FWD resolution is bidirectional:
* it doesn't matter if FWD type was part of canonical graph or candidate one,
* we are recording the mapping anyway. As opposed to carefulness required
* for struct/union correspondence mapping (described below), for FWD resolution
* it's not important, as by the time that FWD type (reference type) will be
* deduplicated all structs/unions will be deduped already anyway.
*
* Recording STRUCT/UNION mapping is purely a performance optimization and is
* not required for correctness. It needs to be done carefully to ensure that
* struct/union from candidate's type graph is not mapped into corresponding
* struct/union from canonical type graph that itself hasn't been resolved into
* canonical representative. The only guarantee we have is that canonical
* struct/union was determined as canonical and that won't change. But any
* types referenced through that struct/union fields could have been not yet
* resolved, so in case like that it's too early to establish any kind of
* correspondence between structs/unions.
*
* No canonical correspondence is derived for primitive types (they are already
* deduplicated completely already anyway) or reference types (they rely on
* stability of struct/union canonical relationship for equivalence checks).
*/
static void btf_dedup_merge_hypot_map(struct btf_dedup *d)
{
__u32 cand_type_id, targ_type_id;
__u16 t_kind, c_kind;
__u32 t_id, c_id;
int i;
for (i = 0; i < d->hypot_cnt; i++) {
cand_type_id = d->hypot_list[i];
targ_type_id = d->hypot_map[cand_type_id];
t_id = resolve_type_id(d, targ_type_id);
c_id = resolve_type_id(d, cand_type_id);
t_kind = btf_kind(d->btf->types[t_id]);
c_kind = btf_kind(d->btf->types[c_id]);
/*
* Resolve FWD into STRUCT/UNION.
* It's ok to resolve FWD into STRUCT/UNION that's not yet
* mapped to canonical representative (as opposed to
* STRUCT/UNION <--> STRUCT/UNION mapping logic below), because
* eventually that struct is going to be mapped and all resolved
* FWDs will automatically resolve to correct canonical
* representative. This will happen before ref type deduping,
* which critically depends on stability of these mapping. This
* stability is not a requirement for STRUCT/UNION equivalence
* checks, though.
*/
if (t_kind != BTF_KIND_FWD && c_kind == BTF_KIND_FWD)
d->map[c_id] = t_id;
else if (t_kind == BTF_KIND_FWD && c_kind != BTF_KIND_FWD)
d->map[t_id] = c_id;
if ((t_kind == BTF_KIND_STRUCT || t_kind == BTF_KIND_UNION) &&
c_kind != BTF_KIND_FWD &&
is_type_mapped(d, c_id) &&
!is_type_mapped(d, t_id)) {
/*
* as a perf optimization, we can map struct/union
* that's part of type graph we just verified for
* equivalence. We can do that for struct/union that has
* canonical representative only, though.
*/
d->map[t_id] = c_id;
}
}
}
/*
* Deduplicate struct/union types.
*
* For each struct/union type its type signature hash is calculated, taking
* into account type's name, size, number, order and names of fields, but
* ignoring type ID's referenced from fields, because they might not be deduped
* completely until after reference types deduplication phase. This type hash
* is used to iterate over all potential canonical types, sharing same hash.
* For each canonical candidate we check whether type graphs that they form
* (through referenced types in fields and so on) are equivalent using algorithm
* implemented in `btf_dedup_is_equiv`. If such equivalence is found and
* BTF_KIND_FWD resolution is allowed, then hypothetical mapping
* (btf_dedup->hypot_map) produced by aforementioned type graph equivalence
* algorithm is used to record FWD -> STRUCT/UNION mapping. It's also used to
* potentially map other structs/unions to their canonical representatives,
* if such relationship hasn't yet been established. This speeds up algorithm
* by eliminating some of the duplicate work.
*
* If no matching canonical representative was found, struct/union is marked
* as canonical for itself and is added into btf_dedup->dedup_table hash map
* for further look ups.
*/
static int btf_dedup_struct_type(struct btf_dedup *d, __u32 type_id)
{
struct btf_type *cand_type, *t;
struct hashmap_entry *hash_entry;
/* if we don't find equivalent type, then we are canonical */
__u32 new_id = type_id;
__u16 kind;
long h;
/* already deduped or is in process of deduping (loop detected) */
if (d->map[type_id] <= BTF_MAX_NR_TYPES)
return 0;
t = d->btf->types[type_id];
kind = btf_kind(t);
if (kind != BTF_KIND_STRUCT && kind != BTF_KIND_UNION)
return 0;
h = btf_hash_struct(t);
for_each_dedup_cand(d, hash_entry, h) {
__u32 cand_id = (__u32)(long)hash_entry->value;
int eq;
/*
* Even though btf_dedup_is_equiv() checks for
* btf_shallow_equal_struct() internally when checking two
* structs (unions) for equivalence, we need to guard here
* from picking matching FWD type as a dedup candidate.
* This can happen due to hash collision. In such case just
* relying on btf_dedup_is_equiv() would lead to potentially
* creating a loop (FWD -> STRUCT and STRUCT -> FWD), because
* FWD and compatible STRUCT/UNION are considered equivalent.
*/
cand_type = d->btf->types[cand_id];
if (!btf_shallow_equal_struct(t, cand_type))
continue;
btf_dedup_clear_hypot_map(d);
eq = btf_dedup_is_equiv(d, type_id, cand_id);
if (eq < 0)
return eq;
if (!eq)
continue;
new_id = cand_id;
btf_dedup_merge_hypot_map(d);
break;
}
d->map[type_id] = new_id;
if (type_id == new_id && btf_dedup_table_add(d, h, type_id))
return -ENOMEM;
return 0;
}
static int btf_dedup_struct_types(struct btf_dedup *d)
{
int i, err;
for (i = 1; i <= d->btf->nr_types; i++) {
err = btf_dedup_struct_type(d, i);
if (err)
return err;
}
return 0;
}
/*
* Deduplicate reference type.
*
* Once all primitive and struct/union types got deduplicated, we can easily
* deduplicate all other (reference) BTF types. This is done in two steps:
*
* 1. Resolve all referenced type IDs into their canonical type IDs. This
* resolution can be done either immediately for primitive or struct/union types
* (because they were deduped in previous two phases) or recursively for
* reference types. Recursion will always terminate at either primitive or
* struct/union type, at which point we can "unwind" chain of reference types
* one by one. There is no danger of encountering cycles because in C type
* system the only way to form type cycle is through struct/union, so any chain
* of reference types, even those taking part in a type cycle, will inevitably
* reach struct/union at some point.
*
* 2. Once all referenced type IDs are resolved into canonical ones, BTF type
* becomes "stable", in the sense that no further deduplication will cause
* any changes to it. With that, it's now possible to calculate type's signature
* hash (this time taking into account referenced type IDs) and loop over all
* potential canonical representatives. If no match was found, current type
* will become canonical representative of itself and will be added into
* btf_dedup->dedup_table as another possible canonical representative.
*/
static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id)
{
struct hashmap_entry *hash_entry;
__u32 new_id = type_id, cand_id;
struct btf_type *t, *cand;
/* if we don't find equivalent type, then we are representative type */
int ref_type_id;
long h;
if (d->map[type_id] == BTF_IN_PROGRESS_ID)
return -ELOOP;
if (d->map[type_id] <= BTF_MAX_NR_TYPES)
return resolve_type_id(d, type_id);
t = d->btf->types[type_id];
d->map[type_id] = BTF_IN_PROGRESS_ID;
switch (btf_kind(t)) {
case BTF_KIND_CONST:
case BTF_KIND_VOLATILE:
case BTF_KIND_RESTRICT:
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
ref_type_id = btf_dedup_ref_type(d, t->type);
if (ref_type_id < 0)
return ref_type_id;
t->type = ref_type_id;
h = btf_hash_common(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = d->btf->types[cand_id];
if (btf_equal_common(t, cand)) {
new_id = cand_id;
break;
}
}
break;
case BTF_KIND_ARRAY: {
struct btf_array *info = btf_array(t);
ref_type_id = btf_dedup_ref_type(d, info->type);
if (ref_type_id < 0)
return ref_type_id;
info->type = ref_type_id;
ref_type_id = btf_dedup_ref_type(d, info->index_type);
if (ref_type_id < 0)
return ref_type_id;
info->index_type = ref_type_id;
h = btf_hash_array(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = d->btf->types[cand_id];
if (btf_equal_array(t, cand)) {
new_id = cand_id;
break;
}
}
break;
}
case BTF_KIND_FUNC_PROTO: {
struct btf_param *param;
__u16 vlen;
int i;
ref_type_id = btf_dedup_ref_type(d, t->type);
if (ref_type_id < 0)
return ref_type_id;
t->type = ref_type_id;
vlen = btf_vlen(t);
param = btf_params(t);
for (i = 0; i < vlen; i++) {
ref_type_id = btf_dedup_ref_type(d, param->type);
if (ref_type_id < 0)
return ref_type_id;
param->type = ref_type_id;
param++;
}
h = btf_hash_fnproto(t);
for_each_dedup_cand(d, hash_entry, h) {
cand_id = (__u32)(long)hash_entry->value;
cand = d->btf->types[cand_id];
if (btf_equal_fnproto(t, cand)) {
new_id = cand_id;
break;
}
}
break;
}
default:
return -EINVAL;
}
d->map[type_id] = new_id;
if (type_id == new_id && btf_dedup_table_add(d, h, type_id))
return -ENOMEM;
return new_id;
}
static int btf_dedup_ref_types(struct btf_dedup *d)
{
int i, err;
for (i = 1; i <= d->btf->nr_types; i++) {
err = btf_dedup_ref_type(d, i);
if (err < 0)
return err;
}
/* we won't need d->dedup_table anymore */
hashmap__free(d->dedup_table);
d->dedup_table = NULL;
return 0;
}
/*
* Compact types.
*
* After we established for each type its corresponding canonical representative
* type, we now can eliminate types that are not canonical and leave only
* canonical ones layed out sequentially in memory by copying them over
* duplicates. During compaction btf_dedup->hypot_map array is reused to store
* a map from original type ID to a new compacted type ID, which will be used
* during next phase to "fix up" type IDs, referenced from struct/union and
* reference types.
*/
static int btf_dedup_compact_types(struct btf_dedup *d)
{
struct btf_type **new_types;
__u32 next_type_id = 1;
char *types_start, *p;
int i, len;
/* we are going to reuse hypot_map to store compaction remapping */
d->hypot_map[0] = 0;
for (i = 1; i <= d->btf->nr_types; i++)
d->hypot_map[i] = BTF_UNPROCESSED_ID;
types_start = d->btf->nohdr_data + d->btf->hdr->type_off;
p = types_start;
for (i = 1; i <= d->btf->nr_types; i++) {
if (d->map[i] != i)
continue;
len = btf_type_size(d->btf->types[i]);
if (len < 0)
return len;
memmove(p, d->btf->types[i], len);
d->hypot_map[i] = next_type_id;
d->btf->types[next_type_id] = (struct btf_type *)p;
p += len;
next_type_id++;
}
/* shrink struct btf's internal types index and update btf_header */
d->btf->nr_types = next_type_id - 1;
d->btf->types_size = d->btf->nr_types;
d->btf->hdr->type_len = p - types_start;
new_types = realloc(d->btf->types,
(1 + d->btf->nr_types) * sizeof(struct btf_type *));
if (!new_types)
return -ENOMEM;
d->btf->types = new_types;
/* make sure string section follows type information without gaps */
d->btf->hdr->str_off = p - (char *)d->btf->nohdr_data;
memmove(p, d->btf->strings, d->btf->hdr->str_len);
d->btf->strings = p;
p += d->btf->hdr->str_len;
d->btf->data_size = p - (char *)d->btf->data;
return 0;
}
/*
* Figure out final (deduplicated and compacted) type ID for provided original
* `type_id` by first resolving it into corresponding canonical type ID and
* then mapping it to a deduplicated type ID, stored in btf_dedup->hypot_map,
* which is populated during compaction phase.
*/
static int btf_dedup_remap_type_id(struct btf_dedup *d, __u32 type_id)
{
__u32 resolved_type_id, new_type_id;
resolved_type_id = resolve_type_id(d, type_id);
new_type_id = d->hypot_map[resolved_type_id];
if (new_type_id > BTF_MAX_NR_TYPES)
return -EINVAL;
return new_type_id;
}
/*
* Remap referenced type IDs into deduped type IDs.
*
* After BTF types are deduplicated and compacted, their final type IDs may
* differ from original ones. The map from original to a corresponding
* deduped type ID is stored in btf_dedup->hypot_map and is populated during
* compaction phase. During remapping phase we are rewriting all type IDs
* referenced from any BTF type (e.g., struct fields, func proto args, etc) to
* their final deduped type IDs.
*/
static int btf_dedup_remap_type(struct btf_dedup *d, __u32 type_id)
{
struct btf_type *t = d->btf->types[type_id];
int i, r;
switch (btf_kind(t)) {
case BTF_KIND_INT:
case BTF_KIND_ENUM:
break;
case BTF_KIND_FWD:
case BTF_KIND_CONST:
case BTF_KIND_VOLATILE:
case BTF_KIND_RESTRICT:
case BTF_KIND_PTR:
case BTF_KIND_TYPEDEF:
case BTF_KIND_FUNC:
case BTF_KIND_VAR:
r = btf_dedup_remap_type_id(d, t->type);
if (r < 0)
return r;
t->type = r;
break;
case BTF_KIND_ARRAY: {
struct btf_array *arr_info = btf_array(t);
r = btf_dedup_remap_type_id(d, arr_info->type);
if (r < 0)
return r;
arr_info->type = r;
r = btf_dedup_remap_type_id(d, arr_info->index_type);
if (r < 0)
return r;
arr_info->index_type = r;
break;
}
case BTF_KIND_STRUCT:
case BTF_KIND_UNION: {
struct btf_member *member = btf_members(t);
__u16 vlen = btf_vlen(t);
for (i = 0; i < vlen; i++) {
r = btf_dedup_remap_type_id(d, member->type);
if (r < 0)
return r;
member->type = r;
member++;
}
break;
}
case BTF_KIND_FUNC_PROTO: {
struct btf_param *param = btf_params(t);
__u16 vlen = btf_vlen(t);
r = btf_dedup_remap_type_id(d, t->type);
if (r < 0)
return r;
t->type = r;
for (i = 0; i < vlen; i++) {
r = btf_dedup_remap_type_id(d, param->type);
if (r < 0)
return r;
param->type = r;
param++;
}
break;
}
case BTF_KIND_DATASEC: {
struct btf_var_secinfo *var = btf_var_secinfos(t);
__u16 vlen = btf_vlen(t);
for (i = 0; i < vlen; i++) {
r = btf_dedup_remap_type_id(d, var->type);
if (r < 0)
return r;
var->type = r;
var++;
}
break;
}
default:
return -EINVAL;
}
return 0;
}
static int btf_dedup_remap_types(struct btf_dedup *d)
{
int i, r;
for (i = 1; i <= d->btf->nr_types; i++) {
r = btf_dedup_remap_type(d, i);
if (r < 0)
return r;
}
return 0;
}
/*
* Probe few well-known locations for vmlinux kernel image and try to load BTF
* data out of it to use for target BTF.
*/
struct btf *libbpf_find_kernel_btf(void)
{
struct {
const char *path_fmt;
bool raw_btf;
} locations[] = {
/* try canonical vmlinux BTF through sysfs first */
{ "/sys/kernel/btf/vmlinux", true /* raw BTF */ },
/* fall back to trying to find vmlinux ELF on disk otherwise */
{ "/boot/vmlinux-%1$s" },
{ "/lib/modules/%1$s/vmlinux-%1$s" },
{ "/lib/modules/%1$s/build/vmlinux" },
{ "/usr/lib/modules/%1$s/kernel/vmlinux" },
{ "/usr/lib/debug/boot/vmlinux-%1$s" },
{ "/usr/lib/debug/boot/vmlinux-%1$s.debug" },
{ "/usr/lib/debug/lib/modules/%1$s/vmlinux" },
};
char path[PATH_MAX + 1];
struct utsname buf;
struct btf *btf;
int i;
uname(&buf);
for (i = 0; i < ARRAY_SIZE(locations); i++) {
snprintf(path, PATH_MAX, locations[i].path_fmt, buf.release);
if (access(path, R_OK))
continue;
if (locations[i].raw_btf)
btf = btf__parse_raw(path);
else
btf = btf__parse_elf(path, NULL);
pr_debug("loading kernel BTF '%s': %ld\n",
path, IS_ERR(btf) ? PTR_ERR(btf) : 0);
if (IS_ERR(btf))
continue;
return btf;
}
pr_warn("failed to find valid kernel BTF\n");
return ERR_PTR(-ESRCH);
}
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