// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
/*
* resolve_btfids scans ELF object for .BTF_ids section and resolves
* its symbols with BTF ID values.
*
* Each symbol points to 4 bytes data and is expected to have
* following name syntax:
*
* __BTF_ID__<type>__<symbol>[__<id>]
*
* type is:
*
* func - lookup BTF_KIND_FUNC symbol with <symbol> name
* and store its ID into the data:
*
* __BTF_ID__func__vfs_close__1:
* .zero 4
*
* struct - lookup BTF_KIND_STRUCT symbol with <symbol> name
* and store its ID into the data:
*
* __BTF_ID__struct__sk_buff__1:
* .zero 4
*
* union - lookup BTF_KIND_UNION symbol with <symbol> name
* and store its ID into the data:
*
* __BTF_ID__union__thread_union__1:
* .zero 4
*
* typedef - lookup BTF_KIND_TYPEDEF symbol with <symbol> name
* and store its ID into the data:
*
* __BTF_ID__typedef__pid_t__1:
* .zero 4
*
* set - store symbol size into first 4 bytes and sort following
* ID list
*
* __BTF_ID__set__list:
* .zero 4
* list:
* __BTF_ID__func__vfs_getattr__3:
* .zero 4
* __BTF_ID__func__vfs_fallocate__4:
* .zero 4
*
* set8 - store symbol size into first 4 bytes and sort following
* ID list
*
* __BTF_ID__set8__list:
* .zero 8
* list:
* __BTF_ID__func__vfs_getattr__3:
* .zero 4
* .word (1 << 0) | (1 << 2)
* __BTF_ID__func__vfs_fallocate__5:
* .zero 4
* .word (1 << 3) | (1 << 1) | (1 << 2)
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <libelf.h>
#include <gelf.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/btf_ids.h>
#include <linux/rbtree.h>
#include <linux/zalloc.h>
#include <linux/err.h>
#include <bpf/btf.h>
#include <bpf/libbpf.h>
#include <subcmd/parse-options.h>
#define BTF_IDS_SECTION ".BTF_ids"
#define BTF_ID_PREFIX "__BTF_ID__"
#define BTF_STRUCT "struct"
#define BTF_UNION "union"
#define BTF_TYPEDEF "typedef"
#define BTF_FUNC "func"
#define BTF_SET "set"
#define BTF_SET8 "set8"
#define ADDR_CNT 100
#if __BYTE_ORDER == __LITTLE_ENDIAN
# define ELFDATANATIVE ELFDATA2LSB
#elif __BYTE_ORDER == __BIG_ENDIAN
# define ELFDATANATIVE ELFDATA2MSB
#else
# error "Unknown machine endianness!"
#endif
struct btf_id {
struct rb_node rb_node;
char *name;
union {
int id;
int cnt;
};
int addr_cnt;
bool is_set;
bool is_set8;
Elf64_Addr addr[ADDR_CNT];
};
struct object {
const char *path;
const char *btf;
const char *base_btf_path;
struct {
int fd;
Elf *elf;
Elf_Data *symbols;
Elf_Data *idlist;
int symbols_shndx;
int idlist_shndx;
size_t strtabidx;
unsigned long idlist_addr;
int encoding;
} efile;
struct rb_root sets;
struct rb_root structs;
struct rb_root unions;
struct rb_root typedefs;
struct rb_root funcs;
int nr_funcs;
int nr_structs;
int nr_unions;
int nr_typedefs;
};
static int verbose;
static int eprintf(int level, int var, const char *fmt, ...)
{
va_list args;
int ret = 0;
if (var >= level) {
va_start(args, fmt);
ret = vfprintf(stderr, fmt, args);
va_end(args);
}
return ret;
}
#ifndef pr_fmt
#define pr_fmt(fmt) fmt
#endif
#define pr_debug(fmt, ...) \
eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debugN(n, fmt, ...) \
eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_err(fmt, ...) \
eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_info(fmt, ...) \
eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
static bool is_btf_id(const char *name)
{
return name && !strncmp(name, BTF_ID_PREFIX, sizeof(BTF_ID_PREFIX) - 1);
}
static struct btf_id *btf_id__find(struct rb_root *root, const char *name)
{
struct rb_node *p = root->rb_node;
struct btf_id *id;
int cmp;
while (p) {
id = rb_entry(p, struct btf_id, rb_node);
cmp = strcmp(id->name, name);
if (cmp < 0)
p = p->rb_left;
else if (cmp > 0)
p = p->rb_right;
else
return id;
}
return NULL;
}
static struct btf_id *
btf_id__add(struct rb_root *root, char *name, bool unique)
{
struct rb_node **p = &root->rb_node;
struct rb_node *parent = NULL;
struct btf_id *id;
int cmp;
while (*p != NULL) {
parent = *p;
id = rb_entry(parent, struct btf_id, rb_node);
cmp = strcmp(id->name, name);
if (cmp < 0)
p = &(*p)->rb_left;
else if (cmp > 0)
p = &(*p)->rb_right;
else
return unique ? NULL : id;
}
id = zalloc(sizeof(*id));
if (id) {
pr_debug("adding symbol %s\n", name);
id->name = name;
rb_link_node(&id->rb_node, parent, p);
rb_insert_color(&id->rb_node, root);
}
return id;
}
static char *get_id(const char *prefix_end)
{
/*
* __BTF_ID__func__vfs_truncate__0
* prefix_end = ^
* pos = ^
*/
int len = strlen(prefix_end);
int pos = sizeof("__") - 1;
char *p, *id;
if (pos >= len)
return NULL;
id = strdup(prefix_end + pos);
if (id) {
/*
* __BTF_ID__func__vfs_truncate__0
* id = ^
*
* cut the unique id part
*/
p = strrchr(id, '_');
p--;
if (*p != '_') {
free(id);
return NULL;
}
*p = '\0';
}
return id;
}
static struct btf_id *add_set(struct object *obj, char *name, bool is_set8)
{
/*
* __BTF_ID__set__name
* name = ^
* id = ^
*/
char *id = name + (is_set8 ? sizeof(BTF_SET8 "__") : sizeof(BTF_SET "__")) - 1;
int len = strlen(name);
if (id >= name + len) {
pr_err("FAILED to parse set name: %s\n", name);
return NULL;
}
return btf_id__add(&obj->sets, id, true);
}
static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
{
char *id;
id = get_id(name + size);
if (!id) {
pr_err("FAILED to parse symbol name: %s\n", name);
return NULL;
}
return btf_id__add(root, id, false);
}
/* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */
#ifndef SHF_COMPRESSED
#define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
#endif
/*
* The data of compressed section should be aligned to 4
* (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
* sets sh_addralign to 1, which makes libelf fail with
* misaligned section error during the update:
* FAILED elf_update(WRITE): invalid section alignment
*
* While waiting for ld fix, we fix the compressed sections
* sh_addralign value manualy.
*/
static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
{
int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;
if (!(sh->sh_flags & SHF_COMPRESSED))
return 0;
if (sh->sh_addralign == expected)
return 0;
pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
sh->sh_addralign, expected);
sh->sh_addralign = expected;
if (gelf_update_shdr(scn, sh) == 0) {
pr_err("FAILED cannot update section header: %s\n",
elf_errmsg(-1));
return -1;
}
return 0;
}
static int elf_collect(struct object *obj)
{
Elf_Scn *scn = NULL;
size_t shdrstrndx;
GElf_Ehdr ehdr;
int idx = 0;
Elf *elf;
int fd;
fd = open(obj->path, O_RDWR, 0666);
if (fd == -1) {
pr_err("FAILED cannot open %s: %s\n",
obj->path, strerror(errno));
return -1;
}
elf_version(EV_CURRENT);
elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
if (!elf) {
close(fd);
pr_err("FAILED cannot create ELF descriptor: %s\n",
elf_errmsg(-1));
return -1;
}
obj->efile.fd = fd;
obj->efile.elf = elf;
elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);
if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) {
pr_err("FAILED cannot get shdr str ndx\n");
return -1;
}
if (gelf_getehdr(obj->efile.elf, &ehdr) == NULL) {
pr_err("FAILED cannot get ELF header: %s\n",
elf_errmsg(-1));
return -1;
}
obj->efile.encoding = ehdr.e_ident[EI_DATA];
/*
* Scan all the elf sections and look for save data
* from .BTF_ids section and symbols.
*/
while ((scn = elf_nextscn(elf, scn)) != NULL) {
Elf_Data *data;
GElf_Shdr sh;
char *name;
idx++;
if (gelf_getshdr(scn, &sh) != &sh) {
pr_err("FAILED get section(%d) header\n", idx);
return -1;
}
name = elf_strptr(elf, shdrstrndx, sh.sh_name);
if (!name) {
pr_err("FAILED get section(%d) name\n", idx);
return -1;
}
data = elf_getdata(scn, 0);
if (!data) {
pr_err("FAILED to get section(%d) data from %s\n",
idx, name);
return -1;
}
pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
idx, name, (unsigned long) data->d_size,
(int) sh.sh_link, (unsigned long) sh.sh_flags,
(int) sh.sh_type);
if (sh.sh_type == SHT_SYMTAB) {
obj->efile.symbols = data;
obj->efile.symbols_shndx = idx;
obj->efile.strtabidx = sh.sh_link;
} else if (!strcmp(name, BTF_IDS_SECTION)) {
obj->efile.idlist = data;
obj->efile.idlist_shndx = idx;
obj->efile.idlist_addr = sh.sh_addr;
} else if (!strcmp(name, BTF_BASE_ELF_SEC)) {
/* If a .BTF.base section is found, do not resolve
* BTF ids relative to vmlinux; resolve relative
* to the .BTF.base section instead. btf__parse_split()
* will take care of this once the base BTF it is
* passed is NULL.
*/
obj->base_btf_path = NULL;
}
if (compressed_section_fix(elf, scn, &sh))
return -1;
}
return 0;
}
static int symbols_collect(struct object *obj)
{
Elf_Scn *scn = NULL;
int n, i;
GElf_Shdr sh;
char *name;
scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx);
if (!scn)
return -1;
if (gelf_getshdr(scn, &sh) != &sh)
return -1;
n = sh.sh_size / sh.sh_entsize;
/*
* Scan symbols and look for the ones starting with
* __BTF_ID__* over .BTF_ids section.
*/
for (i = 0; i < n; i++) {
char *prefix;
struct btf_id *id;
GElf_Sym sym;
if (!gelf_getsym(obj->efile.symbols, i, &sym))
return -1;
if (sym.st_shndx != obj->efile.idlist_shndx)
continue;
name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
sym.st_name);
if (!is_btf_id(name))
continue;
/*
* __BTF_ID__TYPE__vfs_truncate__0
* prefix = ^
*/
prefix = name + sizeof(BTF_ID_PREFIX) - 1;
/* struct */
if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) {
obj->nr_structs++;
id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1);
/* union */
} else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) {
obj->nr_unions++;
id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1);
/* typedef */
} else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) {
obj->nr_typedefs++;
id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1);
/* func */
} else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) {
obj->nr_funcs++;
id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
/* set8 */
} else if (!strncmp(prefix, BTF_SET8, sizeof(BTF_SET8) - 1)) {
id = add_set(obj, prefix, true);
/*
* SET8 objects store list's count, which is encoded
* in symbol's size, together with 'cnt' field hence
* that - 1.
*/
if (id) {
id->cnt = sym.st_size / sizeof(uint64_t) - 1;
id->is_set8 = true;
}
/* set */
} else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
id = add_set(obj, prefix, false);
/*
* SET objects store list's count, which is encoded
* in symbol's size, together with 'cnt' field hence
* that - 1.
*/
if (id) {
id->cnt = sym.st_size / sizeof(int) - 1;
id->is_set = true;
}
} else {
pr_err("FAILED unsupported prefix %s\n", prefix);
return -1;
}
if (!id)
return -ENOMEM;
if (id->addr_cnt >= ADDR_CNT) {
pr_err("FAILED symbol %s crossed the number of allowed lists\n",
id->name);
return -1;
}
id->addr[id->addr_cnt++] = sym.st_value;
}
return 0;
}
static int symbols_resolve(struct object *obj)
{
int nr_typedefs = obj->nr_typedefs;
int nr_structs = obj->nr_structs;
int nr_unions = obj->nr_unions;
int nr_funcs = obj->nr_funcs;
struct btf *base_btf = NULL;
int err, type_id;
struct btf *btf;
__u32 nr_types;
if (obj->base_btf_path) {
base_btf = btf__parse(obj->base_btf_path, NULL);
err = libbpf_get_error(base_btf);
if (err) {
pr_err("FAILED: load base BTF from %s: %s\n",
obj->base_btf_path, strerror(-err));
return -1;
}
}
btf = btf__parse_split(obj->btf ?: obj->path, base_btf);
err = libbpf_get_error(btf);
if (err) {
pr_err("FAILED: load BTF from %s: %s\n",
obj->btf ?: obj->path, strerror(-err));
goto out;
}
err = -1;
nr_types = btf__type_cnt(btf);
/*
* Iterate all the BTF types and search for collected symbol IDs.
*/
for (type_id = 1; type_id < nr_types; type_id++) {
const struct btf_type *type;
struct rb_root *root;
struct btf_id *id;
const char *str;
int *nr;
type = btf__type_by_id(btf, type_id);
if (!type) {
pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n",
type_id);
goto out;
}
if (btf_is_func(type) && nr_funcs) {
nr = &nr_funcs;
root = &obj->funcs;
} else if (btf_is_struct(type) && nr_structs) {
nr = &nr_structs;
root = &obj->structs;
} else if (btf_is_union(type) && nr_unions) {
nr = &nr_unions;
root = &obj->unions;
} else if (btf_is_typedef(type) && nr_typedefs) {
nr = &nr_typedefs;
root = &obj->typedefs;
} else
continue;
str = btf__name_by_offset(btf, type->name_off);
if (!str) {
pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n",
type_id);
goto out;
}
id = btf_id__find(root, str);
if (id) {
if (id->id) {
pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n",
str, id->id, type_id, id->id);
} else {
id->id = type_id;
(*nr)--;
}
}
}
err = 0;
out:
btf__free(base_btf);
btf__free(btf);
return err;
}
static int id_patch(struct object *obj, struct btf_id *id)
{
Elf_Data *data = obj->efile.idlist;
int *ptr = data->d_buf;
int i;
/* For set, set8, id->id may be 0 */
if (!id->id && !id->is_set && !id->is_set8)
pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);
for (i = 0; i < id->addr_cnt; i++) {
unsigned long addr = id->addr[i];
unsigned long idx = addr - obj->efile.idlist_addr;
pr_debug("patching addr %5lu: ID %7d [%s]\n",
idx, id->id, id->name);
if (idx >= data->d_size) {
pr_err("FAILED patching index %lu out of bounds %lu\n",
idx, data->d_size);
return -1;
}
idx = idx / sizeof(int);
ptr[idx] = id->id;
}
return 0;
}
static int __symbols_patch(struct object *obj, struct rb_root *root)
{
struct rb_node *next;
struct btf_id *id;
next = rb_first(root);
while (next) {
id = rb_entry(next, struct btf_id, rb_node);
if (id_patch(obj, id))
return -1;
next = rb_next(next);
}
return 0;
}
static int cmp_id(const void *pa, const void *pb)
{
const int *a = pa, *b = pb;
return *a - *b;
}
static int sets_patch(struct object *obj)
{
Elf_Data *data = obj->efile.idlist;
struct rb_node *next;
next = rb_first(&obj->sets);
while (next) {
struct btf_id_set8 *set8;
struct btf_id_set *set;
unsigned long addr, off;
struct btf_id *id;
id = rb_entry(next, struct btf_id, rb_node);
addr = id->addr[0];
off = addr - obj->efile.idlist_addr;
/* sets are unique */
if (id->addr_cnt != 1) {
pr_err("FAILED malformed data for set '%s'\n",
id->name);
return -1;
}
if (id->is_set) {
set = data->d_buf + off;
qsort(set->ids, set->cnt, sizeof(set->ids[0]), cmp_id);
} else {
set8 = data->d_buf + off;
/*
* Make sure id is at the beginning of the pairs
* struct, otherwise the below qsort would not work.
*/
BUILD_BUG_ON((u32 *)set8->pairs != &set8->pairs[0].id);
qsort(set8->pairs, set8->cnt, sizeof(set8->pairs[0]), cmp_id);
/*
* When ELF endianness does not match endianness of the
* host, libelf will do the translation when updating
* the ELF. This, however, corrupts SET8 flags which are
* already in the target endianness. So, let's bswap
* them to the host endianness and libelf will then
* correctly translate everything.
*/
if (obj->efile.encoding != ELFDATANATIVE) {
int i;
set8->flags = bswap_32(set8->flags);
for (i = 0; i < set8->cnt; i++) {
set8->pairs[i].flags =
bswap_32(set8->pairs[i].flags);
}
}
}
pr_debug("sorting addr %5lu: cnt %6d [%s]\n",
off, id->is_set ? set->cnt : set8->cnt, id->name);
next = rb_next(next);
}
return 0;
}
static int symbols_patch(struct object *obj)
{
off_t err;
if (__symbols_patch(obj, &obj->structs) ||
__symbols_patch(obj, &obj->unions) ||
__symbols_patch(obj, &obj->typedefs) ||
__symbols_patch(obj, &obj->funcs) ||
__symbols_patch(obj, &obj->sets))
return -1;
if (sets_patch(obj))
return -1;
/* Set type to ensure endian translation occurs. */
obj->efile.idlist->d_type = ELF_T_WORD;
elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);
err = elf_update(obj->efile.elf, ELF_C_WRITE);
if (err < 0) {
pr_err("FAILED elf_update(WRITE): %s\n",
elf_errmsg(-1));
}
pr_debug("update %s for %s\n",
err >= 0 ? "ok" : "failed", obj->path);
return err < 0 ? -1 : 0;
}
static const char * const resolve_btfids_usage[] = {
"resolve_btfids [<options>] <ELF object>",
NULL
};
int main(int argc, const char **argv)
{
struct object obj = {
.efile = {
.idlist_shndx = -1,
.symbols_shndx = -1,
},
.structs = RB_ROOT,
.unions = RB_ROOT,
.typedefs = RB_ROOT,
.funcs = RB_ROOT,
.sets = RB_ROOT,
};
struct option btfid_options[] = {
OPT_INCR('v', "verbose", &verbose,
"be more verbose (show errors, etc)"),
OPT_STRING(0, "btf", &obj.btf, "BTF data",
"BTF data"),
OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
"path of file providing base BTF"),
OPT_END()
};
int err = -1;
argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage,
PARSE_OPT_STOP_AT_NON_OPTION);
if (argc != 1)
usage_with_options(resolve_btfids_usage, btfid_options);
obj.path = argv[0];
if (elf_collect(&obj))
goto out;
/*
* We did not find .BTF_ids section or symbols section,
* nothing to do..
*/
if (obj.efile.idlist_shndx == -1 ||
obj.efile.symbols_shndx == -1) {
pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
err = 0;
goto out;
}
if (symbols_collect(&obj))
goto out;
if (symbols_resolve(&obj))
goto out;
if (symbols_patch(&obj))
goto out;
err = 0;
out:
if (obj.efile.elf) {
elf_end(obj.efile.elf);
close(obj.efile.fd);
}
return err;
}
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