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- // 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/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 "__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
- 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;
- } 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, sizeof(BTF_ID) - 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;
- 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;
- }
- /*
- * 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;
- }
- 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) - 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;
- int *ptr = data->d_buf;
- struct rb_node *next;
- next = rb_first(&obj->sets);
- while (next) {
- unsigned long addr, idx;
- struct btf_id *id;
- int *base;
- int cnt;
- id = rb_entry(next, struct btf_id, rb_node);
- addr = id->addr[0];
- idx = 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;
- }
- idx = idx / sizeof(int);
- base = &ptr[idx] + (id->is_set8 ? 2 : 1);
- cnt = ptr[idx];
- pr_debug("sorting addr %5lu: cnt %6d [%s]\n",
- (idx + 1) * sizeof(int), cnt, id->name);
- qsort(base, cnt, id->is_set8 ? sizeof(uint64_t) : sizeof(int), cmp_id);
- next = rb_next(next);
- }
- return 0;
- }
- static int symbols_patch(struct object *obj)
- {
- int 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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