tools/bpf/resolve_btfids/main.c - linux/kernel/git/torvalds/linux - Git at Google

 // 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 <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;
 }
	// 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 <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;
	}