bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object (fbbb68de) · Commits · 戴 / test

tools/bpf/resolve_btfids/Build

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Original line number	Diff line number	Diff line
		resolve_btfids-y += main.o
		resolve_btfids-y += rbtree.o
		resolve_btfids-y += zalloc.o
		resolve_btfids-y += string.o
		resolve_btfids-y += ctype.o
		resolve_btfids-y += str_error_r.o

		$(OUTPUT)%.o: ../../lib/%.c FORCE
		$(call rule_mkdir)
		$(call if_changed_dep,cc_o_c)

tools/bpf/resolve_btfids/Makefile

0 → 100644

+77 −0

Original line number	Diff line number	Diff line
		# SPDX-License-Identifier: GPL-2.0-only
		include ../../scripts/Makefile.include

		ifeq ($(srctree),)
		srctree := $(patsubst %/,%,$(dir $(CURDIR)))
		srctree := $(patsubst %/,%,$(dir $(srctree)))
		srctree := $(patsubst %/,%,$(dir $(srctree)))
		endif

		ifeq ($(V),1)
		Q =
		msg =
		else
		Q = @
		msg = @printf ' %-8s %s%s\n' "$(1)" "$(notdir $(2))" "$(if $(3), $(3))";
		MAKEFLAGS=--no-print-directory
		endif

		OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/

		LIBBPF_SRC := $(srctree)/tools/lib/bpf/
		SUBCMD_SRC := $(srctree)/tools/lib/subcmd/

		BPFOBJ := $(OUTPUT)/libbpf.a
		SUBCMDOBJ := $(OUTPUT)/libsubcmd.a

		BINARY := $(OUTPUT)/resolve_btfids
		BINARY_IN := $(BINARY)-in.o

		all: $(BINARY)

		$(OUTPUT):
		$(call msg,MKDIR,,$@)
		$(Q)mkdir -p $(OUTPUT)

		$(SUBCMDOBJ): fixdep FORCE
		$(Q)$(MAKE) -C $(SUBCMD_SRC) OUTPUT=$(OUTPUT)

		$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) \| $(OUTPUT)
		$(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) OUTPUT=$(abspath $(dir $@))/ $(abspath $@)

		CFLAGS := -g \
		-I$(srctree)/tools/include \
		-I$(srctree)/tools/include/uapi \
		-I$(LIBBPF_SRC) \
		-I$(SUBCMD_SRC)

		LIBS = -lelf -lz

		export srctree OUTPUT CFLAGS Q
		include $(srctree)/tools/build/Makefile.include

		$(BINARY_IN): fixdep FORCE
		$(Q)$(MAKE) $(build)=resolve_btfids

		$(BINARY): $(BPFOBJ) $(SUBCMDOBJ) $(BINARY_IN)
		$(call msg,LINK,$@)
		$(Q)$(CC) $(BINARY_IN) $(LDFLAGS) -o $@ $(BPFOBJ) $(SUBCMDOBJ) $(LIBS)

		libsubcmd-clean:
		$(Q)$(MAKE) -C $(SUBCMD_SRC) OUTPUT=$(OUTPUT) clean

		libbpf-clean:
		$(Q)$(MAKE) -C $(LIBBPF_SRC) OUTPUT=$(OUTPUT) clean

		clean: libsubcmd-clean libbpf-clean fixdep-clean
		$(call msg,CLEAN,$(BINARY))
		$(Q)$(RM) -f $(BINARY); \
		find $(if $(OUTPUT),$(OUTPUT),.) -name \.o -or -name \.o.cmd -or -name \*.o.d \| xargs $(RM)

		tags:
		$(call msg,GEN,,tags)
		$(Q)ctags -R . $(LIBBPF_SRC) $(SUBCMD_SRC)

		FORCE:

		.PHONY: all FORCE clean tags

tools/bpf/resolve_btfids/main.c

0 → 100644

+721 −0

Original line number	Diff line number	Diff line
		// 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
		*/

		#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 <btf.h>
		#include <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 ADDR_CNT 100

		struct btf_id {
		struct rb_node rb_node;
		char *name;
		union {
		int id;
		int cnt;
		};
		int addr_cnt;
		Elf64_Addr addr[ADDR_CNT];
		};

		struct object {
		const char *path;
		const char *btf;

		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;

		int eprintf(int level, int var, const char *fmt, ...)
		{
		va_list args;
		int ret;

		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__)

		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 = ^
		*/
		char p, id = strdup(prefix_end + sizeof("__") - 1);

		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_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);
		}

		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) {
		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;
		}
		}

		return 0;
		}

		static int symbols_collect(struct object *obj)
		{
		Elf_Scn *scn = NULL;
		int n, i, err = 0;
		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; !err && i < n; i++) {
		char tmp, prefix;
		struct btf_id *id;
		GElf_Sym sym;
		int err = -1;

		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);
		/* set */
		} else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
		id = add_symbol(&obj->sets, prefix, sizeof(BTF_SET) - 1);
		/*
		* 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;
		} 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",
		id->name);
		return -1;
		}
		id->addr[id->addr_cnt++] = sym.st_value;
		}

		return 0;
		}

		static struct btf btf__parse_raw(const char file)
		{
		struct btf *btf;
		struct stat st;
		__u8 *buf;
		FILE *f;

		if (stat(file, &st))
		return NULL;

		f = fopen(file, "rb");
		if (!f)
		return NULL;

		buf = malloc(st.st_size);
		if (!buf) {
		btf = ERR_PTR(-ENOMEM);
		goto exit_close;
		}

		if ((size_t) st.st_size != fread(buf, 1, st.st_size, f)) {
		btf = ERR_PTR(-EINVAL);
		goto exit_free;
		}

		btf = btf__new(buf, st.st_size);

		exit_free:
		free(buf);
		exit_close:
		fclose(f);
		return btf;
		}

		static bool is_btf_raw(const char *file)
		{
		__u16 magic = 0;
		int fd, nb_read;

		fd = open(file, O_RDONLY);
		if (fd < 0)
		return false;

		nb_read = read(fd, &magic, sizeof(magic));
		close(fd);
		return nb_read == sizeof(magic) && magic == BTF_MAGIC;
		}

		static struct btf btf_open(const char path)
		{
		if (is_btf_raw(path))
		return btf__parse_raw(path);
		else
		return btf__parse_elf(path, NULL);
		}

		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;
		int err, type_id;
		struct btf *btf;
		__u32 nr;

		btf = btf_open(obj->btf ?: obj->path);
		err = libbpf_get_error(btf);
		if (err) {
		pr_err("FAILED: load BTF from %s: %s",
		obj->path, strerror(err));
		return -1;
		}

		err = -1;
		nr = btf__get_nr_types(btf);

		/*
		* Iterate all the BTF types and search for collected symbol IDs.
		*/
		for (type_id = 1; type_id <= nr; 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) {
		id->id = type_id;
		(*nr)--;
		}
		}

		err = 0;
		out:
		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;

		if (!id->id) {
		pr_err("FAILED unresolved symbol %s\n", id->name);
		return -EINVAL;
		}

		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] + 1;
		cnt = ptr[idx];

		pr_debug("sorting addr %5lu: cnt %6d [%s]\n",
		(idx + 1) * sizeof(int), cnt, id->name);

		qsort(base, cnt, sizeof(int), cmp_id);

		next = rb_next(next);
		}
		}

		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;

		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)
		{
		bool no_fail = false;
		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_BOOLEAN(0, "no-fail", &no_fail,
		"do not fail if " BTF_IDS_SECTION " section is not found"),
		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) {
		if (no_fail)
		return 0;
		pr_err("FAILED to find needed sections\n");
		return -1;
		}

		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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