From fbbb68de80a45ad66b66600bee275485c5073aa7 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Sat, 11 Jul 2020 23:53:21 +0200 Subject: bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object The resolve_btfids tool scans elf object for .BTF_ids section and resolves its symbols with BTF ID values. It will be used to during linking time to resolve arrays of BTF ID values used in verifier, so these IDs do not need to be resolved in runtime. The expected layout of .BTF_ids section is described in main.c header. Related kernel changes are coming in following changes. Build issue reported by 0-DAY CI Kernel Test Service. Signed-off-by: Jiri Olsa Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200711215329.41165-2-jolsa@kernel.org --- tools/bpf/resolve_btfids/main.c | 721 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 721 insertions(+) create mode 100644 tools/bpf/resolve_btfids/main.c (limited to 'tools/bpf/resolve_btfids/main.c') diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c new file mode 100644 index 000000000000..6956b6350cad --- /dev/null +++ b/tools/bpf/resolve_btfids/main.c @@ -0,0 +1,721 @@ +// 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 is: + * + * func - lookup BTF_KIND_FUNC symbol with name + * and store its ID into the data: + * + * __BTF_ID__func__vfs_close__1: + * .zero 4 + * + * struct - lookup BTF_KIND_STRUCT symbol with name + * and store its ID into the data: + * + * __BTF_ID__struct__sk_buff__1: + * .zero 4 + * + * union - lookup BTF_KIND_UNION symbol with name + * and store its ID into the data: + * + * __BTF_ID__union__thread_union__1: + * .zero 4 + * + * typedef - lookup BTF_KIND_TYPEDEF symbol with 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 +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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 [] ", + 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; +} -- cgit v1.2.3 From f86ca3cffef153555a3f4755b3a44881d962754f Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Sat, 1 Aug 2020 18:32:19 -0700 Subject: tools/resolve_btfids: Use libbpf's btf__parse() API Instead of re-implementing generic BTF parsing logic, use libbpf's API. Also add .gitignore for resolve_btfids's build artifacts. Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20200802013219.864880-4-andriin@fb.com --- tools/bpf/resolve_btfids/.gitignore | 4 +++ tools/bpf/resolve_btfids/main.c | 58 +------------------------------------ 2 files changed, 5 insertions(+), 57 deletions(-) create mode 100644 tools/bpf/resolve_btfids/.gitignore (limited to 'tools/bpf/resolve_btfids/main.c') diff --git a/tools/bpf/resolve_btfids/.gitignore b/tools/bpf/resolve_btfids/.gitignore new file mode 100644 index 000000000000..a026df7dc280 --- /dev/null +++ b/tools/bpf/resolve_btfids/.gitignore @@ -0,0 +1,4 @@ +/FEATURE-DUMP.libbpf +/bpf_helper_defs.h +/fixdep +/resolve_btfids diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c index 6956b6350cad..52d883325a23 100644 --- a/tools/bpf/resolve_btfids/main.c +++ b/tools/bpf/resolve_btfids/main.c @@ -403,62 +403,6 @@ static int symbols_collect(struct object *obj) 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; @@ -469,7 +413,7 @@ static int symbols_resolve(struct object *obj) struct btf *btf; __u32 nr; - btf = btf_open(obj->btf ?: obj->path); + btf = btf__parse(obj->btf ?: obj->path, NULL); err = libbpf_get_error(btf); if (err) { pr_err("FAILED: load BTF from %s: %s", -- cgit v1.2.3 From d48556f45608921fa07cb882f9dd15a8a1203427 Mon Sep 17 00:00:00 2001 From: Stanislav Fomichev Date: Thu, 6 Aug 2020 08:52:25 -0700 Subject: bpf: Add missing return to resolve_btfids int sets_patch(struct object *obj) doesn't have a 'return 0' at the end. Fixes: fbbb68de80a4 ("bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object") Signed-off-by: Stanislav Fomichev Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200806155225.637202-1-sdf@google.com --- tools/bpf/resolve_btfids/main.c | 1 + 1 file changed, 1 insertion(+) (limited to 'tools/bpf/resolve_btfids/main.c') diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c index 52d883325a23..4d9ecb975862 100644 --- a/tools/bpf/resolve_btfids/main.c +++ b/tools/bpf/resolve_btfids/main.c @@ -566,6 +566,7 @@ static int sets_patch(struct object *obj) next = rb_next(next); } + return 0; } static int symbols_patch(struct object *obj) -- cgit v1.2.3 From 51f6463aacfbfd322bcaadc606da56acef644b05 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 19 Aug 2020 11:23:42 +0200 Subject: tools/resolve_btfids: Fix sections with wrong alignment 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 as reported by Jesper: FAILED elf_update(WRITE): invalid section alignment While waiting for ld fix, we can fix compressed sections sh_addralign value manually. Adding warning in -vv mode when the fix is triggered: $ ./tools/bpf/resolve_btfids/resolve_btfids -vv vmlinux ... section(36) .comment, size 44, link 0, flags 30, type=1 section(37) .debug_aranges, size 45684, link 0, flags 800, type=1 - fixing wrong alignment sh_addralign 16, expected 8 section(38) .debug_info, size 129104957, link 0, flags 800, type=1 - fixing wrong alignment sh_addralign 1, expected 8 section(39) .debug_abbrev, size 1152583, link 0, flags 800, type=1 - fixing wrong alignment sh_addralign 1, expected 8 section(40) .debug_line, size 7374522, link 0, flags 800, type=1 - fixing wrong alignment sh_addralign 1, expected 8 section(41) .debug_frame, size 702463, link 0, flags 800, type=1 section(42) .debug_str, size 1017571, link 0, flags 830, type=1 - fixing wrong alignment sh_addralign 1, expected 8 section(43) .debug_loc, size 3019453, link 0, flags 800, type=1 - fixing wrong alignment sh_addralign 1, expected 8 section(44) .debug_ranges, size 1744583, link 0, flags 800, type=1 - fixing wrong alignment sh_addralign 16, expected 8 section(45) .symtab, size 2955888, link 46, flags 0, type=2 section(46) .strtab, size 2613072, link 0, flags 0, type=3 ... update ok for vmlinux Another workaround is to disable compressed debug info data CONFIG_DEBUG_INFO_COMPRESSED kernel option. Fixes: fbbb68de80a4 ("bpf: Add resolve_btfids tool to resolve BTF IDs in ELF object") Reported-by: Jesper Dangaard Brouer Signed-off-by: Jiri Olsa Signed-off-by: Alexei Starovoitov Acked-by: Jesper Dangaard Brouer Acked-by: Yonghong Song Cc: Mark Wielaard Cc: Nick Clifton Link: https://lore.kernel.org/bpf/20200819092342.259004-1-jolsa@kernel.org --- tools/bpf/resolve_btfids/main.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) (limited to 'tools/bpf/resolve_btfids/main.c') diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c index 4d9ecb975862..0def0bb1f783 100644 --- a/tools/bpf/resolve_btfids/main.c +++ b/tools/bpf/resolve_btfids/main.c @@ -233,6 +233,39 @@ static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size) return btf_id__add(root, id, false); } +/* + * 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) { + printf("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; @@ -309,6 +342,9 @@ static int elf_collect(struct object *obj) obj->efile.idlist_shndx = idx; obj->efile.idlist_addr = sh.sh_addr; } + + if (compressed_section_fix(elf, scn, &sh)) + return -1; } return 0; -- cgit v1.2.3