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-rw-r--r--tools/lib/bpf/linker.c2900
1 files changed, 2900 insertions, 0 deletions
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
new file mode 100644
index 000000000..4ac02c28e
--- /dev/null
+++ b/tools/lib/bpf/linker.c
@@ -0,0 +1,2900 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+/*
+ * BPF static linker
+ *
+ * Copyright (c) 2021 Facebook
+ */
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <linux/err.h>
+#include <linux/btf.h>
+#include <elf.h>
+#include <libelf.h>
+#include <fcntl.h>
+#include "libbpf.h"
+#include "btf.h"
+#include "libbpf_internal.h"
+#include "strset.h"
+
+#define BTF_EXTERN_SEC ".extern"
+
+struct src_sec {
+ const char *sec_name;
+ /* positional (not necessarily ELF) index in an array of sections */
+ int id;
+ /* positional (not necessarily ELF) index of a matching section in a final object file */
+ int dst_id;
+ /* section data offset in a matching output section */
+ int dst_off;
+ /* whether section is omitted from the final ELF file */
+ bool skipped;
+ /* whether section is an ephemeral section, not mapped to an ELF section */
+ bool ephemeral;
+
+ /* ELF info */
+ size_t sec_idx;
+ Elf_Scn *scn;
+ Elf64_Shdr *shdr;
+ Elf_Data *data;
+
+ /* corresponding BTF DATASEC type ID */
+ int sec_type_id;
+};
+
+struct src_obj {
+ const char *filename;
+ int fd;
+ Elf *elf;
+ /* Section header strings section index */
+ size_t shstrs_sec_idx;
+ /* SYMTAB section index */
+ size_t symtab_sec_idx;
+
+ struct btf *btf;
+ struct btf_ext *btf_ext;
+
+ /* List of sections (including ephemeral). Slot zero is unused. */
+ struct src_sec *secs;
+ int sec_cnt;
+
+ /* mapping of symbol indices from src to dst ELF */
+ int *sym_map;
+ /* mapping from the src BTF type IDs to dst ones */
+ int *btf_type_map;
+};
+
+/* single .BTF.ext data section */
+struct btf_ext_sec_data {
+ size_t rec_cnt;
+ __u32 rec_sz;
+ void *recs;
+};
+
+struct glob_sym {
+ /* ELF symbol index */
+ int sym_idx;
+ /* associated section id for .ksyms, .kconfig, etc, but not .extern */
+ int sec_id;
+ /* extern name offset in STRTAB */
+ int name_off;
+ /* optional associated BTF type ID */
+ int btf_id;
+ /* BTF type ID to which VAR/FUNC type is pointing to; used for
+ * rewriting types when extern VAR/FUNC is resolved to a concrete
+ * definition
+ */
+ int underlying_btf_id;
+ /* sec_var index in the corresponding dst_sec, if exists */
+ int var_idx;
+
+ /* extern or resolved/global symbol */
+ bool is_extern;
+ /* weak or strong symbol, never goes back from strong to weak */
+ bool is_weak;
+};
+
+struct dst_sec {
+ char *sec_name;
+ /* positional (not necessarily ELF) index in an array of sections */
+ int id;
+
+ bool ephemeral;
+
+ /* ELF info */
+ size_t sec_idx;
+ Elf_Scn *scn;
+ Elf64_Shdr *shdr;
+ Elf_Data *data;
+
+ /* final output section size */
+ int sec_sz;
+ /* final output contents of the section */
+ void *raw_data;
+
+ /* corresponding STT_SECTION symbol index in SYMTAB */
+ int sec_sym_idx;
+
+ /* section's DATASEC variable info, emitted on BTF finalization */
+ bool has_btf;
+ int sec_var_cnt;
+ struct btf_var_secinfo *sec_vars;
+
+ /* section's .BTF.ext data */
+ struct btf_ext_sec_data func_info;
+ struct btf_ext_sec_data line_info;
+ struct btf_ext_sec_data core_relo_info;
+};
+
+struct bpf_linker {
+ char *filename;
+ int fd;
+ Elf *elf;
+ Elf64_Ehdr *elf_hdr;
+
+ /* Output sections metadata */
+ struct dst_sec *secs;
+ int sec_cnt;
+
+ struct strset *strtab_strs; /* STRTAB unique strings */
+ size_t strtab_sec_idx; /* STRTAB section index */
+ size_t symtab_sec_idx; /* SYMTAB section index */
+
+ struct btf *btf;
+ struct btf_ext *btf_ext;
+
+ /* global (including extern) ELF symbols */
+ int glob_sym_cnt;
+ struct glob_sym *glob_syms;
+};
+
+#define pr_warn_elf(fmt, ...) \
+ libbpf_print(LIBBPF_WARN, "libbpf: " fmt ": %s\n", ##__VA_ARGS__, elf_errmsg(-1))
+
+static int init_output_elf(struct bpf_linker *linker, const char *file);
+
+static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
+ const struct bpf_linker_file_opts *opts,
+ struct src_obj *obj);
+static int linker_sanity_check_elf(struct src_obj *obj);
+static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec);
+static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec);
+static int linker_sanity_check_btf(struct src_obj *obj);
+static int linker_sanity_check_btf_ext(struct src_obj *obj);
+static int linker_fixup_btf(struct src_obj *obj);
+static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj);
+static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj);
+static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
+ Elf64_Sym *sym, const char *sym_name, int src_sym_idx);
+static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj);
+static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj);
+static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj);
+
+static int finalize_btf(struct bpf_linker *linker);
+static int finalize_btf_ext(struct bpf_linker *linker);
+
+void bpf_linker__free(struct bpf_linker *linker)
+{
+ int i;
+
+ if (!linker)
+ return;
+
+ free(linker->filename);
+
+ if (linker->elf)
+ elf_end(linker->elf);
+
+ if (linker->fd >= 0)
+ close(linker->fd);
+
+ strset__free(linker->strtab_strs);
+
+ btf__free(linker->btf);
+ btf_ext__free(linker->btf_ext);
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ struct dst_sec *sec = &linker->secs[i];
+
+ free(sec->sec_name);
+ free(sec->raw_data);
+ free(sec->sec_vars);
+
+ free(sec->func_info.recs);
+ free(sec->line_info.recs);
+ free(sec->core_relo_info.recs);
+ }
+ free(linker->secs);
+
+ free(linker->glob_syms);
+ free(linker);
+}
+
+struct bpf_linker *bpf_linker__new(const char *filename, struct bpf_linker_opts *opts)
+{
+ struct bpf_linker *linker;
+ int err;
+
+ if (!OPTS_VALID(opts, bpf_linker_opts))
+ return errno = EINVAL, NULL;
+
+ if (elf_version(EV_CURRENT) == EV_NONE) {
+ pr_warn_elf("libelf initialization failed");
+ return errno = EINVAL, NULL;
+ }
+
+ linker = calloc(1, sizeof(*linker));
+ if (!linker)
+ return errno = ENOMEM, NULL;
+
+ linker->fd = -1;
+
+ err = init_output_elf(linker, filename);
+ if (err)
+ goto err_out;
+
+ return linker;
+
+err_out:
+ bpf_linker__free(linker);
+ return errno = -err, NULL;
+}
+
+static struct dst_sec *add_dst_sec(struct bpf_linker *linker, const char *sec_name)
+{
+ struct dst_sec *secs = linker->secs, *sec;
+ size_t new_cnt = linker->sec_cnt ? linker->sec_cnt + 1 : 2;
+
+ secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
+ if (!secs)
+ return NULL;
+
+ /* zero out newly allocated memory */
+ memset(secs + linker->sec_cnt, 0, (new_cnt - linker->sec_cnt) * sizeof(*secs));
+
+ linker->secs = secs;
+ linker->sec_cnt = new_cnt;
+
+ sec = &linker->secs[new_cnt - 1];
+ sec->id = new_cnt - 1;
+ sec->sec_name = strdup(sec_name);
+ if (!sec->sec_name)
+ return NULL;
+
+ return sec;
+}
+
+static Elf64_Sym *add_new_sym(struct bpf_linker *linker, size_t *sym_idx)
+{
+ struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
+ Elf64_Sym *syms, *sym;
+ size_t sym_cnt = symtab->sec_sz / sizeof(*sym);
+
+ syms = libbpf_reallocarray(symtab->raw_data, sym_cnt + 1, sizeof(*sym));
+ if (!syms)
+ return NULL;
+
+ sym = &syms[sym_cnt];
+ memset(sym, 0, sizeof(*sym));
+
+ symtab->raw_data = syms;
+ symtab->sec_sz += sizeof(*sym);
+ symtab->shdr->sh_size += sizeof(*sym);
+ symtab->data->d_size += sizeof(*sym);
+
+ if (sym_idx)
+ *sym_idx = sym_cnt;
+
+ return sym;
+}
+
+static int init_output_elf(struct bpf_linker *linker, const char *file)
+{
+ int err, str_off;
+ Elf64_Sym *init_sym;
+ struct dst_sec *sec;
+
+ linker->filename = strdup(file);
+ if (!linker->filename)
+ return -ENOMEM;
+
+ linker->fd = open(file, O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC, 0644);
+ if (linker->fd < 0) {
+ err = -errno;
+ pr_warn("failed to create '%s': %d\n", file, err);
+ return err;
+ }
+
+ linker->elf = elf_begin(linker->fd, ELF_C_WRITE, NULL);
+ if (!linker->elf) {
+ pr_warn_elf("failed to create ELF object");
+ return -EINVAL;
+ }
+
+ /* ELF header */
+ linker->elf_hdr = elf64_newehdr(linker->elf);
+ if (!linker->elf_hdr) {
+ pr_warn_elf("failed to create ELF header");
+ return -EINVAL;
+ }
+
+ linker->elf_hdr->e_machine = EM_BPF;
+ linker->elf_hdr->e_type = ET_REL;
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB;
+#else
+#error "Unknown __BYTE_ORDER__"
+#endif
+
+ /* STRTAB */
+ /* initialize strset with an empty string to conform to ELF */
+ linker->strtab_strs = strset__new(INT_MAX, "", sizeof(""));
+ if (libbpf_get_error(linker->strtab_strs))
+ return libbpf_get_error(linker->strtab_strs);
+
+ sec = add_dst_sec(linker, ".strtab");
+ if (!sec)
+ return -ENOMEM;
+
+ sec->scn = elf_newscn(linker->elf);
+ if (!sec->scn) {
+ pr_warn_elf("failed to create STRTAB section");
+ return -EINVAL;
+ }
+
+ sec->shdr = elf64_getshdr(sec->scn);
+ if (!sec->shdr)
+ return -EINVAL;
+
+ sec->data = elf_newdata(sec->scn);
+ if (!sec->data) {
+ pr_warn_elf("failed to create STRTAB data");
+ return -EINVAL;
+ }
+
+ str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
+ if (str_off < 0)
+ return str_off;
+
+ sec->sec_idx = elf_ndxscn(sec->scn);
+ linker->elf_hdr->e_shstrndx = sec->sec_idx;
+ linker->strtab_sec_idx = sec->sec_idx;
+
+ sec->shdr->sh_name = str_off;
+ sec->shdr->sh_type = SHT_STRTAB;
+ sec->shdr->sh_flags = SHF_STRINGS;
+ sec->shdr->sh_offset = 0;
+ sec->shdr->sh_link = 0;
+ sec->shdr->sh_info = 0;
+ sec->shdr->sh_addralign = 1;
+ sec->shdr->sh_size = sec->sec_sz = 0;
+ sec->shdr->sh_entsize = 0;
+
+ /* SYMTAB */
+ sec = add_dst_sec(linker, ".symtab");
+ if (!sec)
+ return -ENOMEM;
+
+ sec->scn = elf_newscn(linker->elf);
+ if (!sec->scn) {
+ pr_warn_elf("failed to create SYMTAB section");
+ return -EINVAL;
+ }
+
+ sec->shdr = elf64_getshdr(sec->scn);
+ if (!sec->shdr)
+ return -EINVAL;
+
+ sec->data = elf_newdata(sec->scn);
+ if (!sec->data) {
+ pr_warn_elf("failed to create SYMTAB data");
+ return -EINVAL;
+ }
+
+ str_off = strset__add_str(linker->strtab_strs, sec->sec_name);
+ if (str_off < 0)
+ return str_off;
+
+ sec->sec_idx = elf_ndxscn(sec->scn);
+ linker->symtab_sec_idx = sec->sec_idx;
+
+ sec->shdr->sh_name = str_off;
+ sec->shdr->sh_type = SHT_SYMTAB;
+ sec->shdr->sh_flags = 0;
+ sec->shdr->sh_offset = 0;
+ sec->shdr->sh_link = linker->strtab_sec_idx;
+ /* sh_info should be one greater than the index of the last local
+ * symbol (i.e., binding is STB_LOCAL). But why and who cares?
+ */
+ sec->shdr->sh_info = 0;
+ sec->shdr->sh_addralign = 8;
+ sec->shdr->sh_entsize = sizeof(Elf64_Sym);
+
+ /* .BTF */
+ linker->btf = btf__new_empty();
+ err = libbpf_get_error(linker->btf);
+ if (err)
+ return err;
+
+ /* add the special all-zero symbol */
+ init_sym = add_new_sym(linker, NULL);
+ if (!init_sym)
+ return -EINVAL;
+
+ init_sym->st_name = 0;
+ init_sym->st_info = 0;
+ init_sym->st_other = 0;
+ init_sym->st_shndx = SHN_UNDEF;
+ init_sym->st_value = 0;
+ init_sym->st_size = 0;
+
+ return 0;
+}
+
+int bpf_linker__add_file(struct bpf_linker *linker, const char *filename,
+ const struct bpf_linker_file_opts *opts)
+{
+ struct src_obj obj = {};
+ int err = 0;
+
+ if (!OPTS_VALID(opts, bpf_linker_file_opts))
+ return libbpf_err(-EINVAL);
+
+ if (!linker->elf)
+ return libbpf_err(-EINVAL);
+
+ err = err ?: linker_load_obj_file(linker, filename, opts, &obj);
+ err = err ?: linker_append_sec_data(linker, &obj);
+ err = err ?: linker_append_elf_syms(linker, &obj);
+ err = err ?: linker_append_elf_relos(linker, &obj);
+ err = err ?: linker_append_btf(linker, &obj);
+ err = err ?: linker_append_btf_ext(linker, &obj);
+
+ /* free up src_obj resources */
+ free(obj.btf_type_map);
+ btf__free(obj.btf);
+ btf_ext__free(obj.btf_ext);
+ free(obj.secs);
+ free(obj.sym_map);
+ if (obj.elf)
+ elf_end(obj.elf);
+ if (obj.fd >= 0)
+ close(obj.fd);
+
+ return libbpf_err(err);
+}
+
+static bool is_dwarf_sec_name(const char *name)
+{
+ /* approximation, but the actual list is too long */
+ return strncmp(name, ".debug_", sizeof(".debug_") - 1) == 0;
+}
+
+static bool is_ignored_sec(struct src_sec *sec)
+{
+ Elf64_Shdr *shdr = sec->shdr;
+ const char *name = sec->sec_name;
+
+ /* no special handling of .strtab */
+ if (shdr->sh_type == SHT_STRTAB)
+ return true;
+
+ /* ignore .llvm_addrsig section as well */
+ if (shdr->sh_type == SHT_LLVM_ADDRSIG)
+ return true;
+
+ /* no subprograms will lead to an empty .text section, ignore it */
+ if (shdr->sh_type == SHT_PROGBITS && shdr->sh_size == 0 &&
+ strcmp(sec->sec_name, ".text") == 0)
+ return true;
+
+ /* DWARF sections */
+ if (is_dwarf_sec_name(sec->sec_name))
+ return true;
+
+ if (strncmp(name, ".rel", sizeof(".rel") - 1) == 0) {
+ name += sizeof(".rel") - 1;
+ /* DWARF section relocations */
+ if (is_dwarf_sec_name(name))
+ return true;
+
+ /* .BTF and .BTF.ext don't need relocations */
+ if (strcmp(name, BTF_ELF_SEC) == 0 ||
+ strcmp(name, BTF_EXT_ELF_SEC) == 0)
+ return true;
+ }
+
+ return false;
+}
+
+static struct src_sec *add_src_sec(struct src_obj *obj, const char *sec_name)
+{
+ struct src_sec *secs = obj->secs, *sec;
+ size_t new_cnt = obj->sec_cnt ? obj->sec_cnt + 1 : 2;
+
+ secs = libbpf_reallocarray(secs, new_cnt, sizeof(*secs));
+ if (!secs)
+ return NULL;
+
+ /* zero out newly allocated memory */
+ memset(secs + obj->sec_cnt, 0, (new_cnt - obj->sec_cnt) * sizeof(*secs));
+
+ obj->secs = secs;
+ obj->sec_cnt = new_cnt;
+
+ sec = &obj->secs[new_cnt - 1];
+ sec->id = new_cnt - 1;
+ sec->sec_name = sec_name;
+
+ return sec;
+}
+
+static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
+ const struct bpf_linker_file_opts *opts,
+ struct src_obj *obj)
+{
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ const int host_endianness = ELFDATA2LSB;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ const int host_endianness = ELFDATA2MSB;
+#else
+#error "Unknown __BYTE_ORDER__"
+#endif
+ int err = 0;
+ Elf_Scn *scn;
+ Elf_Data *data;
+ Elf64_Ehdr *ehdr;
+ Elf64_Shdr *shdr;
+ struct src_sec *sec;
+
+ pr_debug("linker: adding object file '%s'...\n", filename);
+
+ obj->filename = filename;
+
+ obj->fd = open(filename, O_RDONLY | O_CLOEXEC);
+ if (obj->fd < 0) {
+ err = -errno;
+ pr_warn("failed to open file '%s': %d\n", filename, err);
+ return err;
+ }
+ obj->elf = elf_begin(obj->fd, ELF_C_READ_MMAP, NULL);
+ if (!obj->elf) {
+ err = -errno;
+ pr_warn_elf("failed to parse ELF file '%s'", filename);
+ return err;
+ }
+
+ /* Sanity check ELF file high-level properties */
+ ehdr = elf64_getehdr(obj->elf);
+ if (!ehdr) {
+ err = -errno;
+ pr_warn_elf("failed to get ELF header for %s", filename);
+ return err;
+ }
+ if (ehdr->e_ident[EI_DATA] != host_endianness) {
+ err = -EOPNOTSUPP;
+ pr_warn_elf("unsupported byte order of ELF file %s", filename);
+ return err;
+ }
+ if (ehdr->e_type != ET_REL
+ || ehdr->e_machine != EM_BPF
+ || ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
+ err = -EOPNOTSUPP;
+ pr_warn_elf("unsupported kind of ELF file %s", filename);
+ return err;
+ }
+
+ if (elf_getshdrstrndx(obj->elf, &obj->shstrs_sec_idx)) {
+ err = -errno;
+ pr_warn_elf("failed to get SHSTRTAB section index for %s", filename);
+ return err;
+ }
+
+ scn = NULL;
+ while ((scn = elf_nextscn(obj->elf, scn)) != NULL) {
+ size_t sec_idx = elf_ndxscn(scn);
+ const char *sec_name;
+
+ shdr = elf64_getshdr(scn);
+ if (!shdr) {
+ err = -errno;
+ pr_warn_elf("failed to get section #%zu header for %s",
+ sec_idx, filename);
+ return err;
+ }
+
+ sec_name = elf_strptr(obj->elf, obj->shstrs_sec_idx, shdr->sh_name);
+ if (!sec_name) {
+ err = -errno;
+ pr_warn_elf("failed to get section #%zu name for %s",
+ sec_idx, filename);
+ return err;
+ }
+
+ data = elf_getdata(scn, 0);
+ if (!data) {
+ err = -errno;
+ pr_warn_elf("failed to get section #%zu (%s) data from %s",
+ sec_idx, sec_name, filename);
+ return err;
+ }
+
+ sec = add_src_sec(obj, sec_name);
+ if (!sec)
+ return -ENOMEM;
+
+ sec->scn = scn;
+ sec->shdr = shdr;
+ sec->data = data;
+ sec->sec_idx = elf_ndxscn(scn);
+
+ if (is_ignored_sec(sec)) {
+ sec->skipped = true;
+ continue;
+ }
+
+ switch (shdr->sh_type) {
+ case SHT_SYMTAB:
+ if (obj->symtab_sec_idx) {
+ err = -EOPNOTSUPP;
+ pr_warn("multiple SYMTAB sections found, not supported\n");
+ return err;
+ }
+ obj->symtab_sec_idx = sec_idx;
+ break;
+ case SHT_STRTAB:
+ /* we'll construct our own string table */
+ break;
+ case SHT_PROGBITS:
+ if (strcmp(sec_name, BTF_ELF_SEC) == 0) {
+ obj->btf = btf__new(data->d_buf, shdr->sh_size);
+ err = libbpf_get_error(obj->btf);
+ if (err) {
+ pr_warn("failed to parse .BTF from %s: %d\n", filename, err);
+ return err;
+ }
+ sec->skipped = true;
+ continue;
+ }
+ if (strcmp(sec_name, BTF_EXT_ELF_SEC) == 0) {
+ obj->btf_ext = btf_ext__new(data->d_buf, shdr->sh_size);
+ err = libbpf_get_error(obj->btf_ext);
+ if (err) {
+ pr_warn("failed to parse .BTF.ext from '%s': %d\n", filename, err);
+ return err;
+ }
+ sec->skipped = true;
+ continue;
+ }
+
+ /* data & code */
+ break;
+ case SHT_NOBITS:
+ /* BSS */
+ break;
+ case SHT_REL:
+ /* relocations */
+ break;
+ default:
+ pr_warn("unrecognized section #%zu (%s) in %s\n",
+ sec_idx, sec_name, filename);
+ err = -EINVAL;
+ return err;
+ }
+ }
+
+ err = err ?: linker_sanity_check_elf(obj);
+ err = err ?: linker_sanity_check_btf(obj);
+ err = err ?: linker_sanity_check_btf_ext(obj);
+ err = err ?: linker_fixup_btf(obj);
+
+ return err;
+}
+
+static int linker_sanity_check_elf(struct src_obj *obj)
+{
+ struct src_sec *sec;
+ int i, err;
+
+ if (!obj->symtab_sec_idx) {
+ pr_warn("ELF is missing SYMTAB section in %s\n", obj->filename);
+ return -EINVAL;
+ }
+ if (!obj->shstrs_sec_idx) {
+ pr_warn("ELF is missing section headers STRTAB section in %s\n", obj->filename);
+ return -EINVAL;
+ }
+
+ for (i = 1; i < obj->sec_cnt; i++) {
+ sec = &obj->secs[i];
+
+ if (sec->sec_name[0] == '\0') {
+ pr_warn("ELF section #%zu has empty name in %s\n", sec->sec_idx, obj->filename);
+ return -EINVAL;
+ }
+
+ if (sec->shdr->sh_addralign && !is_pow_of_2(sec->shdr->sh_addralign))
+ return -EINVAL;
+ if (sec->shdr->sh_addralign != sec->data->d_align)
+ return -EINVAL;
+
+ if (sec->shdr->sh_size != sec->data->d_size)
+ return -EINVAL;
+
+ switch (sec->shdr->sh_type) {
+ case SHT_SYMTAB:
+ err = linker_sanity_check_elf_symtab(obj, sec);
+ if (err)
+ return err;
+ break;
+ case SHT_STRTAB:
+ break;
+ case SHT_PROGBITS:
+ if (sec->shdr->sh_flags & SHF_EXECINSTR) {
+ if (sec->shdr->sh_size % sizeof(struct bpf_insn) != 0)
+ return -EINVAL;
+ }
+ break;
+ case SHT_NOBITS:
+ break;
+ case SHT_REL:
+ err = linker_sanity_check_elf_relos(obj, sec);
+ if (err)
+ return err;
+ break;
+ case SHT_LLVM_ADDRSIG:
+ break;
+ default:
+ pr_warn("ELF section #%zu (%s) has unrecognized type %zu in %s\n",
+ sec->sec_idx, sec->sec_name, (size_t)sec->shdr->sh_type, obj->filename);
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
+static int linker_sanity_check_elf_symtab(struct src_obj *obj, struct src_sec *sec)
+{
+ struct src_sec *link_sec;
+ Elf64_Sym *sym;
+ int i, n;
+
+ if (sec->shdr->sh_entsize != sizeof(Elf64_Sym))
+ return -EINVAL;
+ if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
+ return -EINVAL;
+
+ if (!sec->shdr->sh_link || sec->shdr->sh_link >= obj->sec_cnt) {
+ pr_warn("ELF SYMTAB section #%zu points to missing STRTAB section #%zu in %s\n",
+ sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+ return -EINVAL;
+ }
+ link_sec = &obj->secs[sec->shdr->sh_link];
+ if (link_sec->shdr->sh_type != SHT_STRTAB) {
+ pr_warn("ELF SYMTAB section #%zu points to invalid STRTAB section #%zu in %s\n",
+ sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+ return -EINVAL;
+ }
+
+ n = sec->shdr->sh_size / sec->shdr->sh_entsize;
+ sym = sec->data->d_buf;
+ for (i = 0; i < n; i++, sym++) {
+ int sym_type = ELF64_ST_TYPE(sym->st_info);
+ int sym_bind = ELF64_ST_BIND(sym->st_info);
+ int sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
+
+ if (i == 0) {
+ if (sym->st_name != 0 || sym->st_info != 0
+ || sym->st_other != 0 || sym->st_shndx != 0
+ || sym->st_value != 0 || sym->st_size != 0) {
+ pr_warn("ELF sym #0 is invalid in %s\n", obj->filename);
+ return -EINVAL;
+ }
+ continue;
+ }
+ if (sym_bind != STB_LOCAL && sym_bind != STB_GLOBAL && sym_bind != STB_WEAK) {
+ pr_warn("ELF sym #%d in section #%zu has unsupported symbol binding %d\n",
+ i, sec->sec_idx, sym_bind);
+ return -EINVAL;
+ }
+ if (sym_vis != STV_DEFAULT && sym_vis != STV_HIDDEN) {
+ pr_warn("ELF sym #%d in section #%zu has unsupported symbol visibility %d\n",
+ i, sec->sec_idx, sym_vis);
+ return -EINVAL;
+ }
+ if (sym->st_shndx == 0) {
+ if (sym_type != STT_NOTYPE || sym_bind == STB_LOCAL
+ || sym->st_value != 0 || sym->st_size != 0) {
+ pr_warn("ELF sym #%d is invalid extern symbol in %s\n",
+ i, obj->filename);
+
+ return -EINVAL;
+ }
+ continue;
+ }
+ if (sym->st_shndx < SHN_LORESERVE && sym->st_shndx >= obj->sec_cnt) {
+ pr_warn("ELF sym #%d in section #%zu points to missing section #%zu in %s\n",
+ i, sec->sec_idx, (size_t)sym->st_shndx, obj->filename);
+ return -EINVAL;
+ }
+ if (sym_type == STT_SECTION) {
+ if (sym->st_value != 0)
+ return -EINVAL;
+ continue;
+ }
+ }
+
+ return 0;
+}
+
+static int linker_sanity_check_elf_relos(struct src_obj *obj, struct src_sec *sec)
+{
+ struct src_sec *link_sec, *sym_sec;
+ Elf64_Rel *relo;
+ int i, n;
+
+ if (sec->shdr->sh_entsize != sizeof(Elf64_Rel))
+ return -EINVAL;
+ if (sec->shdr->sh_size % sec->shdr->sh_entsize != 0)
+ return -EINVAL;
+
+ /* SHT_REL's sh_link should point to SYMTAB */
+ if (sec->shdr->sh_link != obj->symtab_sec_idx) {
+ pr_warn("ELF relo section #%zu points to invalid SYMTAB section #%zu in %s\n",
+ sec->sec_idx, (size_t)sec->shdr->sh_link, obj->filename);
+ return -EINVAL;
+ }
+
+ /* SHT_REL's sh_info points to relocated section */
+ if (!sec->shdr->sh_info || sec->shdr->sh_info >= obj->sec_cnt) {
+ pr_warn("ELF relo section #%zu points to missing section #%zu in %s\n",
+ sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
+ return -EINVAL;
+ }
+ link_sec = &obj->secs[sec->shdr->sh_info];
+
+ /* .rel<secname> -> <secname> pattern is followed */
+ if (strncmp(sec->sec_name, ".rel", sizeof(".rel") - 1) != 0
+ || strcmp(sec->sec_name + sizeof(".rel") - 1, link_sec->sec_name) != 0) {
+ pr_warn("ELF relo section #%zu name has invalid name in %s\n",
+ sec->sec_idx, obj->filename);
+ return -EINVAL;
+ }
+
+ /* don't further validate relocations for ignored sections */
+ if (link_sec->skipped)
+ return 0;
+
+ /* relocatable section is data or instructions */
+ if (link_sec->shdr->sh_type != SHT_PROGBITS && link_sec->shdr->sh_type != SHT_NOBITS) {
+ pr_warn("ELF relo section #%zu points to invalid section #%zu in %s\n",
+ sec->sec_idx, (size_t)sec->shdr->sh_info, obj->filename);
+ return -EINVAL;
+ }
+
+ /* check sanity of each relocation */
+ n = sec->shdr->sh_size / sec->shdr->sh_entsize;
+ relo = sec->data->d_buf;
+ sym_sec = &obj->secs[obj->symtab_sec_idx];
+ for (i = 0; i < n; i++, relo++) {
+ size_t sym_idx = ELF64_R_SYM(relo->r_info);
+ size_t sym_type = ELF64_R_TYPE(relo->r_info);
+
+ if (sym_type != R_BPF_64_64 && sym_type != R_BPF_64_32 &&
+ sym_type != R_BPF_64_ABS64 && sym_type != R_BPF_64_ABS32) {
+ pr_warn("ELF relo #%d in section #%zu has unexpected type %zu in %s\n",
+ i, sec->sec_idx, sym_type, obj->filename);
+ return -EINVAL;
+ }
+
+ if (!sym_idx || sym_idx * sizeof(Elf64_Sym) >= sym_sec->shdr->sh_size) {
+ pr_warn("ELF relo #%d in section #%zu points to invalid symbol #%zu in %s\n",
+ i, sec->sec_idx, sym_idx, obj->filename);
+ return -EINVAL;
+ }
+
+ if (link_sec->shdr->sh_flags & SHF_EXECINSTR) {
+ if (relo->r_offset % sizeof(struct bpf_insn) != 0) {
+ pr_warn("ELF relo #%d in section #%zu points to missing symbol #%zu in %s\n",
+ i, sec->sec_idx, sym_idx, obj->filename);
+ return -EINVAL;
+ }
+ }
+ }
+
+ return 0;
+}
+
+static int check_btf_type_id(__u32 *type_id, void *ctx)
+{
+ struct btf *btf = ctx;
+
+ if (*type_id >= btf__type_cnt(btf))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int check_btf_str_off(__u32 *str_off, void *ctx)
+{
+ struct btf *btf = ctx;
+ const char *s;
+
+ s = btf__str_by_offset(btf, *str_off);
+
+ if (!s)
+ return -EINVAL;
+
+ return 0;
+}
+
+static int linker_sanity_check_btf(struct src_obj *obj)
+{
+ struct btf_type *t;
+ int i, n, err = 0;
+
+ if (!obj->btf)
+ return 0;
+
+ n = btf__type_cnt(obj->btf);
+ for (i = 1; i < n; i++) {
+ t = btf_type_by_id(obj->btf, i);
+
+ err = err ?: btf_type_visit_type_ids(t, check_btf_type_id, obj->btf);
+ err = err ?: btf_type_visit_str_offs(t, check_btf_str_off, obj->btf);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
+static int linker_sanity_check_btf_ext(struct src_obj *obj)
+{
+ int err = 0;
+
+ if (!obj->btf_ext)
+ return 0;
+
+ /* can't use .BTF.ext without .BTF */
+ if (!obj->btf)
+ return -EINVAL;
+
+ err = err ?: btf_ext_visit_type_ids(obj->btf_ext, check_btf_type_id, obj->btf);
+ err = err ?: btf_ext_visit_str_offs(obj->btf_ext, check_btf_str_off, obj->btf);
+ if (err)
+ return err;
+
+ return 0;
+}
+
+static int init_sec(struct bpf_linker *linker, struct dst_sec *dst_sec, struct src_sec *src_sec)
+{
+ Elf_Scn *scn;
+ Elf_Data *data;
+ Elf64_Shdr *shdr;
+ int name_off;
+
+ dst_sec->sec_sz = 0;
+ dst_sec->sec_idx = 0;
+ dst_sec->ephemeral = src_sec->ephemeral;
+
+ /* ephemeral sections are just thin section shells lacking most parts */
+ if (src_sec->ephemeral)
+ return 0;
+
+ scn = elf_newscn(linker->elf);
+ if (!scn)
+ return -ENOMEM;
+ data = elf_newdata(scn);
+ if (!data)
+ return -ENOMEM;
+ shdr = elf64_getshdr(scn);
+ if (!shdr)
+ return -ENOMEM;
+
+ dst_sec->scn = scn;
+ dst_sec->shdr = shdr;
+ dst_sec->data = data;
+ dst_sec->sec_idx = elf_ndxscn(scn);
+
+ name_off = strset__add_str(linker->strtab_strs, src_sec->sec_name);
+ if (name_off < 0)
+ return name_off;
+
+ shdr->sh_name = name_off;
+ shdr->sh_type = src_sec->shdr->sh_type;
+ shdr->sh_flags = src_sec->shdr->sh_flags;
+ shdr->sh_size = 0;
+ /* sh_link and sh_info have different meaning for different types of
+ * sections, so we leave it up to the caller code to fill them in, if
+ * necessary
+ */
+ shdr->sh_link = 0;
+ shdr->sh_info = 0;
+ shdr->sh_addralign = src_sec->shdr->sh_addralign;
+ shdr->sh_entsize = src_sec->shdr->sh_entsize;
+
+ data->d_type = src_sec->data->d_type;
+ data->d_size = 0;
+ data->d_buf = NULL;
+ data->d_align = src_sec->data->d_align;
+ data->d_off = 0;
+
+ return 0;
+}
+
+static struct dst_sec *find_dst_sec_by_name(struct bpf_linker *linker, const char *sec_name)
+{
+ struct dst_sec *sec;
+ int i;
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ sec = &linker->secs[i];
+
+ if (strcmp(sec->sec_name, sec_name) == 0)
+ return sec;
+ }
+
+ return NULL;
+}
+
+static bool secs_match(struct dst_sec *dst, struct src_sec *src)
+{
+ if (dst->ephemeral || src->ephemeral)
+ return true;
+
+ if (dst->shdr->sh_type != src->shdr->sh_type) {
+ pr_warn("sec %s types mismatch\n", dst->sec_name);
+ return false;
+ }
+ if (dst->shdr->sh_flags != src->shdr->sh_flags) {
+ pr_warn("sec %s flags mismatch\n", dst->sec_name);
+ return false;
+ }
+ if (dst->shdr->sh_entsize != src->shdr->sh_entsize) {
+ pr_warn("sec %s entsize mismatch\n", dst->sec_name);
+ return false;
+ }
+
+ return true;
+}
+
+static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec)
+{
+ if (dst_sec->sec_sz != src_sec->shdr->sh_size)
+ return false;
+ if (memcmp(dst_sec->raw_data, src_sec->data->d_buf, dst_sec->sec_sz) != 0)
+ return false;
+ return true;
+}
+
+static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src)
+{
+ void *tmp;
+ size_t dst_align, src_align;
+ size_t dst_align_sz, dst_final_sz;
+ int err;
+
+ /* Ephemeral source section doesn't contribute anything to ELF
+ * section data.
+ */
+ if (src->ephemeral)
+ return 0;
+
+ /* Some sections (like .maps) can contain both externs (and thus be
+ * ephemeral) and non-externs (map definitions). So it's possible that
+ * it has to be "upgraded" from ephemeral to non-ephemeral when the
+ * first non-ephemeral entity appears. In such case, we add ELF
+ * section, data, etc.
+ */
+ if (dst->ephemeral) {
+ err = init_sec(linker, dst, src);
+ if (err)
+ return err;
+ }
+
+ dst_align = dst->shdr->sh_addralign;
+ src_align = src->shdr->sh_addralign;
+ if (dst_align == 0)
+ dst_align = 1;
+ if (dst_align < src_align)
+ dst_align = src_align;
+
+ dst_align_sz = (dst->sec_sz + dst_align - 1) / dst_align * dst_align;
+
+ /* no need to re-align final size */
+ dst_final_sz = dst_align_sz + src->shdr->sh_size;
+
+ if (src->shdr->sh_type != SHT_NOBITS) {
+ tmp = realloc(dst->raw_data, dst_final_sz);
+ if (!tmp)
+ return -ENOMEM;
+ dst->raw_data = tmp;
+
+ /* pad dst section, if it's alignment forced size increase */
+ memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz);
+ /* now copy src data at a properly aligned offset */
+ memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size);
+ }
+
+ dst->sec_sz = dst_final_sz;
+ dst->shdr->sh_size = dst_final_sz;
+ dst->data->d_size = dst_final_sz;
+
+ dst->shdr->sh_addralign = dst_align;
+ dst->data->d_align = dst_align;
+
+ src->dst_off = dst_align_sz;
+
+ return 0;
+}
+
+static bool is_data_sec(struct src_sec *sec)
+{
+ if (!sec || sec->skipped)
+ return false;
+ /* ephemeral sections are data sections, e.g., .kconfig, .ksyms */
+ if (sec->ephemeral)
+ return true;
+ return sec->shdr->sh_type == SHT_PROGBITS || sec->shdr->sh_type == SHT_NOBITS;
+}
+
+static bool is_relo_sec(struct src_sec *sec)
+{
+ if (!sec || sec->skipped || sec->ephemeral)
+ return false;
+ return sec->shdr->sh_type == SHT_REL;
+}
+
+static int linker_append_sec_data(struct bpf_linker *linker, struct src_obj *obj)
+{
+ int i, err;
+
+ for (i = 1; i < obj->sec_cnt; i++) {
+ struct src_sec *src_sec;
+ struct dst_sec *dst_sec;
+
+ src_sec = &obj->secs[i];
+ if (!is_data_sec(src_sec))
+ continue;
+
+ dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
+ if (!dst_sec) {
+ dst_sec = add_dst_sec(linker, src_sec->sec_name);
+ if (!dst_sec)
+ return -ENOMEM;
+ err = init_sec(linker, dst_sec, src_sec);
+ if (err) {
+ pr_warn("failed to init section '%s'\n", src_sec->sec_name);
+ return err;
+ }
+ } else {
+ if (!secs_match(dst_sec, src_sec)) {
+ pr_warn("ELF sections %s are incompatible\n", src_sec->sec_name);
+ return -1;
+ }
+
+ /* "license" and "version" sections are deduped */
+ if (strcmp(src_sec->sec_name, "license") == 0
+ || strcmp(src_sec->sec_name, "version") == 0) {
+ if (!sec_content_is_same(dst_sec, src_sec)) {
+ pr_warn("non-identical contents of section '%s' are not supported\n", src_sec->sec_name);
+ return -EINVAL;
+ }
+ src_sec->skipped = true;
+ src_sec->dst_id = dst_sec->id;
+ continue;
+ }
+ }
+
+ /* record mapped section index */
+ src_sec->dst_id = dst_sec->id;
+
+ err = extend_sec(linker, dst_sec, src_sec);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
+static int linker_append_elf_syms(struct bpf_linker *linker, struct src_obj *obj)
+{
+ struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
+ Elf64_Sym *sym = symtab->data->d_buf;
+ int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize, err;
+ int str_sec_idx = symtab->shdr->sh_link;
+ const char *sym_name;
+
+ obj->sym_map = calloc(n + 1, sizeof(*obj->sym_map));
+ if (!obj->sym_map)
+ return -ENOMEM;
+
+ for (i = 0; i < n; i++, sym++) {
+ /* We already validated all-zero symbol #0 and we already
+ * appended it preventively to the final SYMTAB, so skip it.
+ */
+ if (i == 0)
+ continue;
+
+ sym_name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
+ if (!sym_name) {
+ pr_warn("can't fetch symbol name for symbol #%d in '%s'\n", i, obj->filename);
+ return -EINVAL;
+ }
+
+ err = linker_append_elf_sym(linker, obj, sym, sym_name, i);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
+static Elf64_Sym *get_sym_by_idx(struct bpf_linker *linker, size_t sym_idx)
+{
+ struct dst_sec *symtab = &linker->secs[linker->symtab_sec_idx];
+ Elf64_Sym *syms = symtab->raw_data;
+
+ return &syms[sym_idx];
+}
+
+static struct glob_sym *find_glob_sym(struct bpf_linker *linker, const char *sym_name)
+{
+ struct glob_sym *glob_sym;
+ const char *name;
+ int i;
+
+ for (i = 0; i < linker->glob_sym_cnt; i++) {
+ glob_sym = &linker->glob_syms[i];
+ name = strset__data(linker->strtab_strs) + glob_sym->name_off;
+
+ if (strcmp(name, sym_name) == 0)
+ return glob_sym;
+ }
+
+ return NULL;
+}
+
+static struct glob_sym *add_glob_sym(struct bpf_linker *linker)
+{
+ struct glob_sym *syms, *sym;
+
+ syms = libbpf_reallocarray(linker->glob_syms, linker->glob_sym_cnt + 1,
+ sizeof(*linker->glob_syms));
+ if (!syms)
+ return NULL;
+
+ sym = &syms[linker->glob_sym_cnt];
+ memset(sym, 0, sizeof(*sym));
+ sym->var_idx = -1;
+
+ linker->glob_syms = syms;
+ linker->glob_sym_cnt++;
+
+ return sym;
+}
+
+static bool glob_sym_btf_matches(const char *sym_name, bool exact,
+ const struct btf *btf1, __u32 id1,
+ const struct btf *btf2, __u32 id2)
+{
+ const struct btf_type *t1, *t2;
+ bool is_static1, is_static2;
+ const char *n1, *n2;
+ int i, n;
+
+recur:
+ n1 = n2 = NULL;
+ t1 = skip_mods_and_typedefs(btf1, id1, &id1);
+ t2 = skip_mods_and_typedefs(btf2, id2, &id2);
+
+ /* check if only one side is FWD, otherwise handle with common logic */
+ if (!exact && btf_is_fwd(t1) != btf_is_fwd(t2)) {
+ n1 = btf__str_by_offset(btf1, t1->name_off);
+ n2 = btf__str_by_offset(btf2, t2->name_off);
+ if (strcmp(n1, n2) != 0) {
+ pr_warn("global '%s': incompatible forward declaration names '%s' and '%s'\n",
+ sym_name, n1, n2);
+ return false;
+ }
+ /* validate if FWD kind matches concrete kind */
+ if (btf_is_fwd(t1)) {
+ if (btf_kflag(t1) && btf_is_union(t2))
+ return true;
+ if (!btf_kflag(t1) && btf_is_struct(t2))
+ return true;
+ pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
+ sym_name, btf_kflag(t1) ? "union" : "struct", btf_kind_str(t2));
+ } else {
+ if (btf_kflag(t2) && btf_is_union(t1))
+ return true;
+ if (!btf_kflag(t2) && btf_is_struct(t1))
+ return true;
+ pr_warn("global '%s': incompatible %s forward declaration and concrete kind %s\n",
+ sym_name, btf_kflag(t2) ? "union" : "struct", btf_kind_str(t1));
+ }
+ return false;
+ }
+
+ if (btf_kind(t1) != btf_kind(t2)) {
+ pr_warn("global '%s': incompatible BTF kinds %s and %s\n",
+ sym_name, btf_kind_str(t1), btf_kind_str(t2));
+ return false;
+ }
+
+ switch (btf_kind(t1)) {
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ case BTF_KIND_ENUM:
+ case BTF_KIND_ENUM64:
+ case BTF_KIND_FWD:
+ case BTF_KIND_FUNC:
+ case BTF_KIND_VAR:
+ n1 = btf__str_by_offset(btf1, t1->name_off);
+ n2 = btf__str_by_offset(btf2, t2->name_off);
+ if (strcmp(n1, n2) != 0) {
+ pr_warn("global '%s': incompatible %s names '%s' and '%s'\n",
+ sym_name, btf_kind_str(t1), n1, n2);
+ return false;
+ }
+ break;
+ default:
+ break;
+ }
+
+ switch (btf_kind(t1)) {
+ case BTF_KIND_UNKN: /* void */
+ case BTF_KIND_FWD:
+ return true;
+ case BTF_KIND_INT:
+ case BTF_KIND_FLOAT:
+ case BTF_KIND_ENUM:
+ case BTF_KIND_ENUM64:
+ /* ignore encoding for int and enum values for enum */
+ if (t1->size != t2->size) {
+ pr_warn("global '%s': incompatible %s '%s' size %u and %u\n",
+ sym_name, btf_kind_str(t1), n1, t1->size, t2->size);
+ return false;
+ }
+ return true;
+ case BTF_KIND_PTR:
+ /* just validate overall shape of the referenced type, so no
+ * contents comparison for struct/union, and allowd fwd vs
+ * struct/union
+ */
+ exact = false;
+ id1 = t1->type;
+ id2 = t2->type;
+ goto recur;
+ case BTF_KIND_ARRAY:
+ /* ignore index type and array size */
+ id1 = btf_array(t1)->type;
+ id2 = btf_array(t2)->type;
+ goto recur;
+ case BTF_KIND_FUNC:
+ /* extern and global linkages are compatible */
+ is_static1 = btf_func_linkage(t1) == BTF_FUNC_STATIC;
+ is_static2 = btf_func_linkage(t2) == BTF_FUNC_STATIC;
+ if (is_static1 != is_static2) {
+ pr_warn("global '%s': incompatible func '%s' linkage\n", sym_name, n1);
+ return false;
+ }
+
+ id1 = t1->type;
+ id2 = t2->type;
+ goto recur;
+ case BTF_KIND_VAR:
+ /* extern and global linkages are compatible */
+ is_static1 = btf_var(t1)->linkage == BTF_VAR_STATIC;
+ is_static2 = btf_var(t2)->linkage == BTF_VAR_STATIC;
+ if (is_static1 != is_static2) {
+ pr_warn("global '%s': incompatible var '%s' linkage\n", sym_name, n1);
+ return false;
+ }
+
+ id1 = t1->type;
+ id2 = t2->type;
+ goto recur;
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION: {
+ const struct btf_member *m1, *m2;
+
+ if (!exact)
+ return true;
+
+ if (btf_vlen(t1) != btf_vlen(t2)) {
+ pr_warn("global '%s': incompatible number of %s fields %u and %u\n",
+ sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
+ return false;
+ }
+
+ n = btf_vlen(t1);
+ m1 = btf_members(t1);
+ m2 = btf_members(t2);
+ for (i = 0; i < n; i++, m1++, m2++) {
+ n1 = btf__str_by_offset(btf1, m1->name_off);
+ n2 = btf__str_by_offset(btf2, m2->name_off);
+ if (strcmp(n1, n2) != 0) {
+ pr_warn("global '%s': incompatible field #%d names '%s' and '%s'\n",
+ sym_name, i, n1, n2);
+ return false;
+ }
+ if (m1->offset != m2->offset) {
+ pr_warn("global '%s': incompatible field #%d ('%s') offsets\n",
+ sym_name, i, n1);
+ return false;
+ }
+ if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
+ return false;
+ }
+
+ return true;
+ }
+ case BTF_KIND_FUNC_PROTO: {
+ const struct btf_param *m1, *m2;
+
+ if (btf_vlen(t1) != btf_vlen(t2)) {
+ pr_warn("global '%s': incompatible number of %s params %u and %u\n",
+ sym_name, btf_kind_str(t1), btf_vlen(t1), btf_vlen(t2));
+ return false;
+ }
+
+ n = btf_vlen(t1);
+ m1 = btf_params(t1);
+ m2 = btf_params(t2);
+ for (i = 0; i < n; i++, m1++, m2++) {
+ /* ignore func arg names */
+ if (!glob_sym_btf_matches(sym_name, exact, btf1, m1->type, btf2, m2->type))
+ return false;
+ }
+
+ /* now check return type as well */
+ id1 = t1->type;
+ id2 = t2->type;
+ goto recur;
+ }
+
+ /* skip_mods_and_typedefs() make this impossible */
+ case BTF_KIND_TYPEDEF:
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_CONST:
+ case BTF_KIND_RESTRICT:
+ /* DATASECs are never compared with each other */
+ case BTF_KIND_DATASEC:
+ default:
+ pr_warn("global '%s': unsupported BTF kind %s\n",
+ sym_name, btf_kind_str(t1));
+ return false;
+ }
+}
+
+static bool map_defs_match(const char *sym_name,
+ const struct btf *main_btf,
+ const struct btf_map_def *main_def,
+ const struct btf_map_def *main_inner_def,
+ const struct btf *extra_btf,
+ const struct btf_map_def *extra_def,
+ const struct btf_map_def *extra_inner_def)
+{
+ const char *reason;
+
+ if (main_def->map_type != extra_def->map_type) {
+ reason = "type";
+ goto mismatch;
+ }
+
+ /* check key type/size match */
+ if (main_def->key_size != extra_def->key_size) {
+ reason = "key_size";
+ goto mismatch;
+ }
+ if (!!main_def->key_type_id != !!extra_def->key_type_id) {
+ reason = "key type";
+ goto mismatch;
+ }
+ if ((main_def->parts & MAP_DEF_KEY_TYPE)
+ && !glob_sym_btf_matches(sym_name, true /*exact*/,
+ main_btf, main_def->key_type_id,
+ extra_btf, extra_def->key_type_id)) {
+ reason = "key type";
+ goto mismatch;
+ }
+
+ /* validate value type/size match */
+ if (main_def->value_size != extra_def->value_size) {
+ reason = "value_size";
+ goto mismatch;
+ }
+ if (!!main_def->value_type_id != !!extra_def->value_type_id) {
+ reason = "value type";
+ goto mismatch;
+ }
+ if ((main_def->parts & MAP_DEF_VALUE_TYPE)
+ && !glob_sym_btf_matches(sym_name, true /*exact*/,
+ main_btf, main_def->value_type_id,
+ extra_btf, extra_def->value_type_id)) {
+ reason = "key type";
+ goto mismatch;
+ }
+
+ if (main_def->max_entries != extra_def->max_entries) {
+ reason = "max_entries";
+ goto mismatch;
+ }
+ if (main_def->map_flags != extra_def->map_flags) {
+ reason = "map_flags";
+ goto mismatch;
+ }
+ if (main_def->numa_node != extra_def->numa_node) {
+ reason = "numa_node";
+ goto mismatch;
+ }
+ if (main_def->pinning != extra_def->pinning) {
+ reason = "pinning";
+ goto mismatch;
+ }
+
+ if ((main_def->parts & MAP_DEF_INNER_MAP) != (extra_def->parts & MAP_DEF_INNER_MAP)) {
+ reason = "inner map";
+ goto mismatch;
+ }
+
+ if (main_def->parts & MAP_DEF_INNER_MAP) {
+ char inner_map_name[128];
+
+ snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", sym_name);
+
+ return map_defs_match(inner_map_name,
+ main_btf, main_inner_def, NULL,
+ extra_btf, extra_inner_def, NULL);
+ }
+
+ return true;
+
+mismatch:
+ pr_warn("global '%s': map %s mismatch\n", sym_name, reason);
+ return false;
+}
+
+static bool glob_map_defs_match(const char *sym_name,
+ struct bpf_linker *linker, struct glob_sym *glob_sym,
+ struct src_obj *obj, Elf64_Sym *sym, int btf_id)
+{
+ struct btf_map_def dst_def = {}, dst_inner_def = {};
+ struct btf_map_def src_def = {}, src_inner_def = {};
+ const struct btf_type *t;
+ int err;
+
+ t = btf__type_by_id(obj->btf, btf_id);
+ if (!btf_is_var(t)) {
+ pr_warn("global '%s': invalid map definition type [%d]\n", sym_name, btf_id);
+ return false;
+ }
+ t = skip_mods_and_typedefs(obj->btf, t->type, NULL);
+
+ err = parse_btf_map_def(sym_name, obj->btf, t, true /*strict*/, &src_def, &src_inner_def);
+ if (err) {
+ pr_warn("global '%s': invalid map definition\n", sym_name);
+ return false;
+ }
+
+ /* re-parse existing map definition */
+ t = btf__type_by_id(linker->btf, glob_sym->btf_id);
+ t = skip_mods_and_typedefs(linker->btf, t->type, NULL);
+ err = parse_btf_map_def(sym_name, linker->btf, t, true /*strict*/, &dst_def, &dst_inner_def);
+ if (err) {
+ /* this should not happen, because we already validated it */
+ pr_warn("global '%s': invalid dst map definition\n", sym_name);
+ return false;
+ }
+
+ /* Currently extern map definition has to be complete and match
+ * concrete map definition exactly. This restriction might be lifted
+ * in the future.
+ */
+ return map_defs_match(sym_name, linker->btf, &dst_def, &dst_inner_def,
+ obj->btf, &src_def, &src_inner_def);
+}
+
+static bool glob_syms_match(const char *sym_name,
+ struct bpf_linker *linker, struct glob_sym *glob_sym,
+ struct src_obj *obj, Elf64_Sym *sym, size_t sym_idx, int btf_id)
+{
+ const struct btf_type *src_t;
+
+ /* if we are dealing with externs, BTF types describing both global
+ * and extern VARs/FUNCs should be completely present in all files
+ */
+ if (!glob_sym->btf_id || !btf_id) {
+ pr_warn("BTF info is missing for global symbol '%s'\n", sym_name);
+ return false;
+ }
+
+ src_t = btf__type_by_id(obj->btf, btf_id);
+ if (!btf_is_var(src_t) && !btf_is_func(src_t)) {
+ pr_warn("only extern variables and functions are supported, but got '%s' for '%s'\n",
+ btf_kind_str(src_t), sym_name);
+ return false;
+ }
+
+ /* deal with .maps definitions specially */
+ if (glob_sym->sec_id && strcmp(linker->secs[glob_sym->sec_id].sec_name, MAPS_ELF_SEC) == 0)
+ return glob_map_defs_match(sym_name, linker, glob_sym, obj, sym, btf_id);
+
+ if (!glob_sym_btf_matches(sym_name, true /*exact*/,
+ linker->btf, glob_sym->btf_id, obj->btf, btf_id))
+ return false;
+
+ return true;
+}
+
+static bool btf_is_non_static(const struct btf_type *t)
+{
+ return (btf_is_var(t) && btf_var(t)->linkage != BTF_VAR_STATIC)
+ || (btf_is_func(t) && btf_func_linkage(t) != BTF_FUNC_STATIC);
+}
+
+static int find_glob_sym_btf(struct src_obj *obj, Elf64_Sym *sym, const char *sym_name,
+ int *out_btf_sec_id, int *out_btf_id)
+{
+ int i, j, n, m, btf_id = 0;
+ const struct btf_type *t;
+ const struct btf_var_secinfo *vi;
+ const char *name;
+
+ if (!obj->btf) {
+ pr_warn("failed to find BTF info for object '%s'\n", obj->filename);
+ return -EINVAL;
+ }
+
+ n = btf__type_cnt(obj->btf);
+ for (i = 1; i < n; i++) {
+ t = btf__type_by_id(obj->btf, i);
+
+ /* some global and extern FUNCs and VARs might not be associated with any
+ * DATASEC, so try to detect them in the same pass
+ */
+ if (btf_is_non_static(t)) {
+ name = btf__str_by_offset(obj->btf, t->name_off);
+ if (strcmp(name, sym_name) != 0)
+ continue;
+
+ /* remember and still try to find DATASEC */
+ btf_id = i;
+ continue;
+ }
+
+ if (!btf_is_datasec(t))
+ continue;
+
+ vi = btf_var_secinfos(t);
+ for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
+ t = btf__type_by_id(obj->btf, vi->type);
+ name = btf__str_by_offset(obj->btf, t->name_off);
+
+ if (strcmp(name, sym_name) != 0)
+ continue;
+ if (btf_is_var(t) && btf_var(t)->linkage == BTF_VAR_STATIC)
+ continue;
+ if (btf_is_func(t) && btf_func_linkage(t) == BTF_FUNC_STATIC)
+ continue;
+
+ if (btf_id && btf_id != vi->type) {
+ pr_warn("global/extern '%s' BTF is ambiguous: both types #%d and #%u match\n",
+ sym_name, btf_id, vi->type);
+ return -EINVAL;
+ }
+
+ *out_btf_sec_id = i;
+ *out_btf_id = vi->type;
+
+ return 0;
+ }
+ }
+
+ /* free-floating extern or global FUNC */
+ if (btf_id) {
+ *out_btf_sec_id = 0;
+ *out_btf_id = btf_id;
+ return 0;
+ }
+
+ pr_warn("failed to find BTF info for global/extern symbol '%s'\n", sym_name);
+ return -ENOENT;
+}
+
+static struct src_sec *find_src_sec_by_name(struct src_obj *obj, const char *sec_name)
+{
+ struct src_sec *sec;
+ int i;
+
+ for (i = 1; i < obj->sec_cnt; i++) {
+ sec = &obj->secs[i];
+
+ if (strcmp(sec->sec_name, sec_name) == 0)
+ return sec;
+ }
+
+ return NULL;
+}
+
+static int complete_extern_btf_info(struct btf *dst_btf, int dst_id,
+ struct btf *src_btf, int src_id)
+{
+ struct btf_type *dst_t = btf_type_by_id(dst_btf, dst_id);
+ struct btf_type *src_t = btf_type_by_id(src_btf, src_id);
+ struct btf_param *src_p, *dst_p;
+ const char *s;
+ int i, n, off;
+
+ /* We already made sure that source and destination types (FUNC or
+ * VAR) match in terms of types and argument names.
+ */
+ if (btf_is_var(dst_t)) {
+ btf_var(dst_t)->linkage = BTF_VAR_GLOBAL_ALLOCATED;
+ return 0;
+ }
+
+ dst_t->info = btf_type_info(BTF_KIND_FUNC, BTF_FUNC_GLOBAL, 0);
+
+ /* now onto FUNC_PROTO types */
+ src_t = btf_type_by_id(src_btf, src_t->type);
+ dst_t = btf_type_by_id(dst_btf, dst_t->type);
+
+ /* Fill in all the argument names, which for extern FUNCs are missing.
+ * We'll end up with two copies of FUNCs/VARs for externs, but that
+ * will be taken care of by BTF dedup at the very end.
+ * It might be that BTF types for extern in one file has less/more BTF
+ * information (e.g., FWD instead of full STRUCT/UNION information),
+ * but that should be (in most cases, subject to BTF dedup rules)
+ * handled and resolved by BTF dedup algorithm as well, so we won't
+ * worry about it. Our only job is to make sure that argument names
+ * are populated on both sides, otherwise BTF dedup will pedantically
+ * consider them different.
+ */
+ src_p = btf_params(src_t);
+ dst_p = btf_params(dst_t);
+ for (i = 0, n = btf_vlen(dst_t); i < n; i++, src_p++, dst_p++) {
+ if (!src_p->name_off)
+ continue;
+
+ /* src_btf has more complete info, so add name to dst_btf */
+ s = btf__str_by_offset(src_btf, src_p->name_off);
+ off = btf__add_str(dst_btf, s);
+ if (off < 0)
+ return off;
+ dst_p->name_off = off;
+ }
+ return 0;
+}
+
+static void sym_update_bind(Elf64_Sym *sym, int sym_bind)
+{
+ sym->st_info = ELF64_ST_INFO(sym_bind, ELF64_ST_TYPE(sym->st_info));
+}
+
+static void sym_update_type(Elf64_Sym *sym, int sym_type)
+{
+ sym->st_info = ELF64_ST_INFO(ELF64_ST_BIND(sym->st_info), sym_type);
+}
+
+static void sym_update_visibility(Elf64_Sym *sym, int sym_vis)
+{
+ /* libelf doesn't provide setters for ST_VISIBILITY,
+ * but it is stored in the lower 2 bits of st_other
+ */
+ sym->st_other &= ~0x03;
+ sym->st_other |= sym_vis;
+}
+
+static int linker_append_elf_sym(struct bpf_linker *linker, struct src_obj *obj,
+ Elf64_Sym *sym, const char *sym_name, int src_sym_idx)
+{
+ struct src_sec *src_sec = NULL;
+ struct dst_sec *dst_sec = NULL;
+ struct glob_sym *glob_sym = NULL;
+ int name_off, sym_type, sym_bind, sym_vis, err;
+ int btf_sec_id = 0, btf_id = 0;
+ size_t dst_sym_idx;
+ Elf64_Sym *dst_sym;
+ bool sym_is_extern;
+
+ sym_type = ELF64_ST_TYPE(sym->st_info);
+ sym_bind = ELF64_ST_BIND(sym->st_info);
+ sym_vis = ELF64_ST_VISIBILITY(sym->st_other);
+ sym_is_extern = sym->st_shndx == SHN_UNDEF;
+
+ if (sym_is_extern) {
+ if (!obj->btf) {
+ pr_warn("externs without BTF info are not supported\n");
+ return -ENOTSUP;
+ }
+ } else if (sym->st_shndx < SHN_LORESERVE) {
+ src_sec = &obj->secs[sym->st_shndx];
+ if (src_sec->skipped)
+ return 0;
+ dst_sec = &linker->secs[src_sec->dst_id];
+
+ /* allow only one STT_SECTION symbol per section */
+ if (sym_type == STT_SECTION && dst_sec->sec_sym_idx) {
+ obj->sym_map[src_sym_idx] = dst_sec->sec_sym_idx;
+ return 0;
+ }
+ }
+
+ if (sym_bind == STB_LOCAL)
+ goto add_sym;
+
+ /* find matching BTF info */
+ err = find_glob_sym_btf(obj, sym, sym_name, &btf_sec_id, &btf_id);
+ if (err)
+ return err;
+
+ if (sym_is_extern && btf_sec_id) {
+ const char *sec_name = NULL;
+ const struct btf_type *t;
+
+ t = btf__type_by_id(obj->btf, btf_sec_id);
+ sec_name = btf__str_by_offset(obj->btf, t->name_off);
+
+ /* Clang puts unannotated extern vars into
+ * '.extern' BTF DATASEC. Treat them the same
+ * as unannotated extern funcs (which are
+ * currently not put into any DATASECs).
+ * Those don't have associated src_sec/dst_sec.
+ */
+ if (strcmp(sec_name, BTF_EXTERN_SEC) != 0) {
+ src_sec = find_src_sec_by_name(obj, sec_name);
+ if (!src_sec) {
+ pr_warn("failed to find matching ELF sec '%s'\n", sec_name);
+ return -ENOENT;
+ }
+ dst_sec = &linker->secs[src_sec->dst_id];
+ }
+ }
+
+ glob_sym = find_glob_sym(linker, sym_name);
+ if (glob_sym) {
+ /* Preventively resolve to existing symbol. This is
+ * needed for further relocation symbol remapping in
+ * the next step of linking.
+ */
+ obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
+
+ /* If both symbols are non-externs, at least one of
+ * them has to be STB_WEAK, otherwise they are in
+ * a conflict with each other.
+ */
+ if (!sym_is_extern && !glob_sym->is_extern
+ && !glob_sym->is_weak && sym_bind != STB_WEAK) {
+ pr_warn("conflicting non-weak symbol #%d (%s) definition in '%s'\n",
+ src_sym_idx, sym_name, obj->filename);
+ return -EINVAL;
+ }
+
+ if (!glob_syms_match(sym_name, linker, glob_sym, obj, sym, src_sym_idx, btf_id))
+ return -EINVAL;
+
+ dst_sym = get_sym_by_idx(linker, glob_sym->sym_idx);
+
+ /* If new symbol is strong, then force dst_sym to be strong as
+ * well; this way a mix of weak and non-weak extern
+ * definitions will end up being strong.
+ */
+ if (sym_bind == STB_GLOBAL) {
+ /* We still need to preserve type (NOTYPE or
+ * OBJECT/FUNC, depending on whether the symbol is
+ * extern or not)
+ */
+ sym_update_bind(dst_sym, STB_GLOBAL);
+ glob_sym->is_weak = false;
+ }
+
+ /* Non-default visibility is "contaminating", with stricter
+ * visibility overwriting more permissive ones, even if more
+ * permissive visibility comes from just an extern definition.
+ * Currently only STV_DEFAULT and STV_HIDDEN are allowed and
+ * ensured by ELF symbol sanity checks above.
+ */
+ if (sym_vis > ELF64_ST_VISIBILITY(dst_sym->st_other))
+ sym_update_visibility(dst_sym, sym_vis);
+
+ /* If the new symbol is extern, then regardless if
+ * existing symbol is extern or resolved global, just
+ * keep the existing one untouched.
+ */
+ if (sym_is_extern)
+ return 0;
+
+ /* If existing symbol is a strong resolved symbol, bail out,
+ * because we lost resolution battle have nothing to
+ * contribute. We already checked abover that there is no
+ * strong-strong conflict. We also already tightened binding
+ * and visibility, so nothing else to contribute at that point.
+ */
+ if (!glob_sym->is_extern && sym_bind == STB_WEAK)
+ return 0;
+
+ /* At this point, new symbol is strong non-extern,
+ * so overwrite glob_sym with new symbol information.
+ * Preserve binding and visibility.
+ */
+ sym_update_type(dst_sym, sym_type);
+ dst_sym->st_shndx = dst_sec->sec_idx;
+ dst_sym->st_value = src_sec->dst_off + sym->st_value;
+ dst_sym->st_size = sym->st_size;
+
+ /* see comment below about dst_sec->id vs dst_sec->sec_idx */
+ glob_sym->sec_id = dst_sec->id;
+ glob_sym->is_extern = false;
+
+ if (complete_extern_btf_info(linker->btf, glob_sym->btf_id,
+ obj->btf, btf_id))
+ return -EINVAL;
+
+ /* request updating VAR's/FUNC's underlying BTF type when appending BTF type */
+ glob_sym->underlying_btf_id = 0;
+
+ obj->sym_map[src_sym_idx] = glob_sym->sym_idx;
+ return 0;
+ }
+
+add_sym:
+ name_off = strset__add_str(linker->strtab_strs, sym_name);
+ if (name_off < 0)
+ return name_off;
+
+ dst_sym = add_new_sym(linker, &dst_sym_idx);
+ if (!dst_sym)
+ return -ENOMEM;
+
+ dst_sym->st_name = name_off;
+ dst_sym->st_info = sym->st_info;
+ dst_sym->st_other = sym->st_other;
+ dst_sym->st_shndx = dst_sec ? dst_sec->sec_idx : sym->st_shndx;
+ dst_sym->st_value = (src_sec ? src_sec->dst_off : 0) + sym->st_value;
+ dst_sym->st_size = sym->st_size;
+
+ obj->sym_map[src_sym_idx] = dst_sym_idx;
+
+ if (sym_type == STT_SECTION && dst_sym) {
+ dst_sec->sec_sym_idx = dst_sym_idx;
+ dst_sym->st_value = 0;
+ }
+
+ if (sym_bind != STB_LOCAL) {
+ glob_sym = add_glob_sym(linker);
+ if (!glob_sym)
+ return -ENOMEM;
+
+ glob_sym->sym_idx = dst_sym_idx;
+ /* we use dst_sec->id (and not dst_sec->sec_idx), because
+ * ephemeral sections (.kconfig, .ksyms, etc) don't have
+ * sec_idx (as they don't have corresponding ELF section), but
+ * still have id. .extern doesn't have even ephemeral section
+ * associated with it, so dst_sec->id == dst_sec->sec_idx == 0.
+ */
+ glob_sym->sec_id = dst_sec ? dst_sec->id : 0;
+ glob_sym->name_off = name_off;
+ /* we will fill btf_id in during BTF merging step */
+ glob_sym->btf_id = 0;
+ glob_sym->is_extern = sym_is_extern;
+ glob_sym->is_weak = sym_bind == STB_WEAK;
+ }
+
+ return 0;
+}
+
+static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj)
+{
+ struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx];
+ struct dst_sec *dst_symtab;
+ int i, err;
+
+ for (i = 1; i < obj->sec_cnt; i++) {
+ struct src_sec *src_sec, *src_linked_sec;
+ struct dst_sec *dst_sec, *dst_linked_sec;
+ Elf64_Rel *src_rel, *dst_rel;
+ int j, n;
+
+ src_sec = &obj->secs[i];
+ if (!is_relo_sec(src_sec))
+ continue;
+
+ /* shdr->sh_info points to relocatable section */
+ src_linked_sec = &obj->secs[src_sec->shdr->sh_info];
+ if (src_linked_sec->skipped)
+ continue;
+
+ dst_sec = find_dst_sec_by_name(linker, src_sec->sec_name);
+ if (!dst_sec) {
+ dst_sec = add_dst_sec(linker, src_sec->sec_name);
+ if (!dst_sec)
+ return -ENOMEM;
+ err = init_sec(linker, dst_sec, src_sec);
+ if (err) {
+ pr_warn("failed to init section '%s'\n", src_sec->sec_name);
+ return err;
+ }
+ } else if (!secs_match(dst_sec, src_sec)) {
+ pr_warn("sections %s are not compatible\n", src_sec->sec_name);
+ return -1;
+ }
+
+ /* add_dst_sec() above could have invalidated linker->secs */
+ dst_symtab = &linker->secs[linker->symtab_sec_idx];
+
+ /* shdr->sh_link points to SYMTAB */
+ dst_sec->shdr->sh_link = linker->symtab_sec_idx;
+
+ /* shdr->sh_info points to relocated section */
+ dst_linked_sec = &linker->secs[src_linked_sec->dst_id];
+ dst_sec->shdr->sh_info = dst_linked_sec->sec_idx;
+
+ src_sec->dst_id = dst_sec->id;
+ err = extend_sec(linker, dst_sec, src_sec);
+ if (err)
+ return err;
+
+ src_rel = src_sec->data->d_buf;
+ dst_rel = dst_sec->raw_data + src_sec->dst_off;
+ n = src_sec->shdr->sh_size / src_sec->shdr->sh_entsize;
+ for (j = 0; j < n; j++, src_rel++, dst_rel++) {
+ size_t src_sym_idx = ELF64_R_SYM(src_rel->r_info);
+ size_t sym_type = ELF64_R_TYPE(src_rel->r_info);
+ Elf64_Sym *src_sym, *dst_sym;
+ size_t dst_sym_idx;
+
+ src_sym_idx = ELF64_R_SYM(src_rel->r_info);
+ src_sym = src_symtab->data->d_buf + sizeof(*src_sym) * src_sym_idx;
+
+ dst_sym_idx = obj->sym_map[src_sym_idx];
+ dst_sym = dst_symtab->raw_data + sizeof(*dst_sym) * dst_sym_idx;
+ dst_rel->r_offset += src_linked_sec->dst_off;
+ sym_type = ELF64_R_TYPE(src_rel->r_info);
+ dst_rel->r_info = ELF64_R_INFO(dst_sym_idx, sym_type);
+
+ if (ELF64_ST_TYPE(src_sym->st_info) == STT_SECTION) {
+ struct src_sec *sec = &obj->secs[src_sym->st_shndx];
+ struct bpf_insn *insn;
+
+ if (src_linked_sec->shdr->sh_flags & SHF_EXECINSTR) {
+ /* calls to the very first static function inside
+ * .text section at offset 0 will
+ * reference section symbol, not the
+ * function symbol. Fix that up,
+ * otherwise it won't be possible to
+ * relocate calls to two different
+ * static functions with the same name
+ * (rom two different object files)
+ */
+ insn = dst_linked_sec->raw_data + dst_rel->r_offset;
+ if (insn->code == (BPF_JMP | BPF_CALL))
+ insn->imm += sec->dst_off / sizeof(struct bpf_insn);
+ else
+ insn->imm += sec->dst_off;
+ } else {
+ pr_warn("relocation against STT_SECTION in non-exec section is not supported!\n");
+ return -EINVAL;
+ }
+ }
+
+ }
+ }
+
+ return 0;
+}
+
+static Elf64_Sym *find_sym_by_name(struct src_obj *obj, size_t sec_idx,
+ int sym_type, const char *sym_name)
+{
+ struct src_sec *symtab = &obj->secs[obj->symtab_sec_idx];
+ Elf64_Sym *sym = symtab->data->d_buf;
+ int i, n = symtab->shdr->sh_size / symtab->shdr->sh_entsize;
+ int str_sec_idx = symtab->shdr->sh_link;
+ const char *name;
+
+ for (i = 0; i < n; i++, sym++) {
+ if (sym->st_shndx != sec_idx)
+ continue;
+ if (ELF64_ST_TYPE(sym->st_info) != sym_type)
+ continue;
+
+ name = elf_strptr(obj->elf, str_sec_idx, sym->st_name);
+ if (!name)
+ return NULL;
+
+ if (strcmp(sym_name, name) != 0)
+ continue;
+
+ return sym;
+ }
+
+ return NULL;
+}
+
+static int linker_fixup_btf(struct src_obj *obj)
+{
+ const char *sec_name;
+ struct src_sec *sec;
+ int i, j, n, m;
+
+ if (!obj->btf)
+ return 0;
+
+ n = btf__type_cnt(obj->btf);
+ for (i = 1; i < n; i++) {
+ struct btf_var_secinfo *vi;
+ struct btf_type *t;
+
+ t = btf_type_by_id(obj->btf, i);
+ if (btf_kind(t) != BTF_KIND_DATASEC)
+ continue;
+
+ sec_name = btf__str_by_offset(obj->btf, t->name_off);
+ sec = find_src_sec_by_name(obj, sec_name);
+ if (sec) {
+ /* record actual section size, unless ephemeral */
+ if (sec->shdr)
+ t->size = sec->shdr->sh_size;
+ } else {
+ /* BTF can have some sections that are not represented
+ * in ELF, e.g., .kconfig, .ksyms, .extern, which are used
+ * for special extern variables.
+ *
+ * For all but one such special (ephemeral)
+ * sections, we pre-create "section shells" to be able
+ * to keep track of extra per-section metadata later
+ * (e.g., those BTF extern variables).
+ *
+ * .extern is even more special, though, because it
+ * contains extern variables that need to be resolved
+ * by static linker, not libbpf and kernel. When such
+ * externs are resolved, we are going to remove them
+ * from .extern BTF section and might end up not
+ * needing it at all. Each resolved extern should have
+ * matching non-extern VAR/FUNC in other sections.
+ *
+ * We do support leaving some of the externs
+ * unresolved, though, to support cases of building
+ * libraries, which will later be linked against final
+ * BPF applications. So if at finalization we still
+ * see unresolved externs, we'll create .extern
+ * section on our own.
+ */
+ if (strcmp(sec_name, BTF_EXTERN_SEC) == 0)
+ continue;
+
+ sec = add_src_sec(obj, sec_name);
+ if (!sec)
+ return -ENOMEM;
+
+ sec->ephemeral = true;
+ sec->sec_idx = 0; /* will match UNDEF shndx in ELF */
+ }
+
+ /* remember ELF section and its BTF type ID match */
+ sec->sec_type_id = i;
+
+ /* fix up variable offsets */
+ vi = btf_var_secinfos(t);
+ for (j = 0, m = btf_vlen(t); j < m; j++, vi++) {
+ const struct btf_type *vt = btf__type_by_id(obj->btf, vi->type);
+ const char *var_name = btf__str_by_offset(obj->btf, vt->name_off);
+ int var_linkage = btf_var(vt)->linkage;
+ Elf64_Sym *sym;
+
+ /* no need to patch up static or extern vars */
+ if (var_linkage != BTF_VAR_GLOBAL_ALLOCATED)
+ continue;
+
+ sym = find_sym_by_name(obj, sec->sec_idx, STT_OBJECT, var_name);
+ if (!sym) {
+ pr_warn("failed to find symbol for variable '%s' in section '%s'\n", var_name, sec_name);
+ return -ENOENT;
+ }
+
+ vi->offset = sym->st_value;
+ }
+ }
+
+ return 0;
+}
+
+static int remap_type_id(__u32 *type_id, void *ctx)
+{
+ int *id_map = ctx;
+ int new_id = id_map[*type_id];
+
+ /* Error out if the type wasn't remapped. Ignore VOID which stays VOID. */
+ if (new_id == 0 && *type_id != 0) {
+ pr_warn("failed to find new ID mapping for original BTF type ID %u\n", *type_id);
+ return -EINVAL;
+ }
+
+ *type_id = id_map[*type_id];
+
+ return 0;
+}
+
+static int linker_append_btf(struct bpf_linker *linker, struct src_obj *obj)
+{
+ const struct btf_type *t;
+ int i, j, n, start_id, id;
+ const char *name;
+
+ if (!obj->btf)
+ return 0;
+
+ start_id = btf__type_cnt(linker->btf);
+ n = btf__type_cnt(obj->btf);
+
+ obj->btf_type_map = calloc(n + 1, sizeof(int));
+ if (!obj->btf_type_map)
+ return -ENOMEM;
+
+ for (i = 1; i < n; i++) {
+ struct glob_sym *glob_sym = NULL;
+
+ t = btf__type_by_id(obj->btf, i);
+
+ /* DATASECs are handled specially below */
+ if (btf_kind(t) == BTF_KIND_DATASEC)
+ continue;
+
+ if (btf_is_non_static(t)) {
+ /* there should be glob_sym already */
+ name = btf__str_by_offset(obj->btf, t->name_off);
+ glob_sym = find_glob_sym(linker, name);
+
+ /* VARs without corresponding glob_sym are those that
+ * belong to skipped/deduplicated sections (i.e.,
+ * license and version), so just skip them
+ */
+ if (!glob_sym)
+ continue;
+
+ /* linker_append_elf_sym() might have requested
+ * updating underlying type ID, if extern was resolved
+ * to strong symbol or weak got upgraded to non-weak
+ */
+ if (glob_sym->underlying_btf_id == 0)
+ glob_sym->underlying_btf_id = -t->type;
+
+ /* globals from previous object files that match our
+ * VAR/FUNC already have a corresponding associated
+ * BTF type, so just make sure to use it
+ */
+ if (glob_sym->btf_id) {
+ /* reuse existing BTF type for global var/func */
+ obj->btf_type_map[i] = glob_sym->btf_id;
+ continue;
+ }
+ }
+
+ id = btf__add_type(linker->btf, obj->btf, t);
+ if (id < 0) {
+ pr_warn("failed to append BTF type #%d from file '%s'\n", i, obj->filename);
+ return id;
+ }
+
+ obj->btf_type_map[i] = id;
+
+ /* record just appended BTF type for var/func */
+ if (glob_sym) {
+ glob_sym->btf_id = id;
+ glob_sym->underlying_btf_id = -t->type;
+ }
+ }
+
+ /* remap all the types except DATASECs */
+ n = btf__type_cnt(linker->btf);
+ for (i = start_id; i < n; i++) {
+ struct btf_type *dst_t = btf_type_by_id(linker->btf, i);
+
+ if (btf_type_visit_type_ids(dst_t, remap_type_id, obj->btf_type_map))
+ return -EINVAL;
+ }
+
+ /* Rewrite VAR/FUNC underlying types (i.e., FUNC's FUNC_PROTO and VAR's
+ * actual type), if necessary
+ */
+ for (i = 0; i < linker->glob_sym_cnt; i++) {
+ struct glob_sym *glob_sym = &linker->glob_syms[i];
+ struct btf_type *glob_t;
+
+ if (glob_sym->underlying_btf_id >= 0)
+ continue;
+
+ glob_sym->underlying_btf_id = obj->btf_type_map[-glob_sym->underlying_btf_id];
+
+ glob_t = btf_type_by_id(linker->btf, glob_sym->btf_id);
+ glob_t->type = glob_sym->underlying_btf_id;
+ }
+
+ /* append DATASEC info */
+ for (i = 1; i < obj->sec_cnt; i++) {
+ struct src_sec *src_sec;
+ struct dst_sec *dst_sec;
+ const struct btf_var_secinfo *src_var;
+ struct btf_var_secinfo *dst_var;
+
+ src_sec = &obj->secs[i];
+ if (!src_sec->sec_type_id || src_sec->skipped)
+ continue;
+ dst_sec = &linker->secs[src_sec->dst_id];
+
+ /* Mark section as having BTF regardless of the presence of
+ * variables. In some cases compiler might generate empty BTF
+ * with no variables information. E.g., when promoting local
+ * array/structure variable initial values and BPF object
+ * file otherwise has no read-only static variables in
+ * .rodata. We need to preserve such empty BTF and just set
+ * correct section size.
+ */
+ dst_sec->has_btf = true;
+
+ t = btf__type_by_id(obj->btf, src_sec->sec_type_id);
+ src_var = btf_var_secinfos(t);
+ n = btf_vlen(t);
+ for (j = 0; j < n; j++, src_var++) {
+ void *sec_vars = dst_sec->sec_vars;
+ int new_id = obj->btf_type_map[src_var->type];
+ struct glob_sym *glob_sym = NULL;
+
+ t = btf_type_by_id(linker->btf, new_id);
+ if (btf_is_non_static(t)) {
+ name = btf__str_by_offset(linker->btf, t->name_off);
+ glob_sym = find_glob_sym(linker, name);
+ if (glob_sym->sec_id != dst_sec->id) {
+ pr_warn("global '%s': section mismatch %d vs %d\n",
+ name, glob_sym->sec_id, dst_sec->id);
+ return -EINVAL;
+ }
+ }
+
+ /* If there is already a member (VAR or FUNC) mapped
+ * to the same type, don't add a duplicate entry.
+ * This will happen when multiple object files define
+ * the same extern VARs/FUNCs.
+ */
+ if (glob_sym && glob_sym->var_idx >= 0) {
+ __s64 sz;
+
+ dst_var = &dst_sec->sec_vars[glob_sym->var_idx];
+ /* Because underlying BTF type might have
+ * changed, so might its size have changed, so
+ * re-calculate and update it in sec_var.
+ */
+ sz = btf__resolve_size(linker->btf, glob_sym->underlying_btf_id);
+ if (sz < 0) {
+ pr_warn("global '%s': failed to resolve size of underlying type: %d\n",
+ name, (int)sz);
+ return -EINVAL;
+ }
+ dst_var->size = sz;
+ continue;
+ }
+
+ sec_vars = libbpf_reallocarray(sec_vars,
+ dst_sec->sec_var_cnt + 1,
+ sizeof(*dst_sec->sec_vars));
+ if (!sec_vars)
+ return -ENOMEM;
+
+ dst_sec->sec_vars = sec_vars;
+ dst_sec->sec_var_cnt++;
+
+ dst_var = &dst_sec->sec_vars[dst_sec->sec_var_cnt - 1];
+ dst_var->type = obj->btf_type_map[src_var->type];
+ dst_var->size = src_var->size;
+ dst_var->offset = src_sec->dst_off + src_var->offset;
+
+ if (glob_sym)
+ glob_sym->var_idx = dst_sec->sec_var_cnt - 1;
+ }
+ }
+
+ return 0;
+}
+
+static void *add_btf_ext_rec(struct btf_ext_sec_data *ext_data, const void *src_rec)
+{
+ void *tmp;
+
+ tmp = libbpf_reallocarray(ext_data->recs, ext_data->rec_cnt + 1, ext_data->rec_sz);
+ if (!tmp)
+ return NULL;
+ ext_data->recs = tmp;
+
+ tmp += ext_data->rec_cnt * ext_data->rec_sz;
+ memcpy(tmp, src_rec, ext_data->rec_sz);
+
+ ext_data->rec_cnt++;
+
+ return tmp;
+}
+
+static int linker_append_btf_ext(struct bpf_linker *linker, struct src_obj *obj)
+{
+ const struct btf_ext_info_sec *ext_sec;
+ const char *sec_name, *s;
+ struct src_sec *src_sec;
+ struct dst_sec *dst_sec;
+ int rec_sz, str_off, i;
+
+ if (!obj->btf_ext)
+ return 0;
+
+ rec_sz = obj->btf_ext->func_info.rec_size;
+ for_each_btf_ext_sec(&obj->btf_ext->func_info, ext_sec) {
+ struct bpf_func_info_min *src_rec, *dst_rec;
+
+ sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
+ src_sec = find_src_sec_by_name(obj, sec_name);
+ if (!src_sec) {
+ pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
+ return -EINVAL;
+ }
+ dst_sec = &linker->secs[src_sec->dst_id];
+
+ if (dst_sec->func_info.rec_sz == 0)
+ dst_sec->func_info.rec_sz = rec_sz;
+ if (dst_sec->func_info.rec_sz != rec_sz) {
+ pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
+ return -EINVAL;
+ }
+
+ for_each_btf_ext_rec(&obj->btf_ext->func_info, ext_sec, i, src_rec) {
+ dst_rec = add_btf_ext_rec(&dst_sec->func_info, src_rec);
+ if (!dst_rec)
+ return -ENOMEM;
+
+ dst_rec->insn_off += src_sec->dst_off;
+ dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
+ }
+ }
+
+ rec_sz = obj->btf_ext->line_info.rec_size;
+ for_each_btf_ext_sec(&obj->btf_ext->line_info, ext_sec) {
+ struct bpf_line_info_min *src_rec, *dst_rec;
+
+ sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
+ src_sec = find_src_sec_by_name(obj, sec_name);
+ if (!src_sec) {
+ pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
+ return -EINVAL;
+ }
+ dst_sec = &linker->secs[src_sec->dst_id];
+
+ if (dst_sec->line_info.rec_sz == 0)
+ dst_sec->line_info.rec_sz = rec_sz;
+ if (dst_sec->line_info.rec_sz != rec_sz) {
+ pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
+ return -EINVAL;
+ }
+
+ for_each_btf_ext_rec(&obj->btf_ext->line_info, ext_sec, i, src_rec) {
+ dst_rec = add_btf_ext_rec(&dst_sec->line_info, src_rec);
+ if (!dst_rec)
+ return -ENOMEM;
+
+ dst_rec->insn_off += src_sec->dst_off;
+
+ s = btf__str_by_offset(obj->btf, src_rec->file_name_off);
+ str_off = btf__add_str(linker->btf, s);
+ if (str_off < 0)
+ return -ENOMEM;
+ dst_rec->file_name_off = str_off;
+
+ s = btf__str_by_offset(obj->btf, src_rec->line_off);
+ str_off = btf__add_str(linker->btf, s);
+ if (str_off < 0)
+ return -ENOMEM;
+ dst_rec->line_off = str_off;
+
+ /* dst_rec->line_col is fine */
+ }
+ }
+
+ rec_sz = obj->btf_ext->core_relo_info.rec_size;
+ for_each_btf_ext_sec(&obj->btf_ext->core_relo_info, ext_sec) {
+ struct bpf_core_relo *src_rec, *dst_rec;
+
+ sec_name = btf__name_by_offset(obj->btf, ext_sec->sec_name_off);
+ src_sec = find_src_sec_by_name(obj, sec_name);
+ if (!src_sec) {
+ pr_warn("can't find section '%s' referenced from .BTF.ext\n", sec_name);
+ return -EINVAL;
+ }
+ dst_sec = &linker->secs[src_sec->dst_id];
+
+ if (dst_sec->core_relo_info.rec_sz == 0)
+ dst_sec->core_relo_info.rec_sz = rec_sz;
+ if (dst_sec->core_relo_info.rec_sz != rec_sz) {
+ pr_warn("incompatible .BTF.ext record sizes for section '%s'\n", sec_name);
+ return -EINVAL;
+ }
+
+ for_each_btf_ext_rec(&obj->btf_ext->core_relo_info, ext_sec, i, src_rec) {
+ dst_rec = add_btf_ext_rec(&dst_sec->core_relo_info, src_rec);
+ if (!dst_rec)
+ return -ENOMEM;
+
+ dst_rec->insn_off += src_sec->dst_off;
+ dst_rec->type_id = obj->btf_type_map[dst_rec->type_id];
+
+ s = btf__str_by_offset(obj->btf, src_rec->access_str_off);
+ str_off = btf__add_str(linker->btf, s);
+ if (str_off < 0)
+ return -ENOMEM;
+ dst_rec->access_str_off = str_off;
+
+ /* dst_rec->kind is fine */
+ }
+ }
+
+ return 0;
+}
+
+int bpf_linker__finalize(struct bpf_linker *linker)
+{
+ struct dst_sec *sec;
+ size_t strs_sz;
+ const void *strs;
+ int err, i;
+
+ if (!linker->elf)
+ return libbpf_err(-EINVAL);
+
+ err = finalize_btf(linker);
+ if (err)
+ return libbpf_err(err);
+
+ /* Finalize strings */
+ strs_sz = strset__data_size(linker->strtab_strs);
+ strs = strset__data(linker->strtab_strs);
+
+ sec = &linker->secs[linker->strtab_sec_idx];
+ sec->data->d_align = 1;
+ sec->data->d_off = 0LL;
+ sec->data->d_buf = (void *)strs;
+ sec->data->d_type = ELF_T_BYTE;
+ sec->data->d_size = strs_sz;
+ sec->shdr->sh_size = strs_sz;
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ sec = &linker->secs[i];
+
+ /* STRTAB is handled specially above */
+ if (sec->sec_idx == linker->strtab_sec_idx)
+ continue;
+
+ /* special ephemeral sections (.ksyms, .kconfig, etc) */
+ if (!sec->scn)
+ continue;
+
+ sec->data->d_buf = sec->raw_data;
+ }
+
+ /* Finalize ELF layout */
+ if (elf_update(linker->elf, ELF_C_NULL) < 0) {
+ err = -errno;
+ pr_warn_elf("failed to finalize ELF layout");
+ return libbpf_err(err);
+ }
+
+ /* Write out final ELF contents */
+ if (elf_update(linker->elf, ELF_C_WRITE) < 0) {
+ err = -errno;
+ pr_warn_elf("failed to write ELF contents");
+ return libbpf_err(err);
+ }
+
+ elf_end(linker->elf);
+ close(linker->fd);
+
+ linker->elf = NULL;
+ linker->fd = -1;
+
+ return 0;
+}
+
+static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name,
+ size_t align, const void *raw_data, size_t raw_sz)
+{
+ Elf_Scn *scn;
+ Elf_Data *data;
+ Elf64_Shdr *shdr;
+ int name_off;
+
+ name_off = strset__add_str(linker->strtab_strs, sec_name);
+ if (name_off < 0)
+ return name_off;
+
+ scn = elf_newscn(linker->elf);
+ if (!scn)
+ return -ENOMEM;
+ data = elf_newdata(scn);
+ if (!data)
+ return -ENOMEM;
+ shdr = elf64_getshdr(scn);
+ if (!shdr)
+ return -EINVAL;
+
+ shdr->sh_name = name_off;
+ shdr->sh_type = SHT_PROGBITS;
+ shdr->sh_flags = 0;
+ shdr->sh_size = raw_sz;
+ shdr->sh_link = 0;
+ shdr->sh_info = 0;
+ shdr->sh_addralign = align;
+ shdr->sh_entsize = 0;
+
+ data->d_type = ELF_T_BYTE;
+ data->d_size = raw_sz;
+ data->d_buf = (void *)raw_data;
+ data->d_align = align;
+ data->d_off = 0;
+
+ return 0;
+}
+
+static int finalize_btf(struct bpf_linker *linker)
+{
+ LIBBPF_OPTS(btf_dedup_opts, opts);
+ struct btf *btf = linker->btf;
+ const void *raw_data;
+ int i, j, id, err;
+ __u32 raw_sz;
+
+ /* bail out if no BTF data was produced */
+ if (btf__type_cnt(linker->btf) == 1)
+ return 0;
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ struct dst_sec *sec = &linker->secs[i];
+
+ if (!sec->has_btf)
+ continue;
+
+ id = btf__add_datasec(btf, sec->sec_name, sec->sec_sz);
+ if (id < 0) {
+ pr_warn("failed to add consolidated BTF type for datasec '%s': %d\n",
+ sec->sec_name, id);
+ return id;
+ }
+
+ for (j = 0; j < sec->sec_var_cnt; j++) {
+ struct btf_var_secinfo *vi = &sec->sec_vars[j];
+
+ if (btf__add_datasec_var_info(btf, vi->type, vi->offset, vi->size))
+ return -EINVAL;
+ }
+ }
+
+ err = finalize_btf_ext(linker);
+ if (err) {
+ pr_warn(".BTF.ext generation failed: %d\n", err);
+ return err;
+ }
+
+ opts.btf_ext = linker->btf_ext;
+ err = btf__dedup(linker->btf, &opts);
+ if (err) {
+ pr_warn("BTF dedup failed: %d\n", err);
+ return err;
+ }
+
+ /* Emit .BTF section */
+ raw_data = btf__raw_data(linker->btf, &raw_sz);
+ if (!raw_data)
+ return -ENOMEM;
+
+ err = emit_elf_data_sec(linker, BTF_ELF_SEC, 8, raw_data, raw_sz);
+ if (err) {
+ pr_warn("failed to write out .BTF ELF section: %d\n", err);
+ return err;
+ }
+
+ /* Emit .BTF.ext section */
+ if (linker->btf_ext) {
+ raw_data = btf_ext__get_raw_data(linker->btf_ext, &raw_sz);
+ if (!raw_data)
+ return -ENOMEM;
+
+ err = emit_elf_data_sec(linker, BTF_EXT_ELF_SEC, 8, raw_data, raw_sz);
+ if (err) {
+ pr_warn("failed to write out .BTF.ext ELF section: %d\n", err);
+ return err;
+ }
+ }
+
+ return 0;
+}
+
+static int emit_btf_ext_data(struct bpf_linker *linker, void *output,
+ const char *sec_name, struct btf_ext_sec_data *sec_data)
+{
+ struct btf_ext_info_sec *sec_info;
+ void *cur = output;
+ int str_off;
+ size_t sz;
+
+ if (!sec_data->rec_cnt)
+ return 0;
+
+ str_off = btf__add_str(linker->btf, sec_name);
+ if (str_off < 0)
+ return -ENOMEM;
+
+ sec_info = cur;
+ sec_info->sec_name_off = str_off;
+ sec_info->num_info = sec_data->rec_cnt;
+ cur += sizeof(struct btf_ext_info_sec);
+
+ sz = sec_data->rec_cnt * sec_data->rec_sz;
+ memcpy(cur, sec_data->recs, sz);
+ cur += sz;
+
+ return cur - output;
+}
+
+static int finalize_btf_ext(struct bpf_linker *linker)
+{
+ size_t funcs_sz = 0, lines_sz = 0, core_relos_sz = 0, total_sz = 0;
+ size_t func_rec_sz = 0, line_rec_sz = 0, core_relo_rec_sz = 0;
+ struct btf_ext_header *hdr;
+ void *data, *cur;
+ int i, err, sz;
+
+ /* validate that all sections have the same .BTF.ext record sizes
+ * and calculate total data size for each type of data (func info,
+ * line info, core relos)
+ */
+ for (i = 1; i < linker->sec_cnt; i++) {
+ struct dst_sec *sec = &linker->secs[i];
+
+ if (sec->func_info.rec_cnt) {
+ if (func_rec_sz == 0)
+ func_rec_sz = sec->func_info.rec_sz;
+ if (func_rec_sz != sec->func_info.rec_sz) {
+ pr_warn("mismatch in func_info record size %zu != %u\n",
+ func_rec_sz, sec->func_info.rec_sz);
+ return -EINVAL;
+ }
+
+ funcs_sz += sizeof(struct btf_ext_info_sec) + func_rec_sz * sec->func_info.rec_cnt;
+ }
+ if (sec->line_info.rec_cnt) {
+ if (line_rec_sz == 0)
+ line_rec_sz = sec->line_info.rec_sz;
+ if (line_rec_sz != sec->line_info.rec_sz) {
+ pr_warn("mismatch in line_info record size %zu != %u\n",
+ line_rec_sz, sec->line_info.rec_sz);
+ return -EINVAL;
+ }
+
+ lines_sz += sizeof(struct btf_ext_info_sec) + line_rec_sz * sec->line_info.rec_cnt;
+ }
+ if (sec->core_relo_info.rec_cnt) {
+ if (core_relo_rec_sz == 0)
+ core_relo_rec_sz = sec->core_relo_info.rec_sz;
+ if (core_relo_rec_sz != sec->core_relo_info.rec_sz) {
+ pr_warn("mismatch in core_relo_info record size %zu != %u\n",
+ core_relo_rec_sz, sec->core_relo_info.rec_sz);
+ return -EINVAL;
+ }
+
+ core_relos_sz += sizeof(struct btf_ext_info_sec) + core_relo_rec_sz * sec->core_relo_info.rec_cnt;
+ }
+ }
+
+ if (!funcs_sz && !lines_sz && !core_relos_sz)
+ return 0;
+
+ total_sz += sizeof(struct btf_ext_header);
+ if (funcs_sz) {
+ funcs_sz += sizeof(__u32); /* record size prefix */
+ total_sz += funcs_sz;
+ }
+ if (lines_sz) {
+ lines_sz += sizeof(__u32); /* record size prefix */
+ total_sz += lines_sz;
+ }
+ if (core_relos_sz) {
+ core_relos_sz += sizeof(__u32); /* record size prefix */
+ total_sz += core_relos_sz;
+ }
+
+ cur = data = calloc(1, total_sz);
+ if (!data)
+ return -ENOMEM;
+
+ hdr = cur;
+ hdr->magic = BTF_MAGIC;
+ hdr->version = BTF_VERSION;
+ hdr->flags = 0;
+ hdr->hdr_len = sizeof(struct btf_ext_header);
+ cur += sizeof(struct btf_ext_header);
+
+ /* All offsets are in bytes relative to the end of this header */
+ hdr->func_info_off = 0;
+ hdr->func_info_len = funcs_sz;
+ hdr->line_info_off = funcs_sz;
+ hdr->line_info_len = lines_sz;
+ hdr->core_relo_off = funcs_sz + lines_sz;
+ hdr->core_relo_len = core_relos_sz;
+
+ if (funcs_sz) {
+ *(__u32 *)cur = func_rec_sz;
+ cur += sizeof(__u32);
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ struct dst_sec *sec = &linker->secs[i];
+
+ sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->func_info);
+ if (sz < 0) {
+ err = sz;
+ goto out;
+ }
+
+ cur += sz;
+ }
+ }
+
+ if (lines_sz) {
+ *(__u32 *)cur = line_rec_sz;
+ cur += sizeof(__u32);
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ struct dst_sec *sec = &linker->secs[i];
+
+ sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->line_info);
+ if (sz < 0) {
+ err = sz;
+ goto out;
+ }
+
+ cur += sz;
+ }
+ }
+
+ if (core_relos_sz) {
+ *(__u32 *)cur = core_relo_rec_sz;
+ cur += sizeof(__u32);
+
+ for (i = 1; i < linker->sec_cnt; i++) {
+ struct dst_sec *sec = &linker->secs[i];
+
+ sz = emit_btf_ext_data(linker, cur, sec->sec_name, &sec->core_relo_info);
+ if (sz < 0) {
+ err = sz;
+ goto out;
+ }
+
+ cur += sz;
+ }
+ }
+
+ linker->btf_ext = btf_ext__new(data, total_sz);
+ err = libbpf_get_error(linker->btf_ext);
+ if (err) {
+ linker->btf_ext = NULL;
+ pr_warn("failed to parse final .BTF.ext data: %d\n", err);
+ goto out;
+ }
+
+out:
+ free(data);
+ return err;
+}