// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
#include <libelf.h>
#include <gelf.h>
#include <fcntl.h>
#define STRERR_BUFSIZE 128
+/* A SHT_GNU_versym section holds 16-bit words. This bit is set if
+ * the symbol is hidden and can only be seen when referenced using an
+ * explicit version number. This is a GNU extension.
+ */
+#define VERSYM_HIDDEN 0x8000
+
+/* This is the mask for the rest of the data in a word read from a
+ * SHT_GNU_versym section.
+ */
+#define VERSYM_VERSION 0x7fff
+
int elf_open(const char *binary_path, struct elf_fd *elf_fd)
{
char errmsg[STRERR_BUFSIZE];
const char *name;
GElf_Sym sym;
GElf_Shdr sh;
+ int ver;
+ bool hidden;
};
struct elf_sym_iter {
Elf *elf;
Elf_Data *syms;
+ Elf_Data *versyms;
+ Elf_Data *verdefs;
size_t nr_syms;
size_t strtabidx;
+ size_t verdef_strtabidx;
size_t next_sym_idx;
struct elf_sym sym;
int st_type;
iter->nr_syms = iter->syms->d_size / sh.sh_entsize;
iter->elf = elf;
iter->st_type = st_type;
+
+ /* Version symbol table is meaningful to dynsym only */
+ if (sh_type != SHT_DYNSYM)
+ return 0;
+
+ scn = elf_find_next_scn_by_type(elf, SHT_GNU_versym, NULL);
+ if (!scn)
+ return 0;
+ iter->versyms = elf_getdata(scn, 0);
+
+ scn = elf_find_next_scn_by_type(elf, SHT_GNU_verdef, NULL);
+ if (!scn) {
+ pr_debug("elf: failed to find verdef ELF sections in '%s'\n", binary_path);
+ return -ENOENT;
+ }
+ if (!gelf_getshdr(scn, &sh))
+ return -EINVAL;
+ iter->verdef_strtabidx = sh.sh_link;
+ iter->verdefs = elf_getdata(scn, 0);
+
return 0;
}
struct elf_sym *ret = &iter->sym;
GElf_Sym *sym = &ret->sym;
const char *name = NULL;
+ GElf_Versym versym;
Elf_Scn *sym_scn;
size_t idx;
iter->next_sym_idx = idx + 1;
ret->name = name;
+ ret->ver = 0;
+ ret->hidden = false;
+
+ if (iter->versyms) {
+ if (!gelf_getversym(iter->versyms, idx, &versym))
+ continue;
+ ret->ver = versym & VERSYM_VERSION;
+ ret->hidden = versym & VERSYM_HIDDEN;
+ }
return ret;
}
return NULL;
}
+static const char *elf_get_vername(struct elf_sym_iter *iter, int ver)
+{
+ GElf_Verdaux verdaux;
+ GElf_Verdef verdef;
+ int offset;
+
+ offset = 0;
+ while (gelf_getverdef(iter->verdefs, offset, &verdef)) {
+ if (verdef.vd_ndx != ver) {
+ if (!verdef.vd_next)
+ break;
+
+ offset += verdef.vd_next;
+ continue;
+ }
+
+ if (!gelf_getverdaux(iter->verdefs, offset + verdef.vd_aux, &verdaux))
+ break;
+
+ return elf_strptr(iter->elf, iter->verdef_strtabidx, verdaux.vda_name);
+
+ }
+ return NULL;
+}
+
+static bool symbol_match(struct elf_sym_iter *iter, int sh_type, struct elf_sym *sym,
+ const char *name, size_t name_len, const char *lib_ver)
+{
+ const char *ver_name;
+
+ /* Symbols are in forms of func, func@LIB_VER or func@@LIB_VER
+ * make sure the func part matches the user specified name
+ */
+ if (strncmp(sym->name, name, name_len) != 0)
+ return false;
+
+ /* ...but we don't want a search for "foo" to match 'foo2" also, so any
+ * additional characters in sname should be of the form "@@LIB".
+ */
+ if (sym->name[name_len] != '\0' && sym->name[name_len] != '@')
+ return false;
+
+ /* If user does not specify symbol version, then we got a match */
+ if (!lib_ver)
+ return true;
+
+ /* If user specifies symbol version, for dynamic symbols,
+ * get version name from ELF verdef section for comparison.
+ */
+ if (sh_type == SHT_DYNSYM) {
+ ver_name = elf_get_vername(iter, sym->ver);
+ if (!ver_name)
+ return false;
+ return strcmp(ver_name, lib_ver) == 0;
+ }
+
+ /* For normal symbols, it is already in form of func@LIB_VER */
+ return strcmp(sym->name, name) == 0;
+}
/* Transform symbol's virtual address (absolute for binaries and relative
* for shared libs) into file offset, which is what kernel is expecting
long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name)
{
int i, sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB };
- bool is_shared_lib, is_name_qualified;
+ const char *at_symbol, *lib_ver;
+ bool is_shared_lib;
long ret = -ENOENT;
size_t name_len;
GElf_Ehdr ehdr;
/* for shared lib case, we do not need to calculate relative offset */
is_shared_lib = ehdr.e_type == ET_DYN;
- name_len = strlen(name);
- /* Does name specify "@@LIB"? */
- is_name_qualified = strstr(name, "@@") != NULL;
+ /* Does name specify "@@LIB_VER" or "@LIB_VER" ? */
+ at_symbol = strchr(name, '@');
+ if (at_symbol) {
+ name_len = at_symbol - name;
+ /* skip second @ if it's @@LIB_VER case */
+ if (at_symbol[1] == '@')
+ at_symbol++;
+ lib_ver = at_symbol + 1;
+ } else {
+ name_len = strlen(name);
+ lib_ver = NULL;
+ }
/* Search SHT_DYNSYM, SHT_SYMTAB for symbol. This search order is used because if
* a binary is stripped, it may only have SHT_DYNSYM, and a fully-statically
goto out;
while ((sym = elf_sym_iter_next(&iter))) {
- /* User can specify func, func@@LIB or func@@LIB_VERSION. */
- if (strncmp(sym->name, name, name_len) != 0)
- continue;
- /* ...but we don't want a search for "foo" to match 'foo2" also, so any
- * additional characters in sname should be of the form "@@LIB".
- */
- if (!is_name_qualified && sym->name[name_len] != '\0' && sym->name[name_len] != '@')
+ if (!symbol_match(&iter, sh_types[i], sym, name, name_len, lib_ver))
continue;
cur_bind = GELF_ST_BIND(sym->sym.st_info);
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