diff options
Diffstat (limited to 'elf/dl-sym-post.h')
| -rw-r--r-- | elf/dl-sym-post.h | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/elf/dl-sym-post.h b/elf/dl-sym-post.h new file mode 100644 index 0000000000..4c4f574633 --- /dev/null +++ b/elf/dl-sym-post.h @@ -0,0 +1,106 @@ +/* Post-processing of a symbol produced by dlsym, dlvsym. + Copyright (C) 1999-2020 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + + +/* Return the link map containing the caller address. */ +static struct link_map * +_dl_sym_find_caller_link_map (ElfW(Addr) caller) +{ + struct link_map *l = _dl_find_dso_for_object (caller); + if (l != NULL) + return l; + else + /* If the address is not recognized the call comes from the main + program (we hope). */ + return GL(dl_ns)[LM_ID_BASE]._ns_loaded; +} + +/* Translates RESULT, *REF, VALUE into a symbol address from the point + of view of MATCH. Performs IFUNC resolution and auditing if + necessary. If MATCH is NULL, CALLER is used to determine it. */ +static void * +_dl_sym_post (lookup_t result, const ElfW(Sym) *ref, void *value, + ElfW(Addr) caller, struct link_map *match) +{ + /* Resolve indirect function address. */ + if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC)) + { + DL_FIXUP_VALUE_TYPE fixup + = DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value); + fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup)); + value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup); + } + +#ifdef SHARED + /* Auditing checkpoint: we have a new binding. Provide the + auditing libraries the possibility to change the value and + tell us whether further auditing is wanted. */ + if (__glibc_unlikely (GLRO(dl_naudit) > 0)) + { + const char *strtab = (const char *) D_PTR (result, + l_info[DT_STRTAB]); + /* Compute index of the symbol entry in the symbol table of + the DSO with the definition. */ + unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result, + l_info[DT_SYMTAB])); + + if (match == NULL) + match = _dl_sym_find_caller_link_map (caller); + + if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0) + { + unsigned int altvalue = 0; + struct audit_ifaces *afct = GLRO(dl_audit); + /* Synthesize a symbol record where the st_value field is + the result. */ + ElfW(Sym) sym = *ref; + sym.st_value = (ElfW(Addr)) value; + + for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt) + { + struct auditstate *match_audit + = link_map_audit_state (match, cnt); + struct auditstate *result_audit + = link_map_audit_state (result, cnt); + if (afct->symbind != NULL + && ((match_audit->bindflags & LA_FLG_BINDFROM) != 0 + || ((result_audit->bindflags & LA_FLG_BINDTO) + != 0))) + { + unsigned int flags = altvalue | LA_SYMB_DLSYM; + uintptr_t new_value + = afct->symbind (&sym, ndx, + &match_audit->cookie, + &result_audit->cookie, + &flags, strtab + ref->st_name); + if (new_value != (uintptr_t) sym.st_value) + { + altvalue = LA_SYMB_ALTVALUE; + sym.st_value = new_value; + } + } + + afct = afct->next; + } + + value = (void *) sym.st_value; + } + } +#endif + return value; +} |