10565
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/*
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* Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include <unistd.h>
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#include <search.h>
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#include <stdlib.h>
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#include <string.h>
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#include <db.h>
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#include <fcntl.h>
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#include "symtab.h"
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#include "salibelf.h"
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// ----------------------------------------------------
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// functions for symbol lookups
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// ----------------------------------------------------
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struct elf_section {
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ELF_SHDR *c_shdr;
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void *c_data;
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};
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struct elf_symbol {
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char *name;
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uintptr_t offset;
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uintptr_t size;
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};
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typedef struct symtab {
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char *strs;
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size_t num_symbols;
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struct elf_symbol *symbols;
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DB* hash_table;
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} symtab_t;
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// read symbol table from given fd.
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struct symtab* build_symtab(int fd) {
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ELF_EHDR ehdr;
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struct symtab* symtab = NULL;
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// Reading of elf header
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struct elf_section *scn_cache = NULL;
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int cnt = 0;
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ELF_SHDR* shbuf = NULL;
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ELF_SHDR* cursct = NULL;
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ELF_PHDR* phbuf = NULL;
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int symtab_found = 0;
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int dynsym_found = 0;
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uint32_t symsection = SHT_SYMTAB;
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uintptr_t baseaddr = (uintptr_t)-1;
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lseek(fd, (off_t)0L, SEEK_SET);
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if (! read_elf_header(fd, &ehdr)) {
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// not an elf
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return NULL;
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}
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// read ELF header
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if ((shbuf = read_section_header_table(fd, &ehdr)) == NULL) {
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goto quit;
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}
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baseaddr = find_base_address(fd, &ehdr);
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scn_cache = calloc(ehdr.e_shnum, sizeof(*scn_cache));
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if (scn_cache == NULL) {
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goto quit;
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}
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for (cursct = shbuf, cnt = 0; cnt < ehdr.e_shnum; cnt++) {
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scn_cache[cnt].c_shdr = cursct;
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if (cursct->sh_type == SHT_SYMTAB ||
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cursct->sh_type == SHT_STRTAB ||
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cursct->sh_type == SHT_DYNSYM) {
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if ( (scn_cache[cnt].c_data = read_section_data(fd, &ehdr, cursct)) == NULL) {
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goto quit;
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}
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}
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if (cursct->sh_type == SHT_SYMTAB)
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symtab_found++;
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if (cursct->sh_type == SHT_DYNSYM)
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dynsym_found++;
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cursct++;
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}
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if (!symtab_found && dynsym_found)
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symsection = SHT_DYNSYM;
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for (cnt = 1; cnt < ehdr.e_shnum; cnt++) {
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ELF_SHDR *shdr = scn_cache[cnt].c_shdr;
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if (shdr->sh_type == symsection) {
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ELF_SYM *syms;
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int j, n, rslt;
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size_t size;
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// FIXME: there could be multiple data buffers associated with the
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// same ELF section. Here we can handle only one buffer. See man page
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// for elf_getdata on Solaris.
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// guarantee(symtab == NULL, "multiple symtab");
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symtab = calloc(1, sizeof(*symtab));
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if (symtab == NULL) {
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goto quit;
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}
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// the symbol table
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syms = (ELF_SYM *)scn_cache[cnt].c_data;
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// number of symbols
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n = shdr->sh_size / shdr->sh_entsize;
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// create hash table, we use berkeley db to
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// manipulate the hash table.
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symtab->hash_table = dbopen(NULL, O_CREAT | O_RDWR, 0600, DB_HASH, NULL);
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// guarantee(symtab->hash_table, "unexpected failure: dbopen");
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// shdr->sh_link points to the section that contains the actual strings
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// for symbol names. the st_name field in ELF_SYM is just the
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// string table index. we make a copy of the string table so the
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// strings will not be destroyed by elf_end.
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size = scn_cache[shdr->sh_link].c_shdr->sh_size;
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symtab->strs = malloc(size);
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memcpy(symtab->strs, scn_cache[shdr->sh_link].c_data, size);
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// allocate memory for storing symbol offset and size;
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symtab->num_symbols = n;
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symtab->symbols = calloc(n , sizeof(*symtab->symbols));
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// copy symbols info our symtab and enter them info the hash table
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for (j = 0; j < n; j++, syms++) {
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DBT key, value;
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char *sym_name = symtab->strs + syms->st_name;
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// skip non-object and non-function symbols
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int st_type = ELF_ST_TYPE(syms->st_info);
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if ( st_type != STT_FUNC && st_type != STT_OBJECT)
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continue;
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// skip empty strings and undefined symbols
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if (*sym_name == '\0' || syms->st_shndx == SHN_UNDEF) continue;
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symtab->symbols[j].name = sym_name;
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symtab->symbols[j].offset = syms->st_value - baseaddr;
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symtab->symbols[j].size = syms->st_size;
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key.data = sym_name;
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key.size = strlen(sym_name) + 1;
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value.data = &(symtab->symbols[j]);
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value.size = sizeof(void *);
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(*symtab->hash_table->put)(symtab->hash_table, &key, &value, 0);
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}
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}
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}
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quit:
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if (shbuf) free(shbuf);
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if (phbuf) free(phbuf);
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if (scn_cache) {
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for (cnt = 0; cnt < ehdr.e_shnum; cnt++) {
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if (scn_cache[cnt].c_data != NULL) {
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free(scn_cache[cnt].c_data);
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}
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}
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free(scn_cache);
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}
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return symtab;
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}
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void destroy_symtab(struct symtab* symtab) {
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if (!symtab) return;
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if (symtab->strs) free(symtab->strs);
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if (symtab->symbols) free(symtab->symbols);
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if (symtab->hash_table) {
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symtab->hash_table->close(symtab->hash_table);
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}
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free(symtab);
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}
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uintptr_t search_symbol(struct symtab* symtab, uintptr_t base,
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const char *sym_name, int *sym_size) {
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DBT key, value;
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int ret;
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// library does not have symbol table
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if (!symtab || !symtab->hash_table)
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return 0;
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key.data = (char*)(uintptr_t)sym_name;
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key.size = strlen(sym_name) + 1;
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ret = (*symtab->hash_table->get)(symtab->hash_table, &key, &value, 0);
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if (ret == 0) {
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struct elf_symbol *sym = value.data;
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uintptr_t rslt = (uintptr_t) ((char*)base + sym->offset);
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if (sym_size) *sym_size = sym->size;
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return rslt;
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}
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quit:
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return 0;
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}
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const char* nearest_symbol(struct symtab* symtab, uintptr_t offset,
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uintptr_t* poffset) {
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int n = 0;
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if (!symtab) return NULL;
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for (; n < symtab->num_symbols; n++) {
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struct elf_symbol* sym = &(symtab->symbols[n]);
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if (sym->name != NULL &&
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offset >= sym->offset && offset < sym->offset + sym->size) {
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if (poffset) *poffset = (offset - sym->offset);
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return sym->name;
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}
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}
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return NULL;
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}
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