/* $NetBSD: symtab.c,v 1.5 2016/04/20 14:00:16 christos Exp $ */
/*-
* Copyright (c) 2012 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Christos Zoulas.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: symtab.c,v 1.5 2016/04/20 14:00:16 christos Exp $");
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <err.h>
#include <dlfcn.h>
#include <libelf.h>
#include <gelf.h>
#ifndef ELF_ST_BIND
#define ELF_ST_BIND(x) ((x) >> 4)
#endif
#ifndef ELF_ST_TYPE
#define ELF_ST_TYPE(x) (((unsigned int)x) & 0xf)
#endif
#include "symtab.h"
struct symbol {
char *st_name;
uintptr_t st_value;
uintptr_t st_info;
};
struct symtab {
size_t nsymbols;
struct symbol *symbols;
bool ispie;
};
static int
address_compare(const void *a, const void *b)
{
const struct symbol *sa = a;
const struct symbol *sb = b;
return (int)(intmax_t)(sa->st_value - sb->st_value);
}
void
symtab_destroy(symtab_t *s)
{
if (s == NULL)
return;
for (size_t i = 0; i < s->nsymbols; i++)
free(s->symbols[i].st_name);
free(s->symbols);
free(s);
}
symtab_t *
symtab_create(int fd, int bind, int type)
{
Elf *elf;
symtab_t *st;
Elf_Scn *scn = NULL;
GElf_Ehdr ehdr;
if (elf_version(EV_CURRENT) == EV_NONE) {
warnx("Elf Library is out of date.");
return NULL;
}
elf = elf_begin(fd, ELF_C_READ, NULL);
if (elf == NULL) {
warnx("Error opening elf file: %s", elf_errmsg(elf_errno()));
return NULL;
}
st = calloc(1, sizeof(*st));
if (st == NULL) {
warnx("Error allocating symbol table");
elf_end(elf);
return NULL;
}
if (gelf_getehdr(elf, &ehdr) == NULL) {
warnx("Error getting ELF Ehdr");
elf_end(elf);
return NULL;
}
st->ispie = ehdr.e_type == ET_DYN;
while ((scn = elf_nextscn(elf, scn)) != NULL) {
GElf_Shdr shdr;
Elf_Data *edata;
size_t ns;
struct symbol *s;
gelf_getshdr(scn, &shdr);
if(shdr.sh_type != SHT_SYMTAB)
continue;
edata = elf_getdata(scn, NULL);
ns = shdr.sh_size / shdr.sh_entsize;
s = calloc(ns, sizeof(*s));
if (s == NULL) {
warn("Cannot allocate %zu symbols", ns);
goto out;
}
st->symbols = s;
for (size_t i = 0; i < ns; i++) {
GElf_Sym sym;
gelf_getsym(edata, (int)i, &sym);
#ifdef SYMTAB_DEBUG
fprintf(stderr, "%s: %s@%#jx=%d,%d\n", __func__,
elf_strptr(elf, shdr.sh_link, sym.st_name),
(uintmax_t)sym.st_value, ELF_ST_BIND(sym.st_info),
ELF_ST_TYPE(sym.st_info));
#endif
if (bind != -1 &&
(unsigned)bind != ELF_ST_BIND(sym.st_info))
continue;
if (type != -1 &&
(unsigned)type != ELF_ST_TYPE(sym.st_info))
continue;
s->st_value = sym.st_value;
s->st_info = sym.st_info;
s->st_name = strdup(
elf_strptr(elf, shdr.sh_link, sym.st_name));
if (s->st_name == NULL)
goto out;
s++;
}
st->nsymbols = s - st->symbols;
if (st->nsymbols == 0) {
warnx("No symbols found");
goto out;
}
qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
address_compare);
elf_end(elf);
return st;
}
out:
symtab_destroy(st);
elf_end(elf);
return NULL;
}
int
symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
{
struct symbol *s = st->symbols;
size_t ns = st->nsymbols;
size_t hi = ns;
size_t lo = 0;
size_t mid = ns / 2;
uintptr_t fbase = st->ispie ? (uintptr_t)dli->dli_fbase : 0;
uintptr_t dd, sd, me = (uintptr_t)p - fbase;
uintptr_t ad = (uintptr_t)dli->dli_saddr - fbase;
#ifdef SYMTAB_DEBUG
fprintf(stderr, "%s: [fbase=%#jx, saddr=%p, me=%#jx ad=%#jx]\n",
__func__, (uintmax_t)fbase, dli->dli_saddr, (uintmax_t)me,
(uintmax_t)ad);
#endif
for (;;) {
if (s[mid].st_value < me)
lo = mid;
else if (s[mid].st_value > me)
hi = mid;
else
break;
if (hi - lo == 1) {
mid = lo;
break;
}
mid = (hi + lo) / 2;
}
dd = me - ad;
sd = me - s[mid].st_value;
if (dd > sd) {
dli->dli_saddr = (void *)s[mid].st_value;
dli->dli_sname = s[mid].st_name;
#ifdef SYMTAB_DEBUG
fprintf(stderr, "%s: me=%#jx -> [%#jx, %s]\n", __func__,
(uintmax_t)me, (uintmax_t)sd, dli->dli_sname);
#endif
}
#ifdef SYMTAB_DEBUG
else
fprintf(stderr, "%s: %#jx -> [%#jx, ***]\n", __func__,
(uintmax_t)me, (uintmax_t)sd);
#endif
return 1;
}
