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/* ELF functions-only symbol table extractor by David van Moolenbroek.
* Replaces generic a.out version by Philip Homburg.
* Temporary solution until libc's nlist(3) becomes usable.
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <libelf.h>
#include <nlist.h>
static int get_syms(Elf *elf, Elf_Scn *scn, Elf32_Shdr *shdr,
struct nlist **nlistp)
{
Elf_Data *data;
Elf32_Sym *sym;
unsigned long nsyms;
struct nlist *nlp;
char *name;
size_t size;
int i;
if ((data = elf_getdata(scn, NULL)) == NULL) {
errno = ENOEXEC;
return -1;
}
nsyms = data->d_size / sizeof(Elf32_Sym);
size = sizeof(struct nlist) * nsyms;
if ((*nlistp = nlp = malloc(size)) == NULL)
return -1;
memset(nlp, 0, size);
sym = (Elf32_Sym *) data->d_buf;
for (i = 0; i < nsyms; i++, sym++, nlp++) {
nlp->n_value = sym->st_value;
/* The caller only cares about N_TEXT. Properly setting other
* types would involve crosschecking with section types.
*/
switch (ELF32_ST_TYPE(sym->st_info)) {
case STT_FUNC: nlp->n_type = N_TEXT; break;
default: nlp->n_type = N_UNDF; break;
}
name = elf_strptr(elf, shdr->sh_link, (size_t) sym->st_name);
if ((nlp->n_name = strdup(name ? name : "")) == NULL) {
free(*nlistp);
return -1;
}
}
return nsyms;
}
int read_nlist(const char *filename, struct nlist **nlist_table)
{
/* Read in the symbol table of 'filename'. Return the resulting symbols
* as an array, with 'nlist_table' set to point to it, and the number
* of elements as the return value. The caller has no way to free the
* results. Return 0 if the executable contains no symbols. Upon error,
* return -1 and set errno to an appropriate value.
*/
Elf *elf;
Elf_Scn *scn;
Elf32_Shdr *shdr;
int res, fd;
if (elf_version(EV_CURRENT) == EV_NONE) {
errno = EINVAL;
return -1;
}
if ((fd = open(filename, O_RDONLY)) < 0)
return -1;
elf = elf_begin(fd, ELF_C_READ, NULL);
if (elf == NULL) {
errno = ENOEXEC;
close(fd);
return -1;
}
scn = NULL;
res = 0;
while ((scn = elf_nextscn(elf, scn)) != NULL) {
if ((shdr = elf32_getshdr(scn)) == NULL)
continue;
if (shdr->sh_type != SHT_SYMTAB)
continue;
res = get_syms(elf, scn, shdr, nlist_table);
break;
}
elf_end(elf);
close(fd);
return res;
}
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