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