off_t get_elf_func_offset()

in helpers/uprobe_helpers.c [224:289]

• 61 lines of code
• 21 McCabe index (conditional complexity)

off_t get_elf_func_offset(const char *path, const char *func)
{
	off_t ret = -1;
	int i, fd = -1;
	Elf *e;
	Elf_Scn *scn;
	Elf_Data *data;
	GElf_Ehdr ehdr;
	GElf_Shdr shdr[1];
	GElf_Phdr phdr;
	GElf_Sym sym[1];
	size_t shstrndx, nhdrs;
	char *n;

	e = open_elf(path, &fd);

	if (!gelf_getehdr(e, &ehdr))
		goto out;

	if (elf_getshdrstrndx(e, &shstrndx) != 0)
		goto out;

	scn = NULL;
	while ((scn = elf_nextscn(e, scn))) {
		if (!gelf_getshdr(scn, shdr))
			continue;
		if (!(shdr->sh_type == SHT_SYMTAB || shdr->sh_type == SHT_DYNSYM))
			continue;
		data = NULL;
		while ((data = elf_getdata(scn, data))) {
			for (i = 0; gelf_getsym(data, i, sym); i++) {
				n = elf_strptr(e, shdr->sh_link, sym->st_name);
				if (!n)
					continue;
				if (GELF_ST_TYPE(sym->st_info) != STT_FUNC)
					continue;
				if (!strcmp(n, func)) {
					ret = sym->st_value;
					goto check;
				}
			}
		}
	}

check:
	if (ehdr.e_type == ET_EXEC || ehdr.e_type == ET_DYN) {
		if (elf_getphdrnum(e, &nhdrs) != 0) {
			ret = -1;
			goto out;
		}
		for (i = 0; i < (int)nhdrs; i++) {
			if (!gelf_getphdr(e, i, &phdr))
				continue;
			if (phdr.p_type != PT_LOAD || !(phdr.p_flags & PF_X))
				continue;
			if (phdr.p_vaddr <= ret && ret < (phdr.p_vaddr + phdr.p_memsz)) {
				ret = ret - phdr.p_vaddr + phdr.p_offset;
				goto out;
			}
		}
		ret = -1;
	}
out:
	close_elf(e, fd);
	return ret;
}