#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <elf.h>
#include <sys/mman.h>
#include <limits.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <limits.h>
#include <elf.h>
#include <setjmp.h>
#include <pthread.h>
#include <dlfcn.h>
#include "reloc.h"
#if ULONG_MAX == 0xffffffff
typedef Elf32_Ehdr Ehdr;
typedef Elf32_Phdr Phdr;
typedef Elf32_Sym Sym;
#define R_TYPE(x) ((x)&255)
#define R_SYM(x) ((x)>>8)
#else
typedef Elf64_Ehdr Ehdr;
typedef Elf64_Phdr Phdr;
typedef Elf64_Sym Sym;
#define R_TYPE(x) ((x)&0xffffffff)
#define R_SYM(x) ((x)>>32)
#endif
struct dso
{
struct dso *next, *prev;
int refcnt;
size_t *dynv;
Sym *syms;
uint32_t *hashtab;
char *strings;
unsigned char *base;
unsigned char *map;
size_t map_len;
dev_t dev;
ino_t ino;
int global;
int relocated;
struct dso **deps;
char *name;
char buf[];
};
static struct dso *head, *tail, *libc;
static char *env_path, *sys_path;
static int rtld_used;
static int runtime;
static jmp_buf rtld_fail;
static pthread_rwlock_t lock;
#define AUX_CNT 15
#define DYN_CNT 34
static void decode_vec(size_t *v, size_t *a, size_t cnt)
{
memset(a, 0, cnt*sizeof(size_t));
for (; v[0]; v+=2) if (v[0]<cnt) {
a[0] |= 1ULL<<v[0];
a[v[0]] = v[1];
}
}
static uint32_t hash(const char *s)
{
uint_fast32_t h = 0;
while (*s) {
h = 16*h + *s++;
h ^= h>>24 & 0xf0;
}
return h & 0xfffffff;
}
static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
{
size_t i;
for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
if (!strcmp(s, strings+syms[i].st_name))
return syms+i;
}
return 0;
}
#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
static void *find_sym(struct dso *dso, const char *s, int need_def)
{
uint32_t h = hash(s);
if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
for (; dso; dso=dso->next) {
Sym *sym;
if (!dso->global) continue;
sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
if (sym && (!need_def || sym->st_shndx) && sym->st_value
&& (1<<(sym->st_info&0xf) & OK_TYPES))
return dso->base + sym->st_value;
}
return 0;
}
static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
{
Sym *sym;
const char *name;
size_t sym_val, sym_size;
size_t *reloc_addr;
void *ctx;
int type;
int sym_index;
for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
reloc_addr = (void *)(base + rel[0]);
type = R_TYPE(rel[1]);
sym_index = R_SYM(rel[1]);
if (sym_index) {
sym = syms + sym_index;
name = strings + sym->st_name;
ctx = IS_COPY(type) ? dso->next : dso;
sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
if (!sym_val && sym->st_info>>4 != STB_WEAK) {
if (runtime) longjmp(rtld_fail, 1);
dprintf(2, "%s: symbol not found\n", name);
_exit(127);
}
sym_size = sym->st_size;
}
do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
}
}
static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
{
Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
size_t phsize;
size_t addr_min=SIZE_MAX, addr_max=0, map_len;
size_t this_min, this_max;
off_t off_start;
Ehdr *eh;
Phdr *ph;
unsigned prot;
unsigned char *map, *base;
size_t dyn;
size_t i;
ssize_t l = read(fd, buf, sizeof buf);
if (l<sizeof *eh) return 0;
eh = buf;
phsize = eh->e_phentsize * eh->e_phnum;
if (phsize + sizeof *eh > l) return 0;
if (eh->e_phoff + phsize > l) {
l = pread(fd, buf+1, phsize, eh->e_phoff);
if (l != phsize) return 0;
eh->e_phoff = sizeof *eh;
}
ph = (void *)((char *)buf + eh->e_phoff);
for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type == PT_DYNAMIC)
dyn = ph->p_vaddr;
if (ph->p_type != PT_LOAD) continue;
if (ph->p_vaddr < addr_min) {
addr_min = ph->p_vaddr;
off_start = ph->p_offset;
prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
((ph->p_flags&PF_X) ? PROT_EXEC : 0));
}
if (ph->p_vaddr+ph->p_memsz > addr_max) {
addr_max = ph->p_vaddr+ph->p_memsz;
}
}
if (!dyn) return 0;
addr_max += PAGE_SIZE-1;
addr_max &= -PAGE_SIZE;
addr_min &= -PAGE_SIZE;
off_start &= -PAGE_SIZE;
map_len = addr_max - addr_min + off_start;
/* The first time, we map too much, possibly even more than
* the length of the file. This is okay because we will not
* use the invalid part; we just need to reserve the right
* amount of virtual address space to map over later. */
map = mmap(0, map_len, prot, MAP_PRIVATE, fd, off_start);
if (map==MAP_FAILED) return 0;
base = map - addr_min;
ph = (void *)((char *)buf + eh->e_phoff);
for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type != PT_LOAD) continue;
/* Reuse the existing mapping for the lowest-address LOAD */
if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
this_min = ph->p_vaddr & -PAGE_SIZE;
this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
off_start = ph->p_offset & -PAGE_SIZE;
prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
((ph->p_flags&PF_X) ? PROT_EXEC : 0));
if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
munmap(map, map_len);
return 0;
}
if (ph->p_memsz > ph->p_filesz) {
size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
if (pgbrk-(size_t)base < this_max && mmap((void *)pgbrk, (size_t)base+this_max-pgbrk, prot, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) == MAP_FAILED) {
munmap(map, map_len);
return 0;
}
}
}
*lenp = map_len;
*basep = base;
*dynp = dyn;
return map;
}
static int path_open(const char *name, const char *search)
{
char buf[2*NAME_MAX+2];
const char *s=search, *z;
int l, fd;
for (;;) {
while (*s==':') s++;
if (!*s) return -1;
z = strchr(s, ':');
l = z ? z-s : strlen(s);
snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
if ((fd = open(buf, O_RDONLY))>=0) return fd;
s += l;
}
}
static struct dso *load_library(const char *name)
{
unsigned char *base, *map;
size_t dyno, map_len;
struct dso *p;
size_t dyn[DYN_CNT] = {0};
int fd;
struct stat st;
/* Catch and block attempts to reload the implementation itself */
if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
static const char *rp, reserved[] =
"c\0pthread\0rt\0m\0dl\0util\0xnet\0";
char *z = strchr(name, '.');
if (z) {
size_t l = z-name;
for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
if (*rp) {
if (!libc->prev) {
tail->next = libc;
libc->prev = tail;
tail = libc;
}
return libc;
}
}
}
/* Search for the name to see if it's already loaded */
for (p=head->next; p; p=p->next) {
if (!strcmp(p->name, name)) {
p->refcnt++;
return p;
}
}
if (strchr(name, '/')) {
fd = open(name, O_RDONLY);
} else {
if (strlen(name) > NAME_MAX) return 0;
fd = -1;
if (env_path) fd = path_open(name, env_path);
if (fd < 0) {
if (!sys_path) {
FILE *f = fopen(ETC_LDSO_PATH, "r");
if (f) {
if (getline(&sys_path, (size_t[1]){0}, f) > 0)
sys_path[strlen(sys_path)-1]=0;
fclose(f);
}
}
if (sys_path) fd = path_open(name, sys_path);
else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
}
}
if (fd < 0) return 0;
if (fstat(fd, &st) < 0) {
close(fd);
return 0;
}
for (p=head->next; p; p=p->next) {
if (p->dev == st.st_dev && p->ino == st.st_ino) {
close(fd);
p->refcnt++;
return p;
}
}
map = map_library(fd, &map_len, &base, &dyno);
close(fd);
if (!map) return 0;
p = calloc(1, sizeof *p + strlen(name) + 1);
if (!p) {
munmap(map, map_len);
return 0;
}
p->map = map;
p->map_len = map_len;
p->base = base;
p->dynv = (void *)(base + dyno);
decode_vec(p->dynv, dyn, DYN_CNT);
p->syms = (void *)(base + dyn[DT_SYMTAB]);
p->hashtab = (void *)(base + dyn[DT_HASH]);
p->strings = (void *)(base + dyn[DT_STRTAB]);
p->dev = st.st_dev;
p->ino = st.st_ino;
p->refcnt = 1;
p->name = p->buf;
strcpy(p->name, name);
tail->next = p;
p->prev = tail;
tail = p;
return p;
}
static void load_deps(struct dso *p)
{
size_t i, ndeps=0;
struct dso ***deps = &p->deps, **tmp, *dep;
for (; p; p=p->next) {
for (i=0; p->dynv[i]; i+=2) {
if (p->dynv[i] != DT_NEEDED) continue;
dep = load_library(p->strings + p->dynv[i+1]);
if (!dep) {
if (runtime) longjmp(rtld_fail, 1);
dprintf(2, "%s: %m (needed by %s)\n",
p->strings + p->dynv[i+1], p->name);
_exit(127);
}
if (runtime) {
tmp = realloc(*deps, sizeof(*tmp)*(ndeps+2));
if (!tmp) longjmp(rtld_fail, 1);
tmp[ndeps++] = dep;
tmp[ndeps] = 0;
*deps = tmp;
}
}
}
}
static void make_global(struct dso *p)
{
for (; p; p=p->next) p->global = 1;
}
static void reloc_all(struct dso *p)
{
size_t dyn[DYN_CNT] = {0};
for (; p; p=p->next) {
if (p->relocated) continue;
decode_vec(p->dynv, dyn, DYN_CNT);
do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
2, p->syms, p->strings, head);
do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
3, p->syms, p->strings, head);
p->relocated = 1;
}
}
static void free_all(struct dso *p)
{
struct dso *n;
while (p) {
n = p->next;
if (p->map) free(p);
p = n;
}
}
void *__dynlink(int argc, char **argv, size_t *got)
{
size_t *auxv, aux[AUX_CNT] = {0};
size_t app_dyn[DYN_CNT] = {0};
size_t lib_dyn[DYN_CNT] = {0};
size_t i;
Phdr *phdr;
struct dso lib, app;
/* Find aux vector just past environ[] */
for (i=argc+1; argv[i]; i++)
if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
env_path = argv[i]+16;
auxv = (void *)(argv+i+1);
decode_vec(auxv, aux, AUX_CNT);
/* Only trust user/env if kernel says we're not suid/sgid */
if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
|| aux[AT_GID]!=aux[AT_EGID]) {
env_path = 0;
}
/* Relocate ldso's DYNAMIC pointer and load vector */
decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
/* Find the program image's DYNAMIC section and decode it */
phdr = (void *)aux[AT_PHDR];
for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
if (phdr->p_type == PT_DYNAMIC) {
decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
break;
}
}
app = (struct dso){
.base = 0,
.strings = (void *)(app_dyn[DT_STRTAB]),
.hashtab = (void *)(app_dyn[DT_HASH]),
.syms = (void *)(app_dyn[DT_SYMTAB]),
.dynv = (void *)(phdr->p_vaddr),
.name = argv[0],
.global = 1,
.next = &lib
};
lib = (struct dso){
.base = (void *)aux[AT_BASE],
.strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
.hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
.syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
.dynv = (void *)(got[0]),
.name = "libc.so",
.global = 1,
.relocated = 1
};
/* Relocate the dynamic linker/libc */
do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app);
do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app);
/* At this point the standard library is fully functional */
head = tail = &app;
libc = &lib;
app.next = 0;
load_deps(head);
make_global(head);
reloc_all(head->next);
reloc_all(head);
if (rtld_used) {
runtime = 1;
head->next->prev = malloc(sizeof *head);
*head->next->prev = *head;
head = head->next->prev;
libc->prev->next = malloc(sizeof *libc);
*libc->prev->next = *libc;
libc = libc->prev->next;
if (libc->next) libc->next->prev = libc;
if (tail == &lib) tail = libc;
} else {
free_all(head);
free(sys_path);
}
errno = 0;
return (void *)aux[AT_ENTRY];
}
void *dlopen(const char *file, int mode)
{
struct dso *p, *orig_tail = tail, *next;
size_t i;
if (!file) return head;
pthread_rwlock_wrlock(&lock);
if (setjmp(rtld_fail)) {
/* Clean up anything new that was (partially) loaded */
if (p->deps) for (i=0; p->deps[i]; i++)
if (p->deps[i]->global < 0)
p->deps[i]->global = 0;
for (p=orig_tail->next; p; p=next) {
next = p->next;
munmap(p->map, p->map_len);
free(p->deps);
free(p);
}
tail = orig_tail;
tail->next = 0;
pthread_rwlock_unlock(&lock);
return 0;
}
p = load_library(file);
if (!p) goto end;
/* First load handling */
if (!p->deps) {
load_deps(p);
if (p->deps) for (i=0; p->deps[i]; i++)
if (!p->deps[i]->global)
p->deps[i]->global = -1;
if (!p->global) p->global = -1;
reloc_all(p);
if (p->deps) for (i=0; p->deps[i]; i++)
if (p->deps[i]->global < 0)
p->deps[i]->global = 0;
if (p->global < 0) p->global = 0;
}
if (mode & RTLD_GLOBAL) {
if (p->deps) for (i=0; p->deps[i]; i++)
p->deps[i]->global = 1;
p->global = 1;
}
end:
pthread_rwlock_unlock(&lock);
return p;
}
static void *do_dlsym(struct dso *p, const char *s)
{
size_t i;
uint32_t h;
Sym *sym;
if (p == head || p == RTLD_DEFAULT)
return find_sym(head, s, 0);
h = hash(s);
sym = lookup(s, h, p->syms, p->hashtab, p->strings);
if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
return p->base + sym->st_value;
if (p->deps) for (i=0; p->deps[i]; i++) {
sym = lookup(s, h, p->deps[i]->syms,
p->deps[i]->hashtab, p->deps[i]->strings);
if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
return p->deps[i]->base + sym->st_value;
}
return 0;
}
void *dlsym(void *p, const char *s)
{
void *res;
pthread_rwlock_rdlock(&lock);
res = do_dlsym(p, s);
pthread_rwlock_unlock(&lock);
return res;
}
char *dlerror()
{
return "unknown error";
}
int dlclose(void *p)
{
return 0;
}
