21 #if ULONG_MAX == 0xffffffff
22 typedef Elf32_Ehdr Ehdr;
23 typedef Elf32_Phdr Phdr;
24 typedef Elf32_Sym Sym;
25 #define R_TYPE(x) ((x)&255)
26 #define R_SYM(x) ((x)>>8)
28 typedef Elf64_Ehdr Ehdr;
29 typedef Elf64_Phdr Phdr;
30 typedef Elf64_Sym Sym;
31 #define R_TYPE(x) ((x)&0xffffffff)
32 #define R_SYM(x) ((x)>>32)
37 struct dso *next, *prev;
55 static struct dso *head, *tail, *libc;
56 static char *env_path, *sys_path;
59 static jmp_buf rtld_fail;
60 static pthread_rwlock_t lock;
65 static void decode_vec(size_t *v, size_t *a, size_t cnt)
67 memset(a, 0, cnt*sizeof(size_t));
68 for (; v[0]; v+=2) if (v[0]<cnt) {
74 static uint32_t hash(const char *s)
84 static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
87 for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
88 if (!strcmp(s, strings+syms[i].st_name))
94 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
96 static void *find_sym(struct dso *dso, const char *s, int need_def)
99 if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
100 if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
101 for (; dso; dso=dso->next) {
103 if (!dso->global) continue;
104 sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
105 if (sym && (!need_def || sym->st_shndx) && sym->st_value
106 && (1<<(sym->st_info&0xf) & OK_TYPES))
107 return dso->base + sym->st_value;
112 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
116 size_t sym_val, sym_size;
122 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
123 reloc_addr = (void *)(base + rel[0]);
124 type = R_TYPE(rel[1]);
125 sym_index = R_SYM(rel[1]);
127 sym = syms + sym_index;
128 name = strings + sym->st_name;
129 ctx = IS_COPY(type) ? dso->next : dso;
130 sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
131 if (!sym_val && sym->st_info>>4 != STB_WEAK) {
132 if (runtime) longjmp(rtld_fail, 1);
133 dprintf(2, "%s: symbol not found\n", name);
136 sym_size = sym->st_size;
138 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
142 /* A huge hack: to make up for the wastefulness of shared libraries
143 * needing at least a page of dirty memory even if they have no global
144 * data, we reclaim the gaps at the beginning and end of writable maps
145 * and "donate" them to the heap by setting up minimal malloc
146 * structures and then freeing them. */
148 static void reclaim(unsigned char *base, size_t start, size_t end)
151 start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t);
152 end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t);
153 if (start>end || end-start < 4*sizeof(size_t)) return;
154 a = (size_t *)(base + start);
155 z = (size_t *)(base + end);
157 a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1;
162 static void reclaim_gaps(unsigned char *base, Phdr *ph, size_t phent, size_t phcnt)
164 for (; phcnt--; ph=(void *)((char *)ph+phent)) {
165 if (ph->p_type!=PT_LOAD) continue;
166 if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue;
167 reclaim(base, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr);
168 reclaim(base, ph->p_vaddr+ph->p_memsz,
169 ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE);
173 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
175 Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
177 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
178 size_t this_min, this_max;
183 unsigned char *map, *base;
187 ssize_t l = read(fd, buf, sizeof buf);
188 if (l<sizeof *eh) return 0;
190 phsize = eh->e_phentsize * eh->e_phnum;
191 if (phsize + sizeof *eh > l) return 0;
192 if (eh->e_phoff + phsize > l) {
193 l = pread(fd, buf+1, phsize, eh->e_phoff);
194 if (l != phsize) return 0;
195 eh->e_phoff = sizeof *eh;
197 ph = (void *)((char *)buf + eh->e_phoff);
198 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
199 if (ph->p_type == PT_DYNAMIC)
201 if (ph->p_type != PT_LOAD) continue;
202 if (ph->p_vaddr < addr_min) {
203 addr_min = ph->p_vaddr;
204 off_start = ph->p_offset;
205 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
206 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
207 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
209 if (ph->p_vaddr+ph->p_memsz > addr_max) {
210 addr_max = ph->p_vaddr+ph->p_memsz;
214 addr_max += PAGE_SIZE-1;
215 addr_max &= -PAGE_SIZE;
216 addr_min &= -PAGE_SIZE;
217 off_start &= -PAGE_SIZE;
218 map_len = addr_max - addr_min + off_start;
219 /* The first time, we map too much, possibly even more than
220 * the length of the file. This is okay because we will not
221 * use the invalid part; we just need to reserve the right
222 * amount of virtual address space to map over later. */
223 map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start);
224 if (map==MAP_FAILED) return 0;
225 base = map - addr_min;
226 ph = (void *)((char *)buf + eh->e_phoff);
227 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
228 if (ph->p_type != PT_LOAD) continue;
229 /* Reuse the existing mapping for the lowest-address LOAD */
230 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
231 this_min = ph->p_vaddr & -PAGE_SIZE;
232 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
233 off_start = ph->p_offset & -PAGE_SIZE;
234 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
235 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
236 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
237 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
238 munmap(map, map_len);
241 if (ph->p_memsz > ph->p_filesz) {
242 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
243 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
244 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
245 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) {
246 munmap(map, map_len);
251 for (i=0; ((size_t *)(base+dyn))[i]; i+=2)
252 if (((size_t *)(base+dyn))[i]==DT_TEXTREL) {
253 mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC);
256 if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff),
257 eh->e_phentsize, eh->e_phnum);
264 static int path_open(const char *name, const char *search)
266 char buf[2*NAME_MAX+2];
267 const char *s=search, *z;
273 l = z ? z-s : strlen(s);
274 snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
275 if ((fd = open(buf, O_RDONLY))>=0) return fd;
280 static struct dso *load_library(const char *name)
282 unsigned char *base, *map;
283 size_t dyno, map_len;
285 size_t dyn[DYN_CNT] = {0};
289 /* Catch and block attempts to reload the implementation itself */
290 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
291 static const char *rp, reserved[] =
292 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
293 char *z = strchr(name, '.');
296 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
307 /* Search for the name to see if it's already loaded */
308 for (p=head->next; p; p=p->next) {
309 if (!strcmp(p->name, name)) {
314 if (strchr(name, '/')) {
315 fd = open(name, O_RDONLY);
317 if (strlen(name) > NAME_MAX) return 0;
319 if (env_path) fd = path_open(name, env_path);
322 FILE *f = fopen(ETC_LDSO_PATH, "r");
324 if (getline(&sys_path, (size_t[1]){0}, f) > 0)
325 sys_path[strlen(sys_path)-1]=0;
329 if (sys_path) fd = path_open(name, sys_path);
330 else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
333 if (fd < 0) return 0;
334 if (fstat(fd, &st) < 0) {
338 for (p=head->next; p; p=p->next) {
339 if (p->dev == st.st_dev && p->ino == st.st_ino) {
345 map = map_library(fd, &map_len, &base, &dyno);
348 p = calloc(1, sizeof *p + strlen(name) + 1);
350 munmap(map, map_len);
355 p->map_len = map_len;
357 p->dynv = (void *)(base + dyno);
358 decode_vec(p->dynv, dyn, DYN_CNT);
360 p->syms = (void *)(base + dyn[DT_SYMTAB]);
361 p->hashtab = (void *)(base + dyn[DT_HASH]);
362 p->strings = (void *)(base + dyn[DT_STRTAB]);
367 strcpy(p->name, name);
376 static void load_deps(struct dso *p)
379 struct dso ***deps = &p->deps, **tmp, *dep;
380 for (; p; p=p->next) {
381 for (i=0; p->dynv[i]; i+=2) {
382 if (p->dynv[i] != DT_NEEDED) continue;
383 dep = load_library(p->strings + p->dynv[i+1]);
385 if (runtime) longjmp(rtld_fail, 1);
386 dprintf(2, "%s: %m (needed by %s)\n",
387 p->strings + p->dynv[i+1], p->name);
391 tmp = realloc(*deps, sizeof(*tmp)*(ndeps+2));
392 if (!tmp) longjmp(rtld_fail, 1);
401 static void make_global(struct dso *p)
403 for (; p; p=p->next) p->global = 1;
406 static void reloc_all(struct dso *p)
408 size_t dyn[DYN_CNT] = {0};
409 for (; p; p=p->next) {
410 if (p->relocated) continue;
411 decode_vec(p->dynv, dyn, DYN_CNT);
412 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
413 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
414 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
415 2, p->syms, p->strings, head);
416 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
417 3, p->syms, p->strings, head);
422 static void free_all(struct dso *p)
432 void *__dynlink(int argc, char **argv, size_t *got)
434 size_t *auxv, aux[AUX_CNT] = {0};
435 size_t app_dyn[DYN_CNT] = {0};
436 size_t lib_dyn[DYN_CNT] = {0};
442 /* Find aux vector just past environ[] */
443 for (i=argc+1; argv[i]; i++)
444 if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
445 env_path = argv[i]+16;
446 auxv = (void *)(argv+i+1);
448 decode_vec(auxv, aux, AUX_CNT);
450 /* Only trust user/env if kernel says we're not suid/sgid */
451 if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
452 || aux[AT_GID]!=aux[AT_EGID]) {
456 /* Relocate ldso's DYNAMIC pointer and load vector */
457 decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
459 /* Find the program image's DYNAMIC section and decode it */
460 phdr = (void *)aux[AT_PHDR];
461 for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
462 if (phdr->p_type == PT_DYNAMIC) {
463 decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
470 .strings = (void *)(app_dyn[DT_STRTAB]),
471 .hashtab = (void *)(app_dyn[DT_HASH]),
472 .syms = (void *)(app_dyn[DT_SYMTAB]),
473 .dynv = (void *)(phdr->p_vaddr),
480 .base = (void *)aux[AT_BASE],
481 .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
482 .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
483 .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
484 .dynv = (void *)(got[0]),
490 /* Relocate the dynamic linker/libc */
491 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
492 lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app);
493 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
494 lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app);
496 /* At this point the standard library is fully functional */
498 reclaim_gaps(app.base, (void *)aux[AT_PHDR], aux[AT_PHENT], aux[AT_PHNUM]);
499 ehdr = (void *)lib.base;
500 reclaim_gaps(lib.base, (void *)(lib.base+ehdr->e_phoff),
501 ehdr->e_phentsize, ehdr->e_phnum);
509 reloc_all(head->next);
514 head->next->prev = malloc(sizeof *head);
515 *head->next->prev = *head;
516 head = head->next->prev;
517 libc->prev->next = malloc(sizeof *libc);
518 *libc->prev->next = *libc;
519 libc = libc->prev->next;
520 if (libc->next) libc->next->prev = libc;
521 if (tail == &lib) tail = libc;
528 return (void *)aux[AT_ENTRY];
531 void *dlopen(const char *file, int mode)
533 struct dso *p, *orig_tail = tail, *next;
536 if (!file) return head;
538 pthread_rwlock_wrlock(&lock);
540 if (setjmp(rtld_fail)) {
541 /* Clean up anything new that was (partially) loaded */
542 if (p->deps) for (i=0; p->deps[i]; i++)
543 if (p->deps[i]->global < 0)
544 p->deps[i]->global = 0;
545 for (p=orig_tail->next; p; p=next) {
547 munmap(p->map, p->map_len);
553 pthread_rwlock_unlock(&lock);
557 p = load_library(file);
560 /* First load handling */
563 if (p->deps) for (i=0; p->deps[i]; i++)
564 if (!p->deps[i]->global)
565 p->deps[i]->global = -1;
566 if (!p->global) p->global = -1;
568 if (p->deps) for (i=0; p->deps[i]; i++)
569 if (p->deps[i]->global < 0)
570 p->deps[i]->global = 0;
571 if (p->global < 0) p->global = 0;
574 if (mode & RTLD_GLOBAL) {
575 if (p->deps) for (i=0; p->deps[i]; i++)
576 p->deps[i]->global = 1;
581 pthread_rwlock_unlock(&lock);
585 static void *do_dlsym(struct dso *p, const char *s)
590 if (p == head || p == RTLD_DEFAULT)
591 return find_sym(head, s, 0);
593 sym = lookup(s, h, p->syms, p->hashtab, p->strings);
594 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
595 return p->base + sym->st_value;
596 if (p->deps) for (i=0; p->deps[i]; i++) {
597 sym = lookup(s, h, p->deps[i]->syms,
598 p->deps[i]->hashtab, p->deps[i]->strings);
599 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
600 return p->deps[i]->base + sym->st_value;
605 void *dlsym(void *p, const char *s)
608 pthread_rwlock_rdlock(&lock);
609 res = do_dlsym(p, s);
610 pthread_rwlock_unlock(&lock);
616 return "unknown error";