21 static char errbuf[128];
27 #if ULONG_MAX == 0xffffffff
28 typedef Elf32_Ehdr Ehdr;
29 typedef Elf32_Phdr Phdr;
30 typedef Elf32_Sym Sym;
31 #define R_TYPE(x) ((x)&255)
32 #define R_SYM(x) ((x)>>8)
34 typedef Elf64_Ehdr Ehdr;
35 typedef Elf64_Phdr Phdr;
36 typedef Elf64_Sym Sym;
37 #define R_TYPE(x) ((x)&0xffffffff)
38 #define R_SYM(x) ((x)>>32)
43 struct dso *next, *prev;
63 struct __pthread *__pthread_self_init(void);
65 static struct dso *head, *tail, *libc;
66 static char *env_path, *sys_path, *r_path;
70 static jmp_buf rtld_fail;
71 static pthread_rwlock_t lock;
76 static void decode_vec(size_t *v, size_t *a, size_t cnt)
78 memset(a, 0, cnt*sizeof(size_t));
79 for (; v[0]; v+=2) if (v[0]<cnt) {
85 static uint32_t hash(const char *s0)
87 const unsigned char *s = (void *)s0;
96 static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
99 for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
100 if (!strcmp(s, strings+syms[i].st_name))
106 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
107 #define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK)
109 static void *find_sym(struct dso *dso, const char *s, int need_def)
111 uint32_t h = hash(s);
113 if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
114 if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
115 if (h==0x595a4cc && !strcmp(s, "__stack_chk_fail")) ssp_used = 1;
116 for (; dso; dso=dso->next) {
118 if (!dso->global) continue;
119 sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
120 if (sym && (!need_def || sym->st_shndx) && sym->st_value
121 && (1<<(sym->st_info&0xf) & OK_TYPES)
122 && (1<<(sym->st_info>>4) & OK_BINDS)) {
123 if (def && sym->st_info>>4 == STB_WEAK) continue;
124 def = dso->base + sym->st_value;
125 if (sym->st_info>>4 == STB_GLOBAL) break;
131 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
135 size_t sym_val, sym_size;
141 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
142 reloc_addr = (void *)(base + rel[0]);
143 type = R_TYPE(rel[1]);
144 sym_index = R_SYM(rel[1]);
146 sym = syms + sym_index;
147 name = strings + sym->st_name;
148 ctx = IS_COPY(type) ? dso->next : dso;
149 sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
150 if (!sym_val && sym->st_info>>4 != STB_WEAK) {
151 snprintf(errbuf, sizeof errbuf,
152 "Error relocating %s: %s: symbol not found",
154 if (runtime) longjmp(rtld_fail, 1);
155 dprintf(2, "%s\n", errbuf);
158 sym_size = sym->st_size;
160 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
164 /* A huge hack: to make up for the wastefulness of shared libraries
165 * needing at least a page of dirty memory even if they have no global
166 * data, we reclaim the gaps at the beginning and end of writable maps
167 * and "donate" them to the heap by setting up minimal malloc
168 * structures and then freeing them. */
170 static void reclaim(unsigned char *base, size_t start, size_t end)
173 start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t);
174 end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t);
175 if (start>end || end-start < 4*sizeof(size_t)) return;
176 a = (size_t *)(base + start);
177 z = (size_t *)(base + end);
179 a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1;
184 static void reclaim_gaps(unsigned char *base, Phdr *ph, size_t phent, size_t phcnt)
186 for (; phcnt--; ph=(void *)((char *)ph+phent)) {
187 if (ph->p_type!=PT_LOAD) continue;
188 if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue;
189 reclaim(base, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr);
190 reclaim(base, ph->p_vaddr+ph->p_memsz,
191 ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE);
195 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
197 Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
199 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
200 size_t this_min, this_max;
205 unsigned char *map, *base;
209 ssize_t l = read(fd, buf, sizeof buf);
210 if (l<sizeof *eh) return 0;
212 phsize = eh->e_phentsize * eh->e_phnum;
213 if (phsize + sizeof *eh > l) return 0;
214 if (eh->e_phoff + phsize > l) {
215 l = pread(fd, buf+1, phsize, eh->e_phoff);
216 if (l != phsize) return 0;
217 eh->e_phoff = sizeof *eh;
219 ph = (void *)((char *)buf + eh->e_phoff);
220 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
221 if (ph->p_type == PT_DYNAMIC)
223 if (ph->p_type != PT_LOAD) continue;
224 if (ph->p_vaddr < addr_min) {
225 addr_min = ph->p_vaddr;
226 off_start = ph->p_offset;
227 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
228 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
229 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
231 if (ph->p_vaddr+ph->p_memsz > addr_max) {
232 addr_max = ph->p_vaddr+ph->p_memsz;
236 addr_max += PAGE_SIZE-1;
237 addr_max &= -PAGE_SIZE;
238 addr_min &= -PAGE_SIZE;
239 off_start &= -PAGE_SIZE;
240 map_len = addr_max - addr_min + off_start;
241 /* The first time, we map too much, possibly even more than
242 * the length of the file. This is okay because we will not
243 * use the invalid part; we just need to reserve the right
244 * amount of virtual address space to map over later. */
245 map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start);
246 if (map==MAP_FAILED) return 0;
247 base = map - addr_min;
248 ph = (void *)((char *)buf + eh->e_phoff);
249 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
250 if (ph->p_type != PT_LOAD) continue;
251 /* Reuse the existing mapping for the lowest-address LOAD */
252 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
253 this_min = ph->p_vaddr & -PAGE_SIZE;
254 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
255 off_start = ph->p_offset & -PAGE_SIZE;
256 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
257 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
258 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
259 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
260 munmap(map, map_len);
263 if (ph->p_memsz > ph->p_filesz) {
264 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
265 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
266 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
267 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) {
268 munmap(map, map_len);
273 for (i=0; ((size_t *)(base+dyn))[i]; i+=2)
274 if (((size_t *)(base+dyn))[i]==DT_TEXTREL) {
275 mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC);
278 if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff),
279 eh->e_phentsize, eh->e_phnum);
286 static int path_open(const char *name, const char *search)
288 char buf[2*NAME_MAX+2];
289 const char *s=search, *z;
295 l = z ? z-s : strlen(s);
296 snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
297 if ((fd = open(buf, O_RDONLY))>=0) return fd;
302 static void decode_dyn(struct dso *p)
304 size_t dyn[DYN_CNT] = {0};
305 decode_vec(p->dynv, dyn, DYN_CNT);
306 p->syms = (void *)(p->base + dyn[DT_SYMTAB]);
307 p->hashtab = (void *)(p->base + dyn[DT_HASH]);
308 p->strings = (void *)(p->base + dyn[DT_STRTAB]);
311 static struct dso *load_library(const char *name)
313 unsigned char *base, *map;
314 size_t dyno, map_len;
319 /* Catch and block attempts to reload the implementation itself */
320 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
321 static const char *rp, reserved[] =
322 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
323 char *z = strchr(name, '.');
326 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
331 tail = libc->next ? libc->next : libc;
337 /* Search for the name to see if it's already loaded */
338 for (p=head->next; p; p=p->next) {
339 if (!strcmp(p->name, name)) {
344 if (strchr(name, '/')) {
345 fd = open(name, O_RDONLY);
347 if (strlen(name) > NAME_MAX) return 0;
349 if (r_path) fd = path_open(name, r_path);
350 if (fd < 0 && env_path) fd = path_open(name, env_path);
353 FILE *f = fopen(ETC_LDSO_PATH, "r");
355 if (getline(&sys_path, (size_t[1]){0}, f) > 0)
356 sys_path[strlen(sys_path)-1]=0;
360 if (sys_path) fd = path_open(name, sys_path);
361 else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
364 if (fd < 0) return 0;
365 if (fstat(fd, &st) < 0) {
369 for (p=head->next; p; p=p->next) {
370 if (p->dev == st.st_dev && p->ino == st.st_ino) {
376 map = map_library(fd, &map_len, &base, &dyno);
379 p = calloc(1, sizeof *p + strlen(name) + 1);
381 munmap(map, map_len);
386 p->map_len = map_len;
388 p->dynv = (void *)(base + dyno);
395 strcpy(p->name, name);
404 static void load_deps(struct dso *p)
407 struct dso ***deps = &p->deps, **tmp, *dep;
408 for (; p; p=p->next) {
409 for (i=0; p->dynv[i]; i+=2) {
410 if (p->dynv[i] != DT_RPATH) continue;
411 r_path = (void *)(p->strings + p->dynv[i+1]);
413 for (i=0; p->dynv[i]; i+=2) {
414 if (p->dynv[i] != DT_NEEDED) continue;
415 dep = load_library(p->strings + p->dynv[i+1]);
417 snprintf(errbuf, sizeof errbuf,
418 "Error loading shared library %s: %m (needed by %s)",
419 p->strings + p->dynv[i+1], p->name);
420 if (runtime) longjmp(rtld_fail, 1);
421 dprintf(2, "%s\n", errbuf);
425 tmp = realloc(*deps, sizeof(*tmp)*(ndeps+2));
426 if (!tmp) longjmp(rtld_fail, 1);
436 static void load_preload(char *s)
441 for ( ; *s && isspace(*s); s++);
442 for (z=s; *z && !isspace(*z); z++);
450 static void make_global(struct dso *p)
452 for (; p; p=p->next) p->global = 1;
455 static void reloc_all(struct dso *p)
457 size_t dyn[DYN_CNT] = {0};
458 for (; p; p=p->next) {
459 if (p->relocated) continue;
460 decode_vec(p->dynv, dyn, DYN_CNT);
461 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
462 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
463 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
464 2, p->syms, p->strings, head);
465 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
466 3, p->syms, p->strings, head);
471 static void free_all(struct dso *p)
481 static size_t find_dyn(Phdr *ph, size_t cnt, size_t stride)
483 for (; cnt--; ph = (void *)((char *)ph + stride))
484 if (ph->p_type == PT_DYNAMIC)
489 static void do_init_fini(struct dso *p)
491 size_t dyn[DYN_CNT] = {0};
492 for (; p; p=p->prev) {
493 if (p->constructed) return;
494 decode_vec(p->dynv, dyn, DYN_CNT);
495 if (dyn[0] & (1<<DT_FINI))
496 atexit((void (*)(void))(p->base + dyn[DT_FINI]));
497 if (dyn[0] & (1<<DT_INIT))
498 ((void (*)(void))(p->base + dyn[DT_INIT]))();
503 void *__dynlink(int argc, char **argv)
505 size_t *auxv, aux[AUX_CNT] = {0};
509 static struct dso builtin_dsos[3];
510 struct dso *const app = builtin_dsos+0;
511 struct dso *const lib = builtin_dsos+1;
512 struct dso *const vdso = builtin_dsos+2;
515 /* Find aux vector just past environ[] */
516 for (i=argc+1; argv[i]; i++)
517 if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
518 env_path = argv[i]+16;
519 else if (!memcmp(argv[i], "LD_PRELOAD=", 11))
520 env_preload = argv[i]+11;
521 auxv = (void *)(argv+i+1);
523 decode_vec(auxv, aux, AUX_CNT);
525 /* Only trust user/env if kernel says we're not suid/sgid */
526 if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
527 || aux[AT_GID]!=aux[AT_EGID] || aux[AT_SECURE]) {
532 /* The dynamic linker load address is passed by the kernel
533 * in the AUX vector, so this is easy. */
534 lib->base = (void *)aux[AT_BASE];
535 lib->name = "libc.so";
537 ehdr = (void *)lib->base;
538 lib->dynv = (void *)(lib->base + find_dyn(
539 (void *)(aux[AT_BASE]+ehdr->e_phoff),
540 ehdr->e_phnum, ehdr->e_phentsize));
543 /* Find load address of the main program, via AT_PHDR vs PT_PHDR. */
545 phdr = (void *)aux[AT_PHDR];
546 for (i=aux[AT_PHNUM]; i; i--, phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
547 if (phdr->p_type == PT_PHDR)
548 app->base = (void *)(aux[AT_PHDR] - phdr->p_vaddr);
552 app->constructed = 1;
553 app->dynv = (void *)(app->base + find_dyn(
554 (void *)aux[AT_PHDR], aux[AT_PHNUM], aux[AT_PHENT]));
557 /* Attach to vdso, if provided by the kernel */
558 for (i=0; auxv[i]; i+=2) {
559 size_t vdso_base = auxv[i+1];
560 if (auxv[i] != AT_SYSINFO_EHDR) continue;
561 ehdr = (void *)vdso_base;
562 phdr = (void *)(vdso_base + ehdr->e_phoff);
563 for (i=ehdr->e_phnum; i; i--, phdr=(void *)((char *)phdr + ehdr->e_phentsize)) {
564 if (phdr->p_type == PT_DYNAMIC)
565 vdso->dynv = (void *)(vdso_base + phdr->p_offset);
566 if (phdr->p_type == PT_LOAD)
567 vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
569 vdso->name = "linux-gate.so.1";
577 /* Initial dso chain consists only of the app. We temporarily
578 * append the dynamic linker/libc so we can relocate it, then
579 * restore the initial chain in preparation for loading third
580 * party libraries (preload/needed). */
587 /* PAST THIS POINT, ALL LIBC INTERFACES ARE FULLY USABLE. */
589 /* Donate unused parts of app and library mapping to malloc */
590 reclaim_gaps(app->base, (void *)aux[AT_PHDR], aux[AT_PHENT], aux[AT_PHNUM]);
591 ehdr = (void *)lib->base;
592 reclaim_gaps(lib->base, (void *)(lib->base+ehdr->e_phoff),
593 ehdr->e_phentsize, ehdr->e_phnum);
595 /* Load preload/needed libraries, add their symbols to the global
596 * namespace, and perform all remaining relocations. The main
597 * program must be relocated LAST since it may contain copy
598 * relocations which depend on libraries' relocations. */
599 if (env_preload) load_preload(env_preload);
602 reloc_all(app->next);
605 /* Switch to runtime mode: any further failures in the dynamic
606 * linker are a reportable failure rather than a fatal startup
607 * error. If the dynamic loader (dlopen) will not be used, free
608 * all memory used by the dynamic linker. */
616 reclaim((void *)builtin_dsos, 0, sizeof builtin_dsos);
619 if (ssp_used) __pthread_self_init();
622 return (void *)aux[AT_ENTRY];
625 void *dlopen(const char *file, int mode)
627 struct dso *volatile p, *orig_tail = tail, *next;
631 if (!file) return head;
633 pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
634 pthread_rwlock_wrlock(&lock);
636 if (setjmp(rtld_fail)) {
637 /* Clean up anything new that was (partially) loaded */
638 if (p->deps) for (i=0; p->deps[i]; i++)
639 if (p->deps[i]->global < 0)
640 p->deps[i]->global = 0;
641 for (p=orig_tail->next; p; p=next) {
643 munmap(p->map, p->map_len);
652 } else p = load_library(file);
655 snprintf(errbuf, sizeof errbuf,
656 "Error loading shared library %s: %m", file);
661 /* First load handling */
664 if (p->deps) for (i=0; p->deps[i]; i++)
665 if (!p->deps[i]->global)
666 p->deps[i]->global = -1;
667 if (!p->global) p->global = -1;
669 if (p->deps) for (i=0; p->deps[i]; i++)
670 if (p->deps[i]->global < 0)
671 p->deps[i]->global = 0;
672 if (p->global < 0) p->global = 0;
675 if (mode & RTLD_GLOBAL) {
676 if (p->deps) for (i=0; p->deps[i]; i++)
677 p->deps[i]->global = 1;
683 pthread_rwlock_unlock(&lock);
684 pthread_setcancelstate(cs, 0);
688 static void *do_dlsym(struct dso *p, const char *s, void *ra)
693 if (p == RTLD_NEXT) {
694 for (p=head; p && (unsigned char *)ra-p->map>p->map_len; p=p->next);
698 if (p == head || p == RTLD_DEFAULT) {
699 void *res = find_sym(head, s, 0);
700 if (!res) errflag = 1;
704 sym = lookup(s, h, p->syms, p->hashtab, p->strings);
705 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
706 return p->base + sym->st_value;
707 if (p->deps) for (i=0; p->deps[i]; i++) {
708 sym = lookup(s, h, p->deps[i]->syms,
709 p->deps[i]->hashtab, p->deps[i]->strings);
710 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
711 return p->deps[i]->base + sym->st_value;
714 snprintf(errbuf, sizeof errbuf, "Symbol not found: %s", s);
718 void *__dlsym(void *p, const char *s, void *ra)
721 pthread_rwlock_rdlock(&lock);
722 res = do_dlsym(p, s, ra);
723 pthread_rwlock_unlock(&lock);
727 void *dlopen(const char *file, int mode)
731 void *__dlsym(void *p, const char *s, void *ra)
739 if (!errflag) return 0;