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, *r_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)
95 #define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK)
97 static void *find_sym(struct dso *dso, const char *s, int need_def)
101 if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
102 if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
103 for (; dso; dso=dso->next) {
105 if (!dso->global) continue;
106 sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
107 if (sym && (!need_def || sym->st_shndx) && sym->st_value
108 && (1<<(sym->st_info&0xf) & OK_TYPES)
109 && (1<<(sym->st_info>>4) & OK_BINDS)) {
110 if (def && sym->st_info>>4 == STB_WEAK) continue;
111 def = dso->base + sym->st_value;
112 if (sym->st_info>>4 == STB_GLOBAL) break;
118 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
122 size_t sym_val, sym_size;
128 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
129 reloc_addr = (void *)(base + rel[0]);
130 type = R_TYPE(rel[1]);
131 sym_index = R_SYM(rel[1]);
133 sym = syms + sym_index;
134 name = strings + sym->st_name;
135 ctx = IS_COPY(type) ? dso->next : dso;
136 sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
137 if (!sym_val && sym->st_info>>4 != STB_WEAK) {
138 if (runtime) longjmp(rtld_fail, 1);
139 dprintf(2, "%s: symbol not found\n", name);
142 sym_size = sym->st_size;
144 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
148 /* A huge hack: to make up for the wastefulness of shared libraries
149 * needing at least a page of dirty memory even if they have no global
150 * data, we reclaim the gaps at the beginning and end of writable maps
151 * and "donate" them to the heap by setting up minimal malloc
152 * structures and then freeing them. */
154 static void reclaim(unsigned char *base, size_t start, size_t end)
157 start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t);
158 end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t);
159 if (start>end || end-start < 4*sizeof(size_t)) return;
160 a = (size_t *)(base + start);
161 z = (size_t *)(base + end);
163 a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1;
168 static void reclaim_gaps(unsigned char *base, Phdr *ph, size_t phent, size_t phcnt)
170 for (; phcnt--; ph=(void *)((char *)ph+phent)) {
171 if (ph->p_type!=PT_LOAD) continue;
172 if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue;
173 reclaim(base, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr);
174 reclaim(base, ph->p_vaddr+ph->p_memsz,
175 ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE);
179 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
181 Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
183 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
184 size_t this_min, this_max;
189 unsigned char *map, *base;
193 ssize_t l = read(fd, buf, sizeof buf);
194 if (l<sizeof *eh) return 0;
196 phsize = eh->e_phentsize * eh->e_phnum;
197 if (phsize + sizeof *eh > l) return 0;
198 if (eh->e_phoff + phsize > l) {
199 l = pread(fd, buf+1, phsize, eh->e_phoff);
200 if (l != phsize) return 0;
201 eh->e_phoff = sizeof *eh;
203 ph = (void *)((char *)buf + eh->e_phoff);
204 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
205 if (ph->p_type == PT_DYNAMIC)
207 if (ph->p_type != PT_LOAD) continue;
208 if (ph->p_vaddr < addr_min) {
209 addr_min = ph->p_vaddr;
210 off_start = ph->p_offset;
211 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
212 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
213 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
215 if (ph->p_vaddr+ph->p_memsz > addr_max) {
216 addr_max = ph->p_vaddr+ph->p_memsz;
220 addr_max += PAGE_SIZE-1;
221 addr_max &= -PAGE_SIZE;
222 addr_min &= -PAGE_SIZE;
223 off_start &= -PAGE_SIZE;
224 map_len = addr_max - addr_min + off_start;
225 /* The first time, we map too much, possibly even more than
226 * the length of the file. This is okay because we will not
227 * use the invalid part; we just need to reserve the right
228 * amount of virtual address space to map over later. */
229 map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start);
230 if (map==MAP_FAILED) return 0;
231 base = map - addr_min;
232 ph = (void *)((char *)buf + eh->e_phoff);
233 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
234 if (ph->p_type != PT_LOAD) continue;
235 /* Reuse the existing mapping for the lowest-address LOAD */
236 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
237 this_min = ph->p_vaddr & -PAGE_SIZE;
238 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
239 off_start = ph->p_offset & -PAGE_SIZE;
240 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
241 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
242 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
243 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
244 munmap(map, map_len);
247 if (ph->p_memsz > ph->p_filesz) {
248 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
249 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
250 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
251 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) {
252 munmap(map, map_len);
257 for (i=0; ((size_t *)(base+dyn))[i]; i+=2)
258 if (((size_t *)(base+dyn))[i]==DT_TEXTREL) {
259 mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC);
262 if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff),
263 eh->e_phentsize, eh->e_phnum);
270 static int path_open(const char *name, const char *search)
272 char buf[2*NAME_MAX+2];
273 const char *s=search, *z;
279 l = z ? z-s : strlen(s);
280 snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
281 if ((fd = open(buf, O_RDONLY))>=0) return fd;
286 static struct dso *load_library(const char *name)
288 unsigned char *base, *map;
289 size_t dyno, map_len;
291 size_t dyn[DYN_CNT] = {0};
295 /* Catch and block attempts to reload the implementation itself */
296 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
297 static const char *rp, reserved[] =
298 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
299 char *z = strchr(name, '.');
302 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
307 tail = libc->next ? libc->next : libc;
313 /* Search for the name to see if it's already loaded */
314 for (p=head->next; p; p=p->next) {
315 if (!strcmp(p->name, name)) {
320 if (strchr(name, '/')) {
321 fd = open(name, O_RDONLY);
323 if (strlen(name) > NAME_MAX) return 0;
325 if (r_path) fd = path_open(name, r_path);
326 if (fd < 0 && env_path) fd = path_open(name, env_path);
329 FILE *f = fopen(ETC_LDSO_PATH, "r");
331 if (getline(&sys_path, (size_t[1]){0}, f) > 0)
332 sys_path[strlen(sys_path)-1]=0;
336 if (sys_path) fd = path_open(name, sys_path);
337 else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
340 if (fd < 0) return 0;
341 if (fstat(fd, &st) < 0) {
345 for (p=head->next; p; p=p->next) {
346 if (p->dev == st.st_dev && p->ino == st.st_ino) {
352 map = map_library(fd, &map_len, &base, &dyno);
355 p = calloc(1, sizeof *p + strlen(name) + 1);
357 munmap(map, map_len);
362 p->map_len = map_len;
364 p->dynv = (void *)(base + dyno);
365 decode_vec(p->dynv, dyn, DYN_CNT);
367 p->syms = (void *)(base + dyn[DT_SYMTAB]);
368 p->hashtab = (void *)(base + dyn[DT_HASH]);
369 p->strings = (void *)(base + dyn[DT_STRTAB]);
374 strcpy(p->name, name);
383 static void load_deps(struct dso *p)
386 struct dso ***deps = &p->deps, **tmp, *dep;
387 for (; p; p=p->next) {
388 for (i=0; p->dynv[i]; i+=2) {
389 if (p->dynv[i] != DT_RPATH) continue;
390 r_path = (void *)(p->strings + p->dynv[i+1]);
392 for (i=0; p->dynv[i]; i+=2) {
393 if (p->dynv[i] != DT_NEEDED) continue;
394 dep = load_library(p->strings + p->dynv[i+1]);
396 if (runtime) longjmp(rtld_fail, 1);
397 dprintf(2, "%s: %m (needed by %s)\n",
398 p->strings + p->dynv[i+1], p->name);
402 tmp = realloc(*deps, sizeof(*tmp)*(ndeps+2));
403 if (!tmp) longjmp(rtld_fail, 1);
413 static void make_global(struct dso *p)
415 for (; p; p=p->next) p->global = 1;
418 static void reloc_all(struct dso *p)
420 size_t dyn[DYN_CNT] = {0};
421 for (; p; p=p->next) {
422 if (p->relocated) continue;
423 decode_vec(p->dynv, dyn, DYN_CNT);
424 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
425 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
426 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
427 2, p->syms, p->strings, head);
428 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
429 3, p->syms, p->strings, head);
434 static void free_all(struct dso *p)
444 void *__dynlink(int argc, char **argv, size_t *got)
446 size_t *auxv, aux[AUX_CNT] = {0};
447 size_t app_dyn[DYN_CNT] = {0};
448 size_t lib_dyn[DYN_CNT] = {0};
449 size_t vdso_dyn[DYN_CNT] = {0};
453 static struct dso builtin_dsos[3];
454 struct dso *const app = builtin_dsos+0;
455 struct dso *const lib = builtin_dsos+1;
456 struct dso *const vdso = builtin_dsos+2;
459 /* Find aux vector just past environ[] */
460 for (i=argc+1; argv[i]; i++)
461 if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
462 env_path = argv[i]+16;
463 auxv = (void *)(argv+i+1);
465 decode_vec(auxv, aux, AUX_CNT);
467 for (i=0; auxv[i]; i+=2) {
468 if (auxv[i]==AT_SYSINFO_EHDR) {
469 vdso_base = auxv[i+1];
474 /* Only trust user/env if kernel says we're not suid/sgid */
475 if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
476 || aux[AT_GID]!=aux[AT_EGID]) {
480 /* Relocate ldso's DYNAMIC pointer and load vector */
481 decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
483 /* Find the program image's DYNAMIC section and decode it */
484 phdr = (void *)aux[AT_PHDR];
485 for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
486 if (phdr->p_type == PT_DYNAMIC) {
487 decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
494 .strings = (void *)(app_dyn[DT_STRTAB]),
495 .hashtab = (void *)(app_dyn[DT_HASH]),
496 .syms = (void *)(app_dyn[DT_SYMTAB]),
497 .dynv = (void *)(phdr->p_vaddr),
504 .base = (void *)aux[AT_BASE],
505 .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
506 .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
507 .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
508 .dynv = (void *)(got[0]),
515 ehdr = (void *)vdso_base;
516 phdr = (void *)(vdso_base + ehdr->e_phoff);
517 for (i=ehdr->e_phnum; i; i--, phdr=(void *)((char *)phdr + ehdr->e_phentsize)) {
518 if (phdr->p_type == PT_DYNAMIC)
519 vdso->dynv = (void *)(vdso_base + phdr->p_offset);
520 if (phdr->p_type == PT_LOAD)
521 vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
523 decode_vec(vdso->dynv, vdso_dyn, DYN_CNT);
524 vdso->syms = (void *)(vdso->base + vdso_dyn[DT_SYMTAB]);
525 vdso->hashtab = (void *)(vdso->base + vdso_dyn[DT_HASH]);
526 vdso->strings = (void *)(vdso->base + vdso_dyn[DT_STRTAB]);
527 vdso->name = "linux-gate.so.1";
534 /* Relocate the dynamic linker/libc */
535 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
536 lib_dyn[DT_RELSZ], 2, lib->syms, lib->strings, app);
537 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
538 lib_dyn[DT_RELASZ], 3, lib->syms, lib->strings, app);
540 /* At this point the standard library is fully functional */
542 reclaim_gaps(app->base, (void *)aux[AT_PHDR], aux[AT_PHENT], aux[AT_PHNUM]);
543 ehdr = (void *)lib->base;
544 reclaim_gaps(lib->base, (void *)(lib->base+ehdr->e_phoff),
545 ehdr->e_phentsize, ehdr->e_phnum);
553 reloc_all(head->next);
560 reclaim((void *)builtin_dsos, 0, sizeof builtin_dsos);
564 return (void *)aux[AT_ENTRY];
567 void *dlopen(const char *file, int mode)
569 struct dso *volatile p, *orig_tail = tail, *next;
572 if (!file) return head;
574 pthread_rwlock_wrlock(&lock);
576 if (setjmp(rtld_fail)) {
577 /* Clean up anything new that was (partially) loaded */
578 if (p->deps) for (i=0; p->deps[i]; i++)
579 if (p->deps[i]->global < 0)
580 p->deps[i]->global = 0;
581 for (p=orig_tail->next; p; p=next) {
583 munmap(p->map, p->map_len);
589 pthread_rwlock_unlock(&lock);
593 p = load_library(file);
596 /* First load handling */
599 if (p->deps) for (i=0; p->deps[i]; i++)
600 if (!p->deps[i]->global)
601 p->deps[i]->global = -1;
602 if (!p->global) p->global = -1;
604 if (p->deps) for (i=0; p->deps[i]; i++)
605 if (p->deps[i]->global < 0)
606 p->deps[i]->global = 0;
607 if (p->global < 0) p->global = 0;
610 if (mode & RTLD_GLOBAL) {
611 if (p->deps) for (i=0; p->deps[i]; i++)
612 p->deps[i]->global = 1;
617 pthread_rwlock_unlock(&lock);
621 static void *do_dlsym(struct dso *p, const char *s)
626 if (p == head || p == RTLD_DEFAULT)
627 return find_sym(head, s, 0);
629 sym = lookup(s, h, p->syms, p->hashtab, p->strings);
630 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
631 return p->base + sym->st_value;
632 if (p->deps) for (i=0; p->deps[i]; i++) {
633 sym = lookup(s, h, p->deps[i]->syms,
634 p->deps[i]->hashtab, p->deps[i]->strings);
635 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
636 return p->deps[i]->base + sym->st_value;
641 void *dlsym(void *p, const char *s)
644 pthread_rwlock_rdlock(&lock);
645 res = do_dlsym(p, s);
646 pthread_rwlock_unlock(&lock);
652 return "unknown error";