22 #if ULONG_MAX == 0xffffffff
23 typedef Elf32_Ehdr Ehdr;
24 typedef Elf32_Phdr Phdr;
25 typedef Elf32_Sym Sym;
26 #define R_TYPE(x) ((x)&255)
27 #define R_SYM(x) ((x)>>8)
29 typedef Elf64_Ehdr Ehdr;
30 typedef Elf64_Phdr Phdr;
31 typedef Elf64_Sym Sym;
32 #define R_TYPE(x) ((x)&0xffffffff)
33 #define R_SYM(x) ((x)>>32)
38 struct dso *next, *prev;
56 static struct dso *head, *tail, *libc;
57 static char *env_path, *sys_path, *r_path;
60 static jmp_buf rtld_fail;
61 static pthread_rwlock_t lock;
66 static void decode_vec(size_t *v, size_t *a, size_t cnt)
68 memset(a, 0, cnt*sizeof(size_t));
69 for (; v[0]; v+=2) if (v[0]<cnt) {
75 static uint32_t hash(const char *s)
85 static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
88 for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
89 if (!strcmp(s, strings+syms[i].st_name))
95 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
96 #define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK)
98 static void *find_sym(struct dso *dso, const char *s, int need_def)
100 uint32_t h = hash(s);
102 if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
103 if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
104 for (; dso; dso=dso->next) {
106 if (!dso->global) continue;
107 sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
108 if (sym && (!need_def || sym->st_shndx) && sym->st_value
109 && (1<<(sym->st_info&0xf) & OK_TYPES)
110 && (1<<(sym->st_info>>4) & OK_BINDS)) {
111 if (def && sym->st_info>>4 == STB_WEAK) continue;
112 def = dso->base + sym->st_value;
113 if (sym->st_info>>4 == STB_GLOBAL) break;
119 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
123 size_t sym_val, sym_size;
129 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
130 reloc_addr = (void *)(base + rel[0]);
131 type = R_TYPE(rel[1]);
132 sym_index = R_SYM(rel[1]);
134 sym = syms + sym_index;
135 name = strings + sym->st_name;
136 ctx = IS_COPY(type) ? dso->next : dso;
137 sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
138 if (!sym_val && sym->st_info>>4 != STB_WEAK) {
139 if (runtime) longjmp(rtld_fail, 1);
140 dprintf(2, "%s: symbol not found\n", name);
143 sym_size = sym->st_size;
145 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
149 /* A huge hack: to make up for the wastefulness of shared libraries
150 * needing at least a page of dirty memory even if they have no global
151 * data, we reclaim the gaps at the beginning and end of writable maps
152 * and "donate" them to the heap by setting up minimal malloc
153 * structures and then freeing them. */
155 static void reclaim(unsigned char *base, size_t start, size_t end)
158 start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t);
159 end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t);
160 if (start>end || end-start < 4*sizeof(size_t)) return;
161 a = (size_t *)(base + start);
162 z = (size_t *)(base + end);
164 a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1;
169 static void reclaim_gaps(unsigned char *base, Phdr *ph, size_t phent, size_t phcnt)
171 for (; phcnt--; ph=(void *)((char *)ph+phent)) {
172 if (ph->p_type!=PT_LOAD) continue;
173 if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue;
174 reclaim(base, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr);
175 reclaim(base, ph->p_vaddr+ph->p_memsz,
176 ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE);
180 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
182 Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
184 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
185 size_t this_min, this_max;
190 unsigned char *map, *base;
194 ssize_t l = read(fd, buf, sizeof buf);
195 if (l<sizeof *eh) return 0;
197 phsize = eh->e_phentsize * eh->e_phnum;
198 if (phsize + sizeof *eh > l) return 0;
199 if (eh->e_phoff + phsize > l) {
200 l = pread(fd, buf+1, phsize, eh->e_phoff);
201 if (l != phsize) return 0;
202 eh->e_phoff = sizeof *eh;
204 ph = (void *)((char *)buf + eh->e_phoff);
205 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
206 if (ph->p_type == PT_DYNAMIC)
208 if (ph->p_type != PT_LOAD) continue;
209 if (ph->p_vaddr < addr_min) {
210 addr_min = ph->p_vaddr;
211 off_start = ph->p_offset;
212 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
213 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
214 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
216 if (ph->p_vaddr+ph->p_memsz > addr_max) {
217 addr_max = ph->p_vaddr+ph->p_memsz;
221 addr_max += PAGE_SIZE-1;
222 addr_max &= -PAGE_SIZE;
223 addr_min &= -PAGE_SIZE;
224 off_start &= -PAGE_SIZE;
225 map_len = addr_max - addr_min + off_start;
226 /* The first time, we map too much, possibly even more than
227 * the length of the file. This is okay because we will not
228 * use the invalid part; we just need to reserve the right
229 * amount of virtual address space to map over later. */
230 map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start);
231 if (map==MAP_FAILED) return 0;
232 base = map - addr_min;
233 ph = (void *)((char *)buf + eh->e_phoff);
234 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
235 if (ph->p_type != PT_LOAD) continue;
236 /* Reuse the existing mapping for the lowest-address LOAD */
237 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
238 this_min = ph->p_vaddr & -PAGE_SIZE;
239 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
240 off_start = ph->p_offset & -PAGE_SIZE;
241 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
242 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
243 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
244 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
245 munmap(map, map_len);
248 if (ph->p_memsz > ph->p_filesz) {
249 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
250 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
251 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
252 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) {
253 munmap(map, map_len);
258 for (i=0; ((size_t *)(base+dyn))[i]; i+=2)
259 if (((size_t *)(base+dyn))[i]==DT_TEXTREL) {
260 mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC);
263 if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff),
264 eh->e_phentsize, eh->e_phnum);
271 static int path_open(const char *name, const char *search)
273 char buf[2*NAME_MAX+2];
274 const char *s=search, *z;
280 l = z ? z-s : strlen(s);
281 snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
282 if ((fd = open(buf, O_RDONLY))>=0) return fd;
287 static struct dso *load_library(const char *name)
289 unsigned char *base, *map;
290 size_t dyno, map_len;
292 size_t dyn[DYN_CNT] = {0};
296 /* Catch and block attempts to reload the implementation itself */
297 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
298 static const char *rp, reserved[] =
299 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
300 char *z = strchr(name, '.');
303 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
308 tail = libc->next ? libc->next : libc;
314 /* Search for the name to see if it's already loaded */
315 for (p=head->next; p; p=p->next) {
316 if (!strcmp(p->name, name)) {
321 if (strchr(name, '/')) {
322 fd = open(name, O_RDONLY);
324 if (strlen(name) > NAME_MAX) return 0;
326 if (r_path) fd = path_open(name, r_path);
327 if (fd < 0 && env_path) fd = path_open(name, env_path);
330 FILE *f = fopen(ETC_LDSO_PATH, "r");
332 if (getline(&sys_path, (size_t[1]){0}, f) > 0)
333 sys_path[strlen(sys_path)-1]=0;
337 if (sys_path) fd = path_open(name, sys_path);
338 else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
341 if (fd < 0) return 0;
342 if (fstat(fd, &st) < 0) {
346 for (p=head->next; p; p=p->next) {
347 if (p->dev == st.st_dev && p->ino == st.st_ino) {
353 map = map_library(fd, &map_len, &base, &dyno);
356 p = calloc(1, sizeof *p + strlen(name) + 1);
358 munmap(map, map_len);
363 p->map_len = map_len;
365 p->dynv = (void *)(base + dyno);
366 decode_vec(p->dynv, dyn, DYN_CNT);
368 p->syms = (void *)(base + dyn[DT_SYMTAB]);
369 p->hashtab = (void *)(base + dyn[DT_HASH]);
370 p->strings = (void *)(base + dyn[DT_STRTAB]);
375 strcpy(p->name, name);
384 static void load_deps(struct dso *p)
387 struct dso ***deps = &p->deps, **tmp, *dep;
388 for (; p; p=p->next) {
389 for (i=0; p->dynv[i]; i+=2) {
390 if (p->dynv[i] != DT_RPATH) continue;
391 r_path = (void *)(p->strings + p->dynv[i+1]);
393 for (i=0; p->dynv[i]; i+=2) {
394 if (p->dynv[i] != DT_NEEDED) continue;
395 dep = load_library(p->strings + p->dynv[i+1]);
397 if (runtime) longjmp(rtld_fail, 1);
398 dprintf(2, "%s: %m (needed by %s)\n",
399 p->strings + p->dynv[i+1], p->name);
403 tmp = realloc(*deps, sizeof(*tmp)*(ndeps+2));
404 if (!tmp) longjmp(rtld_fail, 1);
414 static void load_preload(char *s)
419 for ( ; *s && isspace(*s); s++);
420 for (z=s; *z && !isspace(*z); z++);
428 static void make_global(struct dso *p)
430 for (; p; p=p->next) p->global = 1;
433 static void reloc_all(struct dso *p)
435 size_t dyn[DYN_CNT] = {0};
436 for (; p; p=p->next) {
437 if (p->relocated) continue;
438 decode_vec(p->dynv, dyn, DYN_CNT);
439 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
440 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
441 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
442 2, p->syms, p->strings, head);
443 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
444 3, p->syms, p->strings, head);
449 static void free_all(struct dso *p)
459 void *__dynlink(int argc, char **argv, size_t *got)
461 size_t *auxv, aux[AUX_CNT] = {0};
462 size_t app_dyn[DYN_CNT] = {0};
463 size_t lib_dyn[DYN_CNT] = {0};
464 size_t vdso_dyn[DYN_CNT] = {0};
468 static struct dso builtin_dsos[3];
469 struct dso *const app = builtin_dsos+0;
470 struct dso *const lib = builtin_dsos+1;
471 struct dso *const vdso = builtin_dsos+2;
475 /* Find aux vector just past environ[] */
476 for (i=argc+1; argv[i]; i++)
477 if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
478 env_path = argv[i]+16;
479 else if (!memcmp(argv[i], "LD_PRELOAD=", 11))
480 env_preload = argv[i]+11;
481 auxv = (void *)(argv+i+1);
483 decode_vec(auxv, aux, AUX_CNT);
485 /* Only trust user/env if kernel says we're not suid/sgid */
486 if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
487 || aux[AT_GID]!=aux[AT_EGID] || aux[AT_SECURE]) {
492 for (i=0; auxv[i]; i+=2) {
493 if (auxv[i]==AT_SYSINFO_EHDR) {
494 vdso_base = auxv[i+1];
499 /* Relocate ldso's DYNAMIC pointer and load vector */
500 decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
502 /* Find the program image's DYNAMIC section and decode it */
503 phdr = (void *)aux[AT_PHDR];
504 for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
505 if (phdr->p_type == PT_DYNAMIC) {
506 decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
513 .strings = (void *)(app_dyn[DT_STRTAB]),
514 .hashtab = (void *)(app_dyn[DT_HASH]),
515 .syms = (void *)(app_dyn[DT_SYMTAB]),
516 .dynv = (void *)(phdr->p_vaddr),
523 .base = (void *)aux[AT_BASE],
524 .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
525 .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
526 .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
527 .dynv = (void *)(got[0]),
534 ehdr = (void *)vdso_base;
535 phdr = (void *)(vdso_base + ehdr->e_phoff);
536 for (i=ehdr->e_phnum; i; i--, phdr=(void *)((char *)phdr + ehdr->e_phentsize)) {
537 if (phdr->p_type == PT_DYNAMIC)
538 vdso->dynv = (void *)(vdso_base + phdr->p_offset);
539 if (phdr->p_type == PT_LOAD)
540 vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
542 decode_vec(vdso->dynv, vdso_dyn, DYN_CNT);
543 vdso->syms = (void *)(vdso->base + vdso_dyn[DT_SYMTAB]);
544 vdso->hashtab = (void *)(vdso->base + vdso_dyn[DT_HASH]);
545 vdso->strings = (void *)(vdso->base + vdso_dyn[DT_STRTAB]);
546 vdso->name = "linux-gate.so.1";
553 /* Relocate the dynamic linker/libc */
554 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
555 lib_dyn[DT_RELSZ], 2, lib->syms, lib->strings, app);
556 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
557 lib_dyn[DT_RELASZ], 3, lib->syms, lib->strings, app);
559 /* At this point the standard library is fully functional */
561 reclaim_gaps(app->base, (void *)aux[AT_PHDR], aux[AT_PHENT], aux[AT_PHNUM]);
562 ehdr = (void *)lib->base;
563 reclaim_gaps(lib->base, (void *)(lib->base+ehdr->e_phoff),
564 ehdr->e_phentsize, ehdr->e_phnum);
569 if (env_preload) load_preload(env_preload);
573 reloc_all(head->next);
580 reclaim((void *)builtin_dsos, 0, sizeof builtin_dsos);
584 return (void *)aux[AT_ENTRY];
587 void *dlopen(const char *file, int mode)
589 struct dso *volatile p, *orig_tail = tail, *next;
592 if (!file) return head;
594 pthread_rwlock_wrlock(&lock);
596 if (setjmp(rtld_fail)) {
597 /* Clean up anything new that was (partially) loaded */
598 if (p->deps) for (i=0; p->deps[i]; i++)
599 if (p->deps[i]->global < 0)
600 p->deps[i]->global = 0;
601 for (p=orig_tail->next; p; p=next) {
603 munmap(p->map, p->map_len);
609 pthread_rwlock_unlock(&lock);
613 p = load_library(file);
616 /* First load handling */
619 if (p->deps) for (i=0; p->deps[i]; i++)
620 if (!p->deps[i]->global)
621 p->deps[i]->global = -1;
622 if (!p->global) p->global = -1;
624 if (p->deps) for (i=0; p->deps[i]; i++)
625 if (p->deps[i]->global < 0)
626 p->deps[i]->global = 0;
627 if (p->global < 0) p->global = 0;
630 if (mode & RTLD_GLOBAL) {
631 if (p->deps) for (i=0; p->deps[i]; i++)
632 p->deps[i]->global = 1;
637 pthread_rwlock_unlock(&lock);
641 static void *do_dlsym(struct dso *p, const char *s, void *ra)
646 if (p == RTLD_NEXT) {
647 for (p=head; p && (unsigned char *)ra-p->map>p->map_len; p=p->next);
651 if (p == head || p == RTLD_DEFAULT)
652 return find_sym(head, s, 0);
654 sym = lookup(s, h, p->syms, p->hashtab, p->strings);
655 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
656 return p->base + sym->st_value;
657 if (p->deps) for (i=0; p->deps[i]; i++) {
658 sym = lookup(s, h, p->deps[i]->syms,
659 p->deps[i]->hashtab, p->deps[i]->strings);
660 if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
661 return p->deps[i]->base + sym->st_value;
666 void *__dlsym(void *p, const char *s, void *ra)
669 pthread_rwlock_rdlock(&lock);
670 res = do_dlsym(p, s, ra);
671 pthread_rwlock_unlock(&lock);
677 return "unknown error";