19 #if ULONG_MAX == 0xffffffff
20 typedef Elf32_Ehdr Ehdr;
21 typedef Elf32_Phdr Phdr;
22 typedef Elf32_Sym Sym;
23 #define R_TYPE(x) ((x)&255)
24 #define R_SYM(x) ((x)>>8)
26 typedef Elf64_Ehdr Ehdr;
27 typedef Elf64_Phdr Phdr;
28 typedef Elf64_Sym Sym;
29 #define R_TYPE(x) ((x)&0xffffffff)
30 #define R_SYM(x) ((x)>>32)
35 struct dso *next, *prev;
52 static struct dso *head, *tail, *libc;
53 static char *env_path, *sys_path;
55 static jmp_buf rtld_fail;
60 static void decode_vec(size_t *v, size_t *a, size_t cnt)
62 memset(a, 0, cnt*sizeof(size_t));
63 for (; v[0]; v+=2) if (v[0]<cnt) {
69 static uint32_t hash(const char *s)
79 static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
82 for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
83 if (!strcmp(s, strings+syms[i].st_name))
89 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
91 static void *find_sym(struct dso *dso, const char *s, int need_def)
94 for (; dso; dso=dso->next) {
95 Sym *sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
96 if (sym && (!need_def || sym->st_shndx) && sym->st_value
97 && (1<<(sym->st_info&0xf) & OK_TYPES))
98 return dso->base + sym->st_value;
103 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
107 size_t sym_val, sym_size;
113 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
114 reloc_addr = (void *)(base + rel[0]);
115 type = R_TYPE(rel[1]);
116 sym_index = R_SYM(rel[1]);
118 sym = syms + sym_index;
119 name = strings + sym->st_name;
120 ctx = IS_COPY(type) ? dso->next : dso;
121 sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
122 if (!sym_val && sym->st_info>>4 != STB_WEAK) {
123 if (runtime) longjmp(rtld_fail, 1);
124 dprintf(2, "%s: symbol not found\n", name);
127 sym_size = sym->st_size;
129 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
133 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
135 Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
137 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
138 size_t this_min, this_max;
143 unsigned char *map, *base;
147 ssize_t l = read(fd, buf, sizeof buf);
148 if (l<sizeof *eh) return 0;
150 phsize = eh->e_phentsize * eh->e_phnum;
151 if (phsize + sizeof *eh > l) return 0;
152 if (eh->e_phoff + phsize > l) {
153 l = pread(fd, buf+1, phsize, eh->e_phoff);
154 if (l != phsize) return 0;
155 eh->e_phoff = sizeof *eh;
157 ph = (void *)((char *)buf + eh->e_phoff);
158 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
159 if (ph->p_type == PT_DYNAMIC)
161 if (ph->p_type != PT_LOAD) continue;
162 if (ph->p_vaddr < addr_min) {
163 addr_min = ph->p_vaddr;
164 off_start = ph->p_offset;
165 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
166 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
167 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
169 if (ph->p_vaddr+ph->p_memsz > addr_max) {
170 addr_max = ph->p_vaddr+ph->p_memsz;
174 addr_max += PAGE_SIZE-1;
175 addr_max &= -PAGE_SIZE;
176 addr_min &= -PAGE_SIZE;
177 off_start &= -PAGE_SIZE;
178 map_len = addr_max - addr_min + off_start;
179 /* The first time, we map too much, possibly even more than
180 * the length of the file. This is okay because we will not
181 * use the invalid part; we just need to reserve the right
182 * amount of virtual address space to map over later. */
183 map = mmap(0, map_len, prot, MAP_PRIVATE, fd, off_start);
184 if (map==MAP_FAILED) return 0;
185 base = map - addr_min;
186 ph = (void *)((char *)buf + eh->e_phoff);
187 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
188 if (ph->p_type != PT_LOAD) continue;
189 /* Reuse the existing mapping for the lowest-address LOAD */
190 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
191 this_min = ph->p_vaddr & -PAGE_SIZE;
192 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
193 off_start = ph->p_offset & -PAGE_SIZE;
194 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
195 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
196 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
197 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
198 munmap(map, map_len);
201 if (ph->p_memsz > ph->p_filesz) {
202 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
203 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
204 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
205 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) {
206 munmap(map, map_len);
217 static int path_open(const char *name, const char *search)
219 char buf[2*NAME_MAX+2];
220 const char *s=search, *z;
226 l = z ? z-s : strlen(s);
227 snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
228 if ((fd = open(buf, O_RDONLY))>=0) return fd;
233 static struct dso *load_library(const char *name)
235 unsigned char *base, *map;
236 size_t dyno, map_len;
238 size_t dyn[DYN_CNT] = {0};
242 /* Catch and block attempts to reload the implementation itself */
243 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
244 static const char *rp, reserved[] =
245 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
246 char *z = strchr(name, '.');
249 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
260 /* Search for the name to see if it's already loaded */
261 for (p=head->next; p; p=p->next) {
262 if (!strcmp(p->name, name)) {
267 if (name[0] == '/') {
268 fd = open(name, O_RDONLY);
270 if (strlen(name) > NAME_MAX || strchr(name, '/')) return 0;
272 if (env_path) fd = path_open(name, env_path);
275 FILE *f = fopen(ETC_LDSO_PATH, "r");
277 if (getline(&sys_path, (size_t[1]){0}, f) > 0)
278 sys_path[strlen(sys_path)-1]=0;
282 if (sys_path) fd = path_open(name, sys_path);
283 else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
286 if (fd < 0) return 0;
287 if (fstat(fd, &st) < 0) {
291 for (p=head->next; p; p=p->next) {
292 if (p->dev == st.st_dev && p->ino == st.st_ino) {
298 map = map_library(fd, &map_len, &base, &dyno);
301 p = calloc(1, sizeof *p + strlen(name) + 1);
303 munmap(map, map_len);
308 p->map_len = map_len;
310 p->dynv = (void *)(base + dyno);
311 decode_vec(p->dynv, dyn, DYN_CNT);
313 p->syms = (void *)(base + dyn[DT_SYMTAB]);
314 p->hashtab = (void *)(base + dyn[DT_HASH]);
315 p->strings = (void *)(base + dyn[DT_STRTAB]);
321 strcpy(p->name, name);
330 static void load_deps(struct dso *p)
333 for (; p; p=p->next) {
334 for (i=0; p->dynv[i]; i+=2) {
335 if (p->dynv[i] != DT_NEEDED) continue;
336 if (!load_library(p->strings + p->dynv[i+1])) {
337 if (runtime) longjmp(rtld_fail, 1);
338 dprintf(2, "%s: %m (needed by %s)\n",
339 p->strings + p->dynv[i+1], p->name);
346 static void reloc_all(struct dso *p)
348 size_t dyn[DYN_CNT] = {0};
349 for (; p; p=p->next) {
350 if (p->relocated) continue;
351 decode_vec(p->dynv, dyn, DYN_CNT);
352 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
353 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
354 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
355 2, p->syms, p->strings, head);
356 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
357 3, p->syms, p->strings, head);
362 static void free_all(struct dso *p)
372 void *__dynlink(int argc, char **argv, size_t *got)
374 size_t *auxv, aux[AUX_CNT] = {0};
375 size_t app_dyn[DYN_CNT] = {0};
376 size_t lib_dyn[DYN_CNT] = {0};
381 /* Find aux vector just past environ[] */
382 for (i=argc+1; argv[i]; i++)
383 if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
384 env_path = argv[i]+16;
385 auxv = (void *)(argv+i+1);
387 decode_vec(auxv, aux, AUX_CNT);
389 /* Only trust user/env if kernel says we're not suid/sgid */
390 if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
391 || aux[AT_GID]!=aux[AT_EGID]) {
395 /* Relocate ldso's DYNAMIC pointer and load vector */
396 decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
398 /* Find the program image's DYNAMIC section and decode it */
399 phdr = (void *)aux[AT_PHDR];
400 for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
401 if (phdr->p_type == PT_DYNAMIC) {
402 decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
409 .strings = (void *)(app_dyn[DT_STRTAB]),
410 .hashtab = (void *)(app_dyn[DT_HASH]),
411 .syms = (void *)(app_dyn[DT_SYMTAB]),
412 .dynv = (void *)(phdr->p_vaddr),
418 .base = (void *)aux[AT_BASE],
419 .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
420 .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
421 .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
422 .dynv = (void *)(got[0]),
427 /* Relocate the dynamic linker/libc */
428 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
429 lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app);
430 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
431 lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app);
433 /* At this point the standard library is fully functional */
446 return (void *)aux[AT_ENTRY];