18 #if ULONG_MAX == 0xffffffff
19 typedef Elf32_Ehdr Ehdr;
20 typedef Elf32_Phdr Phdr;
21 typedef Elf32_Sym Sym;
22 #define R_TYPE(x) ((x)&255)
23 #define R_SYM(x) ((x)>>8)
25 typedef Elf64_Ehdr Ehdr;
26 typedef Elf64_Phdr Phdr;
27 typedef Elf64_Sym Sym;
28 #define R_TYPE(x) ((x)&0xffffffff)
29 #define R_SYM(x) ((x)>>32)
34 struct dso *next, *prev;
50 static struct dso *head, *tail, *libc;
51 static char *env_path, *sys_path;
56 static void decode_vec(size_t *v, size_t *a, size_t cnt)
58 memset(a, 0, cnt*sizeof(size_t));
59 for (; v[0]; v+=2) if (v[0]<cnt) {
65 static uint32_t hash(const char *s)
75 static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
78 for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
79 if (!strcmp(s, strings+syms[i].st_name))
85 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
87 static void *find_sym(struct dso *dso, const char *s, int need_def)
90 for (; dso; dso=dso->next) {
91 Sym *sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
92 if (sym && (!need_def || sym->st_shndx) && sym->st_value
93 && (1<<(sym->st_info&0xf) & OK_TYPES))
94 return dso->base + sym->st_value;
99 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
103 size_t sym_val, sym_size;
109 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
110 reloc_addr = (void *)(base + rel[0]);
111 type = R_TYPE(rel[1]);
112 sym_index = R_SYM(rel[1]);
114 sym = syms + sym_index;
115 name = strings + sym->st_name;
116 ctx = IS_COPY(type) ? dso->next : dso;
117 sym_val = (size_t)find_sym(ctx, name, IS_PLT(type));
118 sym_size = sym->st_size;
120 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
124 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
126 Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
128 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
129 size_t this_min, this_max;
134 unsigned char *map, *base;
138 ssize_t l = read(fd, buf, sizeof buf);
139 if (l<sizeof *eh) return 0;
141 phsize = eh->e_phentsize * eh->e_phnum;
142 if (phsize + sizeof *eh > l) return 0;
143 if (eh->e_phoff + phsize > l) {
144 l = pread(fd, buf+1, phsize, eh->e_phoff);
145 if (l != phsize) return 0;
146 eh->e_phoff = sizeof *eh;
148 ph = (void *)((char *)buf + eh->e_phoff);
149 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
150 if (ph->p_type == PT_DYNAMIC)
152 if (ph->p_type != PT_LOAD) continue;
153 if (ph->p_vaddr < addr_min) {
154 addr_min = ph->p_vaddr;
155 off_start = ph->p_offset;
156 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
157 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
158 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
160 if (ph->p_vaddr+ph->p_memsz > addr_max) {
161 addr_max = ph->p_vaddr+ph->p_memsz;
165 addr_max += PAGE_SIZE-1;
166 addr_max &= -PAGE_SIZE;
167 addr_min &= -PAGE_SIZE;
168 off_start &= -PAGE_SIZE;
169 map_len = addr_max - addr_min + off_start;
170 /* The first time, we map too much, possibly even more than
171 * the length of the file. This is okay because we will not
172 * use the invalid part; we just need to reserve the right
173 * amount of virtual address space to map over later. */
174 map = mmap(0, map_len, prot, MAP_PRIVATE, fd, off_start);
175 if (map==MAP_FAILED) return 0;
176 base = map - addr_min;
177 ph = (void *)((char *)buf + eh->e_phoff);
178 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
179 if (ph->p_type != PT_LOAD) continue;
180 /* Reuse the existing mapping for the lowest-address LOAD */
181 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
182 this_min = ph->p_vaddr & -PAGE_SIZE;
183 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
184 off_start = ph->p_offset & -PAGE_SIZE;
185 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
186 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
187 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
188 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
189 munmap(map, map_len);
192 if (ph->p_memsz > ph->p_filesz) {
193 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
194 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
195 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
196 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) {
197 munmap(map, map_len);
208 static int path_open(const char *name, const char *search)
210 char buf[2*NAME_MAX+2];
211 const char *s=search, *z;
217 l = z ? z-s : strlen(s);
218 snprintf(buf, sizeof buf, "%.*s/%s", l, s, name);
219 if ((fd = open(buf, O_RDONLY))>=0) return fd;
224 static struct dso *load_library(const char *name)
226 unsigned char *base, *map;
227 size_t dyno, map_len;
229 size_t dyn[DYN_CNT] = {0};
233 /* Catch and block attempts to reload the implementation itself */
234 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
235 static const char *rp, reserved[] =
236 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
237 char *z = strchr(name, '.');
240 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
251 /* Search for the name to see if it's already loaded */
252 for (p=head->next; p; p=p->next) {
253 if (!strcmp(p->name, name)) {
258 if (name[0] == '/') {
259 fd = open(name, O_RDONLY);
261 if (strlen(name) > NAME_MAX || strchr(name, '/')) return 0;
263 if (env_path) fd = path_open(name, env_path);
266 FILE *f = fopen(ETC_LDSO_PATH, "r");
268 if (getline(&sys_path, (size_t[1]){0}, f) > 0)
269 sys_path[strlen(sys_path)-1]=0;
273 if (sys_path) fd = path_open(name, sys_path);
274 else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib");
277 if (fd < 0) return 0;
278 if (fstat(fd, &st) < 0) {
282 for (p=head->next; p; p=p->next) {
283 if (p->dev == st.st_dev && p->ino == st.st_ino) {
289 map = map_library(fd, &map_len, &base, &dyno);
292 p = calloc(1, sizeof *p + strlen(name) + 1);
294 munmap(map, map_len);
299 p->map_len = map_len;
301 p->dynv = (void *)(base + dyno);
302 decode_vec(p->dynv, dyn, DYN_CNT);
304 p->syms = (void *)(base + dyn[DT_SYMTAB]);
305 p->hashtab = (void *)(base + dyn[DT_HASH]);
306 p->strings = (void *)(base + dyn[DT_STRTAB]);
311 strcpy(p->name, name);
320 static void load_deps(struct dso *p)
323 for (; p; p=p->next) {
324 for (i=0; p->dynv[i]; i+=2) {
325 if (p->dynv[i] != DT_NEEDED) continue;
326 load_library(p->strings + p->dynv[i+1]);
331 static void reloc_all(struct dso *p)
333 size_t dyn[DYN_CNT] = {0};
334 for (; p; p=p->next) {
335 if (p->relocated) continue;
336 decode_vec(p->dynv, dyn, DYN_CNT);
337 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
338 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head);
339 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
340 2, p->syms, p->strings, head);
341 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
342 3, p->syms, p->strings, head);
347 static void free_all(struct dso *p)
357 void *__dynlink(int argc, char **argv, size_t *got)
359 size_t *auxv, aux[AUX_CNT] = {0};
360 size_t app_dyn[DYN_CNT] = {0};
361 size_t lib_dyn[DYN_CNT] = {0};
366 /* Find aux vector just past environ[] */
367 for (i=argc+1; argv[i]; i++)
368 if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
369 env_path = argv[i]+16;
370 auxv = (void *)(argv+i+1);
372 decode_vec(auxv, aux, AUX_CNT);
374 /* Only trust user/env if kernel says we're not suid/sgid */
375 if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
376 || aux[AT_GID]!=aux[AT_EGID]) {
380 /* Relocate ldso's DYNAMIC pointer and load vector */
381 decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
383 /* Find the program image's DYNAMIC section and decode it */
384 phdr = (void *)aux[AT_PHDR];
385 for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
386 if (phdr->p_type == PT_DYNAMIC) {
387 decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
394 .strings = (void *)(app_dyn[DT_STRTAB]),
395 .hashtab = (void *)(app_dyn[DT_HASH]),
396 .syms = (void *)(app_dyn[DT_SYMTAB]),
397 .dynv = (void *)(phdr->p_vaddr),
402 .base = (void *)aux[AT_BASE],
403 .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
404 .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
405 .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
406 .dynv = (void *)(got[0]),
410 /* Relocate the dynamic linker/libc */
411 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
412 lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app);
413 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
414 lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app);
416 /* At this point the standard library is fully functional */
429 return (void *)aux[AT_ENTRY];