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;
55 static void decode_vec(size_t *v, size_t *a, size_t cnt)
57 memset(a, 0, cnt*sizeof(size_t));
58 for (; v[0]; v+=2) if (v[0]<cnt) {
64 static uint32_t hash(const char *s)
74 static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings)
77 for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
78 if (!strcmp(s, strings+syms[i].st_name))
84 #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
86 static void *find_sym(struct dso *dso, const char *s, int need_def)
89 for (; dso; dso=dso->next) {
90 Sym *sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
91 if (sym && (!need_def || sym->st_shndx) && sym->st_value
92 && (1<<(sym->st_info&0xf) & OK_TYPES))
93 return dso->base + sym->st_value;
98 static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso)
102 size_t sym_val, sym_size;
108 for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
109 reloc_addr = (void *)(base + rel[0]);
110 type = R_TYPE(rel[1]);
111 sym_index = R_SYM(rel[1]);
113 sym = syms + sym_index;
114 name = strings + sym->st_name;
115 ctx = IS_COPY(type) ? dso->next : dso;
116 sym_val = (size_t)find_sym(ctx, name, 1);
117 sym_size = sym->st_size;
119 do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]);
123 static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp)
125 size_t buf[896/sizeof(size_t)];
127 size_t addr_min=SIZE_MAX, addr_max=0, map_len;
128 size_t this_min, this_max;
133 unsigned char *map, *base;
137 ssize_t l = read(fd, buf, sizeof buf);
138 if (l<sizeof *eh) return 0;
140 phsize = eh->e_phentsize * eh->e_phnum;
141 if (phsize + sizeof *eh > l) return 0;
142 if (eh->e_phoff + phsize > l) {
143 l = pread(fd, buf+sizeof *eh, phsize, eh->e_phoff);
144 if (l != phsize) return 0;
145 eh->e_phoff = sizeof *eh;
147 ph = (void *)((char *)buf + eh->e_phoff);
148 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
149 if (ph->p_type == PT_DYNAMIC)
151 if (ph->p_type != PT_LOAD) continue;
152 if (ph->p_vaddr < addr_min) {
153 addr_min = ph->p_vaddr;
154 off_start = ph->p_offset;
155 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
156 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
157 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
159 if (ph->p_vaddr+ph->p_memsz > addr_max) {
160 addr_max = ph->p_vaddr+ph->p_memsz;
164 addr_max += PAGE_SIZE-1;
165 addr_max &= -PAGE_SIZE;
166 addr_min &= -PAGE_SIZE;
167 off_start &= -PAGE_SIZE;
168 map_len = addr_max - addr_min + off_start;
169 /* The first time, we map too much, possibly even more than
170 * the length of the file. This is okay because we will not
171 * use the invalid part; we just need to reserve the right
172 * amount of virtual address space to map over later. */
173 map = mmap(0, map_len, prot, MAP_PRIVATE, fd, off_start);
174 if (map==MAP_FAILED) return 0;
175 base = map - addr_min;
176 ph = (void *)((char *)buf + eh->e_phoff);
177 for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
178 if (ph->p_type != PT_LOAD) continue;
179 /* Reuse the existing mapping for the lowest-address LOAD */
180 if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
181 this_min = ph->p_vaddr & -PAGE_SIZE;
182 this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
183 off_start = ph->p_offset & -PAGE_SIZE;
184 prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
185 ((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
186 ((ph->p_flags&PF_X) ? PROT_EXEC : 0));
187 if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) {
188 munmap(map, map_len);
191 if (ph->p_memsz > ph->p_filesz) {
192 size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
193 size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
194 memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
195 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) {
196 munmap(map, map_len);
207 static struct dso *load_library(const char *name)
209 unsigned char *base, *map;
210 size_t dyno, map_len;
212 size_t dyn[DYN_CNT] = {0};
216 /* Catch and block attempts to reload the implementation itself */
217 if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
218 static const char *rp, reserved[] =
219 "c\0pthread\0rt\0m\0dl\0util\0xnet\0";
220 char *z = strchr(name, '.');
223 for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1);
234 /* Search for the name to see if it's already loaded */
235 for (p=head->next; p; p=p->next) {
236 if (!strcmp(p->name, name)) {
241 if (name[0] == '/') {
242 fd = open(name, O_RDONLY);
244 static const char path[] = "/lib/\0/usr/local/lib/\0/usr/lib/\0";
246 char buf[NAME_MAX+32];
247 if (strlen(name) > NAME_MAX || strchr(name, '/')) return 0;
248 for (s=path; *s; s+=strlen(s)+1) {
251 if ((fd = open(buf, O_RDONLY))>=0) break;
254 if (fd < 0) return 0;
255 if (fstat(fd, &st) < 0) {
259 for (p=head->next; p; p=p->next) {
260 if (p->dev == st.st_dev && p->ino == st.st_ino) {
266 map = map_library(fd, &map_len, &base, &dyno);
269 p = calloc(1, sizeof *p + strlen(name) + 1);
271 munmap(map, map_len);
276 p->map_len = map_len;
278 p->dynv = (void *)(base + dyno);
279 decode_vec(p->dynv, dyn, DYN_CNT);
281 p->syms = (void *)(base + dyn[DT_SYMTAB]);
282 p->hashtab = (void *)(base + dyn[DT_HASH]);
283 p->strings = (void *)(base + dyn[DT_STRTAB]);
288 strcpy(p->name, name);
297 static void load_deps(struct dso *p)
300 for (; p; p=p->next) {
301 for (i=0; p->dynv[i]; i+=2) {
302 if (p->dynv[i] != DT_NEEDED) continue;
303 load_library(p->strings + p->dynv[i+1]);
308 static void reloc_all(struct dso *p)
310 size_t dyn[DYN_CNT] = {0};
311 for (; p; p=p->next) {
312 if (p->relocated) continue;
313 decode_vec(p->dynv, dyn, DYN_CNT);
314 do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ],
315 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, p);
316 do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ],
317 2, p->syms, p->strings, p);
318 do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
319 3, p->syms, p->strings, p);
323 void *__dynlink(int argc, char **argv, size_t *got)
325 size_t *auxv, aux[AUX_CNT] = {0};
326 size_t app_dyn[DYN_CNT] = {0};
327 size_t lib_dyn[DYN_CNT] = {0};
332 /* Find aux vector just past environ[] */
333 for (i=argc+1; argv[i]; i++);
334 auxv = (void *)(argv+i+1);
336 decode_vec(auxv, aux, AUX_CNT);
338 /* Relocate ldso's DYNAMIC pointer and load vector */
339 decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
341 /* Find the program image's DYNAMIC section and decode it */
342 phdr = (void *)aux[AT_PHDR];
343 for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
344 if (phdr->p_type == PT_DYNAMIC) {
345 decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT);
352 .strings = (void *)(app_dyn[DT_STRTAB]),
353 .hashtab = (void *)(app_dyn[DT_HASH]),
354 .syms = (void *)(app_dyn[DT_SYMTAB]),
355 .dynv = (void *)(phdr->p_vaddr),
360 .base = (void *)aux[AT_BASE],
361 .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]),
362 .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]),
363 .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]),
364 .dynv = (void *)(got[0]),
368 /* Relocate the dynamic linker/libc */
369 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]),
370 lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app);
371 do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]),
372 lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app);
374 /* At this point the standard library is fully functional */
384 return (void *)aux[AT_ENTRY];