| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <unistd.h> |
| #include <stdint.h> |
| #include <elf.h> |
| #include <sys/mman.h> |
| #include <limits.h> |
| #include <stdint.h> |
| #include <fcntl.h> |
| #include <sys/stat.h> |
| #include <errno.h> |
| #include <limits.h> |
| #include <elf.h> |
| #include <setjmp.h> |
| #include <pthread.h> |
| #include <dlfcn.h> |
| |
| #include "reloc.h" |
| |
| #if ULONG_MAX == 0xffffffff |
| typedef Elf32_Ehdr Ehdr; |
| typedef Elf32_Phdr Phdr; |
| typedef Elf32_Sym Sym; |
| #define R_TYPE(x) ((x)&255) |
| #define R_SYM(x) ((x)>>8) |
| #else |
| typedef Elf64_Ehdr Ehdr; |
| typedef Elf64_Phdr Phdr; |
| typedef Elf64_Sym Sym; |
| #define R_TYPE(x) ((x)&0xffffffff) |
| #define R_SYM(x) ((x)>>32) |
| #endif |
| |
| struct dso |
| { |
| struct dso *next, *prev; |
| int refcnt; |
| size_t *dynv; |
| Sym *syms; |
| uint32_t *hashtab; |
| char *strings; |
| unsigned char *base; |
| unsigned char *map; |
| size_t map_len; |
| dev_t dev; |
| ino_t ino; |
| int global; |
| int relocated; |
| struct dso **deps; |
| char *name; |
| char buf[]; |
| }; |
| |
| static struct dso *head, *tail, *libc; |
| static char *env_path, *sys_path; |
| static int rtld_used; |
| static int runtime; |
| static jmp_buf rtld_fail; |
| static pthread_rwlock_t lock; |
| |
| #define AUX_CNT 15 |
| #define DYN_CNT 34 |
| |
| static void decode_vec(size_t *v, size_t *a, size_t cnt) |
| { |
| memset(a, 0, cnt*sizeof(size_t)); |
| for (; v[0]; v+=2) if (v[0]<cnt) { |
| a[0] |= 1ULL<<v[0]; |
| a[v[0]] = v[1]; |
| } |
| } |
| |
| static uint32_t hash(const char *s) |
| { |
| uint_fast32_t h = 0; |
| while (*s) { |
| h = 16*h + *s++; |
| h ^= h>>24 & 0xf0; |
| } |
| return h & 0xfffffff; |
| } |
| |
| static Sym *lookup(const char *s, uint32_t h, Sym *syms, uint32_t *hashtab, char *strings) |
| { |
| size_t i; |
| for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) { |
| if (!strcmp(s, strings+syms[i].st_name)) |
| return syms+i; |
| } |
| return 0; |
| } |
| |
| #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON) |
| |
| static void *find_sym(struct dso *dso, const char *s, int need_def) |
| { |
| uint32_t h = hash(s); |
| if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1; |
| if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1; |
| for (; dso; dso=dso->next) { |
| Sym *sym; |
| if (!dso->global) continue; |
| sym = lookup(s, h, dso->syms, dso->hashtab, dso->strings); |
| if (sym && (!need_def || sym->st_shndx) && sym->st_value |
| && (1<<(sym->st_info&0xf) & OK_TYPES)) |
| return dso->base + sym->st_value; |
| } |
| return 0; |
| } |
| |
| static void do_relocs(unsigned char *base, size_t *rel, size_t rel_size, size_t stride, Sym *syms, char *strings, struct dso *dso) |
| { |
| Sym *sym; |
| const char *name; |
| size_t sym_val, sym_size; |
| size_t *reloc_addr; |
| void *ctx; |
| int type; |
| int sym_index; |
| |
| for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) { |
| reloc_addr = (void *)(base + rel[0]); |
| type = R_TYPE(rel[1]); |
| sym_index = R_SYM(rel[1]); |
| if (sym_index) { |
| sym = syms + sym_index; |
| name = strings + sym->st_name; |
| ctx = IS_COPY(type) ? dso->next : dso; |
| sym_val = (size_t)find_sym(ctx, name, IS_PLT(type)); |
| if (!sym_val && sym->st_info>>4 != STB_WEAK) { |
| if (runtime) longjmp(rtld_fail, 1); |
| dprintf(2, "%s: symbol not found\n", name); |
| _exit(127); |
| } |
| sym_size = sym->st_size; |
| } |
| do_single_reloc(reloc_addr, type, sym_val, sym_size, base, rel[2]); |
| } |
| } |
| |
| /* A huge hack: to make up for the wastefulness of shared libraries |
| * needing at least a page of dirty memory even if they have no global |
| * data, we reclaim the gaps at the beginning and end of writable maps |
| * and "donate" them to the heap by setting up minimal malloc |
| * structures and then freeing them. */ |
| |
| static void reclaim(unsigned char *base, size_t start, size_t end) |
| { |
| size_t *a, *z; |
| start = start + 6*sizeof(size_t)-1 & -4*sizeof(size_t); |
| end = (end & -4*sizeof(size_t)) - 2*sizeof(size_t); |
| if (start>end || end-start < 4*sizeof(size_t)) return; |
| a = (size_t *)(base + start); |
| z = (size_t *)(base + end); |
| a[-2] = 1; |
| a[-1] = z[0] = end-start + 2*sizeof(size_t) | 1; |
| z[1] = 1; |
| free(a); |
| } |
| |
| static void reclaim_gaps(unsigned char *base, Phdr *ph, size_t phent, size_t phcnt) |
| { |
| for (; phcnt--; ph=(void *)((char *)ph+phent)) { |
| if (ph->p_type!=PT_LOAD) continue; |
| if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue; |
| reclaim(base, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr); |
| reclaim(base, ph->p_vaddr+ph->p_memsz, |
| ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE); |
| } |
| } |
| |
| static void *map_library(int fd, size_t *lenp, unsigned char **basep, size_t *dynp) |
| { |
| Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)]; |
| size_t phsize; |
| size_t addr_min=SIZE_MAX, addr_max=0, map_len; |
| size_t this_min, this_max; |
| off_t off_start; |
| Ehdr *eh; |
| Phdr *ph; |
| unsigned prot; |
| unsigned char *map, *base; |
| size_t dyn; |
| size_t i; |
| |
| ssize_t l = read(fd, buf, sizeof buf); |
| if (l<sizeof *eh) return 0; |
| eh = buf; |
| phsize = eh->e_phentsize * eh->e_phnum; |
| if (phsize + sizeof *eh > l) return 0; |
| if (eh->e_phoff + phsize > l) { |
| l = pread(fd, buf+1, phsize, eh->e_phoff); |
| if (l != phsize) return 0; |
| eh->e_phoff = sizeof *eh; |
| } |
| ph = (void *)((char *)buf + eh->e_phoff); |
| for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) { |
| if (ph->p_type == PT_DYNAMIC) |
| dyn = ph->p_vaddr; |
| if (ph->p_type != PT_LOAD) continue; |
| if (ph->p_vaddr < addr_min) { |
| addr_min = ph->p_vaddr; |
| off_start = ph->p_offset; |
| prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) | |
| ((ph->p_flags&PF_W) ? PROT_WRITE: 0) | |
| ((ph->p_flags&PF_X) ? PROT_EXEC : 0)); |
| } |
| if (ph->p_vaddr+ph->p_memsz > addr_max) { |
| addr_max = ph->p_vaddr+ph->p_memsz; |
| } |
| } |
| if (!dyn) return 0; |
| addr_max += PAGE_SIZE-1; |
| addr_max &= -PAGE_SIZE; |
| addr_min &= -PAGE_SIZE; |
| off_start &= -PAGE_SIZE; |
| map_len = addr_max - addr_min + off_start; |
| /* The first time, we map too much, possibly even more than |
| * the length of the file. This is okay because we will not |
| * use the invalid part; we just need to reserve the right |
| * amount of virtual address space to map over later. */ |
| map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start); |
| if (map==MAP_FAILED) return 0; |
| base = map - addr_min; |
| ph = (void *)((char *)buf + eh->e_phoff); |
| for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) { |
| if (ph->p_type != PT_LOAD) continue; |
| /* Reuse the existing mapping for the lowest-address LOAD */ |
| if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue; |
| this_min = ph->p_vaddr & -PAGE_SIZE; |
| this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE; |
| off_start = ph->p_offset & -PAGE_SIZE; |
| prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) | |
| ((ph->p_flags&PF_W) ? PROT_WRITE: 0) | |
| ((ph->p_flags&PF_X) ? PROT_EXEC : 0)); |
| if (mmap(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED) { |
| munmap(map, map_len); |
| return 0; |
| } |
| if (ph->p_memsz > ph->p_filesz) { |
| size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz; |
| size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE; |
| memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1); |
| 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) { |
| munmap(map, map_len); |
| return 0; |
| } |
| } |
| } |
| if (!runtime) reclaim_gaps(base, (void *)((char *)buf + eh->e_phoff), |
| eh->e_phentsize, eh->e_phnum); |
| *lenp = map_len; |
| *basep = base; |
| *dynp = dyn; |
| return map; |
| } |
| |
| static int path_open(const char *name, const char *search) |
| { |
| char buf[2*NAME_MAX+2]; |
| const char *s=search, *z; |
| int l, fd; |
| for (;;) { |
| while (*s==':') s++; |
| if (!*s) return -1; |
| z = strchr(s, ':'); |
| l = z ? z-s : strlen(s); |
| snprintf(buf, sizeof buf, "%.*s/%s", l, s, name); |
| if ((fd = open(buf, O_RDONLY))>=0) return fd; |
| s += l; |
| } |
| } |
| |
| static struct dso *load_library(const char *name) |
| { |
| unsigned char *base, *map; |
| size_t dyno, map_len; |
| struct dso *p; |
| size_t dyn[DYN_CNT] = {0}; |
| int fd; |
| struct stat st; |
| |
| /* Catch and block attempts to reload the implementation itself */ |
| if (name[0]=='l' && name[1]=='i' && name[2]=='b') { |
| static const char *rp, reserved[] = |
| "c\0pthread\0rt\0m\0dl\0util\0xnet\0"; |
| char *z = strchr(name, '.'); |
| if (z) { |
| size_t l = z-name; |
| for (rp=reserved; *rp && memcmp(name+3, rp, l-3); rp+=strlen(rp)+1); |
| if (*rp) { |
| if (!libc->prev) { |
| tail->next = libc; |
| libc->prev = tail; |
| tail = libc; |
| } |
| return libc; |
| } |
| } |
| } |
| /* Search for the name to see if it's already loaded */ |
| for (p=head->next; p; p=p->next) { |
| if (!strcmp(p->name, name)) { |
| p->refcnt++; |
| return p; |
| } |
| } |
| if (strchr(name, '/')) { |
| fd = open(name, O_RDONLY); |
| } else { |
| if (strlen(name) > NAME_MAX) return 0; |
| fd = -1; |
| if (env_path) fd = path_open(name, env_path); |
| if (fd < 0) { |
| if (!sys_path) { |
| FILE *f = fopen(ETC_LDSO_PATH, "r"); |
| if (f) { |
| if (getline(&sys_path, (size_t[1]){0}, f) > 0) |
| sys_path[strlen(sys_path)-1]=0; |
| fclose(f); |
| } |
| } |
| if (sys_path) fd = path_open(name, sys_path); |
| else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib"); |
| } |
| } |
| if (fd < 0) return 0; |
| if (fstat(fd, &st) < 0) { |
| close(fd); |
| return 0; |
| } |
| for (p=head->next; p; p=p->next) { |
| if (p->dev == st.st_dev && p->ino == st.st_ino) { |
| close(fd); |
| p->refcnt++; |
| return p; |
| } |
| } |
| map = map_library(fd, &map_len, &base, &dyno); |
| close(fd); |
| if (!map) return 0; |
| p = calloc(1, sizeof *p + strlen(name) + 1); |
| if (!p) { |
| munmap(map, map_len); |
| return 0; |
| } |
| |
| p->map = map; |
| p->map_len = map_len; |
| p->base = base; |
| p->dynv = (void *)(base + dyno); |
| decode_vec(p->dynv, dyn, DYN_CNT); |
| |
| p->syms = (void *)(base + dyn[DT_SYMTAB]); |
| p->hashtab = (void *)(base + dyn[DT_HASH]); |
| p->strings = (void *)(base + dyn[DT_STRTAB]); |
| p->dev = st.st_dev; |
| p->ino = st.st_ino; |
| p->refcnt = 1; |
| p->name = p->buf; |
| strcpy(p->name, name); |
| |
| tail->next = p; |
| p->prev = tail; |
| tail = p; |
| |
| return p; |
| } |
| |
| static void load_deps(struct dso *p) |
| { |
| size_t i, ndeps=0; |
| struct dso ***deps = &p->deps, **tmp, *dep; |
| for (; p; p=p->next) { |
| for (i=0; p->dynv[i]; i+=2) { |
| if (p->dynv[i] != DT_NEEDED) continue; |
| dep = load_library(p->strings + p->dynv[i+1]); |
| if (!dep) { |
| if (runtime) longjmp(rtld_fail, 1); |
| dprintf(2, "%s: %m (needed by %s)\n", |
| p->strings + p->dynv[i+1], p->name); |
| _exit(127); |
| } |
| if (runtime) { |
| tmp = realloc(*deps, sizeof(*tmp)*(ndeps+2)); |
| if (!tmp) longjmp(rtld_fail, 1); |
| tmp[ndeps++] = dep; |
| tmp[ndeps] = 0; |
| *deps = tmp; |
| } |
| } |
| } |
| } |
| |
| static void make_global(struct dso *p) |
| { |
| for (; p; p=p->next) p->global = 1; |
| } |
| |
| static void reloc_all(struct dso *p) |
| { |
| size_t dyn[DYN_CNT] = {0}; |
| for (; p; p=p->next) { |
| if (p->relocated) continue; |
| decode_vec(p->dynv, dyn, DYN_CNT); |
| do_relocs(p->base, (void *)(p->base+dyn[DT_JMPREL]), dyn[DT_PLTRELSZ], |
| 2+(dyn[DT_PLTREL]==DT_RELA), p->syms, p->strings, head); |
| do_relocs(p->base, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ], |
| 2, p->syms, p->strings, head); |
| do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ], |
| 3, p->syms, p->strings, head); |
| p->relocated = 1; |
| } |
| } |
| |
| static void free_all(struct dso *p) |
| { |
| struct dso *n; |
| while (p) { |
| n = p->next; |
| if (p->map) free(p); |
| p = n; |
| } |
| } |
| |
| void *__dynlink(int argc, char **argv, size_t *got) |
| { |
| size_t *auxv, aux[AUX_CNT] = {0}; |
| size_t app_dyn[DYN_CNT] = {0}; |
| size_t lib_dyn[DYN_CNT] = {0}; |
| size_t i; |
| Phdr *phdr; |
| Ehdr *ehdr; |
| struct dso lib, app; |
| |
| /* Find aux vector just past environ[] */ |
| for (i=argc+1; argv[i]; i++) |
| if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16)) |
| env_path = argv[i]+16; |
| auxv = (void *)(argv+i+1); |
| |
| decode_vec(auxv, aux, AUX_CNT); |
| |
| /* Only trust user/env if kernel says we're not suid/sgid */ |
| if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID] |
| || aux[AT_GID]!=aux[AT_EGID]) { |
| env_path = 0; |
| } |
| |
| /* Relocate ldso's DYNAMIC pointer and load vector */ |
| decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT); |
| |
| /* Find the program image's DYNAMIC section and decode it */ |
| phdr = (void *)aux[AT_PHDR]; |
| for (i=aux[AT_PHNUM]; i--; phdr=(void *)((char *)phdr + aux[AT_PHENT])) { |
| if (phdr->p_type == PT_DYNAMIC) { |
| decode_vec((void *)phdr->p_vaddr, app_dyn, DYN_CNT); |
| break; |
| } |
| } |
| |
| app = (struct dso){ |
| .base = 0, |
| .strings = (void *)(app_dyn[DT_STRTAB]), |
| .hashtab = (void *)(app_dyn[DT_HASH]), |
| .syms = (void *)(app_dyn[DT_SYMTAB]), |
| .dynv = (void *)(phdr->p_vaddr), |
| .name = argv[0], |
| .global = 1, |
| .next = &lib |
| }; |
| |
| lib = (struct dso){ |
| .base = (void *)aux[AT_BASE], |
| .strings = (void *)(aux[AT_BASE]+lib_dyn[DT_STRTAB]), |
| .hashtab = (void *)(aux[AT_BASE]+lib_dyn[DT_HASH]), |
| .syms = (void *)(aux[AT_BASE]+lib_dyn[DT_SYMTAB]), |
| .dynv = (void *)(got[0]), |
| .name = "libc.so", |
| .global = 1, |
| .relocated = 1 |
| }; |
| |
| /* Relocate the dynamic linker/libc */ |
| do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_REL]), |
| lib_dyn[DT_RELSZ], 2, lib.syms, lib.strings, &app); |
| do_relocs((void *)aux[AT_BASE], (void *)(aux[AT_BASE]+lib_dyn[DT_RELA]), |
| lib_dyn[DT_RELASZ], 3, lib.syms, lib.strings, &app); |
| |
| /* At this point the standard library is fully functional */ |
| |
| reclaim_gaps(app.base, (void *)aux[AT_PHDR], aux[AT_PHENT], aux[AT_PHNUM]); |
| ehdr = (void *)lib.base; |
| reclaim_gaps(lib.base, (void *)(lib.base+ehdr->e_phoff), |
| ehdr->e_phentsize, ehdr->e_phnum); |
| |
| head = tail = &app; |
| libc = &lib; |
| app.next = 0; |
| load_deps(head); |
| |
| make_global(head); |
| reloc_all(head->next); |
| reloc_all(head); |
| |
| if (rtld_used) { |
| runtime = 1; |
| head->next->prev = malloc(sizeof *head); |
| *head->next->prev = *head; |
| head = head->next->prev; |
| libc->prev->next = malloc(sizeof *libc); |
| *libc->prev->next = *libc; |
| libc = libc->prev->next; |
| if (libc->next) libc->next->prev = libc; |
| if (tail == &lib) tail = libc; |
| } else { |
| free_all(head); |
| free(sys_path); |
| } |
| |
| errno = 0; |
| return (void *)aux[AT_ENTRY]; |
| } |
| |
| void *dlopen(const char *file, int mode) |
| { |
| struct dso *p, *orig_tail = tail, *next; |
| size_t i; |
| |
| if (!file) return head; |
| |
| pthread_rwlock_wrlock(&lock); |
| |
| if (setjmp(rtld_fail)) { |
| /* Clean up anything new that was (partially) loaded */ |
| if (p->deps) for (i=0; p->deps[i]; i++) |
| if (p->deps[i]->global < 0) |
| p->deps[i]->global = 0; |
| for (p=orig_tail->next; p; p=next) { |
| next = p->next; |
| munmap(p->map, p->map_len); |
| free(p->deps); |
| free(p); |
| } |
| tail = orig_tail; |
| tail->next = 0; |
| pthread_rwlock_unlock(&lock); |
| return 0; |
| } |
| |
| p = load_library(file); |
| if (!p) goto end; |
| |
| /* First load handling */ |
| if (!p->deps) { |
| load_deps(p); |
| if (p->deps) for (i=0; p->deps[i]; i++) |
| if (!p->deps[i]->global) |
| p->deps[i]->global = -1; |
| if (!p->global) p->global = -1; |
| reloc_all(p); |
| if (p->deps) for (i=0; p->deps[i]; i++) |
| if (p->deps[i]->global < 0) |
| p->deps[i]->global = 0; |
| if (p->global < 0) p->global = 0; |
| } |
| |
| if (mode & RTLD_GLOBAL) { |
| if (p->deps) for (i=0; p->deps[i]; i++) |
| p->deps[i]->global = 1; |
| p->global = 1; |
| } |
| |
| end: |
| pthread_rwlock_unlock(&lock); |
| return p; |
| } |
| |
| static void *do_dlsym(struct dso *p, const char *s) |
| { |
| size_t i; |
| uint32_t h; |
| Sym *sym; |
| if (p == head || p == RTLD_DEFAULT) |
| return find_sym(head, s, 0); |
| h = hash(s); |
| sym = lookup(s, h, p->syms, p->hashtab, p->strings); |
| if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES)) |
| return p->base + sym->st_value; |
| if (p->deps) for (i=0; p->deps[i]; i++) { |
| sym = lookup(s, h, p->deps[i]->syms, |
| p->deps[i]->hashtab, p->deps[i]->strings); |
| if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES)) |
| return p->deps[i]->base + sym->st_value; |
| } |
| return 0; |
| } |
| |
| void *dlsym(void *p, const char *s) |
| { |
| void *res; |
| pthread_rwlock_rdlock(&lock); |
| res = do_dlsym(p, s); |
| pthread_rwlock_unlock(&lock); |
| return res; |
| } |
| |
| char *dlerror() |
| { |
| return "unknown error"; |
| } |
| |
| int dlclose(void *p) |
| { |
| return 0; |
| } |