+#ifdef __PIC__
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <limits.h>
#include <elf.h>
+#include <setjmp.h>
+#include <pthread.h>
+#include <ctype.h>
+#include <dlfcn.h>
#include "reloc.h"
ino_t ino;
int global;
int relocated;
- char name[];
+ struct dso **deps;
+ char *name;
+ char buf[];
};
static struct dso *head, *tail, *libc;
-static int trust_env;
+static char *env_path, *sys_path, *r_path;
+static int rtld_used;
+static int runtime;
+static jmp_buf rtld_fail;
+static pthread_rwlock_t lock;
-#define AUX_CNT 15
+#define AUX_CNT 24
#define DYN_CNT 34
static void decode_vec(size_t *v, size_t *a, size_t cnt)
}
}
-static uint32_t hash(const char *s)
+static uint32_t hash(const char *s0)
{
+ const unsigned char *s = (void *)s0;
uint_fast32_t h = 0;
while (*s) {
h = 16*h + *s++;
}
#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
+#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK)
static void *find_sym(struct dso *dso, const char *s, int need_def)
{
uint32_t h = hash(s);
+ void *def = 0;
+ 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 = lookup(s, h, dso->syms, dso->hashtab, dso->strings);
+ 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;
+ && (1<<(sym->st_info&0xf) & OK_TYPES)
+ && (1<<(sym->st_info>>4) & OK_BINDS)) {
+ if (def && sym->st_info>>4 == STB_WEAK) continue;
+ def = dso->base + sym->st_value;
+ if (sym->st_info>>4 == STB_GLOBAL) break;
+ }
}
- return 0;
+ return def;
}
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 = syms + sym_index;
name = strings + sym->st_name;
ctx = IS_COPY(type) ? dso->next : dso;
- sym_val = (size_t)find_sym(ctx, name, 1);
+ 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)
{
- size_t buf[896/sizeof(size_t)];
+ 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;
ssize_t l = read(fd, buf, sizeof buf);
if (l<sizeof *eh) return 0;
- eh = (void *)buf;
+ 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+sizeof *eh, phsize, eh->e_phoff);
+ l = pread(fd, buf+1, phsize, eh->e_phoff);
if (l != phsize) return 0;
eh->e_phoff = sizeof *eh;
}
* 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(0, map_len, prot, MAP_PRIVATE, fd, off_start);
+ 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=0; ((size_t *)(base+dyn))[i]; i+=2)
+ if (((size_t *)(base+dyn))[i]==DT_TEXTREL) {
+ mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC);
+ break;
+ }
+ 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 void decode_dyn(struct dso *p)
+{
+ size_t dyn[DYN_CNT] = {0};
+ decode_vec(p->dynv, dyn, DYN_CNT);
+ p->syms = (void *)(p->base + dyn[DT_SYMTAB]);
+ p->hashtab = (void *)(p->base + dyn[DT_HASH]);
+ p->strings = (void *)(p->base + dyn[DT_STRTAB]);
+}
+
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;
if (!libc->prev) {
tail->next = libc;
libc->prev = tail;
- tail = libc;
+ tail = libc->next ? libc->next : libc;
}
return libc;
}
return p;
}
}
- if (name[0] == '/') {
+ if (strchr(name, '/')) {
fd = open(name, O_RDONLY);
} else {
- static const char path[] = "/lib/\0/usr/local/lib/\0/usr/lib/\0";
- const char *s;
- char buf[NAME_MAX+32];
- if (strlen(name) > NAME_MAX || strchr(name, '/')) return 0;
- for (s=path; *s; s+=strlen(s)+1) {
- strcpy(buf, s);
- strcat(buf, name);
- if ((fd = open(buf, O_RDONLY))>=0) break;
+ if (strlen(name) > NAME_MAX) return 0;
+ fd = -1;
+ if (r_path) fd = path_open(name, r_path);
+ if (fd < 0 && 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;
p->map_len = map_len;
p->base = base;
p->dynv = (void *)(base + dyno);
- decode_vec(p->dynv, dyn, DYN_CNT);
+ decode_dyn(p);
- 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->global = 1;
p->refcnt = 1;
+ p->name = p->buf;
strcpy(p->name, name);
tail->next = p;
static void load_deps(struct dso *p)
{
- size_t i;
+ 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_RPATH) continue;
+ r_path = (void *)(p->strings + p->dynv[i+1]);
+ }
for (i=0; p->dynv[i]; i+=2) {
if (p->dynv[i] != DT_NEEDED) continue;
- load_library(p->strings + p->dynv[i+1]);
+ 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;
+ }
}
+ r_path = 0;
+ }
+}
+
+static void load_preload(char *s)
+{
+ int tmp;
+ char *z;
+ for (z=s; *z; s=z) {
+ for ( ; *s && isspace(*s); s++);
+ for (z=s; *z && !isspace(*z); z++);
+ tmp = *z;
+ *z = 0;
+ load_library(s);
+ *z = 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};
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, p);
+ 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, p);
+ 2, p->syms, p->strings, head);
do_relocs(p->base, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ],
- 3, p->syms, p->strings, p);
+ 3, p->syms, p->strings, head);
p->relocated = 1;
}
}
-void *__dynlink(int argc, char **argv, size_t *got)
+static void free_all(struct dso *p)
+{
+ struct dso *n;
+ while (p) {
+ n = p->next;
+ if (p->map) free(p);
+ p = n;
+ }
+}
+
+static size_t find_dyn(Phdr *ph, size_t cnt, size_t stride)
+{
+ for (; cnt--; ph = (void *)((char *)ph + stride))
+ if (ph->p_type == PT_DYNAMIC)
+ return ph->p_vaddr;
+ return 0;
+}
+
+void *__dynlink(int argc, char **argv)
{
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;
- struct dso lib, app;
+ Ehdr *ehdr;
+ static struct dso builtin_dsos[3];
+ struct dso *const app = builtin_dsos+0;
+ struct dso *const lib = builtin_dsos+1;
+ struct dso *const vdso = builtin_dsos+2;
+ char *env_preload=0;
/* Find aux vector just past environ[] */
- for (i=argc+1; argv[i]; i++);
+ for (i=argc+1; argv[i]; i++)
+ if (!memcmp(argv[i], "LD_LIBRARY_PATH=", 16))
+ env_path = argv[i]+16;
+ else if (!memcmp(argv[i], "LD_PRELOAD=", 11))
+ env_preload = argv[i]+11;
auxv = (void *)(argv+i+1);
decode_vec(auxv, aux, AUX_CNT);
- /* Relocate ldso's DYNAMIC pointer and load vector */
- decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_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] || aux[AT_SECURE]) {
+ env_path = 0;
+ env_preload = 0;
+ }
- /* Find the program image's DYNAMIC section and decode it */
+ /* The dynamic linker load address is passed by the kernel
+ * in the AUX vector, so this is easy. */
+ lib->base = (void *)aux[AT_BASE];
+ lib->name = "libc.so";
+ lib->global = 1;
+ ehdr = (void *)lib->base;
+ lib->dynv = (void *)(lib->base + find_dyn(
+ (void *)(aux[AT_BASE]+ehdr->e_phoff),
+ ehdr->e_phnum, ehdr->e_phentsize));
+ decode_dyn(lib);
+
+ /* Find load address of the main program, via AT_PHDR vs PT_PHDR. */
+ app->base = 0;
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;
+ for (i=aux[AT_PHNUM]; i; i--, phdr=(void *)((char *)phdr + aux[AT_PHENT])) {
+ if (phdr->p_type == PT_PHDR)
+ app->base = (void *)(aux[AT_PHDR] - phdr->p_vaddr);
+ }
+ app->name = argv[0];
+ app->global = 1;
+ app->dynv = (void *)(app->base + find_dyn(
+ (void *)aux[AT_PHDR], aux[AT_PHNUM], aux[AT_PHENT]));
+ decode_dyn(app);
+
+ /* Attach to vdso, if provided by the kernel */
+ for (i=0; auxv[i]; i+=2) {
+ size_t vdso_base = auxv[i+1];
+ if (auxv[i] != AT_SYSINFO_EHDR) continue;
+ ehdr = (void *)vdso_base;
+ phdr = (void *)(vdso_base + ehdr->e_phoff);
+ for (i=ehdr->e_phnum; i; i--, phdr=(void *)((char *)phdr + ehdr->e_phentsize)) {
+ if (phdr->p_type == PT_DYNAMIC)
+ vdso->dynv = (void *)(vdso_base + phdr->p_offset);
+ if (phdr->p_type == PT_LOAD)
+ vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
}
+ vdso->name = "linux-gate.so.1";
+ vdso->global = 1;
+ decode_dyn(vdso);
+ vdso->prev = lib;
+ lib->next = vdso;
+ 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),
- .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]),
- .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 */
+ /* Initial dso chain consists only of the app. We temporarily
+ * append the dynamic linker/libc so we can relocate it, then
+ * restore the initial chain in preparation for loading third
+ * party libraries (preload/needed). */
+ head = tail = app;
+ libc = lib;
+ app->next = lib;
+ reloc_all(lib);
+ app->next = 0;
+
+ /* PAST THIS POINT, ALL LIBC INTERFACES ARE FULLY USABLE. */
+
+ /* Donate unused parts of app and library mapping to malloc */
+ 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);
+
+ /* Load preload/needed libraries, add their symbols to the global
+ * namespace, and perform all remaining relocations. The main
+ * program must be relocated LAST since it may contain copy
+ * relocations which depend on libraries' relocations. */
+ if (env_preload) load_preload(env_preload);
+ load_deps(app);
+ make_global(app);
+ reloc_all(app->next);
+ reloc_all(app);
+
+ /* Switch to runtime mode: any further failures in the dynamic
+ * linker are a reportable failure rather than a fatal startup
+ * error. If the dynamic loader (dlopen) will not be used, free
+ * all memory used by the dynamic linker. */
+ runtime = 1;
+ if (!rtld_used) {
+ free_all(head);
+ free(sys_path);
+ reclaim((void *)builtin_dsos, 0, sizeof builtin_dsos);
+ }
- /* Only trust user/env if kernel says we're not suid/sgid */
- trust_env = (aux[0]&0x7800)==0x7800
- && aux[AT_UID]==aux[AT_EUID]
- && aux[AT_GID]==aux[AT_EGID];
+ errno = 0;
+ return (void *)aux[AT_ENTRY];
+}
- head = tail = &app;
- libc = &lib;
- app.next = 0;
- load_deps(head);
+void *dlopen(const char *file, int mode)
+{
+ struct dso *volatile p, *orig_tail = tail, *next;
+ size_t i;
- reloc_all(head);
+ if (!file) return head;
- errno = 0;
- return (void *)aux[AT_ENTRY];
+ 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, void *ra)
+{
+ size_t i;
+ uint32_t h;
+ Sym *sym;
+ if (p == RTLD_NEXT) {
+ for (p=head; p && (unsigned char *)ra-p->map>p->map_len; p=p->next);
+ if (!p) p=head;
+ p=p->next;
+ }
+ 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 *ra)
+{
+ void *res;
+ pthread_rwlock_rdlock(&lock);
+ res = do_dlsym(p, s, ra);
+ pthread_rwlock_unlock(&lock);
+ return res;
+}
+#else
+void *dlopen(const char *file, int mode)
+{
+ return 0;
+}
+void *__dlsym(void *p, const char *s, void *ra)
+{
+ return 0;
+}
+#endif
+
+char *dlerror()
+{
+ return "unknown error";
+}
+
+int dlclose(void *p)
+{
+ return 0;
}
projects / musl / blobdiff