+#ifdef __PIC__
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <elf.h>
#include <setjmp.h>
#include <pthread.h>
+#include <ctype.h>
#include <dlfcn.h>
#include "reloc.h"
};
static struct dso *head, *tail, *libc;
-static char *env_path, *sys_path;
+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) {
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)
}
}
+/* 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)];
* 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;
}
}
+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;
}
} else {
if (strlen(name) > NAME_MAX) return 0;
fd = -1;
- if (env_path) fd = path_open(name, env_path);
+ 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");
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->refcnt = 1;
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;
dep = load_library(p->strings + p->dynv[i+1]);
*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;
}
}
}
}
-void *__dynlink(int argc, char **argv, size_t *got)
+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++)
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);
/* 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_GID]!=aux[AT_EGID] || aux[AT_SECURE]) {
env_path = 0;
+ env_preload = 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 */
+ /* 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),
- .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 */
-
- head = tail = &app;
- libc = &lib;
- app.next = 0;
- load_deps(head);
-
- make_global(head);
- 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;
- } else {
+ /* 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. */
+ if (env_preload) load_preload(env_preload);
+ load_deps(app);
+ make_global(app);
+ 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);
}
errno = 0;
void *dlopen(const char *file, int mode)
{
- struct dso *p, *orig_tail = tail, *next;
+ struct dso *volatile p, *orig_tail = tail, *next;
size_t i;
if (!file) return head;
}
p = load_library(file);
- if (!p) return 0;
+ if (!p) goto end;
/* First load handling */
if (!p->deps) {
p->global = 1;
}
+end:
pthread_rwlock_unlock(&lock);
-
return p;
}
-static void *do_dlsym(struct dso *p, const char *s)
+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);
return 0;
}
-void *dlsym(void *p, const char *s)
+void *__dlsym(void *p, const char *s, void *ra)
{
void *res;
pthread_rwlock_rdlock(&lock);
- res = do_dlsym(p, s);
+ res = do_dlsym(p, s, ra);
pthread_rwlock_unlock(&lock);
return res;
}
{
return 0;
}
+#endif
projects / musl / blobdiff