#include <ctype.h>
#include <dlfcn.h>
+static int errflag;
+static char errbuf[128];
+
+#ifdef __PIC__
+
#include "reloc.h"
#if ULONG_MAX == 0xffffffff
#define R_SYM(x) ((x)>>32)
#endif
-struct dso
-{
+struct debug {
+ int ver;
+ void *head;
+ void (*bp)(void);
+ int state;
+ void *base;
+};
+
+struct dso {
+ unsigned char *base;
+ char *name;
+ size_t *dynv;
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;
+ char global;
+ char relocated;
+ char constructed;
struct dso **deps;
- char *name;
char buf[];
};
+void __init_ssp(size_t *);
+
static struct dso *head, *tail, *libc;
static char *env_path, *sys_path, *r_path;
static int rtld_used;
+static int ssp_used;
static int runtime;
static jmp_buf rtld_fail;
static pthread_rwlock_t lock;
+static struct debug debug;
+
+struct debug *_dl_debug_addr = &debug;
#define AUX_CNT 24
#define DYN_CNT 34
}
}
-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++;
void *def = 0;
if (h==0x6b366be && !strcmp(s, "dlopen")) rtld_used = 1;
if (h==0x6b3afd && !strcmp(s, "dlsym")) rtld_used = 1;
+ if (h==0x595a4cc && !strcmp(s, "__stack_chk_fail")) ssp_used = 1;
for (; dso; dso=dso->next) {
Sym *sym;
if (!dso->global) continue;
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) {
+ snprintf(errbuf, sizeof errbuf,
+ "Error relocating %s: %s: symbol not found",
+ dso->name, name);
if (runtime) longjmp(rtld_fail, 1);
- dprintf(2, "%s: symbol not found\n", name);
+ dprintf(2, "%s\n", errbuf);
_exit(127);
}
sym_size = sym->st_size;
}
}
+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;
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;
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",
+ snprintf(errbuf, sizeof errbuf,
+ "Error loading shared library %s: %m (needed by %s)",
p->strings + p->dynv[i+1], p->name);
+ if (runtime) longjmp(rtld_fail, 1);
+ dprintf(2, "%s\n", errbuf);
_exit(127);
}
if (runtime) {
}
}
-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;
+}
+
+static void do_init_fini(struct dso *p)
+{
+ size_t dyn[DYN_CNT] = {0};
+ for (; p; p=p->prev) {
+ if (p->constructed) return;
+ decode_vec(p->dynv, dyn, DYN_CNT);
+ if (dyn[0] & (1<<DT_FINI))
+ atexit((void (*)(void))(p->base + dyn[DT_FINI]));
+ if (dyn[0] & (1<<DT_INIT))
+ ((void (*)(void))(p->base + dyn[DT_INIT]))();
+ p->constructed = 1;
+ }
+}
+
+void _dl_debug_state(void)
+{
+}
+
+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 vdso_dyn[DYN_CNT] = {0};
size_t i;
Phdr *phdr;
Ehdr *ehdr;
struct dso *const app = builtin_dsos+0;
struct dso *const lib = builtin_dsos+1;
struct dso *const vdso = builtin_dsos+2;
- size_t vdso_base=0;
char *env_preload=0;
/* Find aux vector just past environ[] */
decode_vec(auxv, aux, AUX_CNT);
- for (i=0; auxv[i]; i+=2) {
- if (auxv[i]==AT_SYSINFO_EHDR) {
- vdso_base = auxv[i+1];
- break;
- }
- }
-
/* 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_preload = 0;
}
- /* Relocate ldso's DYNAMIC pointer and load vector */
- decode_vec((void *)(got[0] += aux[AT_BASE]), lib_dyn, DYN_CNT);
+ /* 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 the program image's DYNAMIC section and decode it */
+ /* 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 = (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
- };
-
- if (vdso_base) {
+ app->name = argv[0];
+ app->global = 1;
+ app->constructed = 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_LOAD)
vdso->base = (void *)(vdso_base - phdr->p_vaddr + phdr->p_offset);
}
- decode_vec(vdso->dynv, vdso_dyn, DYN_CNT);
- vdso->syms = (void *)(vdso->base + vdso_dyn[DT_SYMTAB]);
- vdso->hashtab = (void *)(vdso->base + vdso_dyn[DT_HASH]);
- vdso->strings = (void *)(vdso->base + vdso_dyn[DT_STRTAB]);
vdso->name = "linux-gate.so.1";
vdso->global = 1;
-
+ decode_dyn(vdso);
vdso->prev = lib;
lib->next = vdso;
+ break;
}
- /* 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);
+ /* 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;
- /* At this point the standard library is fully functional */
+ /* 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);
- head = tail = app;
- libc = lib;
- app->next = 0;
+ /* 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(head);
+ 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;
- make_global(head);
- reloc_all(head->next);
- reloc_all(head);
+ for (i=0; app->dynv[i]; i+=2)
+ if (app->dynv[i]==DT_DEBUG)
+ app->dynv[i+1] = (size_t)&debug;
+ debug.ver = 1;
+ debug.bp = _dl_debug_state;
+ debug.head = head;
+ debug.base = lib->base;
+ debug.state = 0;
+ _dl_debug_state();
+
+ if (ssp_used) __init_ssp(auxv);
+
+ do_init_fini(tail);
- runtime = 1;
if (!rtld_used) {
free_all(head);
free(sys_path);
{
struct dso *volatile p, *orig_tail = tail, *next;
size_t i;
+ int cs;
if (!file) return head;
+ pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
pthread_rwlock_wrlock(&lock);
if (setjmp(rtld_fail)) {
}
tail = orig_tail;
tail->next = 0;
- pthread_rwlock_unlock(&lock);
- return 0;
- }
+ p = 0;
+ errflag = 1;
+ goto end;
+ } else p = load_library(file);
- p = load_library(file);
- if (!p) goto end;
+ if (!p) {
+ snprintf(errbuf, sizeof errbuf,
+ "Error loading shared library %s: %m", file);
+ errflag = 1;
+ goto end;
+ }
/* First load handling */
if (!p->deps) {
p->global = 1;
}
+ _dl_debug_state();
+
+ do_init_fini(tail);
end:
pthread_rwlock_unlock(&lock);
+ pthread_setcancelstate(cs, 0);
return p;
}
if (!p) p=head;
p=p->next;
}
- if (p == head || p == RTLD_DEFAULT)
- return find_sym(head, s, 0);
+ if (p == head || p == RTLD_DEFAULT) {
+ void *res = find_sym(head, s, 0);
+ if (!res) errflag = 1;
+ return res;
+ }
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))
if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
return p->deps[i]->base + sym->st_value;
}
+ errflag = 1;
+ snprintf(errbuf, sizeof errbuf, "Symbol not found: %s", s);
return 0;
}
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";
+ if (!errflag) return 0;
+ errflag = 0;
+ return errbuf;
}
int dlclose(void *p)
projects / musl / blobdiff