fix dynamic linker handling of empty path file or error reading path file
[musl] / src / ldso / dynlink.c
index e09f071..eac07d9 100644 (file)
 #include <errno.h>
 #include <limits.h>
 #include <elf.h>
+#include <link.h>
 #include <setjmp.h>
 #include <pthread.h>
 #include <ctype.h>
 #include <dlfcn.h>
 #include "pthread_impl.h"
 #include "libc.h"
-#undef libc
 
 static int errflag;
 static char errbuf[128];
@@ -40,6 +40,9 @@ typedef Elf64_Sym Sym;
 #define R_SYM(x) ((x)>>32)
 #endif
 
+#define MAXP2(a,b) (-(-(a)&-(b)))
+#define ALIGN(x,y) ((x)+(y)-1 & -(y))
+
 struct debug {
        int ver;
        void *head;
@@ -54,6 +57,8 @@ struct dso {
        size_t *dynv;
        struct dso *next, *prev;
 
+       Phdr *phdr;
+       int phnum;
        int refcnt;
        Sym *syms;
        uint32_t *hashtab;
@@ -69,6 +74,10 @@ struct dso {
        struct dso **deps;
        void *tls_image;
        size_t tls_len, tls_size, tls_align, tls_id, tls_offset;
+       void **new_dtv;
+       unsigned char *new_tls;
+       int new_dtv_idx, new_tls_idx;
+       struct dso *fini_next;
        char *shortname;
        char buf[];
 };
@@ -83,21 +92,23 @@ struct symdef {
 void __init_ssp(size_t *);
 void *__install_initial_tls(void *);
 
-static struct dso *head, *tail, *libc;
+static struct dso *head, *tail, *ldso, *fini_head;
 static char *env_path, *sys_path, *r_path;
+static unsigned long long gencnt;
 static int ssp_used;
 static int runtime;
 static int ldd_mode;
 static int ldso_fail;
+static int noload;
 static jmp_buf rtld_fail;
 static pthread_rwlock_t lock;
 static struct debug debug;
-static size_t *auxv;
-static size_t tls_cnt, tls_size;
+static size_t tls_cnt, tls_offset, tls_align = 4*sizeof(size_t);
+static pthread_mutex_t init_fini_lock = { ._m_type = PTHREAD_MUTEX_RECURSIVE };
 
 struct debug *_dl_debug_addr = &debug;
 
-#define AUX_CNT 24
+#define AUX_CNT 38
 #define DYN_CNT 34
 
 static void decode_vec(size_t *v, size_t *a, size_t cnt)
@@ -201,14 +212,20 @@ static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
                        if (!h) h = sysv_hash(s);
                        sym = sysv_lookup(s, h, dso);
                }
-               if (sym && (!need_def || sym->st_shndx) && sym->st_value
-                && (1<<(sym->st_info&0xf) & OK_TYPES)
-                && (1<<(sym->st_info>>4) & OK_BINDS)) {
-                       if (def.sym && sym->st_info>>4 == STB_WEAK) continue;
-                       def.sym = sym;
-                       def.dso = dso;
-                       if (sym->st_info>>4 == STB_GLOBAL) break;
-               }
+               if (!sym) continue;
+               if (!sym->st_shndx)
+                       if (need_def || (sym->st_info&0xf) == STT_TLS)
+                               continue;
+               if (!sym->st_value)
+                       if ((sym->st_info&0xf) != STT_TLS)
+                               continue;
+               if (!(1<<(sym->st_info&0xf) & OK_TYPES)) continue;
+               if (!(1<<(sym->st_info>>4) & OK_BINDS)) continue;
+
+               if (def.sym && sym->st_info>>4 == STB_WEAK) continue;
+               def.sym = sym;
+               def.dso = dso;
+               if (sym->st_info>>4 == STB_GLOBAL) break;
        }
        return def;
 }
@@ -310,6 +327,8 @@ static void *map_library(int fd, struct dso *dso)
                eh->e_phoff = sizeof *eh;
        }
        ph = (void *)((char *)buf + eh->e_phoff);
+       dso->phdr = ph;
+       dso->phnum = eh->e_phnum;
        for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
                if (ph->p_type == PT_DYNAMIC)
                        dyn = ph->p_vaddr;
@@ -384,16 +403,16 @@ error:
        return 0;
 }
 
-static int path_open(const char *name, const char *search, char *buf, size_t buf_size)
+static int path_open(const char *name, const char *s, char *buf, size_t buf_size)
 {
-       const char *s=search, *z;
-       int l, fd;
+       size_t l;
+       int fd;
        for (;;) {
-               while (*s==':') s++;
-               if (!*s) return -1;
-               z = strchr(s, ':');
-               l = z ? z-s : strlen(s);
-               snprintf(buf, buf_size, "%.*s/%s", l, s, name);
+               s += strspn(s, ":\n");
+               l = strcspn(s, ":\n");
+               if (l-1 >= INT_MAX) return -1;
+               if (snprintf(buf, buf_size, "%.*s/%s", (int)l, s, name) >= buf_size)
+                       continue;
                if ((fd = open(buf, O_RDONLY|O_CLOEXEC))>=0) return fd;
                s += l;
        }
@@ -415,11 +434,12 @@ static struct dso *load_library(const char *name)
 {
        char buf[2*NAME_MAX+2];
        const char *pathname;
-       unsigned char *base, *map;
-       size_t dyno, map_len;
+       unsigned char *map;
        struct dso *p, temp_dso = {0};
        int fd;
        struct stat st;
+       size_t alloc_size;
+       int n_th = 0;
 
        /* Catch and block attempts to reload the implementation itself */
        if (name[0]=='l' && name[1]=='i' && name[2]=='b') {
@@ -430,12 +450,12 @@ static struct dso *load_library(const char *name)
                        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->next ? libc->next : libc;
+                               if (!ldso->prev) {
+                                       tail->next = ldso;
+                                       ldso->prev = tail;
+                                       tail = ldso->next ? ldso->next : ldso;
                                }
-                               return libc;
+                               return ldso;
                        }
                }
        }
@@ -458,13 +478,15 @@ static struct dso *load_library(const char *name)
                        if (!sys_path) {
                                FILE *f = fopen(ETC_LDSO_PATH, "rbe");
                                if (f) {
-                                       if (getline(&sys_path, (size_t[1]){0}, f) > 0)
-                                               sys_path[strlen(sys_path)-1]=0;
+                                       if (getdelim(&sys_path, (size_t[1]){0}, 0, f) <= 0) {
+                                               if (sys_path) free(sys_path);
+                                               sys_path = "";
+                                       }
                                        fclose(f);
                                }
                        }
-                       if (sys_path) fd = path_open(name, sys_path, buf, sizeof buf);
-                       else fd = path_open(name, "/lib:/usr/local/lib:/usr/lib", buf, sizeof buf);
+                       if (!sys_path) sys_path = "/lib:/usr/local/lib:/usr/lib";
+                       fd = path_open(name, sys_path, buf, sizeof buf);
                }
                pathname = buf;
        }
@@ -478,27 +500,37 @@ static struct dso *load_library(const char *name)
                        /* If this library was previously loaded with a
                         * pathname but a search found the same inode,
                         * setup its shortname so it can be found by name. */
-                       if (!p->shortname) p->shortname = strrchr(p->name, '/')+1;
+                       if (!p->shortname && pathname != name)
+                               p->shortname = strrchr(p->name, '/')+1;
                        close(fd);
                        p->refcnt++;
                        return p;
                }
        }
-       map = map_library(fd, &temp_dso);
+       map = noload ? 0 : map_library(fd, &temp_dso);
        close(fd);
        if (!map) return 0;
-       p = malloc(sizeof *p + strlen(pathname) + 1);
+
+       /* Allocate storage for the new DSO. When there is TLS, this
+        * storage must include a reservation for all pre-existing
+        * threads to obtain copies of both the new TLS, and an
+        * extended DTV capable of storing an additional slot for
+        * the newly-loaded DSO. */
+       alloc_size = sizeof *p + strlen(pathname) + 1;
+       if (runtime && temp_dso.tls_image) {
+               size_t per_th = temp_dso.tls_size + temp_dso.tls_align
+                       + sizeof(void *) * (tls_cnt+3);
+               n_th = libc.threads_minus_1 + 1;
+               if (n_th > SSIZE_MAX / per_th) alloc_size = SIZE_MAX;
+               else alloc_size += n_th * per_th;
+       }
+       p = calloc(1, alloc_size);
        if (!p) {
-               munmap(map, map_len);
+               munmap(map, temp_dso.map_len);
                return 0;
        }
        memcpy(p, &temp_dso, sizeof temp_dso);
        decode_dyn(p);
-       if (p->tls_image) {
-               p->tls_id = ++tls_cnt;
-               tls_size += p->tls_size + p->tls_align + 8*sizeof(size_t) - 1
-                       & -4*sizeof(size_t);
-       }
        p->dev = st.st_dev;
        p->ino = st.st_ino;
        p->refcnt = 1;
@@ -506,12 +538,34 @@ static struct dso *load_library(const char *name)
        strcpy(p->name, pathname);
        /* Add a shortname only if name arg was not an explicit pathname. */
        if (pathname != name) p->shortname = strrchr(p->name, '/')+1;
+       if (p->tls_image) {
+               if (runtime && !__pthread_self_init()) {
+                       munmap(map, p->map_len);
+                       free(p);
+                       return 0;
+               }
+               p->tls_id = ++tls_cnt;
+               tls_align = MAXP2(tls_align, p->tls_align);
+#ifdef TLS_ABOVE_TP
+               p->tls_offset = tls_offset + ( (tls_align-1) &
+                       -(tls_offset + (uintptr_t)p->tls_image) );
+               tls_offset += p->tls_size;
+#else
+               tls_offset += p->tls_size + p->tls_align - 1;
+               tls_offset -= (tls_offset + (uintptr_t)p->tls_image)
+                       & (p->tls_align-1);
+               p->tls_offset = tls_offset;
+#endif
+               p->new_dtv = (void *)(-sizeof(size_t) &
+                       (uintptr_t)(p->name+strlen(p->name)+sizeof(size_t)));
+               p->new_tls = (void *)(p->new_dtv + n_th*(tls_cnt+1));
+       }
 
        tail->next = p;
        p->prev = tail;
        tail = p;
 
-       if (ldd_mode) dprintf(1, "\t%s => %s (%p)\n", name, pathname, base);
+       if (ldd_mode) dprintf(1, "\t%s => %s (%p)\n", name, pathname, p->base);
 
        return p;
 }
@@ -585,16 +639,6 @@ static void reloc_all(struct dso *p)
        }
 }
 
-static void free_all(struct dso *p)
-{
-       struct dso *n;
-       while (p) {
-               n = p->next;
-               if (p->map && p!=libc && p!=head) free(p);
-               p = n;
-       }
-}
-
 static size_t find_dyn(Phdr *ph, size_t cnt, size_t stride)
 {
        for (; cnt--; ph = (void *)((char *)ph + stride))
@@ -619,51 +663,128 @@ static void find_map_range(Phdr *ph, size_t cnt, size_t stride, struct dso *p)
        p->map_len = max_addr - min_addr;
 }
 
+static void do_fini()
+{
+       struct dso *p;
+       size_t dyn[DYN_CNT] = {0};
+       for (p=fini_head; p; p=p->fini_next) {
+               if (!p->constructed) continue;
+               decode_vec(p->dynv, dyn, DYN_CNT);
+               ((void (*)(void))(p->base + dyn[DT_FINI]))();
+       }
+}
+
 static void do_init_fini(struct dso *p)
 {
        size_t dyn[DYN_CNT] = {0};
+       int need_locking = libc.threads_minus_1;
+       /* Allow recursive calls that arise when a library calls
+        * dlopen from one of its constructors, but block any
+        * other threads until all ctors have finished. */
+       if (need_locking) pthread_mutex_lock(&init_fini_lock);
        for (; p; p=p->prev) {
-               if (p->constructed) return;
+               if (p->constructed) continue;
+               p->constructed = 1;
                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_FINI)) {
+                       p->fini_next = fini_head;
+                       fini_head = p;
+               }
                if (dyn[0] & (1<<DT_INIT))
                        ((void (*)(void))(p->base + dyn[DT_INIT]))();
-               p->constructed = 1;
        }
+       if (need_locking) pthread_mutex_unlock(&init_fini_lock);
 }
 
 void _dl_debug_state(void)
 {
 }
 
-void *__copy_tls(unsigned char *mem, size_t cnt)
+void *__copy_tls(unsigned char *mem)
 {
+       pthread_t td;
        struct dso *p;
+
+       if (!tls_cnt) return mem;
+
        void **dtv = (void *)mem;
-       dtv[0] = (void *)cnt;
-       mem = (void *)(dtv + cnt + 1);
-       for (p=tail; p; p=p->prev) {
-               if (p->tls_id-1 >= cnt) continue;
-               mem += -p->tls_len & (4*sizeof(size_t)-1);
-               mem += ((uintptr_t)p->tls_image - (uintptr_t)mem)
-                       & (p->tls_align-1);
-               dtv[p->tls_id] = mem;
-               memcpy(mem, p->tls_image, p->tls_len);
-               mem += p->tls_size;
+       dtv[0] = (void *)tls_cnt;
+
+#ifdef TLS_ABOVE_TP
+       mem += sizeof(void *) * (tls_cnt+1);
+       mem += -((uintptr_t)mem + sizeof(struct pthread)) & (tls_align-1);
+       td = (pthread_t)mem;
+       mem += sizeof(struct pthread);
+
+       for (p=head; p; p=p->next) {
+               if (!p->tls_id) continue;
+               dtv[p->tls_id] = mem + p->tls_offset;
+               memcpy(dtv[p->tls_id], p->tls_image, p->tls_len);
+       }
+#else
+       mem += libc.tls_size - sizeof(struct pthread);
+       mem -= (uintptr_t)mem & (tls_align-1);
+       td = (pthread_t)mem;
+
+       for (p=head; p; p=p->next) {
+               if (!p->tls_id) continue;
+               dtv[p->tls_id] = mem - p->tls_offset;
+               memcpy(dtv[p->tls_id], p->tls_image, p->tls_len);
        }
-       ((pthread_t)mem)->dtv = dtv;
-       return mem;
+#endif
+       td->dtv = dtv;
+       return td;
 }
 
-void *__tls_get_addr(size_t *p)
+void *__tls_get_addr(size_t *v)
 {
        pthread_t self = __pthread_self();
-       if ((size_t)self->dtv[0] < p[0]) {
-               // FIXME: obtain new DTV and TLS from the DSO
-               a_crash();
+       if (v[0]<=(size_t)self->dtv[0] && self->dtv[v[0]])
+               return (char *)self->dtv[v[0]]+v[1];
+
+       /* Block signals to make accessing new TLS async-signal-safe */
+       sigset_t set;
+       pthread_sigmask(SIG_BLOCK, SIGALL_SET, &set);
+       if (v[0]<=(size_t)self->dtv[0] && self->dtv[v[0]]) {
+               pthread_sigmask(SIG_SETMASK, &set, 0);
+               return (char *)self->dtv[v[0]]+v[1];
        }
-       return (char *)self->dtv[p[0]] + p[1];
+
+       /* This is safe without any locks held because, if the caller
+        * is able to request the Nth entry of the DTV, the DSO list
+        * must be valid at least that far out and it was synchronized
+        * at program startup or by an already-completed call to dlopen. */
+       struct dso *p;
+       for (p=head; p->tls_id != v[0]; p=p->next);
+
+       /* Get new DTV space from new DSO if needed */
+       if (v[0] > (size_t)self->dtv[0]) {
+               void **newdtv = p->new_dtv +
+                       (v[0]+1)*sizeof(void *)*a_fetch_add(&p->new_dtv_idx,1);
+               memcpy(newdtv, self->dtv,
+                       ((size_t)self->dtv[0]+1) * sizeof(void *));
+               newdtv[0] = (void *)v[0];
+               self->dtv = newdtv;
+       }
+
+       /* Get new TLS memory from new DSO */
+       unsigned char *mem = p->new_tls +
+               (p->tls_size + p->tls_align) * a_fetch_add(&p->new_tls_idx,1);
+       mem += ((uintptr_t)p->tls_image - (uintptr_t)mem) & (p->tls_align-1);
+       self->dtv[v[0]] = mem;
+       memcpy(mem, p->tls_image, p->tls_len);
+       pthread_sigmask(SIG_SETMASK, &set, 0);
+       return mem + v[1];
+}
+
+static void update_tls_size()
+{
+       libc.tls_size = ALIGN(
+               (1+tls_cnt) * sizeof(void *) +
+               tls_offset +
+               sizeof(struct pthread) +
+               tls_align * 2,
+       tls_align);
 }
 
 void *__dynlink(int argc, char **argv)
@@ -678,6 +799,7 @@ void *__dynlink(int argc, char **argv)
        struct dso *const vdso = builtin_dsos+2;
        char *env_preload=0;
        size_t vdso_base;
+       size_t *auxv;
 
        /* Find aux vector just past environ[] */
        for (i=argc+1; argv[i]; i++)
@@ -711,18 +833,19 @@ void *__dynlink(int argc, char **argv)
        lib->name = lib->shortname = "libc.so";
        lib->global = 1;
        ehdr = (void *)lib->base;
-       find_map_range((void *)(aux[AT_BASE]+ehdr->e_phoff),
-               ehdr->e_phnum, ehdr->e_phentsize, lib);
-       lib->dynv = (void *)(lib->base + find_dyn(
-               (void *)(aux[AT_BASE]+ehdr->e_phoff),
-               ehdr->e_phnum, ehdr->e_phentsize));
+       lib->phnum = ehdr->e_phnum;
+       lib->phdr = (void *)(aux[AT_BASE]+ehdr->e_phoff);
+       find_map_range(lib->phdr, ehdr->e_phnum, ehdr->e_phentsize, lib);
+       lib->dynv = (void *)(lib->base + find_dyn(lib->phdr,
+                    ehdr->e_phnum, ehdr->e_phentsize));
        decode_dyn(lib);
 
        if (aux[AT_PHDR]) {
                size_t interp_off = 0;
                size_t tls_image = 0;
                /* Find load address of the main program, via AT_PHDR vs PT_PHDR. */
-               phdr = (void *)aux[AT_PHDR];
+               app->phdr = phdr = (void *)aux[AT_PHDR];
+               app->phnum = aux[AT_PHNUM];
                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);
@@ -745,7 +868,7 @@ void *__dynlink(int argc, char **argv)
        } else {
                int fd;
                char *ldname = argv[0];
-               size_t dyno, l = strlen(ldname);
+               size_t l = strlen(ldname);
                if (l >= 3 && !strcmp(ldname+l-3, "ldd")) ldd_mode = 1;
                *argv++ = (void *)-1;
                if (argv[0] && !strcmp(argv[0], "--")) *argv++ = (void *)-1;
@@ -770,12 +893,23 @@ void *__dynlink(int argc, char **argv)
                close(fd);
                lib->name = ldname;
                app->name = argv[0];
+               app->phnum = ehdr->e_phnum;
+               app->phdr = (void *)(app->base + ehdr->e_phoff);
                aux[AT_ENTRY] = ehdr->e_entry;
        }
        if (app->tls_size) {
-               app->tls_id = ++tls_cnt;
-               tls_size += app->tls_size+app->tls_align + 8*sizeof(size_t)-1
-                       & -4*sizeof(size_t);
+               app->tls_id = tls_cnt = 1;
+#ifdef TLS_ABOVE_TP
+               app->tls_offset = 0;
+               tls_offset = app->tls_size
+                       + ( -((uintptr_t)app->tls_image + app->tls_size)
+                       & (app->tls_align-1) );
+#else
+               tls_offset = app->tls_offset = app->tls_size
+                       + ( -((uintptr_t)app->tls_image + app->tls_size)
+                       & (app->tls_align-1) );
+#endif
+               tls_align = MAXP2(tls_align, app->tls_align);
        }
        app->global = 1;
        app->constructed = 1;
@@ -784,14 +918,16 @@ void *__dynlink(int argc, char **argv)
        /* Attach to vdso, if provided by the kernel */
        if (search_vec(auxv, &vdso_base, AT_SYSINFO_EHDR)) {
                ehdr = (void *)vdso_base;
-               phdr = (void *)(vdso_base + ehdr->e_phoff);
+               vdso->phdr = phdr = (void *)(vdso_base + ehdr->e_phoff);
+               vdso->phnum = ehdr->e_phnum;
                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 = vdso->shortname = "linux-gate.so.1";
+               vdso->name = "";
+               vdso->shortname = "linux-gate.so.1";
                vdso->global = 1;
                decode_dyn(vdso);
                vdso->prev = lib;
@@ -803,7 +939,7 @@ void *__dynlink(int argc, char **argv)
         * restore the initial chain in preparation for loading third
         * party libraries (preload/needed). */
        head = tail = app;
-       libc = lib;
+       ldso = lib;
        app->next = lib;
        reloc_all(lib);
        app->next = 0;
@@ -824,37 +960,21 @@ void *__dynlink(int argc, char **argv)
        load_deps(app);
        make_global(app);
 
-       /* Make an initial pass setting up TLS before performing relocs.
-        * This provides the TP-based offset of each DSO's TLS for
-        * use in TP-relative relocations. After relocations, we need
-        * to copy the TLS images again in case they had relocs. */
-       tls_size += sizeof(struct pthread) + 4*sizeof(size_t);
-       __libc.tls_size = tls_size;
-       __libc.tls_cnt = tls_cnt;
+       reloc_all(app->next);
+       reloc_all(app);
+
+       update_tls_size();
        if (tls_cnt) {
-               struct dso *p;
-               void *mem = mmap(0, __libc.tls_size, PROT_READ|PROT_WRITE,
+               void *mem = mmap(0, libc.tls_size, PROT_READ|PROT_WRITE,
                        MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
                if (mem==MAP_FAILED ||
-                   !__install_initial_tls(__copy_tls(mem, tls_cnt))) {
+                   !__install_initial_tls(__copy_tls(mem))) {
                        dprintf(2, "%s: Error getting %zu bytes thread-local storage: %m\n",
-                               argv[0], tls_size);
+                               argv[0], libc.tls_size);
                        _exit(127);
                }
-               for (p=head; p; p=p->next) {
-                       if (!p->tls_id) continue;
-                       p->tls_offset = (char *)__pthread_self()
-                               - (char *)__pthread_self()->dtv[p->tls_id];
-               }
        }
 
-       reloc_all(app->next);
-       reloc_all(app);
-
-       /* The initial DTV is located at the base of the memory
-        * allocated for TLS. Repeat copying TLS to pick up relocs. */
-       if (tls_cnt) __copy_tls((void *)__pthread_self()->dtv, tls_cnt);
-
        if (ldso_fail) _exit(127);
        if (ldd_mode) _exit(0);
 
@@ -876,17 +996,22 @@ void *__dynlink(int argc, char **argv)
        debug.state = 0;
        _dl_debug_state();
 
-       if (ssp_used) __init_ssp(auxv);
-
-       do_init_fini(tail);
+       if (ssp_used) __init_ssp((void *)aux[AT_RANDOM]);
 
        errno = 0;
        return (void *)aux[AT_ENTRY];
 }
 
+void __init_ldso_ctors(void)
+{
+       atexit(do_fini);
+       do_init_fini(tail);
+}
+
 void *dlopen(const char *file, int mode)
 {
-       struct dso *volatile p, *orig_tail = tail, *next;
+       struct dso *volatile p, *orig_tail, *next;
+       size_t orig_tls_cnt, orig_tls_offset, orig_tls_align;
        size_t i;
        int cs;
 
@@ -894,10 +1019,18 @@ void *dlopen(const char *file, int mode)
 
        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
        pthread_rwlock_wrlock(&lock);
+       __inhibit_ptc();
+
+       p = 0;
+       orig_tls_cnt = tls_cnt;
+       orig_tls_offset = tls_offset;
+       orig_tls_align = tls_align;
+       orig_tail = tail;
+       noload = mode & RTLD_NOLOAD;
 
        if (setjmp(rtld_fail)) {
                /* Clean up anything new that was (partially) loaded */
-               if (p->deps) for (i=0; p->deps[i]; i++)
+               if (p && 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) {
@@ -906,6 +1039,9 @@ void *dlopen(const char *file, int mode)
                        free(p->deps);
                        free(p);
                }
+               tls_cnt = orig_tls_cnt;
+               tls_offset = orig_tls_offset;
+               tls_align = orig_tls_align;
                tail = orig_tail;
                tail->next = 0;
                p = 0;
@@ -914,8 +1050,10 @@ void *dlopen(const char *file, int mode)
        } else p = load_library(file);
 
        if (!p) {
-               snprintf(errbuf, sizeof errbuf,
-                       "Error loading shared library %s: %m", file);
+               snprintf(errbuf, sizeof errbuf, noload ?
+                       "Library %s is not already loaded" :
+                       "Error loading shared library %s: %m",
+                       file);
                errflag = 1;
                goto end;
        }
@@ -940,31 +1078,51 @@ void *dlopen(const char *file, int mode)
                p->global = 1;
        }
 
-       if (ssp_used) __init_ssp(auxv);
+       update_tls_size();
 
-       _dl_debug_state();
+       if (ssp_used) __init_ssp(libc.auxv);
 
-       do_init_fini(tail);
+       _dl_debug_state();
+       orig_tail = tail;
 end:
+       __release_ptc();
+       if (p) gencnt++;
        pthread_rwlock_unlock(&lock);
+       if (p) do_init_fini(orig_tail);
        pthread_setcancelstate(cs, 0);
        return p;
 }
 
+static int invalid_dso_handle(void *h)
+{
+       struct dso *p;
+       for (p=head; p; p=p->next) if (h==p) return 0;
+       snprintf(errbuf, sizeof errbuf, "Invalid library handle %p", (void *)h);
+       errflag = 1;
+       return 1;
+}
+
 static void *do_dlsym(struct dso *p, const char *s, void *ra)
 {
        size_t i;
        uint32_t h = 0, gh = 0;
        Sym *sym;
        if (p == head || p == RTLD_DEFAULT || p == RTLD_NEXT) {
-               if (p == RTLD_NEXT) {
+               if (p == RTLD_DEFAULT) {
+                       p = head;
+               } else 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;
                }
-               struct symdef def = find_sym(p->next, s, 0);
+               struct symdef def = find_sym(p, s, 0);
                if (!def.sym) goto failed;
+               if ((def.sym->st_info&0xf) == STT_TLS)
+                       return __tls_get_addr((size_t []){def.dso->tls_id, def.sym->st_value});
                return def.dso->base + def.sym->st_value;
        }
+       if (p != RTLD_DEFAULT && p != RTLD_NEXT && invalid_dso_handle(p))
+               return 0;
        if (p->ghashtab) {
                gh = gnu_hash(s);
                sym = gnu_lookup(s, gh, p);
@@ -972,6 +1130,8 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra)
                h = sysv_hash(s);
                sym = sysv_lookup(s, h, p);
        }
+       if (sym && (sym->st_info&0xf) == STT_TLS)
+               return __tls_get_addr((size_t []){p->tls_id, sym->st_value});
        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++) {
@@ -982,6 +1142,8 @@ static void *do_dlsym(struct dso *p, const char *s, void *ra)
                        if (!h) h = sysv_hash(s);
                        sym = sysv_lookup(s, h, p->deps[i]);
                }
+               if (sym && (sym->st_info&0xf) == STT_TLS)
+                       return __tls_get_addr((size_t []){p->deps[i]->tls_id, sym->st_value});
                if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
                        return p->deps[i]->base + sym->st_value;
        }
@@ -1029,7 +1191,7 @@ int __dladdr(void *addr, Dl_info *info)
        }
 
        for (; nsym; nsym--, sym++) {
-               if (sym->st_shndx && sym->st_value
+               if (sym->st_value
                 && (1<<(sym->st_info&0xf) & OK_TYPES)
                 && (1<<(sym->st_info>>4) & OK_BINDS)) {
                        void *symaddr = p->base + sym->st_value;
@@ -1060,7 +1222,39 @@ void *__dlsym(void *restrict p, const char *restrict s, void *restrict ra)
        pthread_rwlock_unlock(&lock);
        return res;
 }
+
+int dl_iterate_phdr(int(*callback)(struct dl_phdr_info *info, size_t size, void *data), void *data)
+{
+       struct dso *current;
+       struct dl_phdr_info info;
+       int ret = 0;
+       for(current = head; current;) {
+               info.dlpi_addr      = (uintptr_t)current->base;
+               info.dlpi_name      = current->name;
+               info.dlpi_phdr      = current->phdr;
+               info.dlpi_phnum     = current->phnum;
+               info.dlpi_adds      = gencnt;
+               info.dlpi_subs      = 0;
+               info.dlpi_tls_modid = current->tls_id;
+               info.dlpi_tls_data  = current->tls_image;
+
+               ret = (callback)(&info, sizeof (info), data);
+
+               if (ret != 0) break;
+
+               pthread_rwlock_rdlock(&lock);
+               current = current->next;
+               pthread_rwlock_unlock(&lock);
+       }
+       return ret;
+}
 #else
+static int invalid_dso_handle(void *h)
+{
+       snprintf(errbuf, sizeof errbuf, "Invalid library handle %p", (void *)h);
+       errflag = 1;
+       return 1;
+}
 void *dlopen(const char *file, int mode)
 {
        return 0;
@@ -1084,5 +1278,5 @@ char *dlerror()
 
 int dlclose(void *p)
 {
-       return 0;
+       return invalid_dso_handle(p);
 }