path: root/main/musl/0001-v1.0.0-to-2b74315d.patch

git diff v1.0.0...2b74315d8a31ad8fbcd369116c82e055e0ec3fb7

diff --git a/src/conf/confstr.c b/src/conf/confstr.c
index 4332f72..6e9c23a 100644
--- a/src/conf/confstr.c
+++ b/src/conf/confstr.c
@@ -13,5 +13,5 @@ size_t confstr(int name, char *buf, size_t len)
 	}
 	// snprintf is overkill but avoid wasting code size to implement
 	// this completely useless function and its truncation semantics
-	return snprintf(buf, len, "%s", s);
+	return snprintf(buf, len, "%s", s) + 1;
 }
diff --git a/src/env/__init_security.c b/src/env/__init_security.c
index 6204c5e..da5ae94 100644
--- a/src/env/__init_security.c
+++ b/src/env/__init_security.c
@@ -15,9 +15,7 @@ void __init_security(size_t *aux)
 	struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
 	int i;
 
-#ifndef SHARED
 	__init_ssp((void *)aux[AT_RANDOM]);
-#endif
 
 	if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
 		&& !aux[AT_SECURE]) return;
diff --git a/src/env/__init_tls.c b/src/env/__init_tls.c
index 5c17681..8ac0036 100644
--- a/src/env/__init_tls.c
+++ b/src/env/__init_tls.c
@@ -5,9 +5,30 @@
 #include "pthread_impl.h"
 #include "libc.h"
 #include "atomic.h"
+#include "syscall.h"
+
+int __init_tp(void *p)
+{
+	pthread_t td = p;
+	td->self = td;
+	if (__set_thread_area(TP_ADJ(p)) < 0)
+		return -1;
+	td->tid = td->pid = __syscall(SYS_set_tid_address, &td->tid);
+	td->errno_ptr = &td->errno_val;
+	/* Currently, both of these predicates depend in the same thing:
+	 * successful initialization of the thread pointer. However, in
+	 * the future, we may support setups where setting the thread
+	 * pointer is possible but threads other than the main thread
+	 * cannot work, so it's best to keep the predicates separate. */
+	libc.has_thread_pointer = 1;
+	libc.can_do_threads = 1;
+	return 0;
+}
 
 #ifndef SHARED
 
+static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)];
+
 struct tls_image {
 	void *image;
 	size_t len, size, align;
@@ -61,10 +82,11 @@ typedef Elf64_Phdr Phdr;
 
 void __init_tls(size_t *aux)
 {
-	unsigned char *p, *mem;
+	unsigned char *p;
 	size_t n;
 	Phdr *phdr, *tls_phdr=0;
 	size_t base = 0;
+	void *mem;
 
 	libc.tls_size = sizeof(struct pthread);
 
@@ -75,21 +97,38 @@ void __init_tls(size_t *aux)
 		if (phdr->p_type == PT_TLS)
 			tls_phdr = phdr;
 	}
-	if (!tls_phdr) return;
 
-	T.image = (void *)(base + tls_phdr->p_vaddr);
-	T.len = tls_phdr->p_filesz;
-	T.size = tls_phdr->p_memsz;
-	T.align = tls_phdr->p_align;
+	if (tls_phdr) {
+		T.image = (void *)(base + tls_phdr->p_vaddr);
+		T.len = tls_phdr->p_filesz;
+		T.size = tls_phdr->p_memsz;
+		T.align = tls_phdr->p_align;
+	}
 
 	T.size += (-T.size - (uintptr_t)T.image) & (T.align-1);
 	if (T.align < 4*sizeof(size_t)) T.align = 4*sizeof(size_t);
 
 	libc.tls_size = 2*sizeof(void *)+T.size+T.align+sizeof(struct pthread);
 
-	mem = __mmap(0, libc.tls_size, PROT_READ|PROT_WRITE,
-		MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
-	if (!__install_initial_tls(__copy_tls(mem))) a_crash();
+	if (libc.tls_size > sizeof builtin_tls) {
+		mem = (void *)__syscall(
+#ifdef SYS_mmap2
+			SYS_mmap2,
+#else
+			SYS_mmap,
+#endif
+			0, libc.tls_size, PROT_READ|PROT_WRITE,
+			MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+		/* -4095...-1 cast to void * will crash on dereference anyway,
+		 * so don't bloat the init code checking for error codes and
+		 * explicitly calling a_crash(). */
+	} else {
+		mem = builtin_tls;
+	}
+
+	/* Failure to initialize thread pointer is fatal if TLS is used. */
+	if (__init_tp(__copy_tls(mem)) < 0 && tls_phdr)
+		a_crash();
 }
 #else
 void __init_tls(size_t *auxv) { }
diff --git a/src/env/__stack_chk_fail.c b/src/env/__stack_chk_fail.c
index daa1b07..87ac473 100644
--- a/src/env/__stack_chk_fail.c
+++ b/src/env/__stack_chk_fail.c
@@ -1,18 +1,16 @@
 #include <string.h>
 #include <stdint.h>
 #include "pthread_impl.h"
-#include "atomic.h"
 
 uintptr_t __stack_chk_guard;
 
 void __init_ssp(void *entropy)
 {
-	pthread_t self = __pthread_self_init();
-	uintptr_t canary;
-	if (entropy) memcpy(&canary, entropy, sizeof canary);
-	else canary = (uintptr_t)&canary * 1103515245;
-	a_cas_l(&__stack_chk_guard, 0, canary);
-	self->canary = __stack_chk_guard;
+	if (entropy) memcpy(&__stack_chk_guard, entropy, sizeof(uintptr_t));
+	else __stack_chk_guard = (uintptr_t)&__stack_chk_guard * 1103515245;
+
+	if (libc.has_thread_pointer)
+		__pthread_self()->canary = __stack_chk_guard;
 }
 
 void __stack_chk_fail(void)
diff --git a/src/errno/__errno_location.c b/src/errno/__errno_location.c
index 3e92d7c..8419107 100644
--- a/src/errno/__errno_location.c
+++ b/src/errno/__errno_location.c
@@ -3,6 +3,6 @@
 int *__errno_location(void)
 {
 	static int e;
-	if (libc.main_thread) return __pthread_self()->errno_ptr;
+	if (libc.has_thread_pointer) return __pthread_self()->errno_ptr;
 	return &e;
 }
diff --git a/src/internal/libc.h b/src/internal/libc.h
index d625b56..fb4d9bc 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -6,12 +6,12 @@
 #include <limits.h>
 
 struct __libc {
-	void *main_thread;
+	int has_thread_pointer;
+	int can_do_threads;
 	int threaded;
 	int secure;
 	size_t *auxv;
 	volatile int threads_minus_1;
-	int canceldisable;
 	FILE *ofl_head;
 	int ofl_lock[2];
 	size_t tls_size;
diff --git a/src/internal/syscall_ret.c b/src/internal/syscall_ret.c
index d99f4a5..a3f4713 100644
--- a/src/internal/syscall_ret.c
+++ b/src/internal/syscall_ret.c
@@ -1,4 +1,5 @@
 #include <errno.h>
+#include "syscall.h"
 
 long __syscall_ret(unsigned long r)
 {
diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index a1bdf0f..1517281 100644
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -56,6 +56,7 @@ struct dso {
 
 	Phdr *phdr;
 	int phnum;
+	size_t phentsize;
 	int refcnt;
 	Sym *syms;
 	uint32_t *hashtab;
@@ -74,6 +75,7 @@ struct dso {
 	char *rpath_orig, *rpath;
 	void *tls_image;
 	size_t tls_len, tls_size, tls_align, tls_id, tls_offset;
+	size_t relro_start, relro_end;
 	void **new_dtv;
 	unsigned char *new_tls;
 	int new_dtv_idx, new_tls_idx;
@@ -89,8 +91,7 @@ struct symdef {
 
 #include "reloc.h"
 
-void __init_ssp(size_t *);
-void *__install_initial_tls(void *);
+int __init_tp(void *);
 void __init_libc(char **, char *);
 
 const char *__libc_get_version(void);
@@ -98,7 +99,6 @@ const char *__libc_get_version(void);
 static struct dso *head, *tail, *ldso, *fini_head;
 static char *env_path, *sys_path;
 static unsigned long long gencnt;
-static int ssp_used;
 static int runtime;
 static int ldd_mode;
 static int ldso_fail;
@@ -108,6 +108,7 @@ static pthread_rwlock_t lock;
 static struct debug debug;
 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 };
+static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)];
 
 struct debug *_dl_debug_addr = &debug;
 
@@ -198,13 +199,6 @@ static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
 {
 	uint32_t h = 0, gh = 0;
 	struct symdef def = {0};
-	if (dso->ghashtab) {
-		gh = gnu_hash(s);
-		if (gh == 0x1f4039c9 && !strcmp(s, "__stack_chk_fail")) ssp_used = 1;
-	} else {
-		h = sysv_hash(s);
-		if (h == 0x595a4cc && !strcmp(s, "__stack_chk_fail")) ssp_used = 1;
-	}
 	for (; dso; dso=dso->next) {
 		Sym *sym;
 		if (!dso->global) continue;
@@ -280,27 +274,32 @@ static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stri
  * 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)
+static void reclaim(struct dso *dso, size_t start, size_t end)
 {
 	size_t *a, *z;
+	if (start >= dso->relro_start && start < dso->relro_end) start = dso->relro_end;
+	if (end   >= dso->relro_start && end   < dso->relro_end) end = dso->relro_start;
 	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 = (size_t *)(dso->base + start);
+	z = (size_t *)(dso->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)
+static void reclaim_gaps(struct dso *dso)
 {
-	for (; phcnt--; ph=(void *)((char *)ph+phent)) {
+	Phdr *ph = dso->phdr;
+	size_t phcnt = dso->phnum;
+
+	for (; phcnt--; ph=(void *)((char *)ph+dso->phentsize)) {
 		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,
+		reclaim(dso, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr);
+		reclaim(dso, ph->p_vaddr+ph->p_memsz,
 			ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE);
 	}
 }
@@ -343,13 +342,16 @@ static void *map_library(int fd, struct dso *dso)
 		ph = ph0 = (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)
+		if (ph->p_type == PT_DYNAMIC) {
 			dyn = ph->p_vaddr;
-		if (ph->p_type == PT_TLS) {
+		} else if (ph->p_type == PT_TLS) {
 			tls_image = ph->p_vaddr;
 			dso->tls_align = ph->p_align;
 			dso->tls_len = ph->p_filesz;
 			dso->tls_size = ph->p_memsz;
+		} else if (ph->p_type == PT_GNU_RELRO) {
+			dso->relro_start = ph->p_vaddr & -PAGE_SIZE;
+			dso->relro_end = (ph->p_vaddr + ph->p_memsz) & -PAGE_SIZE;
 		}
 		if (ph->p_type != PT_LOAD) continue;
 		if (ph->p_vaddr < addr_min) {
@@ -393,6 +395,7 @@ static void *map_library(int fd, struct dso *dso)
 			dso->phdr = (void *)(base + ph->p_vaddr
 				+ (eh->e_phoff-ph->p_offset));
 			dso->phnum = eh->e_phnum;
+			dso->phentsize = eh->e_phentsize;
 		}
 		/* Reuse the existing mapping for the lowest-address LOAD */
 		if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
@@ -418,12 +421,12 @@ static void *map_library(int fd, struct dso *dso)
 				goto error;
 			break;
 		}
-	if (!runtime) reclaim_gaps(base, ph0, eh->e_phentsize, eh->e_phnum);
 	dso->map = map;
 	dso->map_len = map_len;
 	dso->base = base;
 	dso->dynv = (void *)(base+dyn);
 	if (dso->tls_size) dso->tls_image = (void *)(base+tls_image);
+	if (!runtime) reclaim_gaps(dso);
 	free(allocated_buf);
 	return map;
 noexec:
@@ -673,9 +676,10 @@ static struct dso *load_library(const char *name, struct dso *needed_by)
 	/* 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()) {
+		if (runtime && !libc.has_thread_pointer) {
 			munmap(map, p->map_len);
 			free(p);
+			errno = ENOSYS;
 			return 0;
 		}
 		p->tls_id = ++tls_cnt;
@@ -764,22 +768,32 @@ static void reloc_all(struct dso *p)
 			2+(dyn[DT_PLTREL]==DT_RELA));
 		do_relocs(p, (void *)(p->base+dyn[DT_REL]), dyn[DT_RELSZ], 2);
 		do_relocs(p, (void *)(p->base+dyn[DT_RELA]), dyn[DT_RELASZ], 3);
+
+		if (p->relro_start != p->relro_end &&
+		    mprotect(p->base+p->relro_start, p->relro_end-p->relro_start, PROT_READ) < 0) {
+			snprintf(errbuf, sizeof errbuf,
+				"Error relocating %s: RELRO protection failed: %m",
+				p->name);
+			if (runtime) longjmp(*rtld_fail, 1);
+			dprintf(2, "%s\n", errbuf);
+			ldso_fail = 1;
+		}
+
 		p->relocated = 1;
 	}
 }
 
-static size_t find_dyn(Phdr *ph, size_t cnt, size_t stride)
+static void kernel_mapped_dso(struct dso *p)
 {
-	for (; cnt--; ph = (void *)((char *)ph + stride))
-		if (ph->p_type == PT_DYNAMIC)
-			return ph->p_vaddr;
-	return 0;
-}
-
-static void find_map_range(Phdr *ph, size_t cnt, size_t stride, struct dso *p)
-{
-	size_t min_addr = -1, max_addr = 0;
-	for (; cnt--; ph = (void *)((char *)ph + stride)) {
+	size_t min_addr = -1, max_addr = 0, cnt;
+	Phdr *ph = p->phdr;
+	for (cnt = p->phnum; cnt--; ph = (void *)((char *)ph + p->phentsize)) {
+		if (ph->p_type == PT_DYNAMIC) {
+			p->dynv = (void *)(p->base + ph->p_vaddr);
+		} else if (ph->p_type == PT_GNU_RELRO) {
+			p->relro_start = ph->p_vaddr & -PAGE_SIZE;
+			p->relro_end = (ph->p_vaddr + ph->p_memsz) & -PAGE_SIZE;
+		}
 		if (ph->p_type != PT_LOAD) continue;
 		if (ph->p_vaddr < min_addr)
 			min_addr = ph->p_vaddr;
@@ -790,6 +804,7 @@ static void find_map_range(Phdr *ph, size_t cnt, size_t stride, struct dso *p)
 	max_addr = (max_addr + PAGE_SIZE-1) & -PAGE_SIZE;
 	p->map = p->base + min_addr;
 	p->map_len = max_addr - min_addr;
+	p->kernel_mapped = 1;
 }
 
 static void do_fini()
@@ -866,10 +881,13 @@ void *__copy_tls(unsigned char *mem)
 	pthread_t td;
 	struct dso *p;
 
-	if (!tls_cnt) return mem;
-
 	void **dtv = (void *)mem;
 	dtv[0] = (void *)tls_cnt;
+	if (!tls_cnt) {
+		td = (void *)(dtv+1);
+		td->dtv = dtv;
+		return td;
+	}
 
 #ifdef TLS_ABOVE_TP
 	mem += sizeof(void *) * (tls_cnt+1);
@@ -962,6 +980,7 @@ void *__dynlink(int argc, char **argv)
 	size_t vdso_base;
 	size_t *auxv;
 	char **envp = argv+argc+1;
+	void *initial_tls;
 
 	/* Find aux vector just past environ[] */
 	for (i=argc+1; argv[i]; i++)
@@ -996,13 +1015,11 @@ void *__dynlink(int argc, char **argv)
 	lib->base = (void *)aux[AT_BASE];
 	lib->name = lib->shortname = "libc.so";
 	lib->global = 1;
-	lib->kernel_mapped = 1;
 	ehdr = (void *)lib->base;
 	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));
+	lib->phentsize = ehdr->e_phentsize;
+	kernel_mapped_dso(lib);
 	decode_dyn(lib);
 
 	if (aux[AT_PHDR]) {
@@ -1011,6 +1028,7 @@ void *__dynlink(int argc, char **argv)
 		/* Find load address of the main program, via AT_PHDR vs PT_PHDR. */
 		app->phdr = phdr = (void *)aux[AT_PHDR];
 		app->phnum = aux[AT_PHNUM];
+		app->phentsize = aux[AT_PHENT];
 		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);
@@ -1030,11 +1048,7 @@ void *__dynlink(int argc, char **argv)
 			app->name = (char *)aux[AT_EXECFN];
 		else
 			app->name = argv[0];
-		app->kernel_mapped = 1;
-		app->dynv = (void *)(app->base + find_dyn(
-			(void *)aux[AT_PHDR], aux[AT_PHNUM], aux[AT_PHENT]));
-		find_map_range((void *)aux[AT_PHDR],
-			aux[AT_PHNUM], aux[AT_PHENT], app);
+		kernel_mapped_dso(app);
 	} else {
 		int fd;
 		char *ldname = argv[0];
@@ -1100,6 +1114,7 @@ void *__dynlink(int argc, char **argv)
 		ehdr = (void *)vdso_base;
 		vdso->phdr = phdr = (void *)(vdso_base + ehdr->e_phoff);
 		vdso->phnum = ehdr->e_phnum;
+		vdso->phentsize = ehdr->e_phentsize;
 		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);
@@ -1127,10 +1142,8 @@ void *__dynlink(int argc, char **argv)
 	/* 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);
+	reclaim_gaps(app);
+	reclaim_gaps(lib);
 
 	/* Load preload/needed libraries, add their symbols to the global
 	 * namespace, and perform all remaining relocations. The main
@@ -1140,19 +1153,29 @@ void *__dynlink(int argc, char **argv)
 	load_deps(app);
 	make_global(app);
 
+#ifndef DYNAMIC_IS_RO
+	for (i=0; app->dynv[i]; i+=2)
+		if (app->dynv[i]==DT_DEBUG)
+			app->dynv[i+1] = (size_t)&debug;
+#endif
+
 	reloc_all(app->next);
 	reloc_all(app);
 
 	update_tls_size();
-	if (tls_cnt) {
-		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))) {
+	if (libc.tls_size > sizeof builtin_tls) {
+		initial_tls = calloc(libc.tls_size, 1);
+		if (!initial_tls) {
 			dprintf(2, "%s: Error getting %zu bytes thread-local storage: %m\n",
 				argv[0], libc.tls_size);
 			_exit(127);
 		}
+	} else {
+		initial_tls = builtin_tls;
+	}
+	if (__init_tp(__copy_tls(initial_tls)) < 0 && tls_cnt) {
+		dprintf(2, "%s: Thread-local storage not supported by kernel.\n", argv[0]);
+		_exit(127);
 	}
 
 	if (ldso_fail) _exit(127);
@@ -1164,11 +1187,6 @@ void *__dynlink(int argc, char **argv)
 	 * all memory used by the dynamic linker. */
 	runtime = 1;
 
-#ifndef DYNAMIC_IS_RO
-	for (i=0; app->dynv[i]; i+=2)
-		if (app->dynv[i]==DT_DEBUG)
-			app->dynv[i+1] = (size_t)&debug;
-#endif
 	debug.ver = 1;
 	debug.bp = _dl_debug_state;
 	debug.head = head;
@@ -1176,7 +1194,6 @@ void *__dynlink(int argc, char **argv)
 	debug.state = 0;
 	_dl_debug_state();
 
-	if (ssp_used) __init_ssp((void *)aux[AT_RANDOM]);
 	__init_libc(envp, argv[0]);
 	atexit(do_fini);
 	errno = 0;
@@ -1258,9 +1275,6 @@ void *dlopen(const char *file, int mode)
 	}
 
 	update_tls_size();
-
-	if (ssp_used) __init_ssp(libc.auxv);
-
 	_dl_debug_state();
 	orig_tail = tail;
 end:
diff --git a/src/process/fork.c b/src/process/fork.c
index 1a82f42..864c7d7 100644
--- a/src/process/fork.c
+++ b/src/process/fork.c
@@ -17,12 +17,11 @@ pid_t fork(void)
 	__fork_handler(-1);
 	__block_all_sigs(&set);
 	ret = syscall(SYS_fork);
-	if (libc.main_thread && !ret) {
+	if (libc.has_thread_pointer && !ret) {
 		pthread_t self = __pthread_self();
-		self->tid = self->pid = syscall(SYS_getpid);
+		self->tid = self->pid = __syscall(SYS_getpid);
 		memset(&self->robust_list, 0, sizeof self->robust_list);
 		libc.threads_minus_1 = 0;
-		libc.main_thread = self;
 	}
 	__restore_sigs(&set);
 	__fork_handler(!ret);
diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index f7ff4a6..d5f4774 100644
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -8,9 +8,7 @@
 
 void __restore(), __restore_rt();
 
-static pthread_t dummy(void) { return 0; }
-weak_alias(dummy, __pthread_self_def);
-
+static int unmask_done;
 static unsigned long handler_set[_NSIG/(8*sizeof(long))];
 
 void __get_handler_set(sigset_t *set)
@@ -29,7 +27,20 @@ int __libc_sigaction(int sig, const struct sigaction *restrict sa, struct sigact
 		if ((uintptr_t)sa->sa_handler > 1UL) {
 			a_or_l(handler_set+(sig-1)/(8*sizeof(long)),
 				1UL<<(sig-1)%(8*sizeof(long)));
-			__pthread_self_def();
+
+			/* If pthread_create has not yet been called,
+			 * implementation-internal signals might not
+			 * yet have been unblocked. They must be
+			 * unblocked before any signal handler is
+			 * installed, so that an application cannot
+			 * receive an illegal sigset_t (with them
+			 * blocked) as part of the ucontext_t passed
+			 * to the signal handler. */
+			if (!libc.threaded && !unmask_done) {
+				__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
+					SIGPT_SET, 0, _NSIG/8);
+				unmask_done = 1;
+			}
 		}
 		ksa.handler = sa->sa_handler;
 		ksa.flags = sa->sa_flags | SA_RESTORER;
diff --git a/src/stdio/__stdio_read.c b/src/stdio/__stdio_read.c
index 05e56f9..6cd7b07 100644
--- a/src/stdio/__stdio_read.c
+++ b/src/stdio/__stdio_read.c
@@ -16,13 +16,9 @@ size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
 	};
 	ssize_t cnt;
 
-	if (libc.main_thread) {
-		pthread_cleanup_push(cleanup, f);
-		cnt = syscall_cp(SYS_readv, f->fd, iov, 2);
-		pthread_cleanup_pop(0);
-	} else {
-		cnt = syscall(SYS_readv, f->fd, iov, 2);
-	}
+	pthread_cleanup_push(cleanup, f);
+	cnt = syscall_cp(SYS_readv, f->fd, iov, 2);
+	pthread_cleanup_pop(0);
 	if (cnt <= 0) {
 		f->flags |= F_EOF ^ ((F_ERR^F_EOF) & cnt);
 		f->rpos = f->rend = 0;
diff --git a/src/stdio/__stdio_write.c b/src/stdio/__stdio_write.c
index e52e91a..8c89389 100644
--- a/src/stdio/__stdio_write.c
+++ b/src/stdio/__stdio_write.c
@@ -19,13 +19,9 @@ size_t __stdio_write(FILE *f, const unsigned char *buf, size_t len)
 	int iovcnt = 2;
 	ssize_t cnt;
 	for (;;) {
-		if (libc.main_thread) {
-			pthread_cleanup_push(cleanup, f);
-			cnt = syscall_cp(SYS_writev, f->fd, iov, iovcnt);
-			pthread_cleanup_pop(0);
-		} else {
-			cnt = syscall(SYS_writev, f->fd, iov, iovcnt);
-		}
+		pthread_cleanup_push(cleanup, f);
+		cnt = syscall_cp(SYS_writev, f->fd, iov, iovcnt);
+		pthread_cleanup_pop(0);
 		if (cnt == rem) {
 			f->wend = f->buf + f->buf_size;
 			f->wpos = f->wbase = f->buf;
diff --git a/src/thread/cancel_impl.c b/src/thread/cancel_impl.c
index c835813..525d290 100644
--- a/src/thread/cancel_impl.c
+++ b/src/thread/cancel_impl.c
@@ -20,7 +20,7 @@ long (__syscall_cp)(syscall_arg_t nr,
 	pthread_t self;
 	long r;
 
-	if (!libc.main_thread || (self = __pthread_self())->canceldisable)
+	if (!libc.has_thread_pointer || (self = __pthread_self())->canceldisable)
 		return __syscall(nr, u, v, w, x, y, z);
 
 	r = __syscall_cp_asm(&self->cancel, nr, u, v, w, x, y, z);
@@ -57,6 +57,7 @@ static void cancel_handler(int sig, siginfo_t *si, void *ctx)
 
 void __testcancel()
 {
+	if (!libc.has_thread_pointer) return;
 	pthread_t self = pthread_self();
 	if (self->cancel && !self->canceldisable)
 		__cancel();
diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index ee6c31c..e0b5ef1 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -77,6 +77,7 @@ _Noreturn void pthread_exit(void *result)
 
 void __do_cleanup_push(struct __ptcb *cb)
 {
+	if (!libc.has_thread_pointer) return;
 	struct pthread *self = pthread_self();
 	cb->__next = self->cancelbuf;
 	self->cancelbuf = cb;
@@ -84,6 +85,7 @@ void __do_cleanup_push(struct __ptcb *cb)
 
 void __do_cleanup_pop(struct __ptcb *cb)
 {
+	if (!libc.has_thread_pointer) return;
 	__pthread_self()->cancelbuf = cb->__next;
 }
 
@@ -110,6 +112,8 @@ static int start(void *p)
 /* pthread_key_create.c overrides this */
 static const size_t dummy = 0;
 weak_alias(dummy, __pthread_tsd_size);
+static void *const dummy_tsd[1] = { 0 };
+weak_alias(dummy_tsd, __pthread_tsd_main);
 
 static FILE *const dummy_file = 0;
 weak_alias(dummy_file, __stdin_used);
@@ -127,7 +131,7 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp
 {
 	int ret;
 	size_t size, guard;
-	struct pthread *self = pthread_self(), *new;
+	struct pthread *self, *new;
 	unsigned char *map = 0, *stack = 0, *tsd = 0, *stack_limit;
 	unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
 		| CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
@@ -135,13 +139,16 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attrp
 	int do_sched = 0;
 	pthread_attr_t attr = {0};
 
-	if (!self) return ENOSYS;
+	if (!libc.can_do_threads) return ENOSYS;
+	self = __pthread_self();
 	if (!libc.threaded) {
 		for (FILE *f=libc.ofl_head; f; f=f->next)
 			init_file_lock(f);
 		init_file_lock(__stdin_used);
 		init_file_lock(__stdout_used);
 		init_file_lock(__stderr_used);
+		__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK, SIGPT_SET, 0, _NSIG/8);
+		self->tsd = (void **)__pthread_tsd_main;
 		libc.threaded = 1;
 	}
 	if (attrp) attr = *attrp;
diff --git a/src/thread/pthread_key_create.c b/src/thread/pthread_key_create.c
index c29935c..ef8a755 100644
--- a/src/thread/pthread_key_create.c
+++ b/src/thread/pthread_key_create.c
@@ -14,7 +14,13 @@ int pthread_key_create(pthread_key_t *k, void (*dtor)(void *))
 	unsigned i = (uintptr_t)&k / 16 % PTHREAD_KEYS_MAX;
 	unsigned j = i;
 
-	__pthread_self_init();
+	if (libc.has_thread_pointer) {
+		pthread_t self = __pthread_self();
+		/* This can only happen in the main thread before
+		 * pthread_create has been called. */
+		if (!self->tsd) self->tsd = __pthread_tsd_main;
+	}
+
 	if (!dtor) dtor = nodtor;
 	do {
 		if (!a_cas_p(keys+j, 0, (void *)dtor)) {
diff --git a/src/thread/pthread_self.c b/src/thread/pthread_self.c
index aed4b5f..5f9e651 100644
--- a/src/thread/pthread_self.c
+++ b/src/thread/pthread_self.c
@@ -1,45 +1,6 @@
 #include "pthread_impl.h"
 
-static struct pthread *main_thread = &(struct pthread){0};
-
-/* pthread_key_create.c overrides this */
-static const void *dummy[1] = { 0 };
-weak_alias(dummy, __pthread_tsd_main);
-
-static int init_main_thread()
-{
-	__syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
-		SIGPT_SET, 0, _NSIG/8);
-	if (__set_thread_area(TP_ADJ(main_thread)) < 0) return -1;
-	main_thread->canceldisable = libc.canceldisable;
-	main_thread->tsd = (void **)__pthread_tsd_main;
-	main_thread->errno_ptr = __errno_location();
-	main_thread->self = main_thread;
-	main_thread->tid = main_thread->pid =
-		__syscall(SYS_set_tid_address, &main_thread->tid);
-	if (!main_thread->dtv)
-		main_thread->dtv = (void *)dummy;
-	libc.main_thread = main_thread;
-	return 0;
-}
-
-pthread_t __pthread_self_def()
+pthread_t pthread_self()
 {
-	static int init, failed;
-	if (!init) {
-		if (failed) return 0;
-		if (init_main_thread() < 0) failed = 1;
-		if (failed) return 0;
-		init = 1;
-	}
 	return __pthread_self();
 }
-
-weak_alias(__pthread_self_def, pthread_self);
-weak_alias(__pthread_self_def, __pthread_self_init);
-
-void *__install_initial_tls(void *p)
-{
-	main_thread = p;
-	return __pthread_self_def();
-}
diff --git a/src/thread/pthread_setcancelstate.c b/src/thread/pthread_setcancelstate.c
index ba2b231..060bcdc 100644
--- a/src/thread/pthread_setcancelstate.c
+++ b/src/thread/pthread_setcancelstate.c
@@ -3,13 +3,9 @@
 int pthread_setcancelstate(int new, int *old)
 {
 	if (new > 1U) return EINVAL;
-	if (libc.main_thread) {
-		struct pthread *self = __pthread_self();
-		if (old) *old = self->canceldisable;
-		self->canceldisable = new;
-	} else {
-		if (old) *old = libc.canceldisable;
-		libc.canceldisable = new;
-	}
+	if (!libc.has_thread_pointer) return ENOSYS;
+	struct pthread *self = __pthread_self();
+	if (old) *old = self->canceldisable;
+	self->canceldisable = new;
 	return 0;
 }