ensure debugger hook for dynamic linker does not point to a PLT slot

[musl] / src / thread / pthread_create.c

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 1a47ed1..6963f0d 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -4,6 +4,7 @@
 #include "libc.h"
 #include <sys/mman.h>
 #include <string.h>
+#include <stddef.h>
 
 void *__mmap(void *, size_t, int, int, int, off_t);
 int __munmap(void *, size_t);
@@ -15,7 +16,6 @@ static void dummy_0()
 weak_alias(dummy_0, __acquire_ptc);
 weak_alias(dummy_0, __release_ptc);
 weak_alias(dummy_0, __pthread_tsd_run_dtors);
-weak_alias(dummy_0, __do_private_robust_list);
 weak_alias(dummy_0, __do_orphaned_stdio_locks);
 
 _Noreturn void __pthread_exit(void *result)
@@ -23,6 +23,8 @@ _Noreturn void __pthread_exit(void *result)
        pthread_t self = __pthread_self();
        sigset_t set;
 
+       self->canceldisable = 1;
+       self->cancelasync = 0;
        self->result = result;
 
        while (self->cancelbuf) {
@@ -70,7 +72,25 @@ _Noreturn void __pthread_exit(void *result)
                        a_dec(&libc.bytelocale_cnt_minus_1);
        }
 
-       __do_private_robust_list();
+       /* Process robust list in userspace to handle non-pshared mutexes
+        * and the detached thread case where the robust list head will
+        * be invalid when the kernel would process it. */
+       __vm_lock();
+       volatile void *volatile *rp;
+       while ((rp=self->robust_list.head) && rp != &self->robust_list.head) {
+               pthread_mutex_t *m = (void *)((char *)rp
+                       - offsetof(pthread_mutex_t, _m_next));
+               int waiters = m->_m_waiters;
+               int priv = (m->_m_type & 128) ^ 128;
+               self->robust_list.pending = rp;
+               self->robust_list.head = *rp;
+               int cont = a_swap(&m->_m_lock, self->tid|0x40000000);
+               self->robust_list.pending = 0;
+               if (cont < 0 || waiters)
+                       __wake(&m->_m_lock, 1, priv);
+       }
+       __vm_unlock();
+
        __do_orphaned_stdio_locks();
 
        if (self->detached && self->map_base) {
@@ -83,6 +103,15 @@ _Noreturn void __pthread_exit(void *result)
                 * detached later (== 2), we need to clear it here. */
                if (self->detached == 2) __syscall(SYS_set_tid_address, 0);
 
+               /* Robust list will no longer be valid, and was already
+                * processed above, so unregister it with the kernel. */
+               if (self->robust_list.off)
+                       __syscall(SYS_set_robust_list, 0, 3*sizeof(long));
+
+               /* Since __unmapself bypasses the normal munmap code path,
+                * explicitly wait for vmlock holders first. */
+               __vm_wait();
+
                /* The following call unmaps the thread's stack mapping
                 * and then exits without touching the stack. */
                __unmapself(self->map_base, self->map_size);
@@ -93,7 +122,6 @@ _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;
@@ -101,7 +129,6 @@ 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;
 }
 
@@ -139,6 +166,8 @@ weak_alias(dummy, __pthread_tsd_size);
 static void *dummy_tsd[1] = { 0 };
 weak_alias(dummy_tsd, __pthread_tsd_main);
 
+volatile int __block_new_threads = 0;
+
 static FILE *volatile dummy_file = 0;
 weak_alias(dummy_file, __stdin_used);
 weak_alias(dummy_file, __stdout_used);
@@ -178,6 +207,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
        if (attrp && !c11) attr = *attrp;
 
        __acquire_ptc();
+       if (__block_new_threads) __wait(&__block_new_threads, 0, 1, 1);
 
        if (attr._a_stackaddr) {
                size_t need = libc.tls_size + __pthread_tsd_size;
@@ -238,6 +268,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att
                do_sched = new->startlock[0] = 1;
                __block_app_sigs(new->sigmask);
        }
+       new->robust_list.head = &new->robust_list.head;
        new->unblock_cancel = self->cancel;
        new->canary = self->canary;