Fix signal stack release

Uses sigaltstack to get current signal stack
There is no need to record in pthread structure

Issue: #I716J1
Signed-off-by: Nguzhihao4 <guzhihao4@huawei.com>
Change-Id: I22298f9bf1f7a55a10002fba70f9e05ba6b14979

porting/linux/user/src/internal/pthread_impl.h

@@ -74,9 +74,6 @@ struct pthread {
     volatile int killlock[1];
     char *dlerror_buf;
     void *stdio_locks;
-#ifdef RESERVE_SIGNAL_STACK
-    void *signal_stack;
-#endif
 
 	/* Part 3 -- the positions of these fields relative to
 	 * the end of the structure is external and internal ABI. */

porting/linux/user/src/thread/pthread_create.c

@@ -61,7 +61,6 @@ void __pthread_reserve_signal_stack()
 	sigaltstack(&signal_stack, NULL);
 
 	pthread_t self = __pthread_self();
-	self->signal_stack = stack;
 	char name[ANON_STACK_NAME_SIZE];
 	snprintf(name, ANON_STACK_NAME_SIZE, "signal_stack:%d", __pthread_self()->tid);
 	prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, signal_stack.ss_sp, signal_stack.ss_size, name);
@@ -70,17 +69,13 @@ void __pthread_reserve_signal_stack()
 
 void __pthread_release_signal_stack()
 {
-	pthread_t self = __pthread_self();
-	if (self->signal_stack == NULL) {
-		return;
-	}
-
-	stack_t signal_stack;
+	stack_t signal_stack, old_stack;
 	memset(&signal_stack, 0, sizeof(signal_stack));
 	signal_stack.ss_flags = SS_DISABLE;
-	sigaltstack(&signal_stack, NULL);
-	munmap(self->signal_stack, RESERVE_SIGNAL_STACK_SIZE);
-	self->signal_stack = NULL;
+	sigaltstack(&signal_stack, &old_stack);
+	if (old_stack.ss_flags != SS_DISABLE) {
+		munmap(old_stack.ss_sp, old_stack.ss_size);
+	}
 }
 
 weak_alias(__pthread_reserve_signal_stack, pthread_reserve_signal_stack);