!593 clone接口没有清除C库进程相关全局变量

Merge pull request !593 from zhushengle/clone

porting/linux/user/src/linux/clone.c

+#define _GNU_SOURCE
+#include <stdarg.h>
+#include <unistd.h>
+#include <sched.h>
+#include <signal.h>
+#include "pthread_impl.h"
+#include "syscall.h"
+#include "libc.h"
+
+struct __clone_args {
+	int (*func)(void *);
+	void *arg;
+};
+
+static int __start_child(void *clone_args)
+{
+	int status;
+	sigset_t set;
+	int (*func)(void *) = ((struct __clone_args *)clone_args)->func;
+	void *arg = ((struct __clone_args *)clone_args)->arg;
+	free(clone_args);
+
+	__block_all_sigs(&set);
+	pthread_t self = __pthread_self();
+	self->tid = __syscall(SYS_gettid);
+	self->robust_list.off = 0;
+	self->robust_list.pending = 0;
+	self->next = self->prev = self;
+	__thread_list_lock = 0;
+	libc.threads_minus_1 = 0;
+	__restore_sigs(&set);
+
+	status = func(arg);
+	exit(status);
+}
+
+int clone(int (*func)(void *), void *stack, int flags, void *arg, ...)
+{
+	int ret;
+	va_list ap;
+	pid_t *ptid, *ctid;
+	void  *tls;
+	int (*clone_func)(void *) = func;
+	struct __clone_args *clone_args = (struct __clone_args *)arg;
+
+	va_start(ap, arg);
+	ptid = va_arg(ap, pid_t *);
+	tls  = va_arg(ap, void *);
+	ctid = va_arg(ap, pid_t *);
+	va_end(ap);
+	if (!(flags & (CLONE_VM | CLONE_VFORK)) && func) {
+		clone_args = (struct __clone_args *)malloc(sizeof(struct __clone_args));
+		if (clone_args == NULL) {
+			errno = ENOMEM;
+			return -1;
+		}
+		clone_args->func = clone_func;
+		clone_args->arg = arg;
+		clone_func = __start_child;
+	}
+	ret = __syscall_ret(__clone(clone_func, stack, flags, (void *)clone_args, ptid, tls, ctid));
+	if (!(flags & (CLONE_VM | CLONE_VFORK)) && func) {
+		free(clone_args);
+	}
+	return ret;
+}