use glibc clone instead of clone syscall

src/lxc/Makefile.am

@@ -35,7 +35,7 @@ liblxc_la_SOURCES = \
 	lxc.h \
 	utils.c utils.h \
 	lock.c lock.h \
-	namespace.h \
+	namespace.h namespace.c \
 	conf.c conf.h \
 	list.h \
 	state.c state.h \

src/lxc/namespace.c

+/*
+ * lxc: linux Container library
+ *
+ * (C) Copyright IBM Corp. 2007, 2009
+ *
+ * Authors:
+ * Daniel Lezcano <dlezcano at fr.ibm.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <unistd.h>
+#include <alloca.h>
+#include <errno.h>
+#include <signal.h>
+#include <namespace.h>
+
+#include <lxc/lxc.h>
+
+lxc_log_define(lxc_namespace, lxc);
+
+struct clone_arg {
+	int (*fn)(void *);
+	void *arg;
+};
+
+static int do_clone(void *arg)
+{
+	struct clone_arg *clone_arg = arg;
+	return clone_arg->fn(clone_arg->arg);
+}
+
+pid_t lxc_clone(int (*fn)(void *), void *arg, int flags)
+{
+	struct clone_arg clone_arg = {
+		.fn = fn,
+		.arg = arg,
+	};
+
+	long stack_size = sysconf(_SC_PAGESIZE);
+	void *stack = alloca(stack_size) + stack_size;
+	pid_t ret;
+
+	ret = clone(do_clone, stack, flags | SIGCHLD, &clone_arg);
+	if (ret < 0)
+		ERROR("failed to clone(0x%x): %s", flags, strerror(errno));
+
+	return ret;
+}

src/lxc/namespace.h

 /*
  * lxc: linux Container library
  *
- * (C) Copyright IBM Corp. 2007, 2008
+ * (C) Copyright IBM Corp. 2007, 2009
  *
  * Authors:
  * Daniel Lezcano <dlezcano at fr.ibm.com>
@@ -24,6 +24,9 @@
 #define __namespace_h
 
 #include <syscall.h>
+#define _GNU_SOURCE
+#include <sched.h>
+
 #ifndef CLONE_FS
 #  define CLONE_FS                0x00000200
 #endif
@@ -45,21 +48,7 @@
 #ifndef CLONE_NEWNET
 #  define CLONE_NEWNET            0x40000000
 #endif
-#ifndef __NR_unshare
-#  ifdef __i386__
-#    define __NR_unshare 310
-#  elif __x86_64__
-#    define __NR_unshare 272
-#  elif __ia64__
-#    define __NR_unshare 1296
-#  elif __s390__
-#    define __NR_unshare 303
-#  elif __powerpc__
-#    define __NR_unshare 282
-#else
-#    error "unsupported architecture"
-#  endif
-#endif
+
 #if __i386__ || __x86_64__ || __powerpc__
 #   define fork_ns(flags) syscall(SYS_clone, flags|SIGCHLD, NULL)
 #elif __s390__
@@ -69,5 +58,9 @@
 #else
 #   error "unsupported architecture"
 #endif
-#define unshare_ns(flags) syscall(__NR_unshare, flags, NULL)
+
+#define unshare_ns(flags) unshare(flags)
+
+extern pid_t lxc_clone(int (*fn)(void *), void *arg, int flags);
+
 #endif