set 8MB user stack size, add more flags for sys_clone

8MB is the default linux app stack size on x86_64.
gcc app in alpine linux call sys_clone with flags 0x5d0f00.

In case of supporting more other potential flags,
use panic! instead of warn!, then we can get timely panic-style info.

Now python2 hello.py can run correctly, but only one time.
I guess the memory management has some problem,
maybe there are some memory leak.

kernel/src/arch/x86_64/consts.rs

@@ -55,7 +55,7 @@ pub const USER_GRANT_PML4: usize = (USER_GRANT_OFFSET & PML4_MASK) / PML4_SIZE;
 pub const USER_STACK_OFFSET: usize = USER_GRANT_OFFSET + PML4_SIZE;
 pub const USER_STACK_PML4: usize = (USER_STACK_OFFSET & PML4_MASK) / PML4_SIZE;
 /// Size of user stack
-pub const USER_STACK_SIZE: usize = 1024 * 1024; // 1 MB
+pub const USER_STACK_SIZE: usize = 8 * 1024 * 1024; // 8 MB, the default config of Linux
 
 /// Offset to user sigstack
 pub const USER_SIGSTACK_OFFSET: usize = USER_STACK_OFFSET + PML4_SIZE;

kernel/src/syscall/proc.rs

@@ -26,16 +26,17 @@ pub fn sys_clone(
 ) -> SysResult {
     let clone_flags = CloneFlags::from_bits_truncate(flags);
     info!(
-        "clone: flags: {:?}, newsp: {:#x}, parent_tid: {:?}, child_tid: {:?}, newtls: {:#x}",
-        clone_flags, newsp, parent_tid, child_tid, newtls
+        "clone: flags: {:?} == {:#x}, newsp: {:#x}, parent_tid: {:?}, child_tid: {:?}, newtls: {:#x}",
+        clone_flags, flags, newsp, parent_tid, child_tid, newtls
     );
     if flags == 0x4111 || flags == 0x11 {
         warn!("sys_clone is calling sys_fork instead, ignoring other args");
         return sys_fork(tf);
     }
-    if flags != 0x7d0f00 {
-        warn!("sys_clone only support musl pthread_create");
-        return Err(SysError::ENOSYS);
+    if (flags != 0x7d0f00) && (flags!= 0x5d0f00)  { //0x5d0f00 is the args from gcc of alpine linux
+        //warn!("sys_clone only support musl pthread_create");
+        panic!("sys_clone only support sys_fork OR musl pthread_create without flags{:x}", flags);
+        //return Err(SysError::ENOSYS);
     }
     {
         let proc = process();