Wrap syscalls in user_lib & change xstate to exit_code.

os/src/syscall/process.rs

@@ -1,6 +1,6 @@
 use crate::batch::run_next_app;
 
-pub fn sys_exit(xstate: i32) -> ! {
+pub fn sys_exit(exit_code: i32) -> ! {
     println!("[kernel] Application exited with code {}", xstate);
     run_next_app()
 }

user/src/console.rs

@@ -1,11 +1,13 @@
 use core::fmt::{self, Write};
-use crate::syscall::{STDOUT, sys_write};
+use super::write;
 
 struct Stdout;
 
+const STDOUT: usize = 1;
+
 impl Write for Stdout {
     fn write_str(&mut self, s: &str) -> fmt::Result {
-        sys_write(STDOUT, s.as_bytes());
+        write(STDOUT, s.as_bytes());
         Ok(())
     }
 }

user/src/lib.rs

@@ -12,7 +12,7 @@ mod lang_items;
 #[link_section = ".text.entry"]
 pub extern "C" fn _start() -> ! {
     clear_bss();
-    syscall::sys_exit(main());
+    exit(main());
     panic!("unreachable after sys_exit!");
 }
 
@@ -30,4 +30,9 @@ fn clear_bss() {
     (start_bss as usize..end_bss as usize).for_each(|addr| {
         unsafe { (addr as *mut u8).write_volatile(0); }
     });
-}
+}
+
+use syscall::*;
+
+pub fn write(fd: usize, buf: &[u8]) -> isize { sys_write(fd, buf) }
+pub fn exit(exit_code: i32) -> isize { sys_exit(exit_code) }

user/src/syscall.rs

@@ -1,5 +1,3 @@
-pub const STDOUT: usize = 1;
-
 const SYSCALL_WRITE: usize = 64;
 const SYSCALL_EXIT: usize = 93;
 
@@ -20,6 +18,6 @@ pub fn sys_write(fd: usize, buffer: &[u8]) -> isize {
     syscall(SYSCALL_WRITE, [fd, buffer.as_ptr() as usize, buffer.len()])
 }
 
-pub fn sys_exit(xstate: i32) -> isize {
-    syscall(SYSCALL_EXIT, [xstate as usize, 0, 0])
+pub fn sys_exit(exit_code: i32) -> isize {
+    syscall(SYSCALL_EXIT, [exit_code as usize, 0, 0])
 }