Fix fork and syscall return value.

crate/memory/src/memory_set.rs

@@ -205,6 +205,12 @@ impl<T: InactivePageTable> Clone for MemorySet<T> {
     }
 }
 
+impl<T: InactivePageTable> Drop for MemorySet<T> {
+    fn drop(&mut self) {
+        self.clear();
+    }
+}
+
 impl<T: InactivePageTable> Debug for MemorySet<T> {
     fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {
         f.debug_list()

kernel/src/arch/riscv32/context.rs

@@ -153,7 +153,7 @@ impl Context {
             context: ContextData::new(cr3),
             tf: {
                 let mut tf = tf.clone();
-                tf.x[1] = 0; // ra
+                tf.x[10] = 0; // a0
                 tf
             },
         }.push_at(kstack_top)

kernel/src/arch/riscv32/interrupt.rs

@@ -53,9 +53,9 @@ fn timer() {
 }
 
 fn syscall(tf: &mut TrapFrame) {
+    tf.sepc += 4;   // Must before syscall, because of fork.
     let ret = ::syscall::syscall(tf.x[10], [tf.x[11], tf.x[12], tf.x[13], tf.x[14], tf.x[15], tf.x[16]], tf);
-    unsafe { *(&tf.x[10] as *const _ as *mut i32) = ret; }
-    tf.sepc += 4;
+    tf.x[10] = ret as usize;
 }
 
 extern {

kernel/src/arch/x86_64/interrupt/handler.rs

@@ -160,14 +160,14 @@ fn syscall(tf: &mut TrapFrame) {
     trace!("\nInterupt: Syscall {:#x?}", tf.rax);
     use syscall::syscall;
     let ret = syscall(tf.rax, [tf.rdi, tf.rsi, tf.rdx, tf.rcx, tf.r8, tf.r9], tf);
-    unsafe { *(&tf.rax as *const _ as *mut i32) = ret; }
+    tf.rax = ret as usize;
 }
 
 fn syscall32(tf: &mut TrapFrame) {
     trace!("\nInterupt: Syscall {:#x?}", tf.rax);
     use syscall::syscall;
     let ret = syscall(tf.rax, [tf.rdx, tf.rcx, tf.rbx, tf.rdi, tf.rsi, 0], tf);
-    unsafe { *(&tf.rax as *const _ as *mut i32) = ret; }
+    tf.rax = ret as usize;
 }
 
 fn error(tf: &TrapFrame) {

kernel/src/consts.rs

@@ -6,7 +6,7 @@ pub use self::riscv::*;
 pub use self::x86_64::*;
 
 pub const MAX_CPU_NUM: usize = 8;
-pub const MAX_PROCESS_NUM: usize = 32;
+pub const MAX_PROCESS_NUM: usize = 48;
 
 #[cfg(target_arch = "riscv")]
 mod riscv {
@@ -18,7 +18,7 @@ mod riscv {
     pub const KERNEL_OFFSET: usize = 0;
     pub const KERNEL_PML4: usize = 0x8000_0000 >> 22;
     pub const KERNEL_HEAP_OFFSET: usize = 0x8020_0000;
-    pub const KERNEL_HEAP_SIZE: usize = 0x0010_0000;
+    pub const KERNEL_HEAP_SIZE: usize = 0x0020_0000;
     pub const MEMORY_OFFSET: usize = 0x8000_0000;
     pub const MEMORY_END: usize = 0x8080_0000;
     pub const USER_STACK_OFFSET: usize = 0x70000000;