diff --git a/context/mod.rs b/context/mod.rs
index 8975582..ab0ede5 100644
--- a/context/mod.rs
+++ b/context/mod.rs
@@ -138,7 +138,7 @@ pub unsafe fn switch() {
 
     for (_pid, context_lock) in contexts().map.iter() {
         let mut context = context_lock.write();
-        if ! context.running {
+        if ! context.running && ! context.blocked {
             to_ptr = context.deref_mut() as *mut Context;
             break;
         }
@@ -165,6 +165,8 @@ pub struct Context {
     pub id: usize,
     /// Running or not
     pub running: bool,
+    /// Blocked or not
+    pub blocked: bool,
     /// The architecture specific context
     pub arch: ArchContext,
     /// Kernel stack
@@ -179,6 +181,7 @@ impl Context {
         Context {
             id: id,
             running: false,
+            blocked: true,
             arch: ArchContext::new(),
             kstack: None,
             files: Vec::new()
diff --git a/elf.rs b/elf.rs
index 10be116..6a2d93f 100644
--- a/elf.rs
+++ b/elf.rs
@@ -60,6 +60,10 @@ impl<'a> Elf<'a> {
                 let end_page = Page::containing_address(VirtualAddress::new((segment.p_vaddr + segment.p_memsz) as usize));
 
                 for page in Page::range_inclusive(start_page, end_page) {
+                    if active_table.translate_page(page).is_some() {
+                        //TODO panic!("Elf::run: still mapped: {:?}", page);
+                        active_table.unmap(page);
+                    }
                     active_table.map(page, entry::NO_EXECUTE | entry::WRITABLE);
                 }
                 active_table.flush_all();
@@ -100,6 +104,10 @@ impl<'a> Elf<'a> {
         let end_page = Page::containing_address(VirtualAddress::new(0x80000000 + 64*1024 - 1));
 
         for page in Page::range_inclusive(start_page, end_page) {
+            if active_table.translate_page(page).is_some() {
+                //TODO panic!("Elf::run: still mapped: {:?}", page);
+                active_table.unmap(page);
+            }
             active_table.map(page, entry::NO_EXECUTE | entry::WRITABLE | entry::USER_ACCESSIBLE);
         }
         active_table.flush_all();
diff --git a/lib.rs b/lib.rs
index e32d088..3943e02 100644
--- a/lib.rs
+++ b/lib.rs
@@ -133,7 +133,15 @@ pub extern fn kmain() {
     let pid = syscall::getpid();
     println!("BSP: {:?}", pid);
 
-    context::contexts_mut().spawn(userspace_init).expect("failed to spawn userspace_init");
+    match context::contexts_mut().spawn(userspace_init) {
+        Ok(context_lock) => {
+            let mut context = context_lock.write();
+            context.blocked = false;
+        },
+        Err(err) => {
+            panic!("failed to spawn userspace_init: {:?}", err);
+        }
+    }
 
     unsafe { context::switch(); }
 
diff --git a/syscall/process.rs b/syscall/process.rs
index f84be9f..18dfa89 100644
--- a/syscall/process.rs
+++ b/syscall/process.rs
@@ -63,7 +63,7 @@ pub fn brk(address: usize) -> Result<usize> {
 
 pub fn clone(flags: usize) -> Result<usize> {
     println!("Clone {:X}", flags);
-    Err(Error::NoCall)
+    Ok(0)
 }
 
 pub fn exit(status: usize) -> ! {
@@ -76,22 +76,23 @@ pub fn exit(status: usize) -> ! {
 pub fn exec(path: &[u8], _args: &[[usize; 2]]) -> Result<usize> {
     //TODO: Use args
     //TODO: Unmap previous mappings
-    //TODO: Drop init_data
+    //TODO: Drop data vec
+    println!("Exec {}", unsafe { str::from_utf8_unchecked(path) });
 
-    let init_file = syscall::open(path, 0)?;
-    let mut init_data = vec![];
+    let file = syscall::open(path, 0)?;
+    let mut data = vec![];
     loop {
         let mut buf = [0; 4096];
-        let count = syscall::read(init_file, &mut buf)?;
+        let count = syscall::read(file, &mut buf)?;
         if count > 0 {
-            init_data.extend_from_slice(&buf[..count]);
+            data.extend_from_slice(&buf[..count]);
         } else {
             break;
         }
     }
-    let _ = syscall::close(init_file);
+    let _ = syscall::close(file);
 
-    match elf::Elf::from(&init_data) {
+    match elf::Elf::from(&data) {
         Ok(elf) => {
             elf.run();
             Ok(0)