kernel: fix compile errors from futex_wake_index and stack mmap

- syscall/futex.rs: scope the context write guard so futexes.swap_remove
  can borrow mutably after the guard drops
- syscall/process.rs: add missing 'shared' arg to Grant::zeroed

src/syscall/futex.rs

@@ -201,15 +201,22 @@ pub fn futex(
                             i += 1;
                             continue;
                         }
-                        let mut context = futex.context_lock.write(token.token());
-                        if let Some(index) = futex.waitv_index {
-                            if context.futex_wake_index.is_none() {
-                                context.futex_wake_index = Some(index);
+                        let should_wake = {
+                            let mut context = futex.context_lock.write(token.token());
+                            if let Some(index) = futex.waitv_index {
+                                if context.futex_wake_index.is_none() {
+                                    context.futex_wake_index = Some(index);
+                                }
                             }
+                            context.unblock();
+                            true
+                        };
+                        if should_wake {
+                            futexes.swap_remove(i);
+                            woken += 1;
+                        } else {
+                            i += 1;
                         }
-                        context.unblock();
-                        futexes.swap_remove(i);
-                        woken += 1;
                     }
 
                     futexes.is_empty()

src/syscall/process.rs

@@ -332,6 +332,7 @@ pub unsafe fn usermode_bootstrap(bootstrap: &Bootstrap, token: &mut CleanLockTok
                             flags,
                             mapper,
                             flusher,
+                            false, // private mapping for bootstrap stack
                         )?)
                     },
                 );