Fix "clone grant using fmap"

This does the same as the previous MR, but fixes the issue where the
parent process got the mapping (and at the wrong address) and not the
child process.

src/scheme/user.rs

@@ -8,7 +8,7 @@ use spin::{Mutex, RwLock};
 
 use crate::context::{self, Context};
 use crate::context::file::FileDescriptor;
-use crate::context::memory::{DANGLING, page_flags, round_down_pages, Grant, Region};
+use crate::context::memory::{DANGLING, page_flags, round_down_pages, Grant, Region, GrantFileRef};
 use crate::event;
 use crate::paging::{PAGE_SIZE, InactivePageTable, VirtualAddress};
 use crate::scheme::{AtomicSchemeId, SchemeId};
@@ -123,7 +123,7 @@ impl UserInner {
         ).map(|addr| addr.data())
     }
 
-    fn capture_inner(context_weak: &Weak<RwLock<Context>>, dst_address: usize, address: usize, size: usize, flags: MapFlags, desc_opt: Option<FileDescriptor>)
+    fn capture_inner(context_weak: &Weak<RwLock<Context>>, dst_address: usize, address: usize, size: usize, flags: MapFlags, desc_opt: Option<GrantFileRef>)
                      -> Result<VirtualAddress> {
         // TODO: More abstractions over grant creation!
 
@@ -233,7 +233,8 @@ impl UserInner {
                         if address % PAGE_SIZE > 0 {
                             println!("scheme returned unaligned address, causing extra frame to be allocated");
                         }
-                        let res = UserInner::capture_inner(&context_weak, map.address, address, map.size, map.flags, Some(desc));
+                        let file_ref = GrantFileRef { desc, offset: map.offset, flags: map.flags };
+                        let res = UserInner::capture_inner(&context_weak, map.address, address, map.size, map.flags, Some(file_ref));
                         if let Ok(grant_address) = res {
                             if let Some(context_lock) = context_weak.upgrade() {
                                 let context = context_lock.read();