Use isohybrid to generate a USB stick friendly ISO

Add assertions to verify that grants are unmapped
Fix grant unmapping in exec and exit, thus fixing some crashes without network cards

.travis.yml

@@ -7,7 +7,7 @@ os:
 - linux
 dist: trusty
 before_install:
-- if [ `uname` = "Linux" ]; then sudo apt-get install -qq nasm pkg-config fuse libfuse-dev;
+- if [ `uname` = "Linux" ]; then sudo apt-get install -qq nasm pkg-config fuse libfuse-dev syslinux-utils;
   sudo modprobe fuse; sudo chmod 666 /dev/fuse; sudo chown root:$USER /etc/fuse.conf;
   fi
 - if [ `uname` = "Darwin" ]; then brew update; brew install nasm gcc49 pkg-config

Makefile

@@ -233,6 +233,7 @@ build/livedisk.iso: build/livedisk.bin.gz
 	mkisofs -o $@ -b isolinux/isolinux.bin -c isolinux/boot.cat \
 					-no-emul-boot -boot-load-size 4 -boot-info-table \
 					build/iso/
+	isohybrid $@
 
 qemu: build/harddrive.bin
 	$(QEMU) $(QEMUFLAGS) -drive file=$<,format=raw

kernel/context/memory.rs

@@ -12,7 +12,8 @@ use arch::paging::temporary_page::TemporaryPage;
 pub struct Grant {
     start: VirtualAddress,
     size: usize,
-    flags: EntryFlags
+    flags: EntryFlags,
+    mapped: bool
 }
 
 impl Grant {
@@ -36,7 +37,8 @@ impl Grant {
         Grant {
             start: to,
             size: size,
-            flags: flags
+            flags: flags,
+            mapped: true
         }
     }
 
@@ -64,7 +66,8 @@ impl Grant {
         Grant {
             start: to,
             size: size,
-            flags: flags
+            flags: flags,
+            mapped: true
         }
     }
 
@@ -80,7 +83,9 @@ impl Grant {
         self.flags
     }
 
-    pub fn unmap(self) {
+    pub fn unmap(mut self) {
+        assert!(self.mapped);
+
         let mut active_table = unsafe { ActivePageTable::new() };
 
         let mut flush_all = false;
@@ -95,9 +100,13 @@ impl Grant {
         if flush_all {
             active_table.flush_all();
         }
+
+        self.mapped = false;
     }
 
-    pub fn unmap_inactive(self, new_table: &mut InactivePageTable, temporary_page: &mut TemporaryPage) {
+    pub fn unmap_inactive(mut self, new_table: &mut InactivePageTable, temporary_page: &mut TemporaryPage) {
+        assert!(self.mapped);
+
         let mut active_table = unsafe { ActivePageTable::new() };
 
         active_table.with(new_table, temporary_page, |mapper| {
@@ -107,6 +116,14 @@ impl Grant {
                 mapper.unmap_return(page);
             }
         });
+
+        self.mapped = false;
+    }
+}
+
+impl Drop for Grant {
+    fn drop(&mut self) {
+        assert!(!self.mapped);
     }
 }
 

kernel/scheme/user.rs

@@ -106,6 +106,10 @@ impl UserInner {
             for i in 0 .. grants.len() {
                 let start = grants[i].start_address().get();
                 if to_address + full_size < start {
+                    {
+                        let name = context.name.lock();
+                        println!("{}: {}: Can grant {:X} to {:X} size {}", context.id.into(), ::core::str::from_utf8(&name).unwrap_or(""), from_address, to_address, full_size);
+                    }
                     grants.insert(i, Grant::map_inactive(
                         VirtualAddress::new(from_address),
                         VirtualAddress::new(to_address),
@@ -123,6 +127,10 @@ impl UserInner {
                 }
             }
 
+            {
+                let name = context.name.lock();
+                println!("{}: {}: Can grant {:X} to {:X} size {}", context.id.into(), ::core::str::from_utf8(&name).unwrap_or(""), from_address, to_address, full_size);
+            }
             grants.push(Grant::map_inactive(
                 VirtualAddress::new(from_address),
                 VirtualAddress::new(to_address),

kernel/syscall/process.rs

@@ -511,10 +511,22 @@ pub fn exec(path: &[u8], arg_ptrs: &[[usize; 2]]) -> Result<usize> {
                     // Unmap previous image, heap, grants, stack, and tls
                     context.image.clear();
                     drop(context.heap.take());
-                    context.grants = Arc::new(Mutex::new(Vec::new()));
                     drop(context.stack.take());
                     drop(context.tls.take());
 
+                    let mut unmap_grants = Vec::new();
+                    // FIXME: Looks like a race condition.
+                    // Is it possible for Arc::strong_count to return 1 to two contexts that exit at the
+                    // same time, or return 2 to both, thus either double freeing or leaking the grants?
+                    if Arc::strong_count(&context.grants) == 1 {
+                        mem::swap(context.grants.lock().deref_mut(), &mut unmap_grants);
+                    }
+                    context.grants = Arc::new(Mutex::new(Vec::new()));
+
+                    for grant in unmap_grants {
+                        grant.unmap();
+                    }
+
                     if stat.st_mode & syscall::flag::MODE_SETUID == syscall::flag::MODE_SETUID {
                         context.euid = stat.st_uid;
                     }
@@ -753,7 +765,10 @@ pub fn exit(status: usize) -> ! {
         let mut close_files = Vec::new();
         let (pid, ppid) = {
             let mut context = context_lock.write();
-            if Arc::strong_count(&context.files) == 1 { // FIXME: Looks like a race condition.
+            // FIXME: Looks like a race condition.
+            // Is it possible for Arc::strong_count to return 1 to two contexts that exit at the
+            // same time, or return 2 to both, thus either double closing or leaking the files?
+            if Arc::strong_count(&context.files) == 1 {
                 mem::swap(context.files.lock().deref_mut(), &mut close_files);
             }
             context.files = Arc::new(Mutex::new(Vec::new()));
@@ -796,8 +811,20 @@ pub fn exit(status: usize) -> ! {
             drop(context.heap.take());
             drop(context.stack.take());
             drop(context.tls.take());
+
+            let mut unmap_grants = Vec::new();
+            // FIXME: Looks like a race condition.
+            // Is it possible for Arc::strong_count to return 1 to two contexts that exit at the
+            // same time, or return 2 to both, thus either double freeing or leaking the grants?
+            if Arc::strong_count(&context.grants) == 1 {
+                mem::swap(context.grants.lock().deref_mut(), &mut unmap_grants);
+            }
             context.grants = Arc::new(Mutex::new(Vec::new()));
 
+            for grant in unmap_grants {
+                grant.unmap();
+            }
+
             let vfork = context.vfork;
             context.vfork = false;