diff --git a/src/context/context.rs b/src/context/context.rs
index 43cb667e1c..23819cff1b 100644
--- a/src/context/context.rs
+++ b/src/context/context.rs
@@ -20,7 +20,7 @@ use crate::context::memory::AddrSpace;
 use crate::ipi::{ipi, IpiKind, IpiTarget};
 use crate::paging::{RmmA, RmmArch};
 use crate::memory::{RaiiFrame, Frame};
-use crate::scheme::{SchemeNamespace, FileHandle};
+use crate::scheme::{SchemeNamespace, FileHandle, CallerCtx};
 use crate::sync::WaitMap;
 
 use crate::syscall::data::SigAction;
@@ -472,6 +472,9 @@ impl Context {
             0
         ); 128]))
     }
+    pub fn caller_ctx(&self) -> CallerCtx {
+        CallerCtx { pid: self.id.into(), uid: self.euid, gid: self.egid }
+    }
 }
 
 /// Wrapper struct for borrowing the syscall head or tail buf.
diff --git a/src/context/file.rs b/src/context/file.rs
index 85433b3781..fb87a3c470 100644
--- a/src/context/file.rs
+++ b/src/context/file.rs
@@ -32,7 +32,7 @@ pub struct FileDescriptor {
 impl FileDescription {
     /// Try closing a file, although at this point the description will be destroyed anyway, if
     /// doing so fails.
-    pub fn try_close(self) -> Result<usize> {
+    pub fn try_close(self) -> Result<()> {
         event::unregister_file(self.scheme, self.number);
 
         let scheme = Arc::clone(
@@ -44,11 +44,10 @@ impl FileDescription {
 }
 
 impl FileDescriptor {
-    pub fn close(self) -> Result<usize> {
-        let Ok(file) = Arc::try_unwrap(self.description) else {
-            return Ok(0);
-        };
-
-        file.into_inner().try_close()
+    pub fn close(self) -> Result<()> {
+        if let Ok(file) = Arc::try_unwrap(self.description) {
+            file.into_inner().try_close()?;
+        }
+        Ok(())
     }
 }
diff --git a/src/scheme/acpi.rs b/src/scheme/acpi.rs
index 1800f40e53..eded6a6951 100644
--- a/src/scheme/acpi.rs
+++ b/src/scheme/acpi.rs
@@ -20,10 +20,11 @@ use crate::syscall::flag::{
     O_ACCMODE, O_CREAT, O_DIRECTORY, O_EXCL, O_RDONLY, O_STAT, O_SYMLINK,
     SEEK_SET, SEEK_CUR, SEEK_END,
 };
-use crate::syscall::scheme::Scheme;
 use crate::syscall::error::{Error, Result};
 use crate::syscall::usercopy::{UserSliceRo, UserSliceWo};
 
+use super::{KernelScheme, CallerCtx, OpenResult};
+
 /// A scheme used to access the RSDT or XSDT, which is needed for e.g. `acpid` to function.
 pub struct AcpiScheme;
 
@@ -113,11 +114,11 @@ impl AcpiScheme {
     }
 }
 
-impl Scheme for AcpiScheme {
-    fn open(&self, path: &str, flags: usize, opener_uid: u32, _opener_gid: u32) -> Result<usize> {
+impl KernelScheme for AcpiScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
         let path = path.trim_start_matches('/');
 
-        if opener_uid != 0 {
+        if ctx.uid != 0 {
             return Err(Error::new(EACCES));
         }
         if flags & O_CREAT == O_CREAT {
@@ -161,9 +162,9 @@ impl Scheme for AcpiScheme {
             stat: flags & O_STAT == O_STAT,
         });
 
-        Ok(fd)
+        Ok(OpenResult::SchemeLocal(fd))
     }
-    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<isize> {
+    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<usize> {
         let mut handles = HANDLES.write();
         let handle = handles.get_mut(&id).ok_or(Error::new(EBADF))?;
 
@@ -194,7 +195,7 @@ impl Scheme for AcpiScheme {
 
         handle.offset = new_offset;
 
-        Ok(new_offset as isize)
+        Ok(new_offset)
     }
     // TODO
     fn fevent(&self, id: usize, _flags: EventFlags) -> Result<EventFlags> {
@@ -207,14 +208,12 @@ impl Scheme for AcpiScheme {
 
         Ok(EventFlags::empty())
     }
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         if HANDLES.write().remove(&id).is_none() {
             return Err(Error::new(EBADF));
         }
-        Ok(0)
+        Ok(())
     }
-}
-impl crate::scheme::KernelScheme for AcpiScheme {
     fn kwrite(&self, _id: usize, _buf: UserSliceRo) -> Result<usize> {
         Err(Error::new(EBADF))
     }
@@ -260,7 +259,7 @@ impl crate::scheme::KernelScheme for AcpiScheme {
 
         Ok(bytes_copied)
     }
-    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<()> {
         let handles = HANDLES.read();
         let handle = handles.get(&id).ok_or(Error::new(EBADF))?;
 
@@ -286,6 +285,6 @@ impl crate::scheme::KernelScheme for AcpiScheme {
             },
         })?;
 
-        Ok(0)
+        Ok(())
     }
 }
diff --git a/src/scheme/debug.rs b/src/scheme/debug.rs
index e232cc9a2a..f849400969 100644
--- a/src/scheme/debug.rs
+++ b/src/scheme/debug.rs
@@ -1,12 +1,11 @@
 use core::sync::atomic::{AtomicUsize, Ordering};
-use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
+use spin::{Once, RwLock};
 
 use crate::arch::debug::Writer;
 use crate::event;
 use crate::scheme::*;
 use crate::sync::WaitQueue;
 use crate::syscall::flag::{EventFlags, EVENT_READ, F_GETFL, F_SETFL, O_ACCMODE, O_NONBLOCK};
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::UserSliceRo;
 use crate::syscall::usercopy::UserSliceWo;
 
@@ -22,19 +21,7 @@ struct Handle {
     flags: usize,
 }
 
-static HANDLES: Once<RwLock<BTreeMap<usize, Handle>>> = Once::new();
-
-fn init_handles() -> RwLock<BTreeMap<usize, Handle>> {
-    RwLock::new(BTreeMap::new())
-}
-
-fn handles() -> RwLockReadGuard<'static, BTreeMap<usize, Handle>> {
-    HANDLES.call_once(init_handles).read()
-}
-
-fn handles_mut() -> RwLockWriteGuard<'static, BTreeMap<usize, Handle>> {
-    HANDLES.call_once(init_handles).write()
-}
+static HANDLES: RwLock<BTreeMap<usize, Handle>> = RwLock::new(BTreeMap::new());
 
 /// Add to the input queue
 pub fn debug_input(data: u8) {
@@ -47,7 +34,7 @@ pub fn debug_notify() {
         return;
     };
 
-    for (id, _handle) in handles().iter() {
+    for (id, _handle) in HANDLES.read().iter() {
         event::trigger(scheme_id, *id, EVENT_READ);
     }
 }
@@ -61,9 +48,9 @@ impl DebugScheme {
     }
 }
 
-impl Scheme for DebugScheme {
-    fn open(&self, path: &str, flags: usize, uid: u32, _gid: u32) -> Result<usize> {
-        if uid != 0 {
+impl KernelScheme for DebugScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
+        if ctx.uid != 0 {
             return Err(Error::new(EPERM));
         }
 
@@ -71,16 +58,16 @@ impl Scheme for DebugScheme {
             return Err(Error::new(ENOENT));
         }
 
-        let id = NEXT_ID.fetch_add(1, Ordering::SeqCst);
-        handles_mut().insert(id, Handle {
+        let id = NEXT_ID.fetch_add(1, Ordering::Relaxed);
+        HANDLES.write().insert(id, Handle {
             flags: flags & ! O_ACCMODE
         });
 
-        Ok(id)
+        Ok(OpenResult::SchemeLocal(id))
     }
 
     fn fcntl(&self, id: usize, cmd: usize, arg: usize) -> Result<usize> {
-        let mut handles = handles_mut();
+        let mut handles = HANDLES.write();
         if let Some(handle) = handles.get_mut(&id) {
             match cmd {
                 F_GETFL => Ok(handle.flags),
@@ -97,36 +84,34 @@ impl Scheme for DebugScheme {
 
     fn fevent(&self, id: usize, _flags: EventFlags) -> Result<EventFlags> {
         let _handle = {
-            let handles = handles();
+            let handles = HANDLES.read();
             *handles.get(&id).ok_or(Error::new(EBADF))?
         };
 
         Ok(EventFlags::empty())
     }
 
-    fn fsync(&self, id: usize) -> Result<usize> {
+    fn fsync(&self, id: usize) -> Result<()> {
         let _handle = {
-            let handles = handles();
+            let handles = HANDLES.read();
             *handles.get(&id).ok_or(Error::new(EBADF))?
         };
 
-        Ok(0)
+        Ok(())
     }
 
     /// Close the file `number`
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         let _handle = {
-            let mut handles = handles_mut();
+            let mut handles = HANDLES.write();
             handles.remove(&id).ok_or(Error::new(EBADF))?
         };
 
-        Ok(0)
+        Ok(())
     }
-}
-impl crate::scheme::KernelScheme for DebugScheme {
     fn kread(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let handle = {
-            let handles = handles();
+            let handles = HANDLES.read();
             *handles.get(&id).ok_or(Error::new(EBADF))?
         };
 
@@ -136,7 +121,7 @@ impl crate::scheme::KernelScheme for DebugScheme {
 
     fn kwrite(&self, id: usize, buf: UserSliceRo) -> Result<usize> {
         let _handle = {
-            let handles = handles();
+            let handles = HANDLES.read();
             *handles.get(&id).ok_or(Error::new(EBADF))?
         };
 
@@ -156,7 +141,7 @@ impl crate::scheme::KernelScheme for DebugScheme {
     }
     fn kfpath(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let _handle = {
-            let handles = handles();
+            let handles = HANDLES.read();
             *handles.get(&id).ok_or(Error::new(EBADF))?
         };
 
diff --git a/src/scheme/event.rs b/src/scheme/event.rs
index 73ff9b88ac..2bcc2c5ae7 100644
--- a/src/scheme/event.rs
+++ b/src/scheme/event.rs
@@ -4,20 +4,20 @@ use core::mem;
 use crate::event::{EventQueue, EventQueueId, next_queue_id, queues, queues_mut};
 use crate::syscall::data::Event;
 use crate::syscall::error::*;
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::{UserSliceWo, UserSliceRo};
 
+use super::{KernelScheme, CallerCtx, OpenResult};
+
 pub struct EventScheme;
 
-impl Scheme for EventScheme {
-    fn open(&self, _path: &str, _flags: usize, _uid: u32, _gid: u32) -> Result<usize> {
+impl KernelScheme for EventScheme {
+    fn kopen(&self, _path: &str, _flags: usize, _ctx: CallerCtx) -> Result<OpenResult> {
         let id = next_queue_id();
         queues_mut().insert(id, Arc::new(EventQueue::new(id)));
 
-        Ok(id.into())
+        Ok(OpenResult::SchemeLocal(id.get()))
     }
 
-
     fn fcntl(&self, id: usize, _cmd: usize, _arg: usize) -> Result<usize> {
         let id = EventQueueId::from(id);
 
@@ -25,19 +25,17 @@ impl Scheme for EventScheme {
         handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(0))
     }
 
-    fn fsync(&self, id: usize) -> Result<usize> {
+    fn fsync(&self, id: usize) -> Result<()> {
         let id = EventQueueId::from(id);
 
         let handles = queues();
-        handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+        handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(()))
     }
 
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         let id = EventQueueId::from(id);
-        queues_mut().remove(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+        queues_mut().remove(&id).ok_or(Error::new(EBADF)).and(Ok(()))
     }
-}
-impl crate::scheme::KernelScheme for EventScheme {
     fn kread(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let id = EventQueueId::from(id);
 
diff --git a/src/scheme/irq.rs b/src/scheme/irq.rs
index 749560cfd9..fd75baae0b 100644
--- a/src/scheme/irq.rs
+++ b/src/scheme/irq.rs
@@ -16,9 +16,10 @@ use crate::scheme::SchemeId;
 use crate::syscall::data::Stat;
 use crate::syscall::error::*;
 use crate::syscall::flag::{EventFlags, EVENT_READ, O_DIRECTORY, O_CREAT, O_STAT, MODE_CHR, MODE_DIR};
-use crate::syscall::scheme::{calc_seek_offset_usize, Scheme};
 use crate::syscall::usercopy::{UserSliceWo, UserSliceRo};
 
+use super::{OpenResult, CallerCtx, calc_seek_offset};
+
 pub static IRQ_SCHEME_ID: Once<SchemeId> = Once::new();
 
 /// IRQ queues
@@ -146,9 +147,9 @@ const fn vector_to_irq(vector: u8) -> u8 {
     vector - 32
 }
 
-impl Scheme for IrqScheme {
-    fn open(&self, path: &str, flags: usize, uid: u32, _gid: u32) -> Result<usize> {
-        if uid != 0 { return Err(Error::new(EACCES)) }
+impl crate::scheme::KernelScheme for IrqScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
+        if ctx.uid != 0 { return Err(Error::new(EACCES)) }
 
         let path_str = path.trim_start_matches('/');
 
@@ -213,21 +214,21 @@ impl Scheme for IrqScheme {
                 return Err(Error::new(ENOENT));
             }
         };
-        let fd = self.next_fd.fetch_add(1, Ordering::SeqCst);
+        let fd = self.next_fd.fetch_add(1, Ordering::Relaxed);
         HANDLES.write().as_mut().unwrap().insert(fd, handle);
-        Ok(fd)
+        Ok(OpenResult::SchemeLocal(fd))
     }
 
-    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<isize> {
+    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<usize> {
         let handles_guard = HANDLES.read();
         let handle = handles_guard.as_ref().unwrap().get(&id).ok_or(Error::new(EBADF))?;
 
         match handle {
             &Handle::Avail(_, ref buf, ref offset) | &Handle::TopLevel(ref buf, ref offset) => {
                 let cur_offset = offset.load(Ordering::SeqCst);
-                let new_offset = calc_seek_offset_usize(cur_offset, pos, whence, buf.len())?;
+                let new_offset = calc_seek_offset(cur_offset, pos, whence, buf.len())?;
                 offset.store(new_offset as usize, Ordering::SeqCst);
-                Ok(new_offset)
+                Ok(new_offset as usize)
             }
             _ => Err(Error::new(ESPIPE)),
         }
@@ -243,11 +244,11 @@ impl Scheme for IrqScheme {
     }
 
 
-    fn fsync(&self, _file: usize) -> Result<usize> {
-        Ok(0)
+    fn fsync(&self, _file: usize) -> Result<()> {
+        Ok(())
     }
 
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         let handles_guard = HANDLES.read();
         let handle = handles_guard.as_ref().unwrap().get(&id).ok_or(Error::new(EBADF))?;
 
@@ -256,10 +257,8 @@ impl Scheme for IrqScheme {
                 set_reserved(LogicalCpuId::BSP, irq_to_vector(handle_irq), false);
             }
         }
-        Ok(0)
+        Ok(())
     }
-}
-impl crate::scheme::KernelScheme for IrqScheme {
     fn kwrite(&self, file: usize, buffer: UserSliceRo) -> Result<usize> {
         let handles_guard = HANDLES.read();
         let handle = handles_guard.as_ref().unwrap().get(&file).ok_or(Error::new(EBADF))?;
@@ -283,7 +282,7 @@ impl crate::scheme::KernelScheme for IrqScheme {
         }
     }
 
-    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<()> {
         let handles_guard = HANDLES.read();
         let handle = handles_guard.as_ref().unwrap().get(&id).ok_or(Error::new(EBADF))?;
 
@@ -321,7 +320,8 @@ impl crate::scheme::KernelScheme for IrqScheme {
                 ..Default::default()
             },
         })?;
-        Ok(0)
+
+        Ok(())
     }
     fn kfpath(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let handles_guard = HANDLES.read();
diff --git a/src/scheme/itimer.rs b/src/scheme/itimer.rs
index bccc7c6f28..d8babc306a 100644
--- a/src/scheme/itimer.rs
+++ b/src/scheme/itimer.rs
@@ -6,9 +6,10 @@ use spin::RwLock;
 use crate::syscall::data::ITimerSpec;
 use crate::syscall::error::*;
 use crate::syscall::flag::{CLOCK_REALTIME, CLOCK_MONOTONIC, EventFlags};
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::{UserSliceWo, UserSliceRo};
 
+use super::{KernelScheme, CallerCtx, OpenResult};
+
 pub struct ITimerScheme {
     next_id: AtomicUsize,
     handles: RwLock<BTreeMap<usize, usize>>
@@ -23,8 +24,8 @@ impl ITimerScheme {
     }
 }
 
-impl Scheme for ITimerScheme {
-    fn open(&self, path: &str, _flags: usize, _uid: u32, _gid: u32) -> Result<usize> {
+impl KernelScheme for ITimerScheme {
+    fn kopen(&self, path: &str, _flags: usize, _ctx: CallerCtx) -> Result<OpenResult> {
         let clock = path.parse::<usize>().or(Err(Error::new(ENOENT)))?;
 
         match clock {
@@ -33,10 +34,10 @@ impl Scheme for ITimerScheme {
             _ => return Err(Error::new(ENOENT))
         }
 
-        let id = self.next_id.fetch_add(1, Ordering::SeqCst);
+        let id = self.next_id.fetch_add(1, Ordering::Relaxed);
         self.handles.write().insert(id, clock);
 
-        Ok(id)
+        Ok(OpenResult::SchemeLocal(id))
     }
 
     fn fcntl(&self, _id: usize, _cmd: usize, _arg: usize) -> Result<usize> {
@@ -48,16 +49,14 @@ impl Scheme for ITimerScheme {
         handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(EventFlags::empty()))
     }
 
-    fn fsync(&self, id: usize) -> Result<usize> {
+    fn fsync(&self, id: usize) -> Result<()> {
         let handles = self.handles.read();
-        handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+        handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(()))
     }
 
-    fn close(&self, id: usize) -> Result<usize> {
-        self.handles.write().remove(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+    fn close(&self, id: usize) -> Result<()> {
+        self.handles.write().remove(&id).ok_or(Error::new(EBADF)).and(Ok(()))
     }
-}
-impl crate::scheme::KernelScheme for ITimerScheme {
     fn kread(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let _clock = {
             let handles = self.handles.read();
diff --git a/src/scheme/memory.rs b/src/scheme/memory.rs
index 8ff5b6ebd4..fb4c3d2d30 100644
--- a/src/scheme/memory.rs
+++ b/src/scheme/memory.rs
@@ -15,10 +15,9 @@ use crate::paging::entry::EntryFlags;
 use crate::syscall::data::{Map, StatVfs};
 use crate::syscall::flag::MapFlags;
 use crate::syscall::error::*;
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::UserSliceWo;
 
-use super::KernelScheme;
+use super::{KernelScheme, CallerCtx, OpenResult};
 
 pub struct MemoryScheme;
 
@@ -118,8 +117,8 @@ impl MemoryScheme {
 
     }
 }
-impl Scheme for MemoryScheme {
-    fn open(&self, path: &str, _flags: usize, uid: u32, _gid: u32) -> Result<usize> {
+impl KernelScheme for MemoryScheme {
+    fn kopen(&self, path: &str, _flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
         let intended_handle = match path.trim_start_matches('/') {
             "" => Handle::Anonymous,
             "physical" | "physical@wb" => Handle::PhysicalWb,
@@ -129,22 +128,20 @@ impl Scheme for MemoryScheme {
             _ => return Err(Error::new(ENOENT)),
         };
 
-        if uid != 0 && !matches!(intended_handle, Handle::Anonymous) {
+        if ctx.uid != 0 && !matches!(intended_handle, Handle::Anonymous) {
             return Err(Error::new(EACCES));
         }
 
-        Ok(intended_handle as usize)
+        Ok(OpenResult::SchemeLocal(intended_handle as usize))
     }
 
     fn fcntl(&self, _id: usize, _cmd: usize, _arg: usize) -> Result<usize> {
         Ok(0)
     }
 
-    fn close(&self, _id: usize) -> Result<usize> {
-        Ok(0)
+    fn close(&self, _id: usize) -> Result<()> {
+        Ok(())
     }
-}
-impl KernelScheme for MemoryScheme {
     fn kfmap(&self, id: usize, addr_space: &Arc<RwLock<AddrSpace>>, map: &Map, _consume: bool) -> Result<usize> {
         match Handle::from_raw(id).ok_or(Error::new(EBADF))? {
             Handle::Anonymous => Self::fmap_anonymous(addr_space, map),
@@ -163,7 +160,7 @@ impl KernelScheme for MemoryScheme {
         };
         dst.copy_common_bytes_from_slice(src.as_bytes())
     }
-    fn kfstatvfs(&self, _file: usize, dst: UserSliceWo) -> Result<usize> {
+    fn kfstatvfs(&self, _file: usize, dst: UserSliceWo) -> Result<()> {
         let used = used_frames() as u64;
         let free = free_frames() as u64;
 
@@ -175,6 +172,6 @@ impl KernelScheme for MemoryScheme {
         };
         dst.copy_exactly(&stat)?;
 
-        Ok(0)
+        Ok(())
     }
 }
diff --git a/src/scheme/mod.rs b/src/scheme/mod.rs
index 2b1ef18f0c..9c29da2b38 100644
--- a/src/scheme/mod.rs
+++ b/src/scheme/mod.rs
@@ -13,14 +13,13 @@ use alloc::{
     sync::Arc,
     vec::Vec,
 };
-use syscall::{CallerCtx, MunmapFlags, SendFdFlags};
+use syscall::{MunmapFlags, SendFdFlags, EventFlags, SEEK_SET, SEEK_CUR, SEEK_END};
 use core::sync::atomic::AtomicUsize;
 use spin::{Once, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 use crate::context::file::FileDescription;
 use crate::context::{memory::AddrSpace, file::FileDescriptor};
 use crate::syscall::error::*;
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::{UserSliceRo, UserSliceWo};
 
 #[cfg(all(feature = "acpi", any(target_arch = "x86", target_arch = "x86_64")))]
@@ -299,7 +298,11 @@ pub fn schemes_mut() -> RwLockWriteGuard<'static, SchemeList> {
 }
 
 #[allow(unused_variables)]
-pub trait KernelScheme: Scheme + Send + Sync + 'static {
+pub trait KernelScheme: Send + Sync + 'static {
+    fn kopen(&self, path: &str, flags: usize, _ctx: CallerCtx) -> Result<OpenResult> {
+        Err(Error::new(ENOENT))
+    }
+
     fn as_filetable(&self, number: usize) -> Result<Arc<RwLock<Vec<Option<FileDescriptor>>>>> {
         Err(Error::new(EBADF))
     }
@@ -317,9 +320,6 @@ pub trait KernelScheme: Scheme + Send + Sync + 'static {
         Err(Error::new(EOPNOTSUPP))
     }
 
-    fn kopen(&self, path: &str, flags: usize, caller: CallerCtx) -> Result<OpenResult> {
-        self.open(path, flags, caller.uid, caller.gid).map(OpenResult::SchemeLocal)
-    }
     fn kdup(&self, old_id: usize, buf: UserSliceRo, _caller: CallerCtx) -> Result<OpenResult> {
         Err(Error::new(EOPNOTSUPP))
     }
@@ -335,10 +335,10 @@ pub trait KernelScheme: Scheme + Send + Sync + 'static {
     fn kfutimens(&self, id: usize, buf: UserSliceRo) -> Result<usize> {
         Err(Error::new(EBADF))
     }
-    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<()> {
         Err(Error::new(EBADF))
     }
-    fn kfstatvfs(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstatvfs(&self, id: usize, buf: UserSliceWo) -> Result<()> {
         Err(Error::new(EBADF))
     }
 
@@ -346,6 +346,40 @@ pub trait KernelScheme: Scheme + Send + Sync + 'static {
         Err(Error::new(EOPNOTSUPP))
     }
 
+    fn fsync(&self, id: usize) -> Result<()> {
+        Err(Error::new(EBADF))
+    }
+    fn ftruncate(&self, id: usize, len: usize) -> Result<()> {
+        Err(Error::new(EBADF))
+    }
+    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<usize> {
+        Err(Error::new(ESPIPE))
+    }
+    fn fchmod(&self, id: usize, new_mode: u16) -> Result<()> {
+        Err(Error::new(EBADF))
+    }
+    fn fchown(&self, id: usize, new_uid: u32, new_gid: u32) -> Result<()> {
+        Err(Error::new(EBADF))
+    }
+    fn fevent(&self, id: usize, flags: EventFlags) -> Result<EventFlags> {
+        Err(Error::new(EBADF))
+    }
+    fn frename(&self, id: usize, new_path: &str, caller_ctx: CallerCtx) -> Result<()> {
+        Err(Error::new(EBADF))
+    }
+    fn fcntl(&self, id: usize, cmd: usize, arg: usize) -> Result<usize> {
+        Err(Error::new(EBADF))
+    }
+    fn rmdir(&self, path: &str, ctx: CallerCtx) -> Result<()> {
+        Err(Error::new(ENOENT))
+    }
+    fn unlink(&self, path: &str, ctx: CallerCtx) -> Result<()> {
+        Err(Error::new(ENOENT))
+    }
+    fn close(&self, id: usize) -> Result<()> {
+        Err(Error::new(EBADF))
+    }
+
     // TODO: This demonstrates why we need to transition away from a dyn trait.
     fn as_user_inner(&self) -> Option<Result<Arc<UserInner>>> { None }
 }
@@ -355,9 +389,18 @@ pub enum OpenResult {
     SchemeLocal(usize),
     External(Arc<RwLock<FileDescription>>),
 }
+pub struct CallerCtx {
+    pub pid: usize,
+    pub uid: u32,
+    pub gid: u32,
+}
 
-pub fn current_caller_ctx() -> Result<CallerCtx> {
-    match crate::context::current()?.read() {
-        ref context => Ok(CallerCtx { pid: context.id.into(), uid: context.euid, gid: context.egid }),
+pub fn calc_seek_offset(cur_pos: usize, rel_pos: isize, whence: usize, len: usize) -> Result<usize> {
+    match whence {
+        SEEK_SET => usize::try_from(rel_pos).map_err(|_| Error::new(EINVAL)),
+        SEEK_CUR => cur_pos.checked_add_signed(rel_pos).ok_or(Error::new(EOVERFLOW)),
+        SEEK_END => len.checked_add_signed(rel_pos).ok_or(Error::new(EOVERFLOW)),
+
+        _ => return Err(Error::new(EINVAL)),
     }
 }
diff --git a/src/scheme/pipe.rs b/src/scheme/pipe.rs
index edfd6ed565..5cd1503ba3 100644
--- a/src/scheme/pipe.rs
+++ b/src/scheme/pipe.rs
@@ -10,11 +10,10 @@ use crate::scheme::SchemeId;
 use crate::sync::WaitCondition;
 use crate::syscall::error::{Error, Result, EAGAIN, EBADF, EINTR, EINVAL, ENOENT, EPIPE, ESPIPE};
 use crate::syscall::flag::{EventFlags, EVENT_READ, EVENT_WRITE, F_GETFL, F_SETFL, O_ACCMODE, O_NONBLOCK, MODE_FIFO};
-use crate::syscall::scheme::{CallerCtx, Scheme};
 use crate::syscall::data::Stat;
 use crate::syscall::usercopy::{UserSliceWo, UserSliceRo};
 
-use super::{KernelScheme, OpenResult};
+use super::{KernelScheme, OpenResult, CallerCtx};
 
 // TODO: Preallocate a number of scheme IDs, since there can only be *one* root namespace, and
 // therefore only *one* pipe scheme.
@@ -65,8 +64,7 @@ impl PipeScheme {
     }
 }
 
-impl Scheme for PipeScheme {
-
+impl KernelScheme for PipeScheme {
     fn fcntl(&self, id: usize, cmd: usize, arg: usize) -> Result<usize> {
         let (is_writer_not_reader, key) = from_raw_id(id);
         let pipe = Arc::clone(PIPES.read().get(&key).ok_or(Error::new(EBADF))?);
@@ -106,11 +104,11 @@ impl Scheme for PipeScheme {
         Err(Error::new(EBADF))
     }
 
-    fn fsync(&self, _id: usize) -> Result<usize> {
-        Ok(0)
+    fn fsync(&self, _id: usize) -> Result<()> {
+        Ok(())
     }
 
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         let (is_write_not_read, key) = from_raw_id(id);
 
         let pipe = Arc::clone(PIPES.read().get(&key).ok_or(Error::new(EBADF))?);
@@ -136,26 +134,12 @@ impl Scheme for PipeScheme {
             let _ = PIPES.write().remove(&key);
         }
 
-        Ok(0)
+        Ok(())
     }
 
-    fn seek(&self, _id: usize, _pos: isize, _whence: usize) -> Result<isize> {
+    fn seek(&self, _id: usize, _pos: isize, _whence: usize) -> Result<usize> {
         Err(Error::new(ESPIPE))
     }
-}
-
-pub struct Pipe {
-    read_flags: AtomicUsize, // fcntl read flags
-    write_flags: AtomicUsize, // fcntl write flags
-    read_condition: WaitCondition, // signals whether there are available bytes to read
-    write_condition: WaitCondition, // signals whether there is room for additional bytes
-    queue: Mutex<VecDeque<u8>>,
-    reader_is_alive: AtomicBool, // starts set, unset when reader closes
-    writer_is_alive: AtomicBool, // starts set, unset when writer closes
-    has_run_dup: AtomicBool,
-}
-
-impl KernelScheme for PipeScheme {
     fn kdup(&self, old_id: usize, user_buf: UserSliceRo, _ctx: CallerCtx) -> Result<OpenResult> {
         let (is_writer_not_reader, key) = from_raw_id(old_id);
 
@@ -277,12 +261,23 @@ impl KernelScheme for PipeScheme {
             }
         }
     }
-    fn kfstat(&self, _id: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, _id: usize, buf: UserSliceWo) -> Result<()> {
         buf.copy_exactly(&Stat {
             st_mode: MODE_FIFO | 0o666,
             ..Default::default()
         })?;
 
-        Ok(0)
+        Ok(())
     }
 }
+
+pub struct Pipe {
+    read_flags: AtomicUsize, // fcntl read flags
+    write_flags: AtomicUsize, // fcntl write flags
+    read_condition: WaitCondition, // signals whether there are available bytes to read
+    write_condition: WaitCondition, // signals whether there is room for additional bytes
+    queue: Mutex<VecDeque<u8>>,
+    reader_is_alive: AtomicBool, // starts set, unset when reader closes
+    writer_is_alive: AtomicBool, // starts set, unset when writer closes
+    has_run_dup: AtomicBool,
+}
diff --git a/src/scheme/proc.rs b/src/scheme/proc.rs
index ece25f5a29..6183b87b06 100644
--- a/src/scheme/proc.rs
+++ b/src/scheme/proc.rs
@@ -11,7 +11,6 @@ use crate::{
         data::{GrantDesc, Map, PtraceEvent, SigAction, Stat},
         error::*,
         flag::*,
-        scheme::{CallerCtx, Scheme},
         self, usercopy::{UserSliceWo, UserSliceRo},
     }, LogicalCpuId, LogicalCpuSet,
 };
@@ -31,7 +30,7 @@ use core::{
 };
 use spin::{Once, RwLock};
 
-use super::OpenResult;
+use super::{OpenResult, CallerCtx};
 
 fn read_from(dst: UserSliceWo, src: &[u8], offset: &mut usize) -> Result<usize> {
     let avail_src = src.get(*offset..).unwrap_or(&[]);
@@ -514,8 +513,8 @@ impl ProcScheme {
     }
 }
 
-impl Scheme for ProcScheme {
-    fn open(&self, path: &str, flags: usize, uid: u32, gid: u32) -> Result<usize> {
+impl KernelScheme for ProcScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
         let mut parts = path.splitn(2, '/');
         let pid_str = parts.next()
             .ok_or(Error::new(ENOENT))?;
@@ -530,7 +529,7 @@ impl Scheme for ProcScheme {
             ContextId::new(pid_str.parse().map_err(|_| Error::new(ENOENT))?)
         };
 
-        self.open_inner(pid, parts.next(), flags, uid, gid)
+        self.open_inner(pid, parts.next(), flags, ctx.uid, ctx.gid).map(OpenResult::SchemeLocal)
     }
 
     fn fcntl(&self, id: usize, cmd: usize, arg: usize) -> Result<usize> {
@@ -557,7 +556,7 @@ impl Scheme for ProcScheme {
     }
 
 
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         let mut handle = self.handles.write().remove(&id).ok_or(Error::new(EBADF))?;
         handle.continue_ignored_children();
 
@@ -617,10 +616,8 @@ impl Scheme for ProcScheme {
             }
             _ => (),
         }
-        Ok(0)
+        Ok(())
     }
-}
-impl KernelScheme for ProcScheme {
     fn as_addrspace(&self, number: usize) -> Result<Arc<RwLock<AddrSpace>>> {
         if let Operation::AddrSpace { ref addrspace } = self.handles.read().get(&number).ok_or(Error::new(EBADF))?.info.operation {
             Ok(Arc::clone(addrspace))
@@ -1094,7 +1091,7 @@ impl KernelScheme for ProcScheme {
 
         buf.copy_common_bytes_from_slice(path.as_bytes())
     }
-    fn kfstat(&self, id: usize, buffer: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, id: usize, buffer: UserSliceWo) -> Result<()> {
         let handles = self.handles.read();
         let handle = handles.get(&id).ok_or(Error::new(EBADF))?;
 
@@ -1108,7 +1105,7 @@ impl KernelScheme for ProcScheme {
             ..Stat::default()
         })?;
 
-        Ok(0)
+        Ok(())
     }
 
     /// Dup is currently used to implement clone() and execve().
diff --git a/src/scheme/root.rs b/src/scheme/root.rs
index 6a8fb88419..4bdbb6b910 100644
--- a/src/scheme/root.rs
+++ b/src/scheme/root.rs
@@ -13,11 +13,12 @@ use crate::context;
 use crate::syscall::data::Stat;
 use crate::syscall::error::*;
 use crate::syscall::flag::{EventFlags, O_CREAT, MODE_FILE, MODE_DIR};
-use crate::syscall::scheme::{calc_seek_offset_usize, Scheme};
 use crate::scheme::{self, SchemeNamespace, SchemeId};
 use crate::scheme::user::{UserInner, UserScheme};
 use crate::syscall::usercopy::{UserSliceWo, UserSliceRo};
 
+use super::{KernelScheme, CallerCtx, OpenResult, calc_seek_offset};
+
 struct FolderInner {
     data: Box<[u8]>,
     pos: Mutex<usize>
@@ -34,9 +35,9 @@ impl FolderInner {
         Ok(bytes_read)
     }
 
-    fn seek(&self, pos: isize, whence: usize) -> Result<isize> {
+    fn seek(&self, pos: isize, whence: usize) -> Result<usize> {
         let mut seek = self.pos.lock();
-        let new_offset = calc_seek_offset_usize(*seek, pos, whence, self.data.len())?;
+        let new_offset = calc_seek_offset(*seek, pos, whence, self.data.len())?;
         *seek = new_offset as usize;
         Ok(new_offset)
     }
@@ -67,13 +68,13 @@ impl RootScheme {
     }
 }
 
-impl Scheme for RootScheme {
-    fn open(&self, path: &str, flags: usize, uid: u32, _gid: u32) -> Result<usize> {
-        let path = path.trim_matches('/');
+impl KernelScheme for RootScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
+        let path = path.trim_start_matches('/');
 
         //TODO: Make this follow standards for flags and errors
         if flags & O_CREAT == O_CREAT {
-            if uid != 0 {
+            if ctx.uid != 0 {
                 return Err(Error::new(EACCES));
             };
 
@@ -103,7 +104,7 @@ impl Scheme for RootScheme {
 
             self.handles.write().insert(id, Handle::Scheme(inner));
 
-            Ok(id)
+            Ok(OpenResult::SchemeLocal(id))
         } else if path.is_empty() {
             let scheme_ns = {
                 let contexts = context::contexts();
@@ -126,47 +127,46 @@ impl Scheme for RootScheme {
                 pos: Mutex::new(0)
             });
 
-            let id = self.next_id.fetch_add(1, Ordering::SeqCst);
+            let id = self.next_id.fetch_add(1, Ordering::Relaxed);
             self.handles.write().insert(id, Handle::Folder(inner));
-            Ok(id)
+            Ok(OpenResult::SchemeLocal(id))
         } else {
             let inner = Arc::new(
                 path.as_bytes().to_vec().into_boxed_slice()
             );
 
-            let id = self.next_id.fetch_add(1, Ordering::SeqCst);
+            let id = self.next_id.fetch_add(1, Ordering::Relaxed);
             self.handles.write().insert(id, Handle::File(inner));
-            Ok(id)
+            Ok(OpenResult::SchemeLocal(id))
         }
     }
 
-    fn unlink(&self, path: &str, uid: u32, _gid: u32) -> Result<usize> {
+    fn unlink(&self, path: &str, ctx: CallerCtx) -> Result<()> {
         let path = path.trim_matches('/');
 
-        if uid == 0 {
-            let inner = {
-                let handles = self.handles.read();
-                handles.iter().find_map(|(_id, handle)| {
-                    match handle {
-                        Handle::Scheme(inner) => {
-                            if path == inner.name.as_ref() {
-                                return Some(inner.clone());
-                            }
-                        },
-                        _ => (),
-                    }
-                    None
-                }).ok_or(Error::new(ENOENT))?
-            };
-
-            inner.unmount()
-        } else {
-            Err(Error::new(EACCES))
+        if ctx.uid != 0 {
+            return Err(Error::new(EACCES));
         }
+        let inner = {
+            let handles = self.handles.read();
+            handles.iter().find_map(|(_id, handle)| {
+                match handle {
+                    Handle::Scheme(inner) => {
+                        if path == inner.name.as_ref() {
+                            return Some(inner.clone());
+                        }
+                    },
+                    _ => (),
+                }
+                None
+            }).ok_or(Error::new(ENOENT))?
+        };
+
+        inner.unmount()
     }
 
 
-    fn seek(&self, file: usize, pos: isize, whence: usize) -> Result<isize> {
+    fn seek(&self, file: usize, pos: isize, whence: usize) -> Result<usize> {
         let handle = {
             let handles = self.handles.read();
             let handle = handles.get(&file).ok_or(Error::new(EBADF))?;
@@ -206,45 +206,30 @@ impl Scheme for RootScheme {
         }
     }
 
-    fn fpath(&self, file: usize, buf: &mut [u8]) -> Result<usize> {
+    fn kfpath(&self, file: usize, mut buf: UserSliceWo) -> Result<usize> {
         let handle = {
             let handles = self.handles.read();
             let handle = handles.get(&file).ok_or(Error::new(EBADF))?;
             handle.clone()
         };
 
-        let mut i = 0;
-        let scheme_path = b":";
-        while i < buf.len() && i < scheme_path.len() {
-            buf[i] = scheme_path[i];
-            i += 1;
-        }
+        let mut bytes_copied = buf.copy_common_bytes_from_slice(b":")?;
+        buf = buf.advance(bytes_copied).ok_or(Error::new(EINVAL))?;
 
         match handle {
             Handle::Scheme(inner) => {
-                let name = inner.name.as_bytes();
-                let mut j = 0;
-                while i < buf.len() && j < name.len() {
-                    buf[i] = name[j];
-                    i += 1;
-                    j += 1;
-                }
+                bytes_copied += buf.copy_common_bytes_from_slice(inner.name.as_bytes())?;
             },
             Handle::File(inner) => {
-                let mut j = 0;
-                while i < buf.len() && j < inner.len() {
-                    buf[i] = inner[j];
-                    i += 1;
-                    j += 1;
-                }
+                bytes_copied += buf.copy_common_bytes_from_slice(&inner)?;
             },
             Handle::Folder(_) => ()
         }
 
-        Ok(i)
+        Ok(bytes_copied)
     }
 
-    fn fsync(&self, file: usize) -> Result<usize> {
+    fn fsync(&self, file: usize) -> Result<()> {
         let handle = {
             let handles = self.handles.read();
             let handle = handles.get(&file).ok_or(Error::new(EBADF))?;
@@ -264,7 +249,7 @@ impl Scheme for RootScheme {
         }
     }
 
-    fn close(&self, file: usize) -> Result<usize> {
+    fn close(&self, file: usize) -> Result<()> {
         let handle = self.handles.write().remove(&file).ok_or(Error::new(EBADF))?;
         match handle {
             Handle::Scheme(inner) => {
@@ -272,10 +257,8 @@ impl Scheme for RootScheme {
             },
             _ => ()
         }
-        Ok(0)
+        Ok(())
     }
-}
-impl crate::scheme::KernelScheme for RootScheme {
     fn kread(&self, file: usize, buf: UserSliceWo) -> Result<usize> {
         let handle = {
             let handles = self.handles.read();
@@ -316,7 +299,7 @@ impl crate::scheme::KernelScheme for RootScheme {
         }
     }
     
-    fn kfstat(&self, file: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, file: usize, buf: UserSliceWo) -> Result<()> {
         let handle = {
             let handles = self.handles.read();
             let handle = handles.get(&file).ok_or(Error::new(EBADF))?;
@@ -347,7 +330,7 @@ impl crate::scheme::KernelScheme for RootScheme {
             }
         })?;
 
-        Ok(0)
+        Ok(())
     }
 
 }
diff --git a/src/scheme/serio.rs b/src/scheme/serio.rs
index f11bb52f8f..1335d5dca5 100644
--- a/src/scheme/serio.rs
+++ b/src/scheme/serio.rs
@@ -9,7 +9,6 @@ use crate::event;
 use crate::scheme::*;
 use crate::sync::WaitQueue;
 use crate::syscall::flag::{EventFlags, EVENT_READ, F_GETFL, F_SETFL, O_ACCMODE, O_NONBLOCK};
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::UserSliceWo;
 
 static SCHEME_ID: Once<SchemeId> = Once::new();
@@ -49,9 +48,9 @@ impl SerioScheme {
     }
 }
 
-impl Scheme for SerioScheme {
-    fn open(&self, path: &str, flags: usize, uid: u32, _gid: u32) -> Result<usize> {
-        if uid != 0 {
+impl KernelScheme for SerioScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
+        if ctx.uid != 0 {
             return Err(Error::new(EPERM));
         }
 
@@ -68,7 +67,7 @@ impl Scheme for SerioScheme {
             flags: flags & ! O_ACCMODE
         });
 
-        Ok(id)
+        Ok(OpenResult::SchemeLocal(id))
     }
 
     fn fcntl(&self, id: usize, cmd: usize, arg: usize) -> Result<usize> {
@@ -96,26 +95,24 @@ impl Scheme for SerioScheme {
         Ok(EventFlags::empty())
     }
 
-    fn fsync(&self, id: usize) -> Result<usize> {
+    fn fsync(&self, id: usize) -> Result<()> {
         let _handle = {
             let handles = HANDLES.read();
             *handles.get(&id).ok_or(Error::new(EBADF))?
         };
 
-        Ok(0)
+        Ok(())
     }
 
     /// Close the file `number`
-    fn close(&self, id: usize) -> Result<usize> {
+    fn close(&self, id: usize) -> Result<()> {
         let _handle = {
             let mut handles = HANDLES.write();
             handles.remove(&id).ok_or(Error::new(EBADF))?
         };
 
-        Ok(0)
+        Ok(())
     }
-}
-impl crate::scheme::KernelScheme for SerioScheme {
     fn kread(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let handle = {
             let handles = HANDLES.read();
diff --git a/src/scheme/sys/iostat.rs b/src/scheme/sys/iostat.rs
index ee3e96c0e8..c381a3af6b 100644
--- a/src/scheme/sys/iostat.rs
+++ b/src/scheme/sys/iostat.rs
@@ -1,8 +1,6 @@
 use alloc::string::String;
 use alloc::vec::Vec;
 use core::fmt::Write;
-use core::str;
-
 use crate::context;
 use crate::scheme;
 use crate::syscall::error::Result;
@@ -33,7 +31,7 @@ pub fn resource() -> Result<Vec<u8>> {
 
                 let description = file.description.read();
 
-                let scheme = {
+                let _scheme = {
                     let schemes = scheme::schemes();
                     match schemes.get(description.scheme) {
                         Some(scheme) => scheme.clone(),
@@ -44,6 +42,7 @@ pub fn resource() -> Result<Vec<u8>> {
                     }
                 };
 
+                /*
                 let mut fpath = [0; 4096];
                 match scheme.fpath(description.number, &mut fpath) {
                     Ok(path_len) => {
@@ -54,6 +53,7 @@ pub fn resource() -> Result<Vec<u8>> {
                         let _ = writeln!(string, "{:>6}: {:>8} {:>8} {:>08X}: {}", fd, description.scheme.get(), description.number, description.flags, err);
                     }
                 }
+                */
             }
         }
     }
diff --git a/src/scheme/sys/mod.rs b/src/scheme/sys/mod.rs
index de791825f2..da48ea281a 100644
--- a/src/scheme/sys/mod.rs
+++ b/src/scheme/sys/mod.rs
@@ -7,10 +7,11 @@ use spin::RwLock;
 use crate::syscall::data::Stat;
 use crate::syscall::error::{Error, EBADF, ENOENT, Result};
 use crate::syscall::flag::{MODE_DIR, MODE_FILE};
-use crate::syscall::scheme::{calc_seek_offset_usize, Scheme};
 use crate::arch::interrupt;
 use crate::syscall::usercopy::UserSliceWo;
 
+use super::{KernelScheme, CallerCtx, OpenResult, calc_seek_offset};
+
 mod block;
 mod context;
 mod cpu;
@@ -74,8 +75,8 @@ impl SysScheme {
     }
 }
 
-impl Scheme for SysScheme {
-    fn open(&self, path: &str, _flags: usize, _uid: u32, _gid: u32) -> Result<usize> {
+impl KernelScheme for SysScheme {
+    fn kopen(&self, path: &str, _flags: usize, _ctx: CallerCtx) -> Result<OpenResult> {
         let path = path.trim_matches('/');
 
         if path.is_empty() {
@@ -87,19 +88,19 @@ impl Scheme for SysScheme {
                 data.extend_from_slice(entry.0.as_bytes());
             }
 
-            let id = self.next_id.fetch_add(1, Ordering::SeqCst);
+            let id = self.next_id.fetch_add(1, Ordering::Relaxed);
             self.handles.write().insert(id, Handle {
                 path: "",
                 data,
                 mode: MODE_DIR | 0o444,
                 seek: 0
             });
-            return Ok(id)
+            return Ok(OpenResult::SchemeLocal(id))
         } else {
             //Have to iterate to get the path without allocation
             for entry in self.files.iter() {
                 if entry.0 == &path {
-                    let id = self.next_id.fetch_add(1, Ordering::SeqCst);
+                    let id = self.next_id.fetch_add(1, Ordering::Relaxed);
                     let data = entry.1()?;
                     self.handles.write().insert(id, Handle {
                         path: entry.0,
@@ -107,7 +108,7 @@ impl Scheme for SysScheme {
                         mode: MODE_FILE | 0o444,
                         seek: 0
                     });
-                    return Ok(id)
+                    return Ok(OpenResult::SchemeLocal(id));
                 }
             }
         }
@@ -115,24 +116,22 @@ impl Scheme for SysScheme {
         Err(Error::new(ENOENT))
     }
 
-    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<isize> {
+    fn seek(&self, id: usize, pos: isize, whence: usize) -> Result<usize> {
         let mut handles = self.handles.write();
         let handle = handles.get_mut(&id).ok_or(Error::new(EBADF))?;
 
-        let new_offset = calc_seek_offset_usize(handle.seek, pos, whence, handle.data.len())?;
+        let new_offset = calc_seek_offset(handle.seek, pos, whence, handle.data.len())?;
         handle.seek = new_offset as usize;
         Ok(new_offset)
     }
 
-    fn fsync(&self, _id: usize) -> Result<usize> {
-        Ok(0)
+    fn fsync(&self, _id: usize) -> Result<()> {
+        Ok(())
     }
 
-    fn close(&self, id: usize) -> Result<usize> {
-        self.handles.write().remove(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+    fn close(&self, id: usize) -> Result<()> {
+        self.handles.write().remove(&id).ok_or(Error::new(EBADF)).and(Ok(()))
     }
-}
-impl crate::scheme::KernelScheme for SysScheme {
     fn kfpath(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let handles = self.handles.read();
         let handle = handles.get(&id).ok_or(Error::new(EBADF))?;
@@ -159,7 +158,7 @@ impl crate::scheme::KernelScheme for SysScheme {
         Ok(byte_count)
     }
 
-    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, id: usize, buf: UserSliceWo) -> Result<()> {
         let handles = self.handles.read();
         let handle = handles.get(&id).ok_or(Error::new(EBADF))?;
 
@@ -171,6 +170,6 @@ impl crate::scheme::KernelScheme for SysScheme {
             ..Default::default()
         })?;
 
-        Ok(0)
+        Ok(())
     }
 }
diff --git a/src/scheme/time.rs b/src/scheme/time.rs
index 1fbe272f45..a1f85a2290 100644
--- a/src/scheme/time.rs
+++ b/src/scheme/time.rs
@@ -8,10 +8,11 @@ use crate::scheme::SchemeId;
 use crate::syscall::data::TimeSpec;
 use crate::syscall::error::*;
 use crate::syscall::flag::{CLOCK_REALTIME, CLOCK_MONOTONIC, EventFlags};
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::{UserSliceWo, UserSliceRo};
 use crate::time;
 
+use super::{KernelScheme, CallerCtx, OpenResult};
+
 pub struct TimeScheme {
     scheme_id: SchemeId,
     next_id: AtomicUsize,
@@ -28,9 +29,9 @@ impl TimeScheme {
     }
 }
 
-impl Scheme for TimeScheme {
-    fn open(&self, path: &str, _flags: usize, _uid: u32, _gid: u32) -> Result<usize> {
-        let clock = path.parse::<usize>().or(Err(Error::new(ENOENT)))?;
+impl KernelScheme for TimeScheme {
+    fn kopen(&self, path: &str, _flags: usize, _ctx: CallerCtx) -> Result<OpenResult> {
+        let clock = path.parse::<usize>().map_err(|_| Error::new(ENOENT))?;
 
         match clock {
             CLOCK_REALTIME => (),
@@ -38,10 +39,10 @@ impl Scheme for TimeScheme {
             _ => return Err(Error::new(ENOENT))
         }
 
-        let id = self.next_id.fetch_add(1, Ordering::SeqCst);
+        let id = self.next_id.fetch_add(1, Ordering::Relaxed);
         self.handles.write().insert(id, clock);
 
-        Ok(id)
+        Ok(OpenResult::SchemeLocal(id))
     }
 
     fn fcntl(&self, _id: usize, _cmd: usize, _arg: usize) -> Result<usize> {
@@ -53,16 +54,14 @@ impl Scheme for TimeScheme {
         handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(EventFlags::empty()))
     }
 
-    fn fsync(&self, id: usize) -> Result<usize> {
-        let handles = self.handles.read();
-        handles.get(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+    fn fsync(&self, id: usize) -> Result<()> {
+        self.handles.read().get(&id).ok_or(Error::new(EBADF))?;
+        Ok(())
     }
 
-    fn close(&self, id: usize) -> Result<usize> {
-        self.handles.write().remove(&id).ok_or(Error::new(EBADF)).and(Ok(0))
+    fn close(&self, id: usize) -> Result<()> {
+        self.handles.write().remove(&id).ok_or(Error::new(EBADF)).and(Ok(()))
     }
-}
-impl crate::scheme::KernelScheme for TimeScheme {
     fn kread(&self, id: usize, buf: UserSliceWo) -> Result<usize> {
         let clock = {
             let handles = self.handles.read();
diff --git a/src/scheme/user.rs b/src/scheme/user.rs
index cb5aa0cb42..9aeb73ec06 100644
--- a/src/scheme/user.rs
+++ b/src/scheme/user.rs
@@ -3,12 +3,11 @@ use alloc::sync::{Arc, Weak};
 use alloc::boxed::Box;
 use alloc::collections::BTreeMap;
 use alloc::vec::Vec;
-use syscall::{SKMSG_FRETURNFD, CallerCtx, SKMSG_PROVIDE_MMAP, MAP_FIXED_NOREPLACE, MunmapFlags, SKMSG_FOBTAINFD, FobtainFdFlags, SendFdFlags};
+use syscall::{SKMSG_FRETURNFD, SKMSG_PROVIDE_MMAP, MAP_FIXED_NOREPLACE, MunmapFlags, SKMSG_FOBTAINFD, FobtainFdFlags, SendFdFlags};
 use core::mem::size_of;
 use core::num::NonZeroUsize;
 use core::sync::atomic::{AtomicBool, Ordering};
 use core::{mem, usize};
-use core::convert::TryFrom;
 use spin::{Mutex, RwLock};
 
 use crate::context::context::HardBlockedReason;
@@ -25,10 +24,9 @@ use crate::syscall::data::{Map, Packet};
 use crate::syscall::error::*;
 use crate::syscall::flag::{EventFlags, EVENT_READ, O_NONBLOCK, PROT_READ, PROT_WRITE, MapFlags};
 use crate::syscall::number::*;
-use crate::syscall::scheme::Scheme;
 use crate::syscall::usercopy::{UserSlice, UserSliceWo, UserSliceRo};
 
-use super::{FileHandle, OpenResult, KernelScheme, current_caller_ctx};
+use super::{FileHandle, OpenResult, KernelScheme, CallerCtx};
 
 pub struct UserInner {
     root_id: SchemeId,
@@ -74,7 +72,7 @@ impl UserInner {
         }
     }
 
-    pub fn unmount(&self) -> Result<usize> {
+    pub fn unmount(&self) -> Result<()> {
         // First, block new requests and prepare to return EOF
         self.unmounting.store(true, Ordering::SeqCst);
 
@@ -85,7 +83,7 @@ impl UserInner {
         event::trigger(self.root_id, self.handle_id, EVENT_READ);
 
         //TODO: wait for all todo and done to be processed?
-        Ok(0)
+        Ok(())
     }
 
     fn next_id(&self) -> u64 {
@@ -96,7 +94,8 @@ impl UserInner {
     }
 
     pub fn call(&self, a: usize, b: usize, c: usize, d: usize) -> Result<usize> {
-        match self.call_extended(current_caller_ctx()?, None, [a, b, c, d])? {
+        let ctx = context::current()?.read().caller_ctx();
+        match self.call_extended(ctx, None, [a, b, c, d])? {
             Response::Regular(code) => Error::demux(code),
             Response::Fd(_) => {
                 if a & SYS_RET_FILE == SYS_RET_FILE {
@@ -555,8 +554,8 @@ impl UserInner {
         Ok(EventFlags::empty())
     }
 
-    pub fn fsync(&self) -> Result<usize> {
-        Ok(0)
+    pub fn fsync(&self) -> Result<()> {
+        Ok(())
     }
 
     fn fmap_inner(&self, dst_addr_space: Arc<RwLock<AddrSpace>>, file: usize, map: &Map) -> Result<usize> {
@@ -758,45 +757,41 @@ impl UserScheme {
     }
 }
 
-fn handle_open_res(res: OpenResult) -> Result<usize> {
-    match res {
-        OpenResult::SchemeLocal(num) => Ok(num),
-        OpenResult::External(_) => {
-            log::warn!("Used Scheme::open when forwarding fd!");
-            Err(Error::new(EIO))
+impl KernelScheme for UserScheme {
+    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
+        let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
+        let address = inner.copy_and_capture_tail(path.as_bytes())?;
+        match inner.call_extended(ctx, None, [SYS_OPEN, address.base(), address.len(), flags])? {
+            Response::Regular(code) => Error::demux(code).map(OpenResult::SchemeLocal),
+            Response::Fd(desc) => Ok(OpenResult::External(desc)),
         }
     }
-}
-
-impl Scheme for UserScheme {
-    fn open(&self, path: &str, flags: usize, uid: u32, gid: u32) -> Result<usize> {
-        self.kopen(path, flags, CallerCtx { uid, gid, pid: context::context_id().into() }).and_then(handle_open_res)
-    }
-
-    fn rmdir(&self, path: &str, _uid: u32, _gid: u32) -> Result<usize> {
+    fn rmdir(&self, path: &str, _ctx: CallerCtx) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
         let address = inner.copy_and_capture_tail(path.as_bytes())?;
-        inner.call(SYS_RMDIR, address.base(), address.len(), 0)
+        inner.call(SYS_RMDIR, address.base(), address.len(), 0)?;
+        Ok(())
     }
 
-    fn unlink(&self, path: &str, _uid: u32, _gid: u32) -> Result<usize> {
+    fn unlink(&self, path: &str, _ctx: CallerCtx) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
         let address = inner.copy_and_capture_tail(path.as_bytes())?;
-        inner.call(SYS_UNLINK, address.base(), address.len(), 0)
+        inner.call(SYS_UNLINK, address.base(), address.len(), 0)?;
+        Ok(())
     }
 
-    fn seek(&self, file: usize, position: isize, whence: usize) -> Result<isize> {
+    fn seek(&self, file: usize, position: isize, whence: usize) -> Result<usize> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        let new_offset = inner.call(SYS_LSEEK, file, position as usize, whence)?;
-        isize::try_from(new_offset).or_else(|_| Err(Error::new(EOVERFLOW)))
+        inner.call(SYS_LSEEK, file, position as usize, whence)
     }
 
-    fn fchmod(&self, file: usize, mode: u16) -> Result<usize> {
+    fn fchmod(&self, file: usize, mode: u16) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        inner.call(SYS_FCHMOD, file, mode as usize, 0)
+        inner.call(SYS_FCHMOD, file, mode as usize, 0)?;
+        Ok(())
     }
 
-    fn fchown(&self, file: usize, uid: u32, gid: u32) -> Result<usize> {
+    fn fchown(&self, file: usize, uid: u32, gid: u32) -> Result<()> {
         {
             let contexts = context::contexts();
             let context_lock = contexts.current().ok_or(Error::new(ESRCH))?;
@@ -809,7 +804,8 @@ impl Scheme for UserScheme {
         }
 
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        inner.call(SYS_FCHOWN, file, uid as usize, gid as usize)
+        inner.call(SYS_FCHOWN, file, uid as usize, gid as usize)?;
+        Ok(())
     }
 
     fn fcntl(&self, file: usize, cmd: usize, arg: usize) -> Result<usize> {
@@ -867,35 +863,29 @@ impl Scheme for UserScheme {
     }
     */
 
-    fn frename(&self, file: usize, path: &str, _uid: u32, _gid: u32) -> Result<usize> {
+    fn frename(&self, file: usize, path: &str, _ctx: CallerCtx) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
         let address = inner.copy_and_capture_tail(path.as_bytes())?;
-        inner.call(SYS_FRENAME, file, address.base(), address.len())
+        inner.call(SYS_FRENAME, file, address.base(), address.len())?;
+        Ok(())
     }
 
-    fn fsync(&self, file: usize) -> Result<usize> {
+    fn fsync(&self, file: usize) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        inner.call(SYS_FSYNC, file, 0, 0)
+        inner.call(SYS_FSYNC, file, 0, 0)?;
+        Ok(())
     }
 
-    fn ftruncate(&self, file: usize, len: usize) -> Result<usize> {
+    fn ftruncate(&self, file: usize, len: usize) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        inner.call(SYS_FTRUNCATE, file, len, 0)
+        inner.call(SYS_FTRUNCATE, file, len, 0)?;
+        Ok(())
     }
 
-    fn close(&self, file: usize) -> Result<usize> {
+    fn close(&self, file: usize) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        inner.call(SYS_CLOSE, file, 0, 0)
-    }
-}
-impl KernelScheme for UserScheme {
-    fn kopen(&self, path: &str, flags: usize, ctx: CallerCtx) -> Result<OpenResult> {
-        let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
-        let address = inner.copy_and_capture_tail(path.as_bytes())?;
-        match inner.call_extended(ctx, None, [SYS_OPEN, address.base(), address.len(), flags])? {
-            Response::Regular(code) => Error::demux(code).map(OpenResult::SchemeLocal),
-            Response::Fd(desc) => Ok(OpenResult::External(desc)),
-        }
+        inner.call(SYS_CLOSE, file, 0, 0)?;
+        Ok(())
     }
     fn kdup(&self, file: usize, buf: UserSliceRo, ctx: CallerCtx) -> Result<OpenResult> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
@@ -939,19 +929,19 @@ impl KernelScheme for UserScheme {
         address.release()?;
         result
     }
-    fn kfstat(&self, file: usize, stat: UserSliceWo) -> Result<usize> {
+    fn kfstat(&self, file: usize, stat: UserSliceWo) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
         let address = inner.capture_user(stat)?;
         let result = inner.call(SYS_FSTAT, file, address.base(), address.len());
         address.release()?;
-        result
+        result.map(|_| ())
     }
-    fn kfstatvfs(&self, file: usize, stat: UserSliceWo) -> Result<usize> {
+    fn kfstatvfs(&self, file: usize, stat: UserSliceWo) -> Result<()> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
         let address = inner.capture_user(stat)?;
         let result = inner.call(SYS_FSTATVFS, file, address.base(), address.len());
         address.release()?;
-        result
+        result.map(|_| ())
     }
     fn kfmap(&self, file: usize, addr_space: &Arc<RwLock<AddrSpace>>, map: &Map, _consume: bool) -> Result<usize> {
         let inner = self.inner.upgrade().ok_or(Error::new(ENODEV))?;
diff --git a/src/syscall/fs.rs b/src/syscall/fs.rs
index 0403f41269..1d623a9bd6 100644
--- a/src/syscall/fs.rs
+++ b/src/syscall/fs.rs
@@ -7,11 +7,10 @@ use crate::context::file::{FileDescriptor, FileDescription};
 use crate::context;
 use crate::context::memory::{PageSpan, AddrSpace};
 use crate::paging::{PAGE_SIZE, VirtualAddress, Page};
-use crate::scheme::{self, FileHandle, OpenResult, current_caller_ctx, KernelScheme, SchemeId};
+use crate::scheme::{self, FileHandle, OpenResult, KernelScheme, SchemeId, CallerCtx};
 use crate::syscall::data::Stat;
 use crate::syscall::error::*;
 use crate::syscall::flag::*;
-use crate::syscall::scheme::CallerCtx;
 
 use super::usercopy::{UserSlice, UserSliceWo, UserSliceRo};
 
@@ -87,9 +86,9 @@ pub fn open(raw_path: UserSliceRo, flags: usize) -> Result<FileHandle> {
 }
 
 /// rmdir syscall
-pub fn rmdir(raw_path: UserSliceRo) -> Result<usize> {
-    let (uid, gid, scheme_ns) = match context::current()?.read() {
-        ref context => (context.euid, context.egid, context.ens),
+pub fn rmdir(raw_path: UserSliceRo) -> Result<()> {
+    let (scheme_ns, caller_ctx) = match context::current()?.read() {
+        ref context => (context.ens, context.caller_ctx()),
     };
 
     /*
@@ -107,13 +106,13 @@ pub fn rmdir(raw_path: UserSliceRo) -> Result<usize> {
         let (_scheme_id, scheme) = schemes.get_name(scheme_ns, scheme_name).ok_or(Error::new(ENODEV))?;
         Arc::clone(scheme)
     };
-    scheme.rmdir(reference, uid, gid)
+    scheme.rmdir(reference, caller_ctx)
 }
 
 /// Unlink syscall
-pub fn unlink(raw_path: UserSliceRo) -> Result<usize> {
-    let (uid, gid, scheme_ns) = match context::current()?.read() {
-        ref context => (context.euid, context.egid, context.ens),
+pub fn unlink(raw_path: UserSliceRo) -> Result<()> {
+    let (scheme_ns, caller_ctx) = match context::current()?.read() {
+        ref context => (context.ens, context.caller_ctx()),
     };
     /*
     let mut path_buf = BorrowedHtBuf::head()?;
@@ -130,11 +129,11 @@ pub fn unlink(raw_path: UserSliceRo) -> Result<usize> {
         let (_scheme_id, scheme) = schemes.get_name(scheme_ns, scheme_name).ok_or(Error::new(ENODEV))?;
         Arc::clone(scheme)
     };
-    scheme.unlink(reference, uid, gid)
+    scheme.unlink(reference, caller_ctx)
 }
 
 /// Close syscall
-pub fn close(fd: FileHandle) -> Result<usize> {
+pub fn close(fd: FileHandle) -> Result<()> {
     let file = {
         let contexts = context::contexts();
         let context_lock = contexts.current().ok_or(Error::new(ESRCH))?;
@@ -146,8 +145,9 @@ pub fn close(fd: FileHandle) -> Result<usize> {
 }
 
 fn duplicate_file(fd: FileHandle, user_buf: UserSliceRo) -> Result<FileDescriptor> {
-    let file = context::current()?.read()
-        .get_file(fd).ok_or(Error::new(EBADF))?;
+    let (file, caller_ctx) = match context::current()?.read() {
+        ref context => (context.get_file(fd).ok_or(Error::new(EBADF))?, context.caller_ctx()),
+    };
 
     if user_buf.is_empty() {
         Ok(FileDescriptor {
@@ -164,7 +164,7 @@ fn duplicate_file(fd: FileHandle, user_buf: UserSliceRo) -> Result<FileDescripto
                 Arc::clone(scheme)
             };
 
-            match scheme.kdup(description.number, user_buf, current_caller_ctx()?)? {
+            match scheme.kdup(description.number, user_buf, caller_ctx)? {
                 OpenResult::SchemeLocal(number) => Arc::new(RwLock::new(FileDescription {
                     namespace: description.namespace,
                     scheme: description.scheme,
@@ -309,9 +309,9 @@ pub fn fcntl(fd: FileHandle, cmd: usize, arg: usize) -> Result<usize> {
     }
 }
 
-pub fn frename(fd: FileHandle, raw_path: UserSliceRo) -> Result<usize> {
-    let (file, uid, gid, scheme_ns) = match context::current()?.read() {
-        ref context => (context.get_file(fd).ok_or(Error::new(EBADF))?, context.euid, context.egid, context.ens),
+pub fn frename(fd: FileHandle, raw_path: UserSliceRo) -> Result<()> {
+    let (file, caller_ctx, scheme_ns) = match context::current()?.read() {
+        ref context => (context.get_file(fd).ok_or(Error::new(EBADF))?, CallerCtx { uid: context.euid, gid: context.egid, pid: context.id.get() }, context.ens),
     };
 
     /*
@@ -332,15 +332,15 @@ pub fn frename(fd: FileHandle, raw_path: UserSliceRo) -> Result<usize> {
 
     let description = file.description.read();
 
-    if scheme_id == description.scheme {
-        scheme.frename(description.number, reference, uid, gid)
-    } else {
-        Err(Error::new(EXDEV))
+    if scheme_id != description.scheme {
+        return Err(Error::new(EXDEV));
     }
+
+    scheme.frename(description.number, reference, caller_ctx)
 }
 
 /// File status
-pub fn fstat(fd: FileHandle, user_buf: UserSliceWo) -> Result<usize> {
+pub fn fstat(fd: FileHandle, user_buf: UserSliceWo) -> Result<()> {
     file_op_generic_ext(fd, |scheme, scheme_id, _, number| {
         scheme.kfstat(number, user_buf)?;
 
@@ -350,7 +350,7 @@ pub fn fstat(fd: FileHandle, user_buf: UserSliceWo) -> Result<usize> {
         let st_dev = scheme_id.get().try_into().map_err(|_| Error::new(EOVERFLOW))?;
         user_buf.advance(memoffset::offset_of!(Stat, st_dev)).and_then(|b| b.limit(8)).ok_or(Error::new(EIO))?.copy_from_slice(&u64::to_ne_bytes(st_dev))?;
 
-        Ok(0)
+        Ok(())
     })
 }
 
diff --git a/src/syscall/mod.rs b/src/syscall/mod.rs
index 9db10062a7..28d400aa1d 100644
--- a/src/syscall/mod.rs
+++ b/src/syscall/mod.rs
@@ -16,7 +16,6 @@ pub use self::syscall::{
     io,
     number,
     ptrace_event,
-    scheme,
 };
 
 pub use self::driver::*;
@@ -91,8 +90,8 @@ pub fn syscall(a: usize, b: usize, c: usize, d: usize, e: usize, f: usize, stack
                     SYS_ARG_MSLICE => match a {
                         SYS_READ => file_op_generic(fd, |scheme, _, number| scheme.kread(number, UserSlice::wo(c, d)?)),
                         SYS_FPATH => file_op_generic(fd, |scheme, _, number| scheme.kfpath(number, UserSlice::wo(c, d)?)),
-                        SYS_FSTAT => fstat(fd, UserSlice::wo(c, d)?),
-                        SYS_FSTATVFS => file_op_generic(fd, |scheme, _, number| scheme.kfstatvfs(number, UserSlice::wo(c, d)?)),
+                        SYS_FSTAT => fstat(fd, UserSlice::wo(c, d)?).map(|()| 0),
+                        SYS_FSTATVFS => file_op_generic(fd, |scheme, _, number| scheme.kfstatvfs(number, UserSlice::wo(c, d)?).map(|()| 0)),
 
                         _ => return Err(Error::new(ENOSYS)),
                     },
@@ -106,18 +105,19 @@ pub fn syscall(a: usize, b: usize, c: usize, d: usize, e: usize, f: usize, stack
                         #[cfg(target_pointer_width = "64")]
                         SYS_SENDFD => sendfd(fd, FileHandle::from(c), d, e as u64),
 
-                        SYS_LSEEK => file_op_generic(fd, |scheme, _, number| Ok(scheme.seek(number, c as isize, d)? as usize)),
-                        SYS_FCHMOD => file_op_generic(fd, |scheme, _, number| scheme.fchmod(number, c as u16)),
-                        SYS_FCHOWN => file_op_generic(fd, |scheme, _, number| scheme.fchown(number, c as u32, d as u32)),
+                        SYS_LSEEK => file_op_generic(fd, |scheme, _, number| scheme.seek(number, c as isize, d)),
+                        SYS_FCHMOD => file_op_generic(fd, |scheme, _, number| scheme.fchmod(number, c as u16).map(|()| 0)),
+                        SYS_FCHOWN => file_op_generic(fd, |scheme, _, number| scheme.fchown(number, c as u32, d as u32).map(|()| 0)),
                         SYS_FCNTL => fcntl(fd, c, d),
                         SYS_FEVENT => file_op_generic(fd, |scheme, _, number| Ok(scheme.fevent(number, EventFlags::from_bits_truncate(c))?.bits())),
-                        SYS_FRENAME => frename(fd, UserSlice::ro(c, d)?),
+                        SYS_FRENAME => frename(fd, UserSlice::ro(c, d)?).map(|()| 0),
                         SYS_FUNMAP => funmap(b, c),
 
-                        SYS_FSYNC => file_op_generic(fd, |scheme, _, number| scheme.fsync(number)),
-                        SYS_FTRUNCATE => file_op_generic(fd, |scheme, _, number| scheme.ftruncate(number, c)),
+                        SYS_FSYNC => file_op_generic(fd, |scheme, _, number| scheme.fsync(number).map(|()| 0)),
+                        // TODO: 64-bit lengths on 32-bit platforms
+                        SYS_FTRUNCATE => file_op_generic(fd, |scheme, _, number| scheme.ftruncate(number, c).map(|()| 0)),
 
-                        SYS_CLOSE => close(fd),
+                        SYS_CLOSE => close(fd).map(|()| 0),
 
                         _ => return Err(Error::new(ENOSYS)),
                     }
@@ -125,8 +125,8 @@ pub fn syscall(a: usize, b: usize, c: usize, d: usize, e: usize, f: usize, stack
             },
             SYS_CLASS_PATH => match a {
                 SYS_OPEN => open(UserSlice::ro(b, c)?, d).map(FileHandle::into),
-                SYS_RMDIR => rmdir(UserSlice::ro(b, c)?),
-                SYS_UNLINK => unlink(UserSlice::ro(b, c)?),
+                SYS_RMDIR => rmdir(UserSlice::ro(b, c)?).map(|()| 0),
+                SYS_UNLINK => unlink(UserSlice::ro(b, c)?).map(|()| 0),
                 _ => Err(Error::new(ENOSYS))
             },
             _ => match a {