diff --git a/src/fs.rs b/src/fs.rs
index 76b31c307e..674649b544 100644
--- a/src/fs.rs
+++ b/src/fs.rs
@@ -62,7 +62,7 @@ impl File {
 
 impl io::Read for &File {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        match Sys::read(self.fd, buf).or_minus_one_errno() /* TODO */ {
+        match Sys::read(self.fd, buf).map(|read| read as ssize_t).or_minus_one_errno() /* TODO */ {
             -1 => Err(io::last_os_error()),
             ok => Ok(ok as usize),
         }
@@ -71,7 +71,10 @@ impl io::Read for &File {
 
 impl io::Write for &File {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        match Sys::write(self.fd, buf).or_minus_one_errno() {
+        match Sys::write(self.fd, buf)
+            .map(|read| read as ssize_t)
+            .or_minus_one_errno()
+        {
             -1 => Err(io::last_os_error()),
             ok => Ok(ok as usize),
         }
diff --git a/src/header/pty/redox.rs b/src/header/pty/redox.rs
index f22dfc43ed..f99f882a0f 100644
--- a/src/header/pty/redox.rs
+++ b/src/header/pty/redox.rs
@@ -12,7 +12,9 @@ pub(super) unsafe fn openpty(name: &mut [u8]) -> Result<(c_int, c_int), ()> {
     }
 
     // TODO: better error handling
-    let count = Sys::fpath(master, name).or_minus_one_errno();
+    let count = Sys::fpath(master, name)
+        .map(|u| u as ssize_t)
+        .or_minus_one_errno();
     if count < 0 {
         unistd::close(master);
         return Err(());
diff --git a/src/header/stdlib/mod.rs b/src/header/stdlib/mod.rs
index f3486018dc..9a290a9ed3 100644
--- a/src/header/stdlib/mod.rs
+++ b/src/header/stdlib/mod.rs
@@ -986,7 +986,9 @@ pub unsafe extern "C" fn realpath(pathname: *const c_char, resolved: *mut c_char
 
         let len = out.len();
         // TODO: better error handling
-        let read = Sys::fpath(*file, &mut out[..len - 1]).or_minus_one_errno();
+        let read = Sys::fpath(*file, &mut out[..len - 1])
+            .map(|read| read as ssize_t)
+            .or_minus_one_errno();
         if read < 0 {
             return ptr::null_mut();
         }
diff --git a/src/header/sys_random/mod.rs b/src/header/sys_random/mod.rs
index 407739a7b0..36dfc3b408 100644
--- a/src/header/sys_random/mod.rs
+++ b/src/header/sys_random/mod.rs
@@ -14,5 +14,6 @@ pub unsafe extern "C" fn getrandom(buf: *mut c_void, buflen: size_t, flags: c_ui
         slice::from_raw_parts_mut(buf as *mut u8, buflen as usize),
         flags,
     )
+    .map(|read| read as ssize_t)
     .or_minus_one_errno()
 }
diff --git a/src/header/unistd/mod.rs b/src/header/unistd/mod.rs
index 1ead4b0327..df8f8c6fa6 100644
--- a/src/header/unistd/mod.rs
+++ b/src/header/unistd/mod.rs
@@ -647,6 +647,7 @@ pub unsafe extern "C" fn pread(
         slice::from_raw_parts_mut(buf.cast::<u8>(), nbyte),
         offset,
     )
+    .map(|read| read as ssize_t)
     .or_minus_one_errno()
 }
 
@@ -681,6 +682,7 @@ pub unsafe extern "C" fn pwrite(
         slice::from_raw_parts(buf.cast::<u8>(), nbyte),
         offset,
     )
+    .map(|read| read as ssize_t)
     .or_minus_one_errno()
 }
 
@@ -688,7 +690,9 @@ pub unsafe extern "C" fn pwrite(
 pub unsafe extern "C" fn read(fildes: c_int, buf: *const c_void, nbyte: size_t) -> ssize_t {
     let buf = unsafe { slice::from_raw_parts_mut(buf as *mut u8, nbyte as usize) };
     trace_expr!(
-        Sys::read(fildes, buf).or_minus_one_errno(),
+        Sys::read(fildes, buf)
+            .map(|read| read as ssize_t)
+            .or_minus_one_errno(),
         "read({}, {:p}, {})",
         fildes,
         buf,
@@ -704,7 +708,9 @@ pub unsafe extern "C" fn readlink(
 ) -> ssize_t {
     let path = CStr::from_ptr(path);
     let buf = slice::from_raw_parts_mut(buf as *mut u8, bufsize as usize);
-    Sys::readlink(path, buf).or_minus_one_errno()
+    Sys::readlink(path, buf)
+        .map(|read| read as ssize_t)
+        .or_minus_one_errno()
 }
 
 #[no_mangle]
@@ -862,7 +868,9 @@ pub extern "C" fn ttyname_r(fildes: c_int, name: *mut c_char, namesize: size_t)
         return errno::ERANGE;
     }
 
-    let len = Sys::fpath(fildes, &mut name[..namesize - 1]).or_minus_one_errno();
+    let len = Sys::fpath(fildes, &mut name[..namesize - 1])
+        .map(|read| read as ssize_t)
+        .or_minus_one_errno();
     if len < 0 {
         return -platform::ERRNO.get();
     }
@@ -920,5 +928,7 @@ pub extern "C" fn vfork() -> pid_t {
 #[no_mangle]
 pub unsafe extern "C" fn write(fildes: c_int, buf: *const c_void, nbyte: size_t) -> ssize_t {
     let buf = slice::from_raw_parts(buf as *const u8, nbyte as usize);
-    Sys::write(fildes, buf).or_minus_one_errno()
+    Sys::write(fildes, buf)
+        .map(|bytes| bytes as ssize_t)
+        .or_minus_one_errno()
 }
diff --git a/src/platform/linux/mod.rs b/src/platform/linux/mod.rs
index 332244df9f..039f5a4b5d 100644
--- a/src/platform/linux/mod.rs
+++ b/src/platform/linux/mod.rs
@@ -226,7 +226,7 @@ impl Pal for Sys {
         Ok(e_raw(unsafe { syscall!(CLONE, SIGCHLD, 0, 0, 0, 0) })? as pid_t)
     }
 
-    fn fpath(fildes: c_int, out: &mut [u8]) -> Result<ssize_t> {
+    fn fpath(fildes: c_int, out: &mut [u8]) -> Result<usize> {
         let mut proc_path = b"/proc/self/fd/".to_vec();
         write!(proc_path, "{}", fildes).unwrap();
         proc_path.push(0);
@@ -331,8 +331,8 @@ impl Pal for Sys {
         Ok(e_raw(unsafe { syscall!(GETPRIORITY, which, who) })? as c_int)
     }
 
-    fn getrandom(buf: &mut [u8], flags: c_uint) -> Result<ssize_t> {
-        Ok(e_raw(unsafe { syscall!(GETRANDOM, buf.as_mut_ptr(), buf.len(), flags) })? as ssize_t)
+    fn getrandom(buf: &mut [u8], flags: c_uint) -> Result<usize> {
+        e_raw(unsafe { syscall!(GETRANDOM, buf.as_mut_ptr(), buf.len(), flags) })
     }
 
     unsafe fn getrlimit(resource: c_int, rlim: *mut rlimit) -> Result<()> {
@@ -540,17 +540,14 @@ impl Pal for Sys {
         }
     }
 
-    fn read(fildes: c_int, buf: &mut [u8]) -> Result<ssize_t> {
-        Ok(e_raw(unsafe { syscall!(READ, fildes, buf.as_mut_ptr(), buf.len()) })? as ssize_t)
+    fn read(fildes: c_int, buf: &mut [u8]) -> Result<usize> {
+        e_raw(unsafe { syscall!(READ, fildes, buf.as_mut_ptr(), buf.len()) })
     }
-    fn pread(fildes: c_int, buf: &mut [u8], off: off_t) -> Result<ssize_t> {
-        Ok(
-            e_raw(unsafe { syscall!(PREAD64, fildes, buf.as_mut_ptr(), buf.len(), off) })?
-                as ssize_t,
-        )
+    fn pread(fildes: c_int, buf: &mut [u8], off: off_t) -> Result<usize> {
+        e_raw(unsafe { syscall!(PREAD64, fildes, buf.as_mut_ptr(), buf.len(), off) })
     }
 
-    fn readlink(pathname: CStr, out: &mut [u8]) -> Result<ssize_t> {
+    fn readlink(pathname: CStr, out: &mut [u8]) -> Result<usize> {
         e_raw(unsafe {
             syscall!(
                 READLINKAT,
@@ -560,7 +557,6 @@ impl Pal for Sys {
                 out.len()
             )
         })
-        .map(|b| b as ssize_t)
     }
 
     fn rename(old: CStr, new: CStr) -> Result<()> {
@@ -624,11 +620,11 @@ impl Pal for Sys {
         e_raw(unsafe { syscall!(WAIT4, pid, stat_loc, options, 0) }).map(|p| p as pid_t)
     }
 
-    fn write(fildes: c_int, buf: &[u8]) -> Result<ssize_t> {
-        Ok(e_raw(unsafe { syscall!(WRITE, fildes, buf.as_ptr(), buf.len()) })? as ssize_t)
+    fn write(fildes: c_int, buf: &[u8]) -> Result<usize> {
+        e_raw(unsafe { syscall!(WRITE, fildes, buf.as_ptr(), buf.len()) })
     }
-    fn pwrite(fildes: c_int, buf: &[u8], off: off_t) -> Result<ssize_t> {
-        Ok(e_raw(unsafe { syscall!(PWRITE64, fildes, buf.as_ptr(), buf.len(), off) })? as ssize_t)
+    fn pwrite(fildes: c_int, buf: &[u8], off: off_t) -> Result<usize> {
+        e_raw(unsafe { syscall!(PWRITE64, fildes, buf.as_ptr(), buf.len(), off) })
     }
 
     fn verify() -> bool {
diff --git a/src/platform/mod.rs b/src/platform/mod.rs
index 9b51834582..d94cdb7e46 100644
--- a/src/platform/mod.rs
+++ b/src/platform/mod.rs
@@ -86,7 +86,9 @@ pub struct FileWriter(pub c_int);
 
 impl FileWriter {
     pub fn write(&mut self, buf: &[u8]) -> isize {
-        Sys::write(self.0, buf).or_minus_one_errno()
+        Sys::write(self.0, buf)
+            .map(|u| u as isize)
+            .or_minus_one_errno()
     }
 }
 
@@ -107,14 +109,19 @@ impl WriteByte for FileWriter {
 pub struct FileReader(pub c_int);
 
 impl FileReader {
+    // TODO: This is a bad interface. Rustify
     pub fn read(&mut self, buf: &mut [u8]) -> isize {
-        Sys::read(self.0, buf).or_minus_one_errno()
+        Sys::read(self.0, buf)
+            .map(|u| u as isize)
+            .or_minus_one_errno()
     }
 }
 
 impl Read for FileReader {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
-        let i = Sys::read(self.0, buf).or_minus_one_errno(); // TODO
+        let i = Sys::read(self.0, buf)
+            .map(|u| u as isize)
+            .or_minus_one_errno(); // TODO
         if i >= 0 {
             Ok(i as usize)
         } else {
diff --git a/src/platform/pal/mod.rs b/src/platform/pal/mod.rs
index e1f874d3d9..c80069001e 100644
--- a/src/platform/pal/mod.rs
+++ b/src/platform/pal/mod.rs
@@ -79,7 +79,7 @@ pub trait Pal {
 
     unsafe fn fork() -> Result<pid_t>;
 
-    fn fpath(fildes: c_int, out: &mut [u8]) -> Result<ssize_t>;
+    fn fpath(fildes: c_int, out: &mut [u8]) -> Result<usize>;
 
     fn fsync(fildes: c_int) -> Result<()>;
 
@@ -128,7 +128,7 @@ pub trait Pal {
 
     fn getpriority(which: c_int, who: id_t) -> Result<c_int>;
 
-    fn getrandom(buf: &mut [u8], flags: c_uint) -> Result<ssize_t>;
+    fn getrandom(buf: &mut [u8], flags: c_uint) -> Result<usize>;
 
     unsafe fn getrlimit(resource: c_int, rlim: *mut rlimit) -> Result<()>;
 
@@ -203,10 +203,10 @@ pub trait Pal {
 
     fn current_os_tid() -> pthread::OsTid;
 
-    fn read(fildes: c_int, buf: &mut [u8]) -> Result<ssize_t>;
-    fn pread(fildes: c_int, buf: &mut [u8], offset: off_t) -> Result<ssize_t>;
+    fn read(fildes: c_int, buf: &mut [u8]) -> Result<usize>;
+    fn pread(fildes: c_int, buf: &mut [u8], offset: off_t) -> Result<usize>;
 
-    fn readlink(pathname: CStr, out: &mut [u8]) -> Result<ssize_t>;
+    fn readlink(pathname: CStr, out: &mut [u8]) -> Result<usize>;
 
     fn rename(old: CStr, new: CStr) -> Result<()>;
 
@@ -239,8 +239,8 @@ pub trait Pal {
 
     unsafe fn waitpid(pid: pid_t, stat_loc: *mut c_int, options: c_int) -> Result<pid_t>;
 
-    fn write(fildes: c_int, buf: &[u8]) -> Result<ssize_t>;
-    fn pwrite(fildes: c_int, buf: &[u8], offset: off_t) -> Result<ssize_t>;
+    fn write(fildes: c_int, buf: &[u8]) -> Result<usize>;
+    fn pwrite(fildes: c_int, buf: &[u8], offset: off_t) -> Result<usize>;
 
     fn verify() -> bool;
 }
diff --git a/src/platform/redox/epoll.rs b/src/platform/redox/epoll.rs
index 25521854d6..10d271e683 100644
--- a/src/platform/redox/epoll.rs
+++ b/src/platform/redox/epoll.rs
@@ -69,6 +69,7 @@ impl PalEpoll for Sys {
                         data: unsafe { (*event).data.u64 as usize },
                     },
                 )
+                .map(|u| u as ssize_t)
                 .or_minus_one_errno()
                     < 0
                 {
@@ -87,6 +88,7 @@ impl PalEpoll for Sys {
                         data: 0,
                     },
                 )
+                .map(|u| u as ssize_t)
                 .or_minus_one_errno()
                     < 0
                 {
@@ -129,6 +131,7 @@ impl PalEpoll for Sys {
                             data: 0,
                         },
                     )
+                    .map(|u| u as ssize_t)
                     .or_minus_one_errno()
                         == -1
                     {
@@ -158,6 +161,7 @@ impl PalEpoll for Sys {
                 maxevents as usize * mem::size_of::<syscall::Event>(),
             )
         })
+        .map(|u| u as ssize_t)
         .or_minus_one_errno(); // TODO
         if bytes_read == -1 {
             return -1;
diff --git a/src/platform/redox/mod.rs b/src/platform/redox/mod.rs
index 264a09b118..94fcfac5fb 100644
--- a/src/platform/redox/mod.rs
+++ b/src/platform/redox/mod.rs
@@ -446,7 +446,7 @@ impl Pal for Sys {
         Err(Errno(ENOSYS))
     }
 
-    fn getrandom(buf: &mut [u8], flags: c_uint) -> Result<ssize_t> {
+    fn getrandom(buf: &mut [u8], flags: c_uint) -> Result<usize> {
         let path = if flags & sys_random::GRND_RANDOM != 0 {
             //TODO: /dev/random equivalent
             "/scheme/rand"
@@ -461,7 +461,7 @@ impl Pal for Sys {
 
         //TODO: store fd internally
         let fd = FdGuard::new(syscall::open(path, open_flags)?);
-        Ok(syscall::read(*fd, buf)? as ssize_t)
+        Ok(syscall::read(*fd, buf)?)
     }
 
     unsafe fn getrlimit(resource: c_int, rlim: *mut rlimit) -> Result<()> {
@@ -735,11 +735,11 @@ impl Pal for Sys {
         }
     }
 
-    fn read(fd: c_int, buf: &mut [u8]) -> Result<ssize_t> {
+    fn read(fd: c_int, buf: &mut [u8]) -> Result<usize> {
         let fd = usize::try_from(fd).map_err(|_| Errno(EBADF))?;
-        Ok(redox_rt::sys::posix_read(fd, buf)? as ssize_t)
+        Ok(redox_rt::sys::posix_read(fd, buf)?)
     }
-    fn pread(fd: c_int, buf: &mut [u8], offset: off_t) -> Result<ssize_t> {
+    fn pread(fd: c_int, buf: &mut [u8], offset: off_t) -> Result<usize> {
         unsafe {
             Ok(syscall::syscall5(
                 syscall::SYS_READ2,
@@ -748,11 +748,11 @@ impl Pal for Sys {
                 buf.len(),
                 offset as usize,
                 !0,
-            )? as ssize_t)
+            )?)
         }
     }
 
-    fn fpath(fildes: c_int, out: &mut [u8]) -> Result<ssize_t> {
+    fn fpath(fildes: c_int, out: &mut [u8]) -> Result<usize> {
         // Since this is used by realpath, it converts from the old format to the new one for
         // compatibility reasons
         let mut buf = [0; limits::PATH_MAX];
@@ -776,12 +776,12 @@ impl Pal for Sys {
             ),
         };
         match res {
-            Ok(()) => Ok(cursor.position() as ssize_t),
+            Ok(()) => Ok(cursor.position() as usize),
             Err(_err) => Err(Errno(ENAMETOOLONG)),
         }
     }
 
-    fn readlink(pathname: CStr, out: &mut [u8]) -> Result<ssize_t> {
+    fn readlink(pathname: CStr, out: &mut [u8]) -> Result<usize> {
         let file = File::open(
             pathname,
             fcntl::O_RDONLY | fcntl::O_SYMLINK | fcntl::O_CLOEXEC,
@@ -1017,11 +1017,11 @@ impl Pal for Sys {
         Ok(res? as pid_t)
     }
 
-    fn write(fd: c_int, buf: &[u8]) -> Result<ssize_t> {
+    fn write(fd: c_int, buf: &[u8]) -> Result<usize> {
         let fd = usize::try_from(fd).map_err(|_| Errno(EBADFD))?;
-        Ok(redox_rt::sys::posix_write(fd, buf)? as ssize_t)
+        Ok(redox_rt::sys::posix_write(fd, buf)?)
     }
-    fn pwrite(fd: c_int, buf: &[u8], offset: off_t) -> Result<ssize_t> {
+    fn pwrite(fd: c_int, buf: &[u8], offset: off_t) -> Result<usize> {
         unsafe {
             Ok(syscall::syscall5(
                 syscall::SYS_WRITE2,
@@ -1030,7 +1030,7 @@ impl Pal for Sys {
                 buf.len(),
                 offset as usize,
                 !0,
-            )? as ssize_t)
+            )?)
         }
     }
 
diff --git a/src/platform/redox/socket.rs b/src/platform/redox/socket.rs
index 6d91c53991..4f54480052 100644
--- a/src/platform/redox/socket.rs
+++ b/src/platform/redox/socket.rs
@@ -306,7 +306,9 @@ impl PalSocket for Sys {
             return -1;
         }
         if address == ptr::null_mut() || address_len == ptr::null_mut() {
-            Self::read(socket, slice::from_raw_parts_mut(buf as *mut u8, len)).or_minus_one_errno()
+            Self::read(socket, slice::from_raw_parts_mut(buf as *mut u8, len))
+                .map(|u| u as ssize_t)
+                .or_minus_one_errno()
         } else {
             let fd = e(syscall::dup(socket as usize, b"listen"));
             if fd == !0 {
@@ -318,6 +320,7 @@ impl PalSocket for Sys {
             }
 
             let ret = Self::read(fd as c_int, slice::from_raw_parts_mut(buf as *mut u8, len))
+                .map(|u| u as ssize_t)
                 .or_minus_one_errno();
             let _ = syscall::close(fd);
             ret
@@ -351,10 +354,13 @@ impl PalSocket for Sys {
             return -1;
         }
         if dest_addr == ptr::null() || dest_len == 0 {
-            Self::write(socket, slice::from_raw_parts(buf as *const u8, len)).or_minus_one_errno()
+            Self::write(socket, slice::from_raw_parts(buf as *const u8, len))
+                .map(|u| u as ssize_t)
+                .or_minus_one_errno()
         } else {
             let fd = bind_or_connect!(connect copy, socket, dest_addr, dest_len);
             let ret = Self::write(fd as c_int, slice::from_raw_parts(buf as *const u8, len))
+                .map(|u| u as ssize_t)
                 .or_minus_one_errno();
             let _ = syscall::close(fd);
             ret
@@ -389,7 +395,9 @@ impl PalSocket for Sys {
                 tv_nsec: timeval.tv_usec * 1000,
             };
 
-            let ret = Self::write(fd as c_int, &timespec).or_minus_one_errno();
+            let ret = Self::write(fd as c_int, &timespec)
+                .map(|u| u as ssize_t)
+                .or_minus_one_errno();
 
             let _ = syscall::close(fd);
 
diff --git a/src/platform/rlb.rs b/src/platform/rlb.rs
index ec9ed09892..ade9555892 100644
--- a/src/platform/rlb.rs
+++ b/src/platform/rlb.rs
@@ -61,7 +61,9 @@ impl RawLineBuffer {
                 self.buf.set_len(capacity);
             }
 
-            let read = Sys::read(self.fd, &mut self.buf[len..]).or_minus_one_errno();
+            let read = Sys::read(self.fd, &mut self.buf[len..])
+                .map(|u| u as isize)
+                .or_minus_one_errno();
 
             let read_usize = read.max(0) as usize;