diff --git a/library/std/src/sys/pal/sgx/abi/usercalls/alloc.rs b/library/std/src/sys/pal/sgx/abi/usercalls/alloc.rs
index 301e3299c0572..3fe6dee3d6f4f 100644
--- a/library/std/src/sys/pal/sgx/abi/usercalls/alloc.rs
+++ b/library/std/src/sys/pal/sgx/abi/usercalls/alloc.rs
@@ -6,7 +6,7 @@ use super::super::mem::{is_enclave_range, is_user_range};
 use crate::arch::asm;
 use crate::cell::UnsafeCell;
 use crate::convert::TryInto;
-use crate::mem::{self, ManuallyDrop};
+use crate::mem::{self, ManuallyDrop, MaybeUninit};
 use crate::ops::{CoerceUnsized, Deref, DerefMut, Index, IndexMut};
 use crate::pin::PinCoerceUnsized;
 use crate::ptr::{self, NonNull};
@@ -209,6 +209,45 @@ impl<T: ?Sized> NewUserRef<NonNull<T>> for NonNull<UserRef<T>> {
     }
 }
 
+/// A type which can a destination for safely copying from userspace.
+///
+/// # Safety
+///
+/// Requires that `T` and `Self` have identical layouts.
+#[unstable(feature = "sgx_platform", issue = "56975")]
+pub unsafe trait UserSafeCopyDestination<T: ?Sized> {
+    /// Returns a pointer for writing to the value.
+    fn as_mut_ptr(&mut self) -> *mut T;
+}
+
+#[unstable(feature = "sgx_platform", issue = "56975")]
+unsafe impl<T> UserSafeCopyDestination<T> for T {
+    fn as_mut_ptr(&mut self) -> *mut T {
+        self as _
+    }
+}
+
+#[unstable(feature = "sgx_platform", issue = "56975")]
+unsafe impl<T> UserSafeCopyDestination<[T]> for [T] {
+    fn as_mut_ptr(&mut self) -> *mut [T] {
+        self as _
+    }
+}
+
+#[unstable(feature = "sgx_platform", issue = "56975")]
+unsafe impl<T> UserSafeCopyDestination<T> for MaybeUninit<T> {
+    fn as_mut_ptr(&mut self) -> *mut T {
+        self as *mut Self as _
+    }
+}
+
+#[unstable(feature = "sgx_platform", issue = "56975")]
+unsafe impl<T> UserSafeCopyDestination<[T]> for [MaybeUninit<T>] {
+    fn as_mut_ptr(&mut self) -> *mut [T] {
+        self as *mut Self as _
+    }
+}
+
 #[unstable(feature = "sgx_platform", issue = "56975")]
 impl<T: ?Sized> User<T>
 where
@@ -544,12 +583,12 @@ where
     /// # Panics
     /// This function panics if the destination doesn't have the same size as
     /// the source. This can happen for dynamically-sized types such as slices.
-    pub fn copy_to_enclave(&self, dest: &mut T) {
+    pub fn copy_to_enclave<U: ?Sized + UserSafeCopyDestination<T>>(&self, dest: &mut U) {
         unsafe {
             assert_eq!(size_of_val(dest), size_of_val(&*self.0.get()));
             copy_from_userspace(
                 self.0.get() as *const T as *const u8,
-                dest as *mut T as *mut u8,
+                dest.as_mut_ptr() as *mut u8,
                 size_of_val(dest),
             );
         }
@@ -639,25 +678,18 @@ where
         unsafe { (*self.0.get()).len() }
     }
 
-    /// Copies the value from user memory and place it into `dest`. Afterwards,
-    /// `dest` will contain exactly `self.len()` elements.
-    ///
-    /// # Panics
-    /// This function panics if the destination doesn't have the same size as
-    /// the source. This can happen for dynamically-sized types such as slices.
-    pub fn copy_to_enclave_vec(&self, dest: &mut Vec<T>) {
-        if let Some(missing) = self.len().checked_sub(dest.capacity()) {
-            dest.reserve(missing)
-        }
+    /// Copies the value from user memory and appends it to `dest`.
+    pub fn append_to_enclave_vec(&self, dest: &mut Vec<T>) {
+        dest.reserve(self.len());
+        self.copy_to_enclave(&mut dest.spare_capacity_mut()[..self.len()]);
         // SAFETY: We reserve enough space above.
-        unsafe { dest.set_len(self.len()) };
-        self.copy_to_enclave(&mut dest[..]);
+        unsafe { dest.set_len(dest.len() + self.len()) };
     }
 
     /// Copies the value from user memory into a vector in enclave memory.
     pub fn to_enclave(&self) -> Vec<T> {
         let mut ret = Vec::with_capacity(self.len());
-        self.copy_to_enclave_vec(&mut ret);
+        self.append_to_enclave_vec(&mut ret);
         ret
     }
 
diff --git a/library/std/src/sys/pal/sgx/abi/usercalls/mod.rs b/library/std/src/sys/pal/sgx/abi/usercalls/mod.rs
index 90b9b59471a52..cbdaf439b2847 100644
--- a/library/std/src/sys/pal/sgx/abi/usercalls/mod.rs
+++ b/library/std/src/sys/pal/sgx/abi/usercalls/mod.rs
@@ -1,5 +1,7 @@
 use crate::cmp;
-use crate::io::{Error as IoError, ErrorKind, IoSlice, IoSliceMut, Result as IoResult};
+use crate::io::{
+    BorrowedCursor, Error as IoError, ErrorKind, IoSlice, IoSliceMut, Result as IoResult,
+};
 use crate::random::{DefaultRandomSource, Random};
 use crate::time::{Duration, Instant};
 
@@ -36,6 +38,19 @@ pub fn read(fd: Fd, bufs: &mut [IoSliceMut<'_>]) -> IoResult<usize> {
     }
 }
 
+/// Usercall `read` with an uninitialized buffer. See the ABI documentation for
+/// more information.
+#[unstable(feature = "sgx_platform", issue = "56975")]
+pub fn read_buf(fd: Fd, mut buf: BorrowedCursor<'_>) -> IoResult<()> {
+    unsafe {
+        let mut userbuf = alloc::User::<[u8]>::uninitialized(buf.capacity());
+        let len = raw::read(fd, userbuf.as_mut_ptr().cast(), userbuf.len()).from_sgx_result()?;
+        userbuf[..len].copy_to_enclave(&mut buf.as_mut()[..len]);
+        buf.advance_unchecked(len);
+        Ok(())
+    }
+}
+
 /// Usercall `read_alloc`. See the ABI documentation for more information.
 #[unstable(feature = "sgx_platform", issue = "56975")]
 pub fn read_alloc(fd: Fd) -> IoResult<Vec<u8>> {
diff --git a/library/std/src/sys/pal/sgx/fd.rs b/library/std/src/sys/pal/sgx/fd.rs
index 3bb3189a1d127..399f6a1648984 100644
--- a/library/std/src/sys/pal/sgx/fd.rs
+++ b/library/std/src/sys/pal/sgx/fd.rs
@@ -29,7 +29,7 @@ impl FileDesc {
     }
 
     pub fn read_buf(&self, buf: BorrowedCursor<'_>) -> io::Result<()> {
-        crate::io::default_read_buf(|b| self.read(b), buf)
+        usercalls::read_buf(self.fd, buf)
     }
 
     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
diff --git a/library/std/src/sys/stdio/sgx.rs b/library/std/src/sys/stdio/sgx.rs
index 03d754cb2173f..1894c098d1851 100644
--- a/library/std/src/sys/stdio/sgx.rs
+++ b/library/std/src/sys/stdio/sgx.rs
@@ -1,6 +1,6 @@
 use fortanix_sgx_abi as abi;
 
-use crate::io;
+use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::sys::fd::FileDesc;
 
 pub struct Stdin(());
@@ -24,6 +24,19 @@ impl io::Read for Stdin {
     fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
         with_std_fd(abi::FD_STDIN, |fd| fd.read(buf))
     }
+
+    fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> io::Result<()> {
+        with_std_fd(abi::FD_STDIN, |fd| fd.read_buf(buf))
+    }
+
+    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        with_std_fd(abi::FD_STDIN, |fd| fd.read_vectored(bufs))
+    }
+
+    #[inline]
+    fn is_read_vectored(&self) -> bool {
+        true
+    }
 }
 
 impl Stdout {
@@ -40,6 +53,15 @@ impl io::Write for Stdout {
     fn flush(&mut self) -> io::Result<()> {
         with_std_fd(abi::FD_STDOUT, |fd| fd.flush())
     }
+
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        with_std_fd(abi::FD_STDOUT, |fd| fd.write_vectored(bufs))
+    }
+
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
 }
 
 impl Stderr {
@@ -56,6 +78,15 @@ impl io::Write for Stderr {
     fn flush(&mut self) -> io::Result<()> {
         with_std_fd(abi::FD_STDERR, |fd| fd.flush())
     }
+
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        with_std_fd(abi::FD_STDERR, |fd| fd.write_vectored(bufs))
+    }
+
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        true
+    }
 }
 
 pub const STDIN_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;