diff --git a/library/std/src/os/fortanix_sgx/ffi.rs b/library/std/src/os/fortanix_sgx/ffi.rs
deleted file mode 100644
index ac1db0e5e39cc..0000000000000
--- a/library/std/src/os/fortanix_sgx/ffi.rs
+++ /dev/null
@@ -1,41 +0,0 @@
-//! SGX-specific extension to the primitives in the `std::ffi` module
-//!
-//! # Examples
-//!
-//! ```
-//! use std::ffi::OsString;
-//! use std::os::fortanix_sgx::ffi::OsStringExt;
-//!
-//! let bytes = b"foo".to_vec();
-//!
-//! // OsStringExt::from_vec
-//! let os_string = OsString::from_vec(bytes);
-//! assert_eq!(os_string.to_str(), Some("foo"));
-//!
-//! // OsStringExt::into_vec
-//! let bytes = os_string.into_vec();
-//! assert_eq!(bytes, b"foo");
-//! ```
-//!
-//! ```
-//! use std::ffi::OsStr;
-//! use std::os::fortanix_sgx::ffi::OsStrExt;
-//!
-//! let bytes = b"foo";
-//!
-//! // OsStrExt::from_bytes
-//! let os_str = OsStr::from_bytes(bytes);
-//! assert_eq!(os_str.to_str(), Some("foo"));
-//!
-//! // OsStrExt::as_bytes
-//! let bytes = os_str.as_bytes();
-//! assert_eq!(bytes, b"foo");
-//! ```
-
-#![unstable(feature = "sgx_platform", issue = "56975")]
-
-#[path = "../unix/ffi/os_str.rs"]
-mod os_str;
-
-#[unstable(feature = "sgx_platform", issue = "56975")]
-pub use self::os_str::{OsStrExt, OsStringExt};
diff --git a/library/std/src/os/fortanix_sgx/mod.rs b/library/std/src/os/fortanix_sgx/mod.rs
index 2b5ccbe98f1b3..73210a90769ce 100644
--- a/library/std/src/os/fortanix_sgx/mod.rs
+++ b/library/std/src/os/fortanix_sgx/mod.rs
@@ -38,6 +38,7 @@ pub mod mem {
 }
 
 pub mod arch;
+#[path = "../../sys/ffi/bytes.rs"]
 pub mod ffi;
 pub mod io;
 
diff --git a/library/std/src/os/hermit/ffi.rs b/library/std/src/os/hermit/ffi.rs
deleted file mode 100644
index 19761fd99b400..0000000000000
--- a/library/std/src/os/hermit/ffi.rs
+++ /dev/null
@@ -1,41 +0,0 @@
-//! HermitCore-specific extension to the primitives in the `std::ffi` module
-//!
-//! # Examples
-//!
-//! ```
-//! use std::ffi::OsString;
-//! use std::os::hermit::ffi::OsStringExt;
-//!
-//! let bytes = b"foo".to_vec();
-//!
-//! // OsStringExt::from_vec
-//! let os_string = OsString::from_vec(bytes);
-//! assert_eq!(os_string.to_str(), Some("foo"));
-//!
-//! // OsStringExt::into_vec
-//! let bytes = os_string.into_vec();
-//! assert_eq!(bytes, b"foo");
-//! ```
-//!
-//! ```
-//! use std::ffi::OsStr;
-//! use std::os::hermit::ffi::OsStrExt;
-//!
-//! let bytes = b"foo";
-//!
-//! // OsStrExt::from_bytes
-//! let os_str = OsStr::from_bytes(bytes);
-//! assert_eq!(os_str.to_str(), Some("foo"));
-//!
-//! // OsStrExt::as_bytes
-//! let bytes = os_str.as_bytes();
-//! assert_eq!(bytes, b"foo");
-//! ```
-
-#![stable(feature = "rust1", since = "1.0.0")]
-
-#[path = "../unix/ffi/os_str.rs"]
-mod os_str;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::os_str::{OsStrExt, OsStringExt};
diff --git a/library/std/src/os/hermit/mod.rs b/library/std/src/os/hermit/mod.rs
index 5812206a25759..08e922bb09300 100644
--- a/library/std/src/os/hermit/mod.rs
+++ b/library/std/src/os/hermit/mod.rs
@@ -5,6 +5,7 @@
 #[stable(feature = "rust1", since = "1.0.0")]
 pub extern crate hermit_abi;
 
+#[path = "../../sys/ffi/bytes.rs"]
 pub mod ffi;
 pub mod io;
 
diff --git a/library/std/src/os/motor/mod.rs b/library/std/src/os/motor/mod.rs
index 18da079c74a15..adc2d7d053289 100644
--- a/library/std/src/os/motor/mod.rs
+++ b/library/std/src/os/motor/mod.rs
@@ -1,4 +1,5 @@
 #![unstable(feature = "motor_ext", issue = "147456")]
 
+#[path = "../../sys/ffi/utf8.rs"]
 pub mod ffi;
 pub mod process;
diff --git a/library/std/src/os/solid/ffi.rs b/library/std/src/os/solid/ffi.rs
deleted file mode 100644
index aaa2070a6abe9..0000000000000
--- a/library/std/src/os/solid/ffi.rs
+++ /dev/null
@@ -1,41 +0,0 @@
-//! SOLID-specific extension to the primitives in the `std::ffi` module
-//!
-//! # Examples
-//!
-//! ```
-//! use std::ffi::OsString;
-//! use std::os::solid::ffi::OsStringExt;
-//!
-//! let bytes = b"foo".to_vec();
-//!
-//! // OsStringExt::from_vec
-//! let os_string = OsString::from_vec(bytes);
-//! assert_eq!(os_string.to_str(), Some("foo"));
-//!
-//! // OsStringExt::into_vec
-//! let bytes = os_string.into_vec();
-//! assert_eq!(bytes, b"foo");
-//! ```
-//!
-//! ```
-//! use std::ffi::OsStr;
-//! use std::os::solid::ffi::OsStrExt;
-//!
-//! let bytes = b"foo";
-//!
-//! // OsStrExt::from_bytes
-//! let os_str = OsStr::from_bytes(bytes);
-//! assert_eq!(os_str.to_str(), Some("foo"));
-//!
-//! // OsStrExt::as_bytes
-//! let bytes = os_str.as_bytes();
-//! assert_eq!(bytes, b"foo");
-//! ```
-
-#![stable(feature = "rust1", since = "1.0.0")]
-
-#[path = "../unix/ffi/os_str.rs"]
-mod os_str;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::os_str::{OsStrExt, OsStringExt};
diff --git a/library/std/src/os/solid/mod.rs b/library/std/src/os/solid/mod.rs
index 75824048e2498..80e81800092a1 100644
--- a/library/std/src/os/solid/mod.rs
+++ b/library/std/src/os/solid/mod.rs
@@ -1,6 +1,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 #![forbid(unsafe_op_in_unsafe_fn)]
 
+#[path = "../../sys/ffi/bytes.rs"]
 pub mod ffi;
 pub mod io;
 
diff --git a/library/std/src/os/uefi/mod.rs b/library/std/src/os/uefi/mod.rs
index b42d796b28f69..4c2d1f6707872 100644
--- a/library/std/src/os/uefi/mod.rs
+++ b/library/std/src/os/uefi/mod.rs
@@ -5,5 +5,5 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
 pub mod env;
-#[path = "../windows/ffi.rs"]
+#[path = "../../sys/ffi/windows.rs"]
 pub mod ffi;
diff --git a/library/std/src/os/unix/ffi/mod.rs b/library/std/src/os/unix/ffi/mod.rs
deleted file mode 100644
index 5b49f50763d74..0000000000000
--- a/library/std/src/os/unix/ffi/mod.rs
+++ /dev/null
@@ -1,42 +0,0 @@
-//! Unix-specific extensions to primitives in the [`std::ffi`] module.
-//!
-//! # Examples
-//!
-//! ```
-//! use std::ffi::OsString;
-//! use std::os::unix::ffi::OsStringExt;
-//!
-//! let bytes = b"foo".to_vec();
-//!
-//! // OsStringExt::from_vec
-//! let os_string = OsString::from_vec(bytes);
-//! assert_eq!(os_string.to_str(), Some("foo"));
-//!
-//! // OsStringExt::into_vec
-//! let bytes = os_string.into_vec();
-//! assert_eq!(bytes, b"foo");
-//! ```
-//!
-//! ```
-//! use std::ffi::OsStr;
-//! use std::os::unix::ffi::OsStrExt;
-//!
-//! let bytes = b"foo";
-//!
-//! // OsStrExt::from_bytes
-//! let os_str = OsStr::from_bytes(bytes);
-//! assert_eq!(os_str.to_str(), Some("foo"));
-//!
-//! // OsStrExt::as_bytes
-//! let bytes = os_str.as_bytes();
-//! assert_eq!(bytes, b"foo");
-//! ```
-//!
-//! [`std::ffi`]: crate::ffi
-
-#![stable(feature = "rust1", since = "1.0.0")]
-
-mod os_str;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::os_str::{OsStrExt, OsStringExt};
diff --git a/library/std/src/os/unix/ffi/os_str.rs b/library/std/src/os/unix/ffi/os_str.rs
deleted file mode 100644
index 650f712bc6eef..0000000000000
--- a/library/std/src/os/unix/ffi/os_str.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-use crate::ffi::{OsStr, OsString};
-use crate::mem;
-use crate::sealed::Sealed;
-use crate::sys::os_str::Buf;
-use crate::sys_common::{AsInner, FromInner, IntoInner};
-
-// Note: this file is currently reused in other `std::os::{platform}::ffi` modules to reduce duplication.
-// Keep this in mind when applying changes to this file that only apply to `unix`.
-
-/// Platform-specific extensions to [`OsString`].
-///
-/// This trait is sealed: it cannot be implemented outside the standard library.
-/// This is so that future additional methods are not breaking changes.
-#[stable(feature = "rust1", since = "1.0.0")]
-pub trait OsStringExt: Sealed {
-    /// Creates an [`OsString`] from a byte vector.
-    ///
-    /// See the module documentation for an example.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    fn from_vec(vec: Vec<u8>) -> Self;
-
-    /// Yields the underlying byte vector of this [`OsString`].
-    ///
-    /// See the module documentation for an example.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    fn into_vec(self) -> Vec<u8>;
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl OsStringExt for OsString {
-    #[inline]
-    fn from_vec(vec: Vec<u8>) -> OsString {
-        FromInner::from_inner(Buf { inner: vec })
-    }
-    #[inline]
-    fn into_vec(self) -> Vec<u8> {
-        self.into_inner().inner
-    }
-}
-
-/// Platform-specific extensions to [`OsStr`].
-///
-/// This trait is sealed: it cannot be implemented outside the standard library.
-/// This is so that future additional methods are not breaking changes.
-#[stable(feature = "rust1", since = "1.0.0")]
-pub trait OsStrExt: Sealed {
-    #[stable(feature = "rust1", since = "1.0.0")]
-    /// Creates an [`OsStr`] from a byte slice.
-    ///
-    /// See the module documentation for an example.
-    fn from_bytes(slice: &[u8]) -> &Self;
-
-    /// Gets the underlying byte view of the [`OsStr`] slice.
-    ///
-    /// See the module documentation for an example.
-    #[stable(feature = "rust1", since = "1.0.0")]
-    fn as_bytes(&self) -> &[u8];
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl OsStrExt for OsStr {
-    #[inline]
-    fn from_bytes(slice: &[u8]) -> &OsStr {
-        unsafe { mem::transmute(slice) }
-    }
-    #[inline]
-    fn as_bytes(&self) -> &[u8] {
-        &self.as_inner().inner
-    }
-}
diff --git a/library/std/src/os/unix/mod.rs b/library/std/src/os/unix/mod.rs
index 78c957270c451..4013088407977 100644
--- a/library/std/src/os/unix/mod.rs
+++ b/library/std/src/os/unix/mod.rs
@@ -87,6 +87,7 @@ mod platform {
     pub use crate::os::vxworks::*;
 }
 
+#[path = "../../sys/ffi/bytes.rs"]
 pub mod ffi;
 pub mod fs;
 pub mod io;
diff --git a/library/std/src/os/wasi/ffi.rs b/library/std/src/os/wasi/ffi.rs
deleted file mode 100644
index 41dd8702e98e9..0000000000000
--- a/library/std/src/os/wasi/ffi.rs
+++ /dev/null
@@ -1,11 +0,0 @@
-//! WASI-specific extensions to primitives in the [`std::ffi`] module
-//!
-//! [`std::ffi`]: crate::ffi
-
-#![stable(feature = "rust1", since = "1.0.0")]
-
-#[path = "../unix/ffi/os_str.rs"]
-mod os_str;
-
-#[stable(feature = "rust1", since = "1.0.0")]
-pub use self::os_str::{OsStrExt, OsStringExt};
diff --git a/library/std/src/os/wasi/mod.rs b/library/std/src/os/wasi/mod.rs
index 2ee6aa4660094..15f142f5089ba 100644
--- a/library/std/src/os/wasi/mod.rs
+++ b/library/std/src/os/wasi/mod.rs
@@ -33,6 +33,7 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 #![doc(cfg(target_os = "wasi"))]
 
+#[path = "../../sys/ffi/bytes.rs"]
 pub mod ffi;
 pub mod fs;
 pub mod io;
diff --git a/library/std/src/os/windows/mod.rs b/library/std/src/os/windows/mod.rs
index f452403ee8426..2923d89656942 100644
--- a/library/std/src/os/windows/mod.rs
+++ b/library/std/src/os/windows/mod.rs
@@ -26,6 +26,7 @@
 #![doc(cfg(windows))]
 #![deny(unsafe_op_in_unsafe_fn)]
 
+#[path = "../../sys/ffi/windows.rs"]
 pub mod ffi;
 pub mod fs;
 pub mod io;
diff --git a/library/std/src/os/xous/ffi.rs b/library/std/src/os/xous/ffi.rs
index 9394f0a0496b2..cbc5d6b118711 100644
--- a/library/std/src/os/xous/ffi.rs
+++ b/library/std/src/os/xous/ffi.rs
@@ -2,7 +2,7 @@
 #![allow(unused_variables)]
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[path = "../unix/ffi/os_str.rs"]
+#[path = "../../sys/ffi/bytes.rs"]
 mod os_str;
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/std/src/sys/ffi/bytes.rs b/library/std/src/sys/ffi/bytes.rs
new file mode 100644
index 0000000000000..5fb63532c04c0
--- /dev/null
+++ b/library/std/src/sys/ffi/bytes.rs
@@ -0,0 +1,143 @@
+// Note: This file is publicly exported as various modules to reduce
+// duplication. Currently they are:
+// - `std::os::unix::ffi`
+// - `std::os::hermit::ffi`
+// - `std::os::fortanix_sgx::ffi`
+// - `std::os::solid::ffi`
+// - `std::os::wasi::ffi`
+// - `std::os::xous::ffi`
+
+#![doc = cfg_select! {
+    target_family = "unix" => "Unix-specific",
+    target_os = "hermit" => "HermitCore-specific",
+    all(target_vendor = "fortanix", target_env = "sgx") => "SGX-specific",
+    target_os = "solid_asp3" => "SOLID-specific",
+    target_os = "wasi" => "WASI-specific",
+    target_os = "xous" => "Xous-specific",
+}]
+//! extensions to primitives in the [`std::ffi`] module.
+//!
+//! # Examples
+//!
+//! ```
+//! use std::ffi::OsString;
+#![doc = cfg_select! {
+    target_family = "unix" => "use std::os::unix::ffi::OsStringExt;",
+    target_os = "hermit" => "use std::os::hermit::ffi::OsStringExt;",
+    all(target_vendor = "fortanix", target_env = "sgx") => "use std::os::fortanix_sgx::ffi::OsStringExt;",
+    target_os = "solid_asp3" => "use std::os::solid::ffi::OsStringExt;",
+    target_os = "wasi" => "use std::os::wasi::ffi::OsStringExt;",
+    target_os = "xous" => "use std::os::xous::ffi::OsStringExt;",
+}]
+//!
+//! let bytes = b"foo".to_vec();
+//!
+//! // OsStringExt::from_vec
+//! let os_string = OsString::from_vec(bytes);
+//! assert_eq!(os_string.to_str(), Some("foo"));
+//!
+//! // OsStringExt::into_vec
+//! let bytes = os_string.into_vec();
+//! assert_eq!(bytes, b"foo");
+//! ```
+//!
+//! ```
+//! use std::ffi::OsStr;
+#![doc = cfg_select! {
+    target_family = "unix" => "use std::os::unix::ffi::OsStrExt;",
+    target_os = "hermit" => "use std::os::hermit::ffi::OsStrExt;",
+    all(target_vendor = "fortanix", target_env = "sgx") => "use std::os::fortanix_sgx::ffi::OsStrExt;",
+    target_os = "solid_asp3" => "use std::os::solid::ffi::OsStrExt;",
+    target_os = "wasi" => "use std::os::wasi::ffi::OsStrExt;",
+    target_os = "xous" => "use std::os::xous::ffi::OsStrExt;",
+}]
+//!
+//! let bytes = b"foo";
+//!
+//! // OsStrExt::from_bytes
+//! let os_str = OsStr::from_bytes(bytes);
+//! assert_eq!(os_str.to_str(), Some("foo"));
+//!
+//! // OsStrExt::as_bytes
+//! let bytes = os_str.as_bytes();
+//! assert_eq!(bytes, b"foo");
+//! ```
+//!
+//! [`std::ffi`]: crate::ffi
+
+#![cfg_attr(
+    not(all(target_vendor = "fortanix", target_env = "sgx")),
+    stable(feature = "rust1", since = "1.0.0")
+)]
+#![cfg_attr(
+    all(target_vendor = "fortanix", target_env = "sgx"),
+    unstable(feature = "sgx_platform", issue = "56975")
+)]
+
+use crate::ffi::{OsStr, OsString};
+use crate::mem;
+use crate::sealed::Sealed;
+use crate::sys::os_str::Buf;
+use crate::sys_common::{AsInner, FromInner, IntoInner};
+
+/// Platform-specific extensions to [`OsString`].
+///
+/// This trait is sealed: it cannot be implemented outside the standard library.
+/// This is so that future additional methods are not breaking changes.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait OsStringExt: Sealed {
+    /// Creates an [`OsString`] from a byte vector.
+    ///
+    /// See the module documentation for an example.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn from_vec(vec: Vec<u8>) -> Self;
+
+    /// Yields the underlying byte vector of this [`OsString`].
+    ///
+    /// See the module documentation for an example.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn into_vec(self) -> Vec<u8>;
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl OsStringExt for OsString {
+    #[inline]
+    fn from_vec(vec: Vec<u8>) -> OsString {
+        FromInner::from_inner(Buf { inner: vec })
+    }
+    #[inline]
+    fn into_vec(self) -> Vec<u8> {
+        self.into_inner().inner
+    }
+}
+
+/// Platform-specific extensions to [`OsStr`].
+///
+/// This trait is sealed: it cannot be implemented outside the standard library.
+/// This is so that future additional methods are not breaking changes.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub trait OsStrExt: Sealed {
+    #[stable(feature = "rust1", since = "1.0.0")]
+    /// Creates an [`OsStr`] from a byte slice.
+    ///
+    /// See the module documentation for an example.
+    fn from_bytes(slice: &[u8]) -> &Self;
+
+    /// Gets the underlying byte view of the [`OsStr`] slice.
+    ///
+    /// See the module documentation for an example.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn as_bytes(&self) -> &[u8];
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl OsStrExt for OsStr {
+    #[inline]
+    fn from_bytes(slice: &[u8]) -> &OsStr {
+        unsafe { mem::transmute(slice) }
+    }
+    #[inline]
+    fn as_bytes(&self) -> &[u8] {
+        &self.as_inner().inner
+    }
+}
diff --git a/library/std/src/os/motor/ffi.rs b/library/std/src/sys/ffi/utf8.rs
similarity index 88%
rename from library/std/src/os/motor/ffi.rs
rename to library/std/src/sys/ffi/utf8.rs
index 10e8da392dcc5..e27644b471ce9 100644
--- a/library/std/src/os/motor/ffi.rs
+++ b/library/std/src/sys/ffi/utf8.rs
@@ -1,3 +1,7 @@
+// Note: This file is publicly exported as various modules to reduce
+// duplication. Currently it is only `std::os::motor::ffi`, so the documentation
+// is specific to Motor OS.
+
 //! Motor OS-specific extensions to primitives in the [`std::ffi`] module.
 #![unstable(feature = "motor_ext", issue = "147456")]
 
diff --git a/library/std/src/os/windows/ffi.rs b/library/std/src/sys/ffi/windows.rs
similarity index 97%
rename from library/std/src/os/windows/ffi.rs
rename to library/std/src/sys/ffi/windows.rs
index 20e5383dc09e0..0842fbf16d34d 100644
--- a/library/std/src/os/windows/ffi.rs
+++ b/library/std/src/sys/ffi/windows.rs
@@ -1,3 +1,8 @@
+// Note: This file is publicly exported as various modules to reduce
+// duplication. Currently they are:
+// - `std::os::windows::ffi`
+// - `std::os::uefi::ffi`
+
 //! Windows-specific extensions to primitives in the [`std::ffi`] module.
 //!
 //! # Overview