diff --git a/src/header/sys_mman/mod.rs b/src/header/sys_mman/mod.rs
index 3133a74159..f3f6f628b9 100644
--- a/src/header/sys_mman/mod.rs
+++ b/src/header/sys_mman/mod.rs
@@ -1,3 +1,7 @@
+//! `sys/mman.h` implementation.
+//!
+//! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_mman.h.html>.
+
 use crate::{
     c_str::{CStr, CString},
     error::{Errno, ResultExt},
@@ -44,16 +48,27 @@ pub const POSIX_MADV_SEQUENTIAL: c_int = 2;
 pub const POSIX_MADV_WILLNEED: c_int = 3;
 pub const POSIX_MADV_WONTNEED: c_int = 4;
 
+/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man2/madvise.2.html>.
+#[no_mangle]
+pub unsafe extern "C" fn madvise(addr: *mut c_void, len: size_t, flags: c_int) -> c_int {
+    Sys::madvise(addr, len, flags)
+        .map(|()| 0)
+        .or_minus_one_errno()
+}
+
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/mlock.html>.
 #[no_mangle]
 pub unsafe extern "C" fn mlock(addr: *const c_void, len: usize) -> c_int {
     Sys::mlock(addr, len).map(|()| 0).or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/mlockall.html>.
 #[no_mangle]
 pub unsafe extern "C" fn mlockall(flags: c_int) -> c_int {
     Sys::mlockall(flags).map(|()| 0).or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/mmap.html>.
 #[no_mangle]
 pub unsafe extern "C" fn mmap(
     addr: *mut c_void,
@@ -72,8 +87,17 @@ pub unsafe extern "C" fn mmap(
     }
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/mprotect.html>.
 #[no_mangle]
-unsafe extern "C" fn mremap(
+pub unsafe extern "C" fn mprotect(addr: *mut c_void, len: size_t, prot: c_int) -> c_int {
+    Sys::mprotect(addr, len, prot)
+        .map(|()| 0)
+        .or_minus_one_errno()
+}
+
+/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man2/mremap.2.html>.
+#[no_mangle]
+pub unsafe extern "C" fn mremap(
     old_address: *mut c_void,
     old_size: usize,
     new_size: usize,
@@ -90,13 +114,7 @@ unsafe extern "C" fn mremap(
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn mprotect(addr: *mut c_void, len: size_t, prot: c_int) -> c_int {
-    Sys::mprotect(addr, len, prot)
-        .map(|()| 0)
-        .or_minus_one_errno()
-}
-
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/msync.html>.
 #[no_mangle]
 pub unsafe extern "C" fn msync(addr: *mut c_void, len: size_t, flags: c_int) -> c_int {
     Sys::msync(addr, len, flags)
@@ -104,28 +122,24 @@ pub unsafe extern "C" fn msync(addr: *mut c_void, len: size_t, flags: c_int) ->
         .or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/mlock.html>.
 #[no_mangle]
 pub unsafe extern "C" fn munlock(addr: *const c_void, len: usize) -> c_int {
     Sys::munlock(addr, len).map(|()| 0).or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/mlockall.html>.
 #[no_mangle]
 pub unsafe extern "C" fn munlockall() -> c_int {
     Sys::munlockall().map(|()| 0).or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/munmap.html>.
 #[no_mangle]
 pub unsafe extern "C" fn munmap(addr: *mut c_void, len: size_t) -> c_int {
     Sys::munmap(addr, len).map(|()| 0).or_minus_one_errno()
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn madvise(addr: *mut c_void, len: size_t, flags: c_int) -> c_int {
-    Sys::madvise(addr, len, flags)
-        .map(|()| 0)
-        .or_minus_one_errno()
-}
-
 #[cfg(target_os = "linux")]
 static SHM_PATH: &'static [u8] = b"/dev/shm/";
 
@@ -152,12 +166,14 @@ unsafe fn shm_path(name: *const c_char) -> CString {
     CString::from_vec_unchecked(path)
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/shm_open.html>.
 #[no_mangle]
 pub unsafe extern "C" fn shm_open(name: *const c_char, oflag: c_int, mode: mode_t) -> c_int {
     let path = shm_path(name);
     fcntl::open(path.as_ptr(), oflag, mode)
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/shm_unlink.html>.
 #[no_mangle]
 pub unsafe extern "C" fn shm_unlink(name: *const c_char) -> c_int {
     let path = shm_path(name);