diff --git a/libc/include/fcntl.h b/libc/include/fcntl.h
index 1c5d64c..c45c91f 100644
--- a/libc/include/fcntl.h
+++ b/libc/include/fcntl.h
@@ -26,9 +26,14 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _FCNTL_H
+#pragma once
 #define _FCNTL_H
 
+/**
+ * @file fcntl.h
+ * @brief File control operations.
+ */
+
 #include <sys/cdefs.h>
 #include <sys/types.h>
 #include <linux/fadvise.h>
@@ -48,47 +53,180 @@
 
 #ifdef __LP64__
 /* LP64 kernels don't have F_*64 defines because their flock is 64-bit. */
+/** Flag for flock(). */
 #define F_GETLK64  F_GETLK
+/** Flag for flock(). */
 #define F_SETLK64  F_SETLK
+/** Flag for flock(). */
 #define F_SETLKW64 F_SETLKW
 #endif
 
+/** Flag for open(). */
 #define O_ASYNC FASYNC
+/** Flag for open(). */
 #define O_RSYNC O_SYNC
 
 #if __ANDROID_API__ >= __ANDROID_API_L__
+/** Flag for splice(). */
 #define SPLICE_F_MOVE 1
+/** Flag for splice(). */
 #define SPLICE_F_NONBLOCK 2
+/** Flag for splice(). */
 #define SPLICE_F_MORE 4
+/** Flag for splice(). */
 #define SPLICE_F_GIFT 8
 #endif
 
 #if __ANDROID_API__ >= __ANDROID_API_O__
+/** Flag for sync_file_range(). */
 #define SYNC_FILE_RANGE_WAIT_BEFORE 1
+/** Flag for sync_file_range(). */
 #define SYNC_FILE_RANGE_WRITE 2
+/** Flag for sync_file_range(). */
 #define SYNC_FILE_RANGE_WAIT_AFTER 4
 #endif
 
+/**
+ * [creat(2)](http://man7.org/linux/man-pages/man2/creat.2.html)
+ * creates a file.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int creat(const char* __path, mode_t __mode);
+/** See creat(). */
 int creat64(const char* __path, mode_t __mode) __INTRODUCED_IN(21);
+
+/**
+ * [openat(2)](http://man7.org/linux/man-pages/man2/openat.2.html)
+ * opens (and possibly creates) a file.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int openat(int __dir_fd, const char* __path, int __flags, ...);
+/** See openat(). */
 int openat64(int __dir_fd, const char* __path, int __flags, ...) __INTRODUCED_IN(21);
+
+/**
+ * [open(2)](http://man7.org/linux/man-pages/man2/open.2.html)
+ * opens (and possibly creates) a file.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int open(const char* __path, int __flags, ...);
+/** See open(). */
 int open64(const char* __path, int __flags, ...) __INTRODUCED_IN(21);
+
+/**
+ * [splice(2)](http://man7.org/linux/man-pages/man2/splice.2.html)
+ * splices data to/from a pipe.
+ *
+ * Valid flags are `SPLICE_F_MOVE`, `SPLICE_F_NONBLOCK`, `SPLICE_F_MORE`, and
+ * `SPLICE_F_GIFT`.
+ *
+ * Returns the number of bytes spliced on success and returns -1 and sets
+ * `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 ssize_t splice(int __in_fd, off64_t* __in_offset, int __out_fd, off64_t* __out_offset, size_t __length, unsigned int __flags) __INTRODUCED_IN(21);
+
+/**
+ * [tee(2)](http://man7.org/linux/man-pages/man2/tee.2.html)
+ * duplicates data from one pipe to another.
+ *
+ * Valid flags are `SPLICE_F_MOVE`, `SPLICE_F_NONBLOCK`, `SPLICE_F_MORE`, and
+ * `SPLICE_F_GIFT`.
+ *
+ * Returns the number of bytes duplicated on success and returns -1 and sets
+ * `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 ssize_t tee(int __in_fd, int __out_fd, size_t __length, unsigned int __flags) __INTRODUCED_IN(21);
+
+/**
+ * [vmsplice(2)](http://man7.org/linux/man-pages/man2/vmsplice.2.html)
+ * splices data to/from a pipe.
+ *
+ * Valid flags are `SPLICE_F_MOVE`, `SPLICE_F_NONBLOCK`, `SPLICE_F_MORE`, and
+ * `SPLICE_F_GIFT`.
+ *
+ * Returns the number of bytes spliced on success and returns -1 and sets
+ * `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 ssize_t vmsplice(int __fd, const struct iovec* __iov, size_t __count, unsigned int __flags) __INTRODUCED_IN(21);
 
+/**
+ * [fallocate(2)](http://man7.org/linux/man-pages/man2/fallocate.2.html)
+ * is a Linux-specific extension of posix_fallocate().
+ *
+ * Valid flags are `FALLOC_FL_KEEP_SIZE`, `FALLOC_FL_PUNCH_HOLE`,
+ * `FALLOC_FL_NO_HIDE_STALE`, `FALLOC_FL_COLLAPSE_RANGE`,
+ * `FALLOC_FL_ZERO_RANGE`, `FALLOC_FL_INSERT_RANGE`, and
+ * `FALLOC_FL_UNSHARE_RANGE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ *
+ * Available since API level 21.
+ */
 int fallocate(int __fd, int __mode, off_t __offset, off_t __length) __RENAME_IF_FILE_OFFSET64(fallocate64) __INTRODUCED_IN(21);
+/** See fallocate(). */
 int fallocate64(int __fd, int __mode, off64_t __offset, off64_t __length) __INTRODUCED_IN(21);
+
+/**
+ * [posix_fadvise(2)](http://man7.org/linux/man-pages/man2/posix_fadvise.2.html)
+ * declares an expected access pattern for file data.
+ *
+ * Valid flags are `POSIX_FADV_NORMAL`, `POSIX_FADV_RANDOM`,
+ * `POSIX_FADV_SEQUENTIAL`, `POSIX_FADV_WILLNEED`, `POSIX_FADV_DONTNEED`,
+ * and `POSIX_FADV_NOREUSE`.
+ *
+ * Returns 0 on success and returns an error number on failure.
+ *
+ * Available since API level 21.
+ */
 int posix_fadvise(int __fd, off_t __offset, off_t __length, int __advice) __RENAME_IF_FILE_OFFSET64(posix_fadvise64) __INTRODUCED_IN(21);
+/** See posix_fadvise(). */
 int posix_fadvise64(int __fd, off64_t __offset, off64_t __length, int __advice) __INTRODUCED_IN(21);
+
+/**
+ * [posix_fallocate(2)](http://man7.org/linux/man-pages/man2/posix_fallocate.2.html)
+ * allocates file space.
+ *
+ * Returns 0 on success and returns an error number on failure.
+ *
+ * Available since API level 21.
+ */
 int posix_fallocate(int __fd, off_t __offset, off_t __length) __RENAME_IF_FILE_OFFSET64(posix_fallocate64) __INTRODUCED_IN(21);
+/** See posix_fallocate(). */
 int posix_fallocate64(int __fd, off64_t __offset, off64_t __length) __INTRODUCED_IN(21);
 
 #if defined(__USE_GNU)
-ssize_t readahead(int __fd, off64_t __offset, size_t __length) __INTRODUCED_IN(16);
+
+/**
+ * [readahead(2)](http://man7.org/linux/man-pages/man2/readahead.2.html)
+ * initiates readahead for the given file.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+ssize_t readahead(int __fd, off64_t __offset, size_t __length);
+
+/**
+ * [sync_file_range(2)](http://man7.org/linux/man-pages/man2/sync_file_range.2.html)
+ * syncs part of a file with disk.
+ *
+ * Valid flags are `SYNC_FILE_RANGE_WAIT_BEFORE`, `SYNC_FILE_RANGE_WRITE`, and
+ * `SYNC_FILE_RANGE_WAIT_AFTER`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
 int sync_file_range(int __fd, off64_t __offset, off64_t __length, unsigned int __flags) __INTRODUCED_IN(26);
+
 #endif
 
 #if defined(__BIONIC_INCLUDE_FORTIFY_HEADERS)
@@ -96,5 +234,3 @@
 #endif
 
 __END_DECLS
-
-#endif
diff --git a/libc/include/sys/xattr.h b/libc/include/sys/xattr.h
index d15b3fc..dc58026 100644
--- a/libc/include/sys/xattr.h
+++ b/libc/include/sys/xattr.h
@@ -26,8 +26,12 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _SYS_XATTR_H_
-#define _SYS_XATTR_H_
+#pragma once
+
+/**
+ * @file sys/xattr.h
+ * @brief Extended attribute functions.
+ */
 
 #include <linux/xattr.h>
 #include <sys/cdefs.h>
@@ -35,25 +39,120 @@
 
 __BEGIN_DECLS
 
-int fsetxattr(int __fd, const char* __name, const void* __value, size_t __size, int __flags)
-  __INTRODUCED_IN(16);
-int setxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags)
-  __INTRODUCED_IN(16);
-int lsetxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags)
-  __INTRODUCED_IN(16);
+/**
+ * [fsetxattr(2)](http://man7.org/linux/man-pages/man2/fsetxattr.2.html)
+ * sets an extended attribute on the file referred to by the given file
+ * descriptor.
+ *
+ * Valid flags are `XATTR_CREATE` and `XATTR_REPLACE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int fsetxattr(int __fd, const char* __name, const void* __value, size_t __size, int __flags);
 
-ssize_t fgetxattr(int __fd, const char* __name, void* __value, size_t __size) __INTRODUCED_IN(16);
-ssize_t getxattr(const char* __path, const char* __name, void* __value, size_t __size) __INTRODUCED_IN(16);
-ssize_t lgetxattr(const char* __path, const char* __name, void* __value, size_t __size) __INTRODUCED_IN(16);
+/**
+ * [setxattr(2)](http://man7.org/linux/man-pages/man2/setxattr.2.html)
+ * sets an extended attribute on the file referred to by the given path.
+ *
+ * Valid flags are `XATTR_CREATE` and `XATTR_REPLACE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int setxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags);
 
-ssize_t listxattr(const char* __path, char* __list, size_t __size) __INTRODUCED_IN(16);
-ssize_t llistxattr(const char* __path, char* __list, size_t __size) __INTRODUCED_IN(16);
-ssize_t flistxattr(int __fd, char* __list, size_t __size) __INTRODUCED_IN(16);
+/**
+ * [lsetxattr(2)](http://man7.org/linux/man-pages/man2/lsetxattr.2.html)
+ * sets an extended attribute on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Valid flags are `XATTR_CREATE` and `XATTR_REPLACE`.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int lsetxattr(const char* __path, const char* __name, const void* __value, size_t __size, int __flags);
 
-int removexattr(const char* __path, const char* __name) __INTRODUCED_IN(16);
-int lremovexattr(const char* __path, const char* __name) __INTRODUCED_IN(16);
-int fremovexattr(int __fd, const char* __name) __INTRODUCED_IN(16);
+/**
+ * [fgetxattr(2)](http://man7.org/linux/man-pages/man2/fgetxattr.2.html)
+ * gets an extended attribute on the file referred to by the given file
+ * descriptor.
+ *
+ * Returns the non-negative length of the value on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t fgetxattr(int __fd, const char* __name, void* __value, size_t __size);
+
+/**
+ * [getxattr(2)](http://man7.org/linux/man-pages/man2/getxattr.2.html)
+ * gets an extended attribute on the file referred to by the given path.
+ *
+ * Returns the non-negative length of the value on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t getxattr(const char* __path, const char* __name, void* __value, size_t __size);
+
+/**
+ * [lgetxattr(2)](http://man7.org/linux/man-pages/man2/lgetxattr.2.html)
+ * gets an extended attribute on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Returns the non-negative length of the value on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t lgetxattr(const char* __path, const char* __name, void* __value, size_t __size);
+
+/**
+ * [flistxattr(2)](http://man7.org/linux/man-pages/man2/flistxattr.2.html)
+ * lists the extended attributes on the file referred to by the given file
+ * descriptor.
+ *
+ * Returns the non-negative length of the list on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t flistxattr(int __fd, char* __list, size_t __size);
+
+/**
+ * [listxattr(2)](http://man7.org/linux/man-pages/man2/listxattr.2.html)
+ * lists the extended attributes on the file referred to by the given path.
+ *
+ * Returns the non-negative length of the list on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t listxattr(const char* __path, char* __list, size_t __size);
+
+/**
+ * [llistxattr(2)](http://man7.org/linux/man-pages/man2/llistxattr.2.html)
+ * lists the extended attributes on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Returns the non-negative length of the list on success, or
+ * returns -1 and sets `errno` on failure.
+ */
+ssize_t llistxattr(const char* __path, char* __list, size_t __size);
+
+/**
+ * [fremovexattr(2)](http://man7.org/linux/man-pages/man2/fremovexattr.2.html)
+ * removes an extended attribute on the file referred to by the given file
+ * descriptor.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int fremovexattr(int __fd, const char* __name);
+
+/**
+ * [lremovexattr(2)](http://man7.org/linux/man-pages/man2/lremovexattr.2.html)
+ * removes an extended attribute on the file referred to by the given path, which
+ * is the link itself rather than its target in the case of a symbolic link.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int lremovexattr(const char* __path, const char* __name);
+
+/**
+ * [removexattr(2)](http://man7.org/linux/man-pages/man2/removexattr.2.html)
+ * removes an extended attribute on the file referred to by the given path.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
+int removexattr(const char* __path, const char* __name);
 
 __END_DECLS
-
-#endif