diff --git a/src/fcntl.rs b/src/fcntl.rs
index a5dca8a539..a6ade08207 100644
--- a/src/fcntl.rs
+++ b/src/fcntl.rs
@@ -2,7 +2,7 @@
 use crate::errno::Errno;
 #[cfg(all(target_os = "freebsd", target_arch = "x86_64"))]
 use core::slice;
-use libc::{c_int, c_uint, size_t, ssize_t};
+use libc::{self, c_int, c_uint, size_t, ssize_t};
 #[cfg(any(
     target_os = "netbsd",
     apple_targets,
@@ -163,8 +163,12 @@ libc_bitflags!(
                   all(target_os = "linux", not(target_env = "musl"), not(target_env = "ohos")),
                   target_os = "redox"))]
         O_FSYNC;
-        /// Allow files whose sizes can't be represented in an `off_t` to be opened.
+        /// On 32-bit Linux, O_LARGEFILE allows the use of file
+        /// offsets greater than 32 bits. Nix accepts the flag for
+        /// compatibility, but always opens files in large file mode
+        /// even if it isn't specified.
         #[cfg(linux_android)]
+        #[cfg_attr(docsrs, doc(cfg(all())))]
         O_LARGEFILE;
         /// Do not update the file last access time during `read(2)`s.
         #[cfg(linux_android)]
@@ -249,7 +253,7 @@ pub fn open<P: ?Sized + NixPath>(
     use std::os::fd::FromRawFd;
 
     let fd = path.with_nix_path(|cstr| unsafe {
-        libc::open(cstr.as_ptr(), oflag.bits(), mode.bits() as c_uint)
+        largefile_fn![open](cstr.as_ptr(), oflag.bits(), mode.bits() as c_uint)
     })?;
     Errno::result(fd)?;
 
@@ -280,7 +284,11 @@ pub fn openat<P: ?Sized + NixPath, Fd: std::os::fd::AsFd>(
     use std::os::fd::FromRawFd;
 
     let fd = path.with_nix_path(|cstr| unsafe {
-        libc::openat(dirfd.as_fd().as_raw_fd(), cstr.as_ptr(), oflag.bits(), mode.bits() as c_uint)
+         largefile_fn![openat](
+	     dirfd.as_fd().as_raw_fd(),
+	     cstr.as_ptr(),
+	     oflag.bits(),
+	     mode.bits() as c_uint)
     })?;
     Errno::result(fd)?;
 
@@ -1303,15 +1311,18 @@ feature! {
 /// file referred to by fd.
 #[cfg(target_os = "linux")]
 #[cfg(feature = "fs")]
-pub fn fallocate<Fd: std::os::fd::AsFd>(
+pub fn fallocate<Fd: std::os::fd::AsFd, Off: Into<i64>>(
     fd: Fd,
     mode: FallocateFlags,
-    offset: libc::off_t,
-    len: libc::off_t,
+    offset: Off,
+    len: Off,
 ) -> Result<()> {
     use std::os::fd::AsRawFd;
 
-    let res = unsafe { libc::fallocate(fd.as_fd().as_raw_fd(), mode.bits(), offset, len) };
+    let res = unsafe {
+	largefile_fn![fallocate](
+	    fd.as_fd().as_raw_fd(), mode.bits(), offset.into(), len.into())
+    };
     Errno::result(res).map(drop)
 }
 
@@ -1319,7 +1330,7 @@ pub fn fallocate<Fd: std::os::fd::AsFd>(
 /// the file offset, and the second is the length of the region.
 #[cfg(any(target_os = "freebsd"))]
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
-pub struct SpacectlRange(pub libc::off_t, pub libc::off_t);
+pub struct SpacectlRange(pub i64, pub i64);
 
 #[cfg(any(target_os = "freebsd"))]
 impl SpacectlRange {
@@ -1334,13 +1345,13 @@ impl SpacectlRange {
 
     /// Remaining length of the range
     #[inline]
-    pub fn len(&self) -> libc::off_t {
+    pub fn len(&self) -> i64 {
         self.1
     }
 
     /// Next file offset to operate on
     #[inline]
-    pub fn offset(&self) -> libc::off_t {
+    pub fn offset(&self) -> i64 {
         self.0
     }
 }
@@ -1439,8 +1450,8 @@ pub fn fspacectl<Fd: std::os::fd::AsFd>(fd: Fd, range: SpacectlRange) -> Result<
 #[inline] // Delays codegen, preventing linker errors with dylibs and --no-allow-shlib-undefined
 pub fn fspacectl_all<Fd: std::os::fd::AsFd>(
     fd: Fd,
-    offset: libc::off_t,
-    len: libc::off_t,
+    offset: i64,
+    len: i64,
 ) -> Result<()> {
     use std::os::fd::AsRawFd;
 
@@ -1505,15 +1516,21 @@ mod posix_fadvise {
     ///
     /// # See Also
     /// * [`posix_fadvise`](https://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_fadvise.html)
-    pub fn posix_fadvise<Fd: std::os::fd::AsFd>(
+    pub fn posix_fadvise<Fd: std::os::fd::AsFd, Off: Into<i64>>(
         fd: Fd,
-        offset: libc::off_t,
-        len: libc::off_t,
+        offset: Off,
+        len: Off,
         advice: PosixFadviseAdvice,
     ) -> Result<()> {
         use std::os::fd::AsRawFd;
 
-        let res = unsafe { libc::posix_fadvise(fd.as_fd().as_raw_fd(), offset, len, advice as libc::c_int) };
+        let res = unsafe {
+	    largefile_fn![posix_fadvise](
+		fd.as_fd().as_raw_fd(),
+		offset.into(),
+		len.into(),
+		advice as libc::c_int)
+	};
 
         if res == 0 {
             Ok(())
@@ -1535,14 +1552,19 @@ mod posix_fadvise {
     target_os = "fuchsia",
     target_os = "wasi",
 ))]
-pub fn posix_fallocate<Fd: std::os::fd::AsFd>(
+pub fn posix_fallocate<Fd: std::os::fd::AsFd, Off: Into<i64>>(
     fd: Fd,
-    offset: libc::off_t,
-    len: libc::off_t,
+    offset: Off,
+    len: Off,
 ) -> Result<()> {
     use std::os::fd::AsRawFd;
 
-    let res = unsafe { libc::posix_fallocate(fd.as_fd().as_raw_fd(), offset, len) };
+    let res = unsafe {
+	largefile_fn![posix_fallocate](
+	    fd.as_fd().as_raw_fd(),
+	    offset.into(),
+	    len.into())
+    };
     match Errno::result(res) {
         Err(err) => Err(err),
         Ok(0) => Ok(()),
diff --git a/src/macros.rs b/src/macros.rs
index 3010a1a053..4cfe365df8 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -1,3 +1,5 @@
+use cfg_if::cfg_if;
+
 // Thanks to Tokio for this macro
 macro_rules! feature {
     (
@@ -329,3 +331,45 @@ macro_rules! libc_enum {
         }
     };
 }
+
+cfg_if! {
+    if #[cfg(all(target_os = "linux", target_env = "gnu"))] {
+        /// Function variant that supports large file positions.
+        ///
+        /// On some platforms, the standard I/O functions support a limited
+        /// range of file positions, and there is an alternate set of
+        /// functions that support larger file positions. This macro takes
+        /// the identifier of a standard I/O function and returns the
+        /// identifier of the corresponding I/O function with large file
+        /// support.
+        #[allow(unused_macro_rules)]
+        macro_rules! largefile_fn {
+            [fallocate] => (libc::fallocate64);
+            [ftruncate] => (libc::ftruncate64);
+            [lseek] => (libc::lseek64);
+            [mmap] => (libc::mmap64);
+            [open] => (libc::open64);
+            [openat] => (libc::openat64);
+            [posix_fadvise] => (libc::posix_fadvise64);
+            [posix_fallocate] => (libc::posix_fallocate64);
+            [pread] => (libc::pread64);
+            [preadv] => (libc::preadv64);
+            [pwrite] => (libc::pwrite64);
+            [pwritev] => (libc::pwritev64);
+            [sendfile] => (libc::sendfile64);
+            [truncate] => (libc::truncate64);
+        }
+    } else {
+        /// Function variant that supports large file positions.
+        ///
+        /// On some platforms, the standard I/O functions support a limited
+        /// range of file positions, and there is an alternate set of
+        /// functions that support larger file positions. This macro takes
+        /// the identifier of a standard I/O function and returns the
+        /// identifier of the corresponding I/O function with large file
+        /// support.
+        macro_rules! largefile_fn {
+            [$id:ident] => (libc::$id);
+        }
+    }
+}
diff --git a/src/sys/mman.rs b/src/sys/mman.rs
index a64f14f588..90d8da766d 100644
--- a/src/sys/mman.rs
+++ b/src/sys/mman.rs
@@ -7,7 +7,7 @@ use crate::Result;
 #[cfg(not(target_os = "android"))]
 #[cfg(feature = "fs")]
 use crate::{fcntl::OFlag, sys::stat::Mode};
-use libc::{self, c_int, c_void, off_t, size_t};
+use libc::{self, c_int, c_void, size_t};
 use std::ptr::NonNull;
 use std::{
     num::NonZeroUsize,
@@ -398,13 +398,14 @@ pub unsafe fn mmap<F: AsFd>(
     prot: ProtFlags,
     flags: MapFlags,
     f: F,
-    offset: off_t,
+    offset: i64,
 ) -> Result<NonNull<c_void>> {
     let ptr = addr.map_or(std::ptr::null_mut(), |a| a.get() as *mut c_void);
 
     let fd = f.as_fd().as_raw_fd();
     let ret = unsafe {
-        libc::mmap(ptr, length.into(), prot.bits(), flags.bits(), fd, offset)
+        largefile_fn![mmap](
+	    ptr, length.into(), prot.bits(), flags.bits(), fd, offset)
     };
 
     if ret == libc::MAP_FAILED {
diff --git a/src/sys/sendfile.rs b/src/sys/sendfile.rs
index d7452edd7c..52c9045932 100644
--- a/src/sys/sendfile.rs
+++ b/src/sys/sendfile.rs
@@ -4,7 +4,7 @@ use cfg_if::cfg_if;
 use std::os::unix::io::{AsFd, AsRawFd};
 use std::ptr;
 
-use libc::{self, off_t};
+use libc;
 
 use crate::errno::Errno;
 use crate::Result;
@@ -26,14 +26,14 @@ use crate::Result;
 pub fn sendfile<F1: AsFd, F2: AsFd>(
     out_fd: F1,
     in_fd: F2,
-    offset: Option<&mut off_t>,
+    offset: Option<&mut i64>,
     count: usize,
 ) -> Result<usize> {
     let offset = offset
         .map(|offset| offset as *mut _)
         .unwrap_or(ptr::null_mut());
     let ret = unsafe {
-        libc::sendfile(
+        largefile_fn![sendfile](
             out_fd.as_fd().as_raw_fd(),
             in_fd.as_fd().as_raw_fd(),
             offset,
@@ -208,19 +208,19 @@ cfg_if! {
         pub fn sendfile<F1: AsFd, F2: AsFd>(
             in_fd: F1,
             out_sock: F2,
-            offset: off_t,
+            offset: i64,
             count: Option<usize>,
             headers: Option<&[&[u8]]>,
             trailers: Option<&[&[u8]]>,
             flags: SfFlags,
             readahead: u16
-        ) -> (Result<()>, off_t) {
+        ) -> (Result<()>, i64) {
             // Readahead goes in upper 16 bits
             // Flags goes in lower 16 bits
             // see `man 2 sendfile`
             let ra32 = u32::from(readahead);
             let flags: u32 = (ra32 << 16) | (flags.bits() as u32);
-            let mut bytes_sent: off_t = 0;
+            let mut bytes_sent: i64 = 0;
             let hdtr = headers.or(trailers).map(|_| SendfileHeaderTrailer::new(headers, trailers));
             let hdtr_ptr = hdtr.as_ref().map_or(ptr::null(), |s| &s.raw as *const libc::sf_hdtr);
             let return_code = unsafe {
@@ -229,7 +229,7 @@ cfg_if! {
                                offset,
                                count.unwrap_or(0),
                                hdtr_ptr as *mut libc::sf_hdtr,
-                               &mut bytes_sent as *mut off_t,
+                               &mut bytes_sent as *mut i64,
                                flags as c_int)
             };
             (Errno::result(return_code).and(Ok(())), bytes_sent)
@@ -258,12 +258,12 @@ cfg_if! {
         pub fn sendfile<F1: AsFd, F2: AsFd>(
             in_fd: F1,
             out_sock: F2,
-            offset: off_t,
+            offset: i64,
             count: Option<usize>,
             headers: Option<&[&[u8]]>,
             trailers: Option<&[&[u8]]>,
-        ) -> (Result<()>, off_t) {
-            let mut bytes_sent: off_t = 0;
+        ) -> (Result<()>, i64) {
+            let mut bytes_sent: i64 = 0;
             let hdtr = headers.or(trailers).map(|_| SendfileHeaderTrailer::new(headers, trailers));
             let hdtr_ptr = hdtr.as_ref().map_or(ptr::null(), |s| &s.raw as *const libc::sf_hdtr);
             let return_code = unsafe {
@@ -272,7 +272,7 @@ cfg_if! {
                                offset,
                                count.unwrap_or(0),
                                hdtr_ptr as *mut libc::sf_hdtr,
-                               &mut bytes_sent as *mut off_t,
+                               &mut bytes_sent as *mut i64,
                                0)
             };
             (Errno::result(return_code).and(Ok(())), bytes_sent)
@@ -304,11 +304,11 @@ cfg_if! {
         pub fn sendfile<F1: AsFd, F2: AsFd>(
             in_fd: F1,
             out_sock: F2,
-            offset: off_t,
-            count: Option<off_t>,
+            offset: i64,
+            count: Option<i64>,
             headers: Option<&[&[u8]]>,
             trailers: Option<&[&[u8]]>
-        ) -> (Result<()>, off_t) {
+        ) -> (Result<()>, i64) {
             let mut len = count.unwrap_or(0);
             let hdtr = headers.or(trailers).map(|_| SendfileHeaderTrailer::new(headers, trailers));
             let hdtr_ptr = hdtr.as_ref().map_or(ptr::null(), |s| &s.raw as *const libc::sf_hdtr);
@@ -316,7 +316,7 @@ cfg_if! {
                 libc::sendfile(in_fd.as_fd().as_raw_fd(),
                                out_sock.as_fd().as_raw_fd(),
                                offset,
-                               &mut len as *mut off_t,
+                               &mut len as *mut i64,
                                hdtr_ptr as *mut libc::sf_hdtr,
                                0)
             };
diff --git a/src/sys/uio.rs b/src/sys/uio.rs
index cdf380dd11..b3c2b95742 100644
--- a/src/sys/uio.rs
+++ b/src/sys/uio.rs
@@ -2,7 +2,7 @@
 
 use crate::errno::Errno;
 use crate::Result;
-use libc::{self, c_int, off_t, size_t};
+use libc::{self, c_int, size_t};
 use std::io::{IoSlice, IoSliceMut};
 use std::os::unix::io::{AsFd, AsRawFd};
 
@@ -54,17 +54,20 @@ pub fn readv<Fd: AsFd>(fd: Fd, iov: &mut [IoSliceMut<'_>]) -> Result<usize> {
 ///
 /// See also: [`writev`](fn.writev.html) and [`pwrite`](fn.pwrite.html)
 #[cfg(not(any(target_os = "redox", target_os = "haiku", target_os = "solaris")))]
-pub fn pwritev<Fd: AsFd>(
+pub fn pwritev<Fd: AsFd, Off: Into<i64>>(
     fd: Fd,
     iov: &[IoSlice<'_>],
-    offset: off_t,
+    offset: Off,
 ) -> Result<usize> {
+    let offset = offset.into();
+    // uclibc uses 64-bit offsets for pwritev even if it otherwise uses
+    // 32-bit file offsets.
     #[cfg(target_env = "uclibc")]
-    let offset = offset as libc::off64_t; // uclibc doesn't use off_t
+    let offset = offset as libc::off64_t;
 
     // SAFETY: same as in writev()
     let res = unsafe {
-        libc::pwritev(
+        largefile_fn![pwritev](
             fd.as_fd().as_raw_fd(),
             iov.as_ptr().cast(),
             iov.len() as c_int,
@@ -86,17 +89,20 @@ pub fn pwritev<Fd: AsFd>(
 // Clippy doesn't know that we need to pass iov mutably only because the
 // mutation happens after converting iov to a pointer
 #[allow(clippy::needless_pass_by_ref_mut)]
-pub fn preadv<Fd: AsFd>(
+pub fn preadv<Fd: AsFd, Off: Into<i64>>(
     fd: Fd,
     iov: &mut [IoSliceMut<'_>],
-    offset: off_t,
+    offset: Off,
 ) -> Result<usize> {
+    let offset = offset.into();
+    // uclibc uses 64-bit offsets for preadv even if it otherwise uses
+    // 32-bit file offsets.
     #[cfg(target_env = "uclibc")]
-    let offset = offset as libc::off64_t; // uclibc doesn't use off_t
+    let offset = offset as libc::off64_t;
 
     // SAFETY: same as in readv()
     let res = unsafe {
-        libc::preadv(
+        largefile_fn![preadv](
             fd.as_fd().as_raw_fd(),
             iov.as_ptr().cast(),
             iov.len() as c_int,
@@ -111,13 +117,17 @@ pub fn preadv<Fd: AsFd>(
 ///
 /// See also [pwrite(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/pwrite.html)
 // TODO: move to unistd
-pub fn pwrite<Fd: AsFd>(fd: Fd, buf: &[u8], offset: off_t) -> Result<usize> {
+pub fn pwrite<Fd: AsFd, Off: Into<i64>>(
+    fd: Fd,
+    buf: &[u8],
+    offset: Off,
+) -> Result<usize> {
     let res = unsafe {
-        libc::pwrite(
+        largefile_fn![pwrite](
             fd.as_fd().as_raw_fd(),
             buf.as_ptr().cast(),
             buf.len() as size_t,
-            offset,
+            offset.into(),
         )
     };
 
@@ -128,13 +138,17 @@ pub fn pwrite<Fd: AsFd>(fd: Fd, buf: &[u8], offset: off_t) -> Result<usize> {
 ///
 /// See also [pread(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/pread.html)
 // TODO: move to unistd
-pub fn pread<Fd: AsFd>(fd: Fd, buf: &mut [u8], offset: off_t) -> Result<usize> {
+pub fn pread<Fd: AsFd, Off: Into<i64>>(
+    fd: Fd,
+    buf: &mut [u8],
+    offset: Off,
+) -> Result<usize> {
     let res = unsafe {
-        libc::pread(
+        largefile_fn![pread](
             fd.as_fd().as_raw_fd(),
             buf.as_mut_ptr().cast(),
             buf.len() as size_t,
-            offset,
+            offset.into(),
         )
     };
 
diff --git a/src/unistd.rs b/src/unistd.rs
index 382333af3e..68b0801d12 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -23,7 +23,7 @@ use crate::sys::stat::FileFlag;
 use crate::{Error, NixPath, Result};
 #[cfg(not(target_os = "redox"))]
 use cfg_if::cfg_if;
-use libc::{c_char, c_int, c_long, c_uint, gid_t, off_t, pid_t, size_t, uid_t};
+use libc::{self, c_char, c_int, c_long, c_uint, gid_t, pid_t, size_t, uid_t};
 use std::convert::Infallible;
 #[cfg(not(target_os = "redox"))]
 use std::ffi::CString;
@@ -1447,12 +1447,20 @@ pub enum Whence {
 /// Move the read/write file offset.
 ///
 /// See also [lseek(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/lseek.html)
-pub fn lseek<Fd: std::os::fd::AsFd>(fd: Fd, offset: off_t, whence: Whence) -> Result<off_t> {
+pub fn lseek<Fd: std::os::fd::AsFd, Off: Into<i64>>(
+    fd: Fd,
+    offset: Off,
+    whence: Whence,
+) -> Result<i64> {
     use std::os::fd::AsRawFd;
 
-    let res = unsafe { libc::lseek(fd.as_fd().as_raw_fd(), offset, whence as i32) };
+    let res = unsafe {
+	largefile_fn![lseek](fd.as_fd().as_raw_fd(), offset.into(), whence as i32)
+    };
 
-    Errno::result(res).map(|r| r as off_t)
+    // r may or may not already be i64; suppress unnecessary_cast diagnostic.
+    #[allow(clippy::unnecessary_cast)]
+    Errno::result(res).map(|r| r as i64)
 }
 
 /// Move the read/write file offset.
@@ -1533,9 +1541,14 @@ pub fn pipe2(flags: OFlag) -> Result<(std::os::fd::OwnedFd, std::os::fd::OwnedFd
 /// See also
 /// [truncate(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/truncate.html)
 #[cfg(not(any(target_os = "redox", target_os = "fuchsia")))]
-pub fn truncate<P: ?Sized + NixPath>(path: &P, len: off_t) -> Result<()> {
+pub fn truncate<P: ?Sized + NixPath, Off: Into<i64>>(
+    path: &P,
+    len: Off,
+) -> Result<()> {
     let res = path
-        .with_nix_path(|cstr| unsafe { libc::truncate(cstr.as_ptr(), len) })?;
+        .with_nix_path(|cstr| unsafe {
+            largefile_fn![truncate](cstr.as_ptr(), len.into())
+        })?;
 
     Errno::result(res).map(drop)
 }
@@ -1544,10 +1557,15 @@ pub fn truncate<P: ?Sized + NixPath>(path: &P, len: off_t) -> Result<()> {
 ///
 /// See also
 /// [ftruncate(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/ftruncate.html)
-pub fn ftruncate<Fd: std::os::fd::AsFd>(fd: Fd, len: off_t) -> Result<()> {
+pub fn ftruncate<Fd: std::os::fd::AsFd, Off: Into<i64>>(
+    fd: Fd,
+    len: Off,
+) -> Result<()> {
     use std::os::fd::AsRawFd;
 
-    Errno::result(unsafe { libc::ftruncate(fd.as_fd().as_raw_fd(), len) }).map(drop)
+    Errno::result(unsafe {
+	largefile_fn![ftruncate](fd.as_fd().as_raw_fd(), len.into())
+    }).map(drop)
 }
 
 /// Determines if the file descriptor refers to a valid terminal type device.
diff --git a/test/common/mod.rs b/test/common/mod.rs
index ab0e746367..933025df1e 100644
--- a/test/common/mod.rs
+++ b/test/common/mod.rs
@@ -32,6 +32,25 @@ cfg_if! {
     }
 }
 
+/// Skip the test if we cannot handle offsets larger than 32 bits.
+///
+/// This is generally the case if libc::off_t::MAX is 1 << 32 or less.
+/// However, glibc on Linux provides variants of the standard I/O
+/// functions that do support 64-bit offsets (e.g. lseek64 instead of lseek).
+#[macro_export]
+macro_rules! require_largefile {
+    ($name:expr) => {
+        #[cfg(not(all(target_os = "linux", target_env = "gnu")))]
+        if (libc::off_t::MAX >> 31) <= 1 {
+            $crate::skip!(
+                "{} requires file offsets \
+                          larger than 32 bits. Skipping test.",
+                $name
+            );
+        }
+    };
+}
+
 /// Skip the test if we don't have the ability to mount file systems.
 #[cfg(target_os = "freebsd")]
 #[macro_export]
diff --git a/test/sys/test_mman.rs b/test/sys/test_mman.rs
index 3689f642be..f80da43bf7 100644
--- a/test/sys/test_mman.rs
+++ b/test/sys/test_mman.rs
@@ -1,7 +1,11 @@
 #![allow(clippy::redundant_slicing)]
 
-use nix::sys::mman::{mmap_anonymous, MapFlags, ProtFlags};
+use nix::sys::mman::{mmap, mmap_anonymous, MapFlags, ProtFlags};
+use nix::unistd::{lseek, sysconf, write, SysconfVar, Whence};
 use std::num::NonZeroUsize;
+use tempfile::tempfile;
+
+use crate::{require_largefile, skip};
 
 #[test]
 fn test_mmap_anonymous() {
@@ -20,6 +24,43 @@ fn test_mmap_anonymous() {
     }
 }
 
+#[test]
+fn test_mmap_largefile() {
+    require_largefile!("test_mmap_largefile");
+
+    // Calculate an offset that requires more than 32 bits to represent
+    // and is a multiple of the page size.
+    #[allow(clippy::unnecessary_cast)] // Some platforms need the cast.
+    let pagesize = match sysconf(SysconfVar::PAGE_SIZE) {
+        Ok(Some(x)) => x,
+        _ => {
+            skip!("test_mmap_largefile: Could not determine page size. Skipping test.");
+        }
+    } as i64;
+    let pages_in_32bits = 1_0000_0000i64 / pagesize;
+    // Silence Clippy warning - offset's type varies by platform.
+    #[allow(clippy::useless_conversion)]
+    let offset = ((pages_in_32bits + 2) * pagesize).try_into().unwrap();
+    // Create a file, seek to offset, and write some bytes.
+    let file = tempfile().unwrap();
+    lseek(&file, offset, Whence::SeekSet).unwrap();
+    write(&file, b"xyzzy").unwrap();
+    // Check that we can map it and see the bytes.
+    let slice = unsafe {
+        let res = mmap(
+            None,
+            NonZeroUsize::new(5).unwrap(),
+            ProtFlags::PROT_READ,
+            MapFlags::MAP_PRIVATE,
+            &file,
+            offset,
+        );
+        assert!(res.is_ok());
+        std::slice::from_raw_parts(res.unwrap().as_ptr() as *const u8, 5)
+    };
+    assert_eq!(slice, b"xyzzy");
+}
+
 #[test]
 #[cfg(any(target_os = "linux", target_os = "netbsd"))]
 fn test_mremap_grow() {
diff --git a/test/sys/test_sockopt.rs b/test/sys/test_sockopt.rs
index fd055ef3dd..41919df4f8 100644
--- a/test/sys/test_sockopt.rs
+++ b/test/sys/test_sockopt.rs
@@ -1,5 +1,6 @@
 #[cfg(linux_android)]
 use crate::*;
+use cfg_if::cfg_if;
 use nix::sys::socket::{
     getsockopt, setsockopt, socket, sockopt, AddressFamily, SockFlag,
     SockProtocol, SockType,
diff --git a/test/sys/test_uio.rs b/test/sys/test_uio.rs
index f7d648403e..4851199817 100644
--- a/test/sys/test_uio.rs
+++ b/test/sys/test_uio.rs
@@ -1,13 +1,18 @@
+#[cfg(not(target_os = "redox"))]
+use crate::require_largefile;
+#[cfg(not(target_os = "redox"))]
 use nix::sys::uio::*;
 use nix::unistd::*;
 use rand::distributions::Alphanumeric;
 use rand::{thread_rng, Rng};
 use std::fs::OpenOptions;
-use std::io::IoSlice;
+use std::io::{IoSlice, Write};
+#[cfg(not(any(target_os = "haiku", target_os = "redox")))]
+use std::os::unix::fs::FileExt;
 use std::{cmp, iter};
 
 #[cfg(not(target_os = "redox"))]
-use std::io::IoSliceMut;
+use std::io::{IoSliceMut, Read, Seek, SeekFrom};
 
 use tempfile::tempdir;
 #[cfg(not(target_os = "redox"))]
@@ -103,8 +108,6 @@ fn test_readv() {
 #[test]
 #[cfg(not(target_os = "redox"))]
 fn test_pwrite() {
-    use std::io::Read;
-
     let mut file = tempfile().unwrap();
     let buf = [1u8; 8];
     assert_eq!(Ok(8), pwrite(&file, &buf, 8));
@@ -116,9 +119,23 @@ fn test_pwrite() {
 }
 
 #[test]
-fn test_pread() {
-    use std::io::Write;
+#[cfg(not(target_os = "redox"))]
+fn test_pwrite_largefile() {
+    require_largefile!("test_pwrite_largefile");
 
+    let mut file = tempfile().unwrap();
+    let buf = [255u8; 1];
+    let pos = 0x1_0000_0002i64;
+    assert_eq!(pwrite(&file, &buf, pos), Ok(1));
+    assert_eq!(file.metadata().unwrap().len(), 0x1_0000_0003);
+    file.seek(SeekFrom::End(-1)).unwrap();
+    let mut file_content = Vec::new();
+    file.read_to_end(&mut file_content).unwrap();
+    assert_eq!(file_content, [255u8; 1]);
+}
+
+#[test]
+fn test_pread() {
     let tempdir = tempdir().unwrap();
 
     let path = tempdir.path().join("pread_test_file");
@@ -144,9 +161,20 @@ fn test_pread() {
     target_os = "haiku",
     target_os = "solaris"
 )))]
-fn test_pwritev() {
-    use std::io::Read;
+fn test_pread_largefile() {
+    require_largefile!("test_pread_largefile");
+
+    let file = tempfile().unwrap();
+    file.write_all_at(b"The text", 0x1_0000_0005).unwrap();
+    let mut buf = [0u8; 4];
+    let pos = 0x1_0000_0009i64;
+    assert_eq!(pread(&file, &mut buf, pos), Ok(4));
+    assert_eq!(&buf, b"text");
+}
 
+#[test]
+#[cfg(not(any(target_os = "redox", target_os = "haiku")))]
+fn test_pwritev() {
     let to_write: Vec<u8> = (0..128).collect();
     let expected: Vec<u8> = [vec![0; 100], to_write.clone()].concat();
 
@@ -184,8 +212,6 @@ fn test_pwritev() {
     target_os = "solaris"
 )))]
 fn test_preadv() {
-    use std::io::Write;
-
     let to_write: Vec<u8> = (0..200).collect();
     let expected: Vec<u8> = (100..200).collect();
 
diff --git a/test/test.rs b/test/test.rs
index 3427b2c3db..c234613333 100644
--- a/test/test.rs
+++ b/test/test.rs
@@ -1,5 +1,3 @@
-#[macro_use]
-extern crate cfg_if;
 #[cfg_attr(not(any(target_os = "redox", target_os = "haiku")), macro_use)]
 extern crate nix;
 
diff --git a/test/test_fcntl.rs b/test/test_fcntl.rs
index d49f49670f..f5ecba579c 100644
--- a/test/test_fcntl.rs
+++ b/test/test_fcntl.rs
@@ -1,4 +1,6 @@
 #[cfg(not(target_os = "redox"))]
+use crate::require_largefile;
+#[cfg(not(target_os = "redox"))]
 use nix::errno::*;
 #[cfg(not(target_os = "redox"))]
 use nix::fcntl::{open, readlink, OFlag};
@@ -21,7 +23,7 @@ use nix::fcntl::{renameat2, RenameFlags};
 #[cfg(not(target_os = "redox"))]
 use nix::sys::stat::Mode;
 #[cfg(not(target_os = "redox"))]
-use nix::unistd::read;
+use nix::unistd::{close, lseek, read, write, Whence};
 #[cfg(not(target_os = "redox"))]
 use std::fs::File;
 #[cfg(not(target_os = "redox"))]
@@ -29,7 +31,31 @@ use std::io::prelude::*;
 #[cfg(not(target_os = "redox"))]
 use std::os::unix::fs;
 #[cfg(not(target_os = "redox"))]
-use tempfile::NamedTempFile;
+use tempfile::{self, tempdir, NamedTempFile};
+
+#[test]
+#[cfg(not(target_os = "redox"))]
+fn test_open_largefile() {
+    // Checks that files opened with open can grow beyond 32-bit file size.
+    // On some platforms, this requires opening the file with an alternative
+    // open() function or a flag.
+    require_largefile!("test_open_largefile");
+
+    let tempdir = tempdir().unwrap();
+    let path = tempdir.path().join("file");
+    File::create(&path).unwrap();
+    let fd = open(&path, OFlag::O_WRONLY, Mode::empty()).unwrap();
+    // Seek to a position that requires more than 32 bits to represent.
+    let pos = (0x1_0000_0004u64).try_into().unwrap();
+    let result = lseek(&fd, pos, Whence::SeekSet);
+    assert_eq!(result, Ok(pos));
+    // Write a byte there, close the file, and check its size.
+    write(&fd, b"x").unwrap();
+    unsafe {
+        close(fd).unwrap();
+    }
+    assert_eq!(std::fs::metadata(&path).unwrap().len(), 0x1_0000_0005);
+}
 
 #[test]
 #[cfg(not(target_os = "redox"))]
@@ -112,6 +138,31 @@ fn test_openat2_forbidden() {
     assert_eq!(res.unwrap_err(), Errno::EXDEV);
 }
 
+#[test]
+#[cfg(not(target_os = "redox"))]
+// QEMU does not handle openat well enough to satisfy this test
+// https://gitlab.com/qemu-project/qemu/-/issues/829
+#[cfg_attr(qemu, ignore)]
+fn test_openat_largefile() {
+    require_largefile!("test_openat_largefile");
+
+    let tempdir = tempdir().unwrap();
+    let dirfd = open(tempdir.path(), OFlag::empty(), Mode::empty()).unwrap();
+    let path = tempdir.path().join("file");
+    File::create(&path).unwrap();
+    let fd = openat(dirfd, "file", OFlag::O_WRONLY, Mode::empty()).unwrap();
+    // Seek to a position that requires more than 32 bits to represent.
+    let pos = (0x1_0000_0004u64).try_into().unwrap();
+    let result = lseek(&fd, pos, Whence::SeekSet);
+    assert_eq!(result, Ok(pos));
+    // Write a byte there, close the file, and check its size.
+    write(&fd, b"x").unwrap();
+    unsafe {
+        close(fd).unwrap();
+    }
+    assert_eq!(std::fs::metadata(&path).unwrap().len(), 0x1_0000_0005);
+}
+
 #[test]
 #[cfg(not(target_os = "redox"))]
 fn test_renameat() {
@@ -497,8 +548,11 @@ mod test_posix_fadvise {
     use nix::errno::Errno;
     use nix::fcntl::*;
     use nix::unistd::pipe;
+    use std::io::{Seek, Write};
     use tempfile::NamedTempFile;
 
+    use crate::require_largefile;
+
     #[test]
     fn test_success() {
         let tmp = NamedTempFile::new().unwrap();
@@ -513,6 +567,23 @@ mod test_posix_fadvise {
             posix_fadvise(&rd, 0, 100, PosixFadviseAdvice::POSIX_FADV_WILLNEED);
         assert_eq!(res, Err(Errno::ESPIPE));
     }
+
+    #[test]
+    fn test_posix_fadvise_largefile() {
+        require_largefile!("test_posix_fadvise_largefile");
+
+        let mut tmp = tempfile::tempfile().unwrap();
+        tmp.seek(std::io::SeekFrom::Start(0xfffffffc)).unwrap();
+        tmp.write_all(b"forty-two").unwrap();
+        let pos = 0x1_0000_0004i64;
+        assert!(posix_fadvise(
+            &tmp,
+            0,
+            pos,
+            PosixFadviseAdvice::POSIX_FADV_DONTNEED,
+        )
+        .is_ok());
+    }
 }
 
 #[cfg(any(
@@ -534,7 +605,7 @@ mod test_posix_fallocate {
     fn success() {
         const LEN: usize = 100;
         let mut tmp = NamedTempFile::new().unwrap();
-        let res = posix_fallocate(&tmp, 0, LEN as libc::off_t);
+        let res = posix_fallocate(&tmp, 0, LEN as i64);
         match res {
             Ok(_) => {
                 let mut data = [1u8; LEN];
diff --git a/test/test_sendfile.rs b/test/test_sendfile.rs
index 3ca8092fc6..0f55b5c7b9 100644
--- a/test/test_sendfile.rs
+++ b/test/test_sendfile.rs
@@ -1,6 +1,8 @@
+#[cfg(any(target_os = "android", target_os = "linux"))]
+use crate::require_largefile;
+use cfg_if::cfg_if;
 use std::io::prelude::*;
 
-use libc::off_t;
 use nix::sys::sendfile::*;
 use tempfile::tempfile;
 
@@ -21,7 +23,7 @@ fn test_sendfile_linux() {
     tmp.write_all(CONTENTS).unwrap();
 
     let (rd, wr) = pipe().unwrap();
-    let mut offset: off_t = 5;
+    let mut offset: i64 = 5;
     let res = sendfile(&wr, &tmp, Some(&mut offset), 2).unwrap();
 
     assert_eq!(2, res);
@@ -32,6 +34,24 @@ fn test_sendfile_linux() {
     assert_eq!(7, offset);
 }
 
+#[cfg(any(target_os = "android", target_os = "linux"))]
+#[test]
+fn test_sendfile_largefile() {
+    require_largefile!("test_sendfile_largefile");
+
+    let mut offset = 0x100000000i64;
+    let start: u64 = (offset - 4).try_into().unwrap();
+    let mut src = tempfile().unwrap();
+    let mut dst = tempfile().unwrap();
+    src.seek(std::io::SeekFrom::Start(start)).unwrap();
+    src.write_all(b"The example text").unwrap();
+    assert_eq!(sendfile(&dst, &src, Some(&mut offset), 12), Ok(12));
+    dst.rewind().unwrap();
+    let mut buf = [0u8; 12];
+    assert_eq!(read(&dst, &mut buf), Ok(12));
+    assert_eq!(b"example text", &buf);
+}
+
 #[cfg(target_os = "linux")]
 #[test]
 fn test_sendfile64_linux() {
@@ -78,7 +98,7 @@ fn test_sendfile_freebsd() {
     let (res, bytes_written) = sendfile(
         &tmp,
         &wr,
-        body_offset as off_t,
+        body_offset as libc::off_t,
         None,
         Some(headers.as_slice()),
         Some(trailers.as_slice()),
@@ -129,7 +149,7 @@ fn test_sendfile_dragonfly() {
     let (res, bytes_written) = sendfile(
         &tmp,
         &wr,
-        body_offset as off_t,
+        body_offset as libc::off_t,
         None,
         Some(headers.as_slice()),
         Some(trailers.as_slice()),
@@ -178,7 +198,7 @@ fn test_sendfile_darwin() {
     let (res, bytes_written) = sendfile(
         &tmp,
         &wr,
-        body_offset as off_t,
+        body_offset as libc::off_t,
         None,
         Some(headers.as_slice()),
         Some(trailers.as_slice()),
@@ -231,7 +251,7 @@ fn test_sendfilev() {
         ),
         SendfileVec::new(
             body_data.as_fd(),
-            body_offset as off_t,
+            body_offset as libc::off_t,
             body.len() - body_offset,
         ),
         SendfileVec::new(
diff --git a/test/test_unistd.rs b/test/test_unistd.rs
index 5cb019bd95..438a6b730c 100644
--- a/test/test_unistd.rs
+++ b/test/test_unistd.rs
@@ -1,4 +1,5 @@
-use libc::{_exit, mode_t, off_t};
+use cfg_if::cfg_if;
+use libc::{_exit, mode_t};
 use nix::errno::Errno;
 #[cfg(not(any(target_os = "redox", target_os = "haiku")))]
 use nix::fcntl::readlink;
@@ -25,7 +26,7 @@ use std::ffi::CString;
 #[cfg(not(target_os = "redox"))]
 use std::fs::DirBuilder;
 use std::fs::{self, File};
-use std::io::Write;
+use std::io::{Seek, Write};
 #[cfg(not(any(
     target_os = "fuchsia",
     target_os = "redox",
@@ -582,14 +583,39 @@ fn test_lseek() {
     let mut tmp = tempfile().unwrap();
     tmp.write_all(CONTENTS).unwrap();
 
-    let offset: off_t = 5;
-    lseek(&tmp, offset, Whence::SeekSet).unwrap();
+    lseek(&tmp, 5, Whence::SeekSet).unwrap();
 
     let mut buf = [0u8; 7];
     crate::read_exact(&tmp, &mut buf);
     assert_eq!(b"f123456", &buf);
 }
 
+#[test]
+fn test_lseek_largefile() {
+    require_largefile!("test_lseek_largefile");
+
+    const CONTENTS: &[u8] = b"The example text";
+    let mut tmp = tempfile().unwrap();
+    let start = 0xffff_fffci64; // 4 bytes before exceeding 32-bit capacity
+    let offset = start + 4;
+
+    // The version of seek in std::io supports 64-bit offsets, so we
+    // use that to write contents to the file. Many platforms and filesystems
+    // support files with holes, which allows them to avoid writing the ~4GiB
+    // before the content we are writing. However, it is possible for the seek
+    // or write to fail (e.g. on platforms that actually do not support large
+    // files), in which case we provide a descriptive message to indicate that
+    // we were unable to test the part we're actually interested in.
+    tmp.seek(std::io::SeekFrom::Start(start as u64))
+        .expect("Cannot test lseek with large offsets: std::io seek failed");
+    tmp.write_all(CONTENTS)
+        .expect("Cannot test lseek with large offsets: write_all failed");
+    assert_eq!(lseek(&tmp, offset, Whence::SeekSet), Ok(offset));
+    let mut buf = [0u8; 12];
+    crate::read_exact(&tmp, &mut buf);
+    assert_eq!(b"example text", &buf);
+}
+
 #[cfg(linux_android)]
 #[test]
 fn test_lseek64() {
@@ -782,6 +808,20 @@ fn test_truncate() {
     assert_eq!(4, metadata.len());
 }
 
+#[test]
+#[cfg(not(any(target_os = "redox", target_os = "fuchsia")))]
+fn test_truncate_largefile() {
+    require_largefile!("test_truncate_largefile");
+
+    let tempdir = tempdir().unwrap();
+    let path = tempdir.path().join("file");
+    File::create(&path).unwrap();
+    let length = 0x1_0000_0008i64;
+    truncate(&path, length).unwrap();
+    let metadata = fs::metadata(&path).unwrap();
+    assert_eq!(0x1_0000_0008, metadata.len());
+}
+
 #[test]
 fn test_ftruncate() {
     let tempdir = tempdir().unwrap();
@@ -798,6 +838,17 @@ fn test_ftruncate() {
     assert_eq!(2, metadata.len());
 }
 
+#[test]
+fn test_ftruncate_largefile() {
+    require_largefile!("test_ftruncate_largefile");
+
+    let tmp = tempfile().unwrap();
+    let length = 0x1_0000_000ci64;
+    ftruncate(&tmp, length).unwrap();
+    let metadata = tmp.metadata().unwrap();
+    assert_eq!(0x1_0000_000c, metadata.len());
+}
+
 // Used in `test_alarm`.
 #[cfg(not(target_os = "redox"))]
 static mut ALARM_CALLED: bool = false;