expose memfd on freebsd

CHANGELOG.md

@@ -10,6 +10,8 @@ This project adheres to [Semantic Versioning](https://semver.org/).
   ([#1804](https://github.com/nix-rust/nix/pull/1804))
 - Added `line_discipline` field to `Termios` on Linux, Android and Haiku
   ([#1805](https://github.com/nix-rust/nix/pull/1805))
+- Expose the memfd module on FreeBSD (memfd was added in FreeBSD 13)
+  ([#1808](https://github.com/nix-rust/nix/pull/1808))
 
 ### Changed
 

src/sys/memfd.rs

@@ -1,6 +1,8 @@
 //! Interfaces for managing memory-backed files.
 
 use std::os::unix::io::RawFd;
+use cfg_if::cfg_if;
+
 use crate::Result;
 use crate::errno::Errno;
 use std::ffi::CStr;
@@ -40,7 +42,22 @@ libc_bitflags!(
 /// [`memfd_create(2)`]: https://man7.org/linux/man-pages/man2/memfd_create.2.html
 pub fn memfd_create(name: &CStr, flags: MemFdCreateFlag) -> Result<RawFd> {
     let res = unsafe {
-        libc::syscall(libc::SYS_memfd_create, name.as_ptr(), flags.bits())
+        cfg_if! {
+            if #[cfg(all(
+                // Android does not have a memfd_create symbol
+                not(target_os = "android"),
+                any(
+                    target_os = "freebsd",
+                    // If the OS is Linux, gnu and musl expose a memfd_create symbol but not uclibc
+                    target_env = "gnu",
+                    target_env = "musl",
+                )))]
+            {
+                libc::memfd_create(name.as_ptr(), flags.bits())
+            } else {
+                libc::syscall(libc::SYS_memfd_create, name.as_ptr(), flags.bits())
+            }
+        }
     };
 
     Errno::result(res).map(|r| r as RawFd)

src/sys/mod.rs

@@ -50,7 +50,7 @@ feature! {
 #[macro_use]
 pub mod ioctl;
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "freebsd", target_os = "linux"))]
 feature! {
     #![feature = "fs"]
     pub mod memfd;