1 files changed, 65 insertions, 0 deletions
diff --git a/third_party/rust/nix/src/sys/memfd.rs b/third_party/rust/nix/src/sys/memfd.rs
new file mode 100644
index 0000000000..516ffd3262
--- /dev/null
+++ b/third_party/rust/nix/src/sys/memfd.rs
@@ -0,0 +1,65 @@
+//! Interfaces for managing memory-backed files.
+
+use cfg_if::cfg_if;
+use std::os::unix::io::{FromRawFd, OwnedFd, RawFd};
+
+use crate::errno::Errno;
+use crate::Result;
+use std::ffi::CStr;
+
+libc_bitflags!(
+    /// Options that change the behavior of [`memfd_create`].
+    pub struct MemFdCreateFlag: libc::c_uint {
+        /// Set the close-on-exec ([`FD_CLOEXEC`]) flag on the new file descriptor.
+        ///
+        /// By default, the new file descriptor is set to remain open across an [`execve`]
+        /// (the `FD_CLOEXEC` flag is initially disabled). This flag can be used to change
+        /// this default. The file offset is set to the beginning of the file (see [`lseek`]).
+        ///
+        /// See also the description of the `O_CLOEXEC` flag in [`open(2)`].
+        ///
+        /// [`execve`]: crate::unistd::execve
+        /// [`lseek`]: crate::unistd::lseek
+        /// [`FD_CLOEXEC`]: crate::fcntl::FdFlag::FD_CLOEXEC
+        /// [`open(2)`]: https://man7.org/linux/man-pages/man2/open.2.html
+        MFD_CLOEXEC;
+        /// Allow sealing operations on this file.
+        ///
+        /// See also the file sealing notes given in [`memfd_create(2)`].
+        ///
+        /// [`memfd_create(2)`]: https://man7.org/linux/man-pages/man2/memfd_create.2.html
+        MFD_ALLOW_SEALING;
+    }
+);
+
+/// Creates an anonymous file that lives in memory, and return a file-descriptor to it.
+///
+/// The file behaves like a regular file, and so can be modified, truncated, memory-mapped, and so on.
+/// However, unlike a regular file, it lives in RAM and has a volatile backing storage.
+///
+/// For more information, see [`memfd_create(2)`].
+///
+/// [`memfd_create(2)`]: https://man7.org/linux/man-pages/man2/memfd_create.2.html
+#[inline] // Delays codegen, preventing linker errors with dylibs and --no-allow-shlib-undefined
+pub fn memfd_create(name: &CStr, flags: MemFdCreateFlag) -> Result<OwnedFd> {
+    let res = unsafe {
+        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| unsafe { OwnedFd::from_raw_fd(r as RawFd) })
+}