host_env: Use Rustix for copy_file_range (#8099)

Rustix bypasses `libc` to make direct syscalls on Linux. Rustix is also
semantically cleaner than `libc` itself. For `copy_file_range`, the
offsets can't be negative but `libc`'s `off_t` type is an `i64` because
it's used elsewhere, including for functions that CAN take a negative
offset. Rustix is cleaner because the offsets are `u64`.

Cargo.toml

@@ -284,7 +284,7 @@ radium = "1.1.1"
 rand = "0.10"
 rapidhash = "4.4.1"
 result-like = "0.5.0"
-rustix = { version = "1.1", features = ["event", "param", "system"] }
+rustix = { version = "1.1", features = ["event", "fs", "param", "system"] }
 rustls = { version = "0.23.39", default-features = false }
 rustls-graviola = "0.3"
 rustls-native-certs = "0.8"

crates/host_env/src/os.rs

@@ -256,30 +256,14 @@ pub fn system(command: &CStr) -> libc::c_int {
 #[cfg(target_os = "linux")]
 pub fn copy_file_range(
     src: crt_fd::Borrowed<'_>,
-    offset_src: Option<&mut crt_fd::Offset>,
+    offset_src: Option<&mut u64>,
     dst: crt_fd::Borrowed<'_>,
-    offset_dst: Option<&mut crt_fd::Offset>,
+    offset_dst: Option<&mut u64>,
     count: usize,
-) -> io::Result<usize> {
-    #[allow(clippy::unnecessary_option_map_or_else)]
-    let p_offset_src = offset_src.map_or_else(core::ptr::null_mut, |x| x as *mut _);
-    #[allow(clippy::unnecessary_option_map_or_else)]
-    let p_offset_dst = offset_dst.map_or_else(core::ptr::null_mut, |x| x as *mut _);
-
-    // Why not use `libc::copy_file_range`: On musl, the libc wrapper may be missing.
-    let ret = unsafe {
-        libc::syscall(
-            libc::SYS_copy_file_range,
-            src.as_raw(),
-            p_offset_src,
-            dst.as_raw(),
-            p_offset_dst,
-            count,
-            0u32,
-        )
-    };
-
-    usize::try_from(ret).map_err(|_| io::Error::last_os_error())
+) -> rustix::io::Result<usize> {
+    // `copy_file_range` isn't wrapped in every libc (i.e. musl).
+    // However, Rustix is a safe wrapper around the syscall that bypasses libc.
+    rustix::fs::copy_file_range(src, offset_src, dst, offset_dst, count)
 }
 
 pub fn rename(
@@ -369,6 +353,13 @@ impl ErrorExt for io::Error {
     }
 }
 
+#[cfg(all(not(windows), not(target_arch = "wasm32")))]
+impl ErrorExt for rustix::io::Errno {
+    fn posix_errno(&self) -> i32 {
+        self.raw_os_error()
+    }
+}
+
 /// Get the last error from C runtime library functions (like _dup, _dup2, _fstat, etc.)
 /// CRT functions set errno, not GetLastError(), so we need to read errno directly.
 #[cfg(windows)]

crates/vm/src/stdlib/os.rs

@@ -1709,20 +1709,30 @@ pub(super) mod _os {
 
     #[cfg(target_os = "linux")]
     #[pyfunction]
-    fn copy_file_range(mut args: CopyFileRangeArgs<'_>, vm: &VirtualMachine) -> PyResult<usize> {
+    fn copy_file_range(args: CopyFileRangeArgs<'_>, vm: &VirtualMachine) -> PyResult<usize> {
         let count: usize = args
             .count
             .try_into()
             .map_err(|_| vm.new_value_error("count should >= 0"))?;
+        let mut offset_src = args
+            .offset_src
+            .map(TryInto::try_into)
+            .transpose()
+            .map_err(|_| vm.new_value_error("offset_src should be >= 0"))?;
+        let mut offset_dst = args
+            .offset_dst
+            .map(TryInto::try_into)
+            .transpose()
+            .map_err(|_| vm.new_value_error("offset_dst should be >= 0"))?;
 
         crate::host_env::os::copy_file_range(
             args.src,
-            args.offset_src.as_mut(),
+            offset_src.as_mut(),
             args.dst,
-            args.offset_dst.as_mut(),
+            offset_dst.as_mut(),
             count,
         )
-        .map_err(|_| vm.new_last_errno_error())
+        .map_err(|e| vm.new_errno_error(e.raw_os_error(), e.to_string()).upcast())
     }
 
     #[pyfunction]