Auto merge of #1143 - christianpoveda:symlink-shim, r=RalfJung

Add shim for symbolic link creation

r? @RalfJung

src/shims/foreign_items.rs

@@ -494,11 +494,21 @@ fn emulate_foreign_item(
                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
             }
 
+            "symlink" => {
+                let result = this.symlink(args[0], args[1])?;
+                this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
+            }
+
             "stat$INODE64" => {
                 let result = this.stat(args[0], args[1])?;
                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
             }
 
+            "lstat$INODE64" => {
+                let result = this.lstat(args[0], args[1])?;
+                this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
+            }
+
             "clock_gettime" => {
                 let result = this.clock_gettime(args[0], args[1])?;
                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;

src/shims/fs.rs

@@ -276,15 +276,68 @@ fn unlink(&mut self, path_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
         this.try_unwrap_io_result(result)
     }
 
+    fn symlink(
+        &mut self,
+        target_op: OpTy<'tcx, Tag>,
+        linkpath_op: OpTy<'tcx, Tag>
+    ) -> InterpResult<'tcx, i32> {
+        #[cfg(target_family = "unix")]
+        fn create_link(src: PathBuf, dst: PathBuf) -> std::io::Result<()> {
+            std::os::unix::fs::symlink(src, dst)
+        }
+
+        #[cfg(target_family = "windows")]
+        fn create_link(src: PathBuf, dst: PathBuf) -> std::io::Result<()> {
+            use std::os::windows::fs;
+            if src.is_dir() {
+                fs::symlink_dir(src, dst)
+            } else {
+                fs::symlink_file(src, dst)
+            }
+        }
+
+        let this = self.eval_context_mut();
+
+        this.check_no_isolation("symlink")?;
+
+        let target = this.read_os_str_from_c_str(this.read_scalar(target_op)?.not_undef()?)?.into();
+        let linkpath = this.read_os_str_from_c_str(this.read_scalar(linkpath_op)?.not_undef()?)?.into();
+
+        this.try_unwrap_io_result(create_link(target, linkpath).map(|_| 0))
+    }
+
     fn stat(
         &mut self,
         path_op: OpTy<'tcx, Tag>,
         buf_op: OpTy<'tcx, Tag>,
     ) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
+        this.check_no_isolation("stat")?;
+        // `stat` always follows symlinks.
+        this.stat_or_lstat(true, path_op, buf_op)
+    }
+
+    // `lstat` is used to get symlink metadata.
+    fn lstat(
+        &mut self,
+        path_op: OpTy<'tcx, Tag>,
+        buf_op: OpTy<'tcx, Tag>,
+    ) -> InterpResult<'tcx, i32> {
+        let this = self.eval_context_mut();
+        this.check_no_isolation("lstat")?;
+        this.stat_or_lstat(false, path_op, buf_op)
+    }
+
+    fn stat_or_lstat(
+        &mut self,
+        follow_symlink: bool,
+        path_op: OpTy<'tcx, Tag>,
+        buf_op: OpTy<'tcx, Tag>,
+    ) -> InterpResult<'tcx, i32> {
+        let this = self.eval_context_mut();
 
         if this.tcx.sess.target.target.target_os.to_lowercase() != "macos" {
-            throw_unsup_format!("The `stat` shim is only available for `macos` targets.")
+            throw_unsup_format!("The `stat` and `lstat` shims are only available for `macos` targets.")
         }
 
         let path_scalar = this.read_scalar(path_op)?.not_undef()?;
@@ -292,8 +345,7 @@ fn stat(
 
         let buf = this.deref_operand(buf_op)?;
 
-        // `stat` always follows symlinks. `lstat` is used to get symlink metadata.
-        let metadata = match FileMetadata::new(this, path, true)? {
+        let metadata = match FileMetadata::new(this, path, follow_symlink)? {
             Some(metadata) => metadata,
             None => return Ok(-1),
         };
@@ -545,7 +597,6 @@ fn new<'tcx, 'mir>(
         let metadata = if follow_symlink {
             std::fs::metadata(path)
         } else {
-            // FIXME: metadata for symlinks need testing.
             std::fs::symlink_metadata(path)
         };
 

tests/run-pass/fs.rs

@@ -19,7 +19,11 @@ fn main() {
     let tmp = std::env::temp_dir();
     let filename = PathBuf::from("miri_test_fs.txt");
     let path = tmp.join(&filename);
+    let symlink_path = tmp.join("miri_test_fs_symlink.txt");
     let bytes = b"Hello, World!\n";
+    // Clean the paths for robustness.
+    remove_file(&path).ok();
+    remove_file(&symlink_path).ok();
 
     // Test creating, writing and closing a file (closing is tested when `file` is dropped).
     let mut file = File::create(&path).unwrap();
@@ -39,9 +43,23 @@ fn main() {
     // Test that metadata of an absolute path is correct.
     test_metadata(bytes, &path).unwrap();
     // Test that metadata of a relative path is correct.
-    std::env::set_current_dir(tmp).unwrap();
+    std::env::set_current_dir(&tmp).unwrap();
     test_metadata(bytes, &filename).unwrap();
 
+    // Creating a symbolic link should succeed.
+    std::os::unix::fs::symlink(&path, &symlink_path).unwrap();
+    // Test that the symbolic link has the same contents as the file.
+    let mut symlink_file = File::open(&symlink_path).unwrap();
+    let mut contents = Vec::new();
+    symlink_file.read_to_end(&mut contents).unwrap();
+    assert_eq!(bytes, contents.as_slice());
+    // Test that metadata of a symbolic link is correct.
+    test_metadata(bytes, &symlink_path).unwrap();
+    // Test that the metadata of a symbolic link is correct when not following it.
+    assert!(symlink_path.symlink_metadata().unwrap().file_type().is_symlink());
+    // Removing symbolic link should succeed.
+    remove_file(&symlink_path).unwrap();
+
     // Removing file should succeed.
     remove_file(&path).unwrap();