Update error code for fs ops in isolation

Change the code to either `EACCES` (if the op is performed on the
path), or `EBADF` (if the op is performed the fd)

Updated ops: `stat`, `opendir`, `ftruncate64`, and `readlink`

Add a new test for fs ops in isolation.

src/shims/posix/fs.rs

@@ -851,8 +851,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`stat`", reject_with)?;
-            // macos stat never sets "EPERM". Set error code "ENOENT".
-            this.set_last_error_from_io_error(ErrorKind::NotFound)?;
+            let eacc = this.eval_libc("EACCES")?;
+            this.set_last_error(eacc)?;
             return Ok(-1);
         }
 
@@ -872,8 +872,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`lstat`", reject_with)?;
-            // macos lstat never sets "EPERM". Set error code "ENOENT".
-            this.set_last_error_from_io_error(ErrorKind::NotFound)?;
+            let eacc = this.eval_libc("EACCES")?;
+            this.set_last_error(eacc)?;
             return Ok(-1);
         }
 
@@ -917,14 +917,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
         this.assert_target_os("linux", "statx");
 
-        // Reject if isolation is enabled.
-        if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
-            this.reject_in_isolation("`statx`", reject_with)?;
-            // statx never sets "EPERM". Set error code "ENOENT".
-            this.set_last_error_from_io_error(ErrorKind::NotFound)?;
-            return Ok(-1);
-        }
-
         let statxbuf_ptr = this.read_pointer(statxbuf_op)?;
         let pathname_ptr = this.read_pointer(pathname_op)?;
 
@@ -973,6 +965,22 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             )
         }
 
+        // Reject if isolation is enabled.
+        if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
+            this.reject_in_isolation("`statx`", reject_with)?;
+            let ecode = if path.is_absolute() || dirfd == this.eval_libc_i32("AT_FDCWD")? {
+                // since `path` is provided, either absolute or
+                // relative to CWD, `EACCES` is the most relevant.
+                this.eval_libc("EACCES")?
+            } else {
+                // `dirfd` is set to target file, and `path` is
+                // empty. `EACCES` would violate the spec.
+                this.eval_libc("EBADF")?
+            };
+            this.set_last_error(ecode)?;
+            return Ok(-1);
+        }
+
         // the `_mask_op` paramter specifies the file information that the caller requested.
         // However `statx` is allowed to return information that was not requested or to not
         // return information that was requested. This `mask` represents the information we can
@@ -1167,8 +1175,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`opendir`", reject_with)?;
-            // opendir function never sets "EPERM". Set "ENOENT".
-            this.set_last_error_from_io_error(ErrorKind::NotFound)?;
+            let eacc = this.eval_libc("EACCES")?;
+            this.set_last_error(eacc)?;
             return Ok(Scalar::null_ptr(this));
         }
 
@@ -1422,8 +1430,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`ftruncate64`", reject_with)?;
-            this.set_last_error_from_io_error(ErrorKind::PermissionDenied)?;
-            return Ok(-1);
+            // Set error code as "EBADF" (bad fd)
+            return this.handle_not_found();
         }
 
         let fd = this.read_scalar(fd_op)?.to_i32()?;
@@ -1554,8 +1562,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         // Reject if isolation is enabled.
         if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
             this.reject_in_isolation("`readlink`", reject_with)?;
-            // readlink never sets "EPERM". Set "ENOENT".
-            this.set_last_error_from_io_error(ErrorKind::NotFound)?;
+            let eacc = this.eval_libc("EACCES")?;
+            this.set_last_error(eacc)?;
             return Ok(-1);
         }
 

tests/run-pass/fs_with_isolation.rs

@@ -0,0 +1,54 @@
+// ignore-windows: File handling is not implemented yet
+// compile-flags: -Zmiri-isolation-error=warn-nobacktrace
+// normalize-stderr-test "(stat|statx)" -> "$$STAT"
+
+#![feature(rustc_private)]
+
+extern crate libc;
+
+use std::ffi::CString;
+use std::os::unix;
+use std::fs::{self, File};
+use std::io::{Error, ErrorKind};
+
+fn main() {
+    // test `open`
+    assert_eq!(File::create("foo.txt").unwrap_err().kind(), ErrorKind::PermissionDenied);
+
+    // test `fcntl`
+    unsafe {
+        assert_eq!(libc::fcntl(1, libc::F_DUPFD, 0), -1);
+        assert_eq!(Error::last_os_error().raw_os_error(), Some(libc::EPERM));
+    }
+
+    // test `unlink`
+    assert_eq!(fs::remove_file("foo.txt").unwrap_err().kind(), ErrorKind::PermissionDenied);
+
+    // test `symlink`
+    assert_eq!(unix::fs::symlink("foo.txt", "foo_link.txt").unwrap_err().kind(), ErrorKind::PermissionDenied);
+
+    // test `readlink`
+    let symlink_c_str = CString::new("foo.txt").unwrap();
+    let mut buf = vec![0; "foo_link.txt".len() + 1];
+    unsafe {
+        assert_eq!(libc::readlink(symlink_c_str.as_ptr(), buf.as_mut_ptr(), buf.len()), -1);
+        assert_eq!(Error::last_os_error().raw_os_error(), Some(libc::EACCES));
+    }
+
+    // test `stat`
+    assert_eq!(fs::metadata("foo.txt").unwrap_err().kind(), ErrorKind::PermissionDenied);
+    assert_eq!(Error::last_os_error().raw_os_error(), Some(libc::EACCES));
+
+    // test `rename`
+    assert_eq!(fs::rename("a.txt", "b.txt").unwrap_err().kind(), ErrorKind::PermissionDenied);
+
+    // test `mkdir`
+    assert_eq!(fs::create_dir("foo/bar").unwrap_err().kind(), ErrorKind::PermissionDenied);
+
+    // test `rmdir`
+    assert_eq!(fs::remove_dir("foo/bar").unwrap_err().kind(), ErrorKind::PermissionDenied);
+
+    // test `opendir`
+    assert_eq!(fs::read_dir("foo/bar").unwrap_err().kind(), ErrorKind::PermissionDenied);
+    assert_eq!(Error::last_os_error().raw_os_error(), Some(libc::EACCES));
+}

tests/run-pass/fs_with_isolation.stderr

@@ -0,0 +1,20 @@
+warning: `open` was made to return an error due to isolation
+
+warning: `fcntl` was made to return an error due to isolation
+
+warning: `unlink` was made to return an error due to isolation
+
+warning: `symlink` was made to return an error due to isolation
+
+warning: `readlink` was made to return an error due to isolation
+
+warning: `$STAT` was made to return an error due to isolation
+
+warning: `rename` was made to return an error due to isolation
+
+warning: `mkdir` was made to return an error due to isolation
+
+warning: `rmdir` was made to return an error due to isolation
+
+warning: `opendir` was made to return an error due to isolation
+