Move read_byte_helper_ev to eventfd.rs and fix minor bug caused by re…

…base

src/shims/unix/fd.rs

@@ -623,9 +623,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
 
         let bytes = this.read_bytes_ptr_strip_provenance(buf, Size::from_bytes(count))?.to_owned();
         // We temporarily dup the FD to be able to retain mutable access to `this`.
-        let Some(fd) = this.machine.fds.get(fd_num) else {
-            let res = this.fd_not_found()?;
-            this.write_scalar(Scalar::from_target_isize(res, this), dest)?;
         let Some(fd) = this.machine.fds.get(fd_num) else {
             let res: i32 = this.fd_not_found()?;
             this.write_int(res, dest)?;
@@ -679,38 +676,6 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         }
     }
 
-    /// This function either writes to the user supplied buffer and to dest place, or return error.
-    // TODO: this is only used for eventfd
-    fn read_byte_helper_ev(
-        &mut self,
-        buf_place: &MPlaceTy<'tcx>,
-        read_val: Option<u64>,
-        result: io::Result<usize>,
-        dest: &MPlaceTy<'tcx>,
-    ) -> InterpResult<'tcx> {
-        let this = self.eval_context_mut();
-        // `File::read` never returns a value larger than `count`, so this cannot fail.
-        match result.map(|c| i64::try_from(c).unwrap()) {
-            // try to pass this the write_ptr inside write
-            // Pass the pointer inside the write function.
-            Ok(read_bytes) => {
-                // If reading to `bytes` did not fail, we write those bytes to the buffer.
-                // Crucially, if fewer than `bytes.len()` bytes were read, only write
-                // that much into the output buffer!
-                // Write to the user supplied buffer.
-                this.write_int(read_val.unwrap(), buf_place)?;
-                // Write to the function return value place.
-                this.write_int(read_bytes, dest)?;
-                return Ok(());
-            }
-            Err(e) => {
-                this.set_last_error_from_io_error(e)?;
-                this.write_int(-1, dest)?;
-                return Ok(());
-            }
-        }
-    }
-
     /// This function either writes the number of written bytes to dest place or return error.
     fn write_byte_helper(
         &mut self,

src/shims/unix/linux/eventfd.rs

@@ -72,7 +72,7 @@ impl FileDescription for Event {
         // Check the size of slice, and return error only if the size of the slice < 8.
         if len < U64_ARRAY_SIZE.try_into().unwrap() {
             let result = Err(Error::from(ErrorKind::InvalidInput));
-            ecx.read_byte_helper_ev(&buf_place, None, result, dest)?;
+            read_byte_helper_ev(&buf_place, None, result, dest, ecx)?;
             return Ok(());
         }
 
@@ -81,7 +81,7 @@ impl FileDescription for Event {
         if counter == 0 {
             if self.is_nonblock {
                 let result = Err(Error::from(ErrorKind::WouldBlock));
-                ecx.read_byte_helper_ev(&buf_place, None, result, dest)?;
+                read_byte_helper_ev(&buf_place, None, result, dest, ecx)?;
                 return Ok(());
             } else {
                 //FIXME: blocking is not supported
@@ -91,7 +91,7 @@ impl FileDescription for Event {
             // Synchronize with all prior `write` calls to this FD.
             ecx.acquire_clock(&self.clock.borrow());
             let result = Ok(U64_ARRAY_SIZE);
-            ecx.read_byte_helper_ev(&buf_place, Some(counter), result, dest)?;
+            read_byte_helper_ev(&buf_place, Some(counter), result, dest, ecx)?;
             self.counter.set(0);
             // When any of the event happened, we check and update the status of all supported event
             // types for current file description.
@@ -230,3 +230,27 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         Ok(Scalar::from_i32(fd_value))
     }
 }
+
+/// This function either writes to the user supplied buffer and to dest place, or return error.
+fn read_byte_helper_ev<'tcx>(
+    buf_place: &MPlaceTy<'tcx>,
+    read_val: Option<u64>,
+    result: io::Result<usize>,
+    dest: &MPlaceTy<'tcx>,
+    ecx: &mut MiriInterpCx<'tcx>,
+) -> InterpResult<'tcx> {
+    match result.map(|c| i64::try_from(c).unwrap()) {
+        Ok(read_bytes) => {
+            // Write to the user supplied buffer.
+            ecx.write_int(read_val.unwrap(), buf_place)?;
+            // Write to the function return value place.
+            ecx.write_int(read_bytes, dest)?;
+            return Ok(());
+        }
+        Err(e) => {
+            ecx.set_last_error_from_io_error(e)?;
+            ecx.write_int(-1, dest)?;
+            return Ok(());
+        }
+    }
+}