Add fn blocking_epoll_callback

Author: tiif

src/shims/unix/linux/epoll.rs

@@ -473,4 +473,51 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         }
         Ok(())
     }
+
+    /// Callback function after epoll_wait unblocks
+    fn blocking_epoll_callback(
+        &mut self,
+        epfd: i32,
+        place: &MPlaceTy<'tcx>,
+        event: &MPlaceTy<'tcx>,
+    ) -> InterpResult<'tcx> {
+        let this = self.eval_context_mut();
+
+        let Some(epfd) = this.machine.fds.get_ref(epfd) else {
+            let result_value = this.fd_not_found()?;
+            this.write_scalar(Scalar::from_i32(result_value), place)?;
+            return Ok(());
+        };
+        let mut binding = epfd.borrow_mut();
+        let epoll_file_description = &mut binding
+            .downcast_mut::<Epoll>()
+            .ok_or_else(|| err_unsup_format!("non-epoll FD passed to `epoll_wait`"))?;
+
+        let binding = epoll_file_description.get_ready_list();
+        let mut ready_list = binding.borrow_mut();
+        let mut num_of_events: i32 = 0;
+        let mut array_iter = this.project_array_fields(event)?;
+
+        while let Some((epoll_key, epoll_return)) = ready_list.pop_first() {
+            // If the file description is fully close, the entry for corresponding FdID in the
+            // global epoll event interest table would be empty.
+            if this.machine.epoll_interests.get_epoll_interest(epoll_key.0).is_some() {
+                // Return notification to the caller if the file description is not fully closed.
+                if let Some(des) = array_iter.next(this)? {
+                    this.write_int_fields_named(
+                        &[
+                            ("events", epoll_return.events.into()),
+                            ("u64", epoll_return.data.into()),
+                        ],
+                        &des.1,
+                    )?;
+                    num_of_events = num_of_events.checked_add(1).unwrap();
+                } else {
+                    break;
+                }
+            }
+        }
+        this.write_scalar(Scalar::from_i32(num_of_events), place)?;
+        Ok(())
+    }
 }