update failure message

src/shims/unix/fs.rs

@@ -31,6 +31,10 @@ struct FileHandle {
 trait FileDescriptor: std::fmt::Debug {
     fn as_file_handle<'tcx>(&self) -> InterpResult<'tcx, &FileHandle>;
 
+    fn as_epoll_handle<'tcx>(&mut self) -> InterpResult<'tcx, &mut Epoll> {
+        throw_unsup_format!("not an epoll file descriptor");
+    }
+
     fn read<'tcx>(
         &mut self,
         communicate_allowed: bool,
@@ -774,29 +778,32 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         }
 
         let fh = &mut this.machine.file_handler;
-        let fd = fh.insert_fd(Box::new(Epoll));
+        let fd = fh.insert_fd(Box::new(Epoll::default()));
         Ok(fd)
     }
 
     fn epoll_ctl(
         &mut self,
-        _epfd: &OpTy<'tcx, Provenance>,
+        epfd: &OpTy<'tcx, Provenance>,
         op: &OpTy<'tcx, Provenance>,
         fd: &OpTy<'tcx, Provenance>,
         _event: &OpTy<'tcx, Provenance>,
     ) -> InterpResult<'tcx, i32> {
         let this = self.eval_context_mut();
 
         let values = this.read_scalar(op)?.to_i32()?;
+        let epfd = this.read_scalar(epfd)?.to_i32()?;
         let fd = this.read_scalar(fd)?.to_i32()?;
 
         let epoll_ctl_add = this.eval_libc_i32("EPOLL_CTL_ADD")?;
         let epoll_ctl_mod = this.eval_libc_i32("EPOLL_CTL_MOD")?;
         let epoll_ctl_del = this.eval_libc_i32("EPOLL_CTL_DEL")?;
 
         if values == epoll_ctl_add {
-            if let Some(_file_descriptor) = this.machine.file_handler.handles.get(&fd) {
-                Ok(-1)
+            if let Some(epfd) = this.machine.file_handler.handles.get_mut(&epfd) {
+                let epfd = epfd.as_epoll_handle()?;
+                epfd.file_descriptors.insert(fd, ());
+                Ok(0)
             } else {
                 this.handle_not_found()
             }

src/shims/unix/fs/epoll.rs

@@ -5,17 +5,24 @@ use crate::*;
 use super::FileDescriptor;
 use super::FileHandle;
 
+use std::collections::HashMap;
 use std::io;
 use std::io::SeekFrom;
 
-#[derive(Debug)]
-pub struct Epoll;
+#[derive(Clone, Debug, Default)]
+pub struct Epoll {
+    pub file_descriptors: HashMap<i32, ()>,
+}
 
 impl FileDescriptor for Epoll {
     fn as_file_handle<'tcx>(&self) -> InterpResult<'tcx, &FileHandle> {
         throw_unsup_format!("epoll file descriptors cannot be used as FileHandle");
     }
 
+    fn as_epoll_handle<'tcx>(&mut self) -> InterpResult<'tcx, &mut Epoll> {
+        Ok(self)
+    }
+
     fn read<'tcx>(
         &mut self,
         _communicate_allowed: bool,
@@ -48,7 +55,7 @@ impl FileDescriptor for Epoll {
     }
 
     fn dup<'tcx>(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
-        Ok(Box::new(Epoll))
+        Ok(Box::new(self.clone()))
     }
 
     fn as_unix_host_fd(&self) -> Option<i32> {

tests/fail/crates/tokio_mvp.rs

@@ -1,5 +1,5 @@
 //@compile-flags: -Zmiri-disable-isolation
-//@error-pattern: unsupported operation: event file descriptors cannot be closed
+//@error-pattern: unsupported operation: can't call foreign function: socketpair
 //@normalize-stderr-test: "   = note: inside .*\n" -> ""
 //@only-target-linux: the errors differ too much between platforms
 

tests/fail/crates/tokio_mvp.stderr

@@ -1,8 +1,8 @@
-error: unsupported operation: event file descriptors cannot be closed
-  --> RUSTLIB/std/src/os/fd/owned.rs:LL:CC
+error: unsupported operation: can't call foreign function: socketpair
+  --> CARGO_REGISTRY/.../mod.rs:LL:CC
    |
-LL |             let _ = libc::close(self.fd);
-   |                     ^^^^^^^^^^^^^^^^^^^^ event file descriptors cannot be closed
+LL |         syscall!(socketpair(libc::AF_UNIX, flags, 0, fds.as_mut_ptr()))?;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't call foreign function: socketpair
    |
    = help: this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support
    = note: backtrace:
@@ -11,7 +11,7 @@ note: inside `main` at $DIR/tokio_mvp.rs:LL:CC
    |
 LL | #[tokio::main]
    | ^^^^^^^^^^^^^^
-   = note: this error originates in the attribute macro `tokio::main` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `syscall` which comes from the expansion of the attribute macro `tokio::main` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace