Auto merge of rust-lang#3836 - tiif:einval_ctl, r=oli-obk

epoll: Add a EINVAL case

In ``epoll_ctl`` documentation, it is mentioned that:
> EINVAL epfd is not an epoll file descriptor, or fd is the same as epfd, or the requested operation op is not supported by this interface.

So I added this EINVAL case for ``epfd == fd`` in ``epoll_ctl``

src/tools/miri/src/shims/unix/linux/epoll.rs

@@ -251,6 +251,13 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
             throw_unsup_format!("epoll_ctl: encountered unknown unsupported operation {:#x}", op);
         }
 
+        // Throw EINVAL if epfd and fd have the same value.
+        if epfd_value == fd {
+            let einval = this.eval_libc("EINVAL");
+            this.set_last_error(einval)?;
+            return Ok(Scalar::from_i32(-1));
+        }
+
         // Check if epfd is a valid epoll file descriptor.
         let Some(epfd) = this.machine.fds.get(epfd_value) else {
             return Ok(Scalar::from_i32(this.fd_not_found()?));

src/tools/miri/tests/pass-dep/libc/libc-epoll.rs

@@ -21,6 +21,7 @@ fn main() {
     test_socketpair_epollerr();
     test_epoll_lost_events();
     test_ready_list_fetching_logic();
+    test_epoll_ctl_epfd_equal_fd();
 }
 
 // Using `as` cast since `EPOLLET` wraps around
@@ -630,3 +631,16 @@ fn test_ready_list_fetching_logic() {
     let expected_value1 = fd1 as u64;
     check_epoll_wait::<1>(epfd, &[(expected_event1, expected_value1)]);
 }
+
+// In epoll_ctl, if the value of epfd equals to fd, EINVAL should be returned.
+fn test_epoll_ctl_epfd_equal_fd() {
+    // Create an epoll instance.
+    let epfd = unsafe { libc::epoll_create1(0) };
+    assert_ne!(epfd, -1);
+
+    let array_ptr = std::ptr::without_provenance_mut::<libc::epoll_event>(0x100);
+    let res = unsafe { libc::epoll_ctl(epfd, libc::EPOLL_CTL_ADD, epfd, array_ptr) };
+    let e = std::io::Error::last_os_error();
+    assert_eq!(e.raw_os_error(), Some(libc::EINVAL));
+    assert_eq!(res, -1);
+}