implement minimal epoll_create1 shim

Author: DebugSteven

src/shims/unix/foreign_items.rs

@@ -62,6 +62,11 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
                 let result = this.open(args)?;
                 this.write_scalar(Scalar::from_i32(result), dest)?;
             }
+            "epoll_create1" => {
+                let [flag] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
+                let result = this.epoll_create1(flag)?;
+                this.write_scalar(Scalar::from_i32(result), dest)?;
+            }
             "close" => {
                 let [fd] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
                 let result = this.close(fd)?;

src/shims/unix/fs.rs

@@ -14,9 +14,12 @@ use rustc_middle::ty::{self, layout::LayoutOf};
 use rustc_target::abi::{Align, Size};
 
 use crate::*;
+use epoll::Epoll;
 use shims::os_str::os_str_to_bytes;
 use shims::time::system_time_to_duration;
 
+mod epoll;
+
 #[derive(Debug)]
 struct FileHandle {
     file: File,
@@ -725,6 +728,25 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
         }
     }
 
+    fn epoll_create1(&mut self, flags: &OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
+        let this = self.eval_context_mut();
+
+        let flags = this.read_scalar(flags)?.to_i32()?;
+
+        let o_cloexec = this.eval_libc_i32("O_CLOEXEC")?;
+        // TODO actually do the thing
+        if flags == o_cloexec {
+        } else if flags != 0 {
+            let einval = this.eval_libc("EINVAL")?;
+            this.set_last_error(einval)?;
+            return Ok(-1);
+        }
+
+        let fh = &mut this.machine.file_handler;
+        let fd = fh.insert_fd(Box::new(Epoll));
+        Ok(fd)
+    }
+
     fn read(&mut self, fd: i32, buf: Pointer<Option<Tag>>, count: u64) -> InterpResult<'tcx, i64> {
         let this = self.eval_context_mut();
 

src/shims/unix/fs/epoll.rs

@@ -0,0 +1,54 @@
+// use crate::shims::unix::fs::FileDescriptor;
+// use crate::shims::unix::fs::SeekFrom;
+use crate::*;
+
+use super::FileDescriptor;
+use super::FileHandle;
+
+use std::io;
+use std::io::SeekFrom;
+
+#[derive(Debug)]
+pub struct Epoll;
+
+impl FileDescriptor for Epoll {
+    fn as_file_handle<'tcx>(&self) -> InterpResult<'tcx, &FileHandle> {
+        throw_unsup_format!("stderr and stdout cannot be used as FileHandle");
+    }
+
+    fn read<'tcx>(
+        &mut self,
+        _communicate_allowed: bool,
+        _bytes: &mut [u8],
+    ) -> InterpResult<'tcx, io::Result<usize>> {
+        throw_unsup_format!("cannot read from stderr or stdout");
+    }
+
+    fn write<'tcx>(
+        &self,
+        _communicate_allowed: bool,
+        bytes: &[u8],
+    ) -> InterpResult<'tcx, io::Result<usize>> {
+        // We just don't write anything, but report to the user that we did.
+        Ok(Ok(bytes.len()))
+    }
+
+    fn seek<'tcx>(
+        &mut self,
+        _communicate_allowed: bool,
+        _offset: SeekFrom,
+    ) -> InterpResult<'tcx, io::Result<u64>> {
+        throw_unsup_format!("cannot seek on stderr or stdout");
+    }
+
+    fn close<'tcx>(
+        self: Box<Self>,
+        _communicate_allowed: bool,
+    ) -> InterpResult<'tcx, io::Result<i32>> {
+        throw_unsup_format!("stderr and stdout cannot be closed");
+    }
+
+    fn dup<'tcx>(&mut self) -> io::Result<Box<dyn FileDescriptor>> {
+        Ok(Box::new(Epoll))
+    }
+}