Auto merge of rust-lang#2857 - RalfJung:endian, r=RalfJung

fix endianess handling in eventfd::write

Fixes rust-lang/miri#2800

Author: bors

src/tools/miri/src/shims/unix/fs.rs

@@ -11,6 +11,7 @@ use std::time::SystemTime;
 use log::trace;
 
 use rustc_data_structures::fx::FxHashMap;
+use rustc_middle::ty::TyCtxt;
 use rustc_target::abi::{Align, Size};
 
 use crate::shims::os_str::bytes_to_os_str;
@@ -31,6 +32,7 @@ pub trait FileDescriptor: std::fmt::Debug + helpers::AsAny {
         &mut self,
         _communicate_allowed: bool,
         _bytes: &mut [u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         throw_unsup_format!("cannot read from {}", self.name());
     }
@@ -39,6 +41,7 @@ pub trait FileDescriptor: std::fmt::Debug + helpers::AsAny {
         &self,
         _communicate_allowed: bool,
         _bytes: &[u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         throw_unsup_format!("cannot write to {}", self.name());
     }
@@ -79,6 +82,7 @@ impl FileDescriptor for FileHandle {
         &mut self,
         communicate_allowed: bool,
         bytes: &mut [u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         assert!(communicate_allowed, "isolation should have prevented even opening a file");
         Ok(self.file.read(bytes))
@@ -88,6 +92,7 @@ impl FileDescriptor for FileHandle {
         &self,
         communicate_allowed: bool,
         bytes: &[u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         assert!(communicate_allowed, "isolation should have prevented even opening a file");
         Ok((&mut &self.file).write(bytes))
@@ -153,6 +158,7 @@ impl FileDescriptor for io::Stdin {
         &mut self,
         communicate_allowed: bool,
         bytes: &mut [u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         if !communicate_allowed {
             // We want isolation mode to be deterministic, so we have to disallow all reads, even stdin.
@@ -184,6 +190,7 @@ impl FileDescriptor for io::Stdout {
         &self,
         _communicate_allowed: bool,
         bytes: &[u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         // We allow writing to stderr even with isolation enabled.
         let result = Write::write(&mut { self }, bytes);
@@ -220,6 +227,7 @@ impl FileDescriptor for io::Stderr {
         &self,
         _communicate_allowed: bool,
         bytes: &[u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         // We allow writing to stderr even with isolation enabled.
         // No need to flush, stderr is not buffered.
@@ -252,6 +260,7 @@ impl FileDescriptor for NullOutput {
         &self,
         _communicate_allowed: bool,
         bytes: &[u8],
+        _tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         // We just don't write anything, but report to the user that we did.
         Ok(Ok(bytes.len()))
@@ -756,8 +765,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
             let mut bytes = vec![0; usize::try_from(count).unwrap()];
             // `File::read` never returns a value larger than `count`,
             // so this cannot fail.
-            let result =
-                file_descriptor.read(communicate, &mut bytes)?.map(|c| i64::try_from(c).unwrap());
+            let result = file_descriptor
+                .read(communicate, &mut bytes, *this.tcx)?
+                .map(|c| i64::try_from(c).unwrap());
 
             match result {
                 Ok(read_bytes) => {
@@ -803,8 +813,9 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
         if let Some(file_descriptor) = this.machine.file_handler.handles.get(&fd) {
             let bytes = this.read_bytes_ptr_strip_provenance(buf, Size::from_bytes(count))?;
-            let result =
-                file_descriptor.write(communicate, bytes)?.map(|c| i64::try_from(c).unwrap());
+            let result = file_descriptor
+                .write(communicate, bytes, *this.tcx)?
+                .map(|c| i64::try_from(c).unwrap());
             this.try_unwrap_io_result(result)
         } else {
             this.handle_not_found()

src/tools/miri/src/shims/unix/linux/fd/event.rs

@@ -1,6 +1,8 @@
 use crate::shims::unix::fs::FileDescriptor;
 
 use rustc_const_eval::interpret::InterpResult;
+use rustc_middle::ty::TyCtxt;
+use rustc_target::abi::Endian;
 
 use std::cell::Cell;
 use std::io;
@@ -36,7 +38,7 @@ impl FileDescriptor for Event {
     }
 
     /// A write call adds the 8-byte integer value supplied in
-    /// its buffer to the counter.  The maximum value that may be
+    /// its buffer (in native endianess) to the counter.  The maximum value that may be
     /// stored in the counter is the largest unsigned 64-bit value
     /// minus 1 (i.e., 0xfffffffffffffffe).  If the addition would
     /// cause the counter's value to exceed the maximum, then the
@@ -47,17 +49,22 @@ impl FileDescriptor for Event {
     /// A write fails with the error EINVAL if the size of the
     /// supplied buffer is less than 8 bytes, or if an attempt is
     /// made to write the value 0xffffffffffffffff.
-    ///
-    /// FIXME: use endianness
     fn write<'tcx>(
         &self,
         _communicate_allowed: bool,
         bytes: &[u8],
+        tcx: TyCtxt<'tcx>,
     ) -> InterpResult<'tcx, io::Result<usize>> {
         let v1 = self.val.get();
+        let bytes: [u8; 8] = bytes.try_into().unwrap(); // FIXME fail gracefully when this has the wrong size
+        // Convert from target endianess to host endianess.
+        let num = match tcx.sess.target.endian {
+            Endian::Little => u64::from_le_bytes(bytes),
+            Endian::Big => u64::from_be_bytes(bytes),
+        };
         // FIXME handle blocking when addition results in exceeding the max u64 value
         // or fail with EAGAIN if the file descriptor is nonblocking.
-        let v2 = v1.checked_add(u64::from_be_bytes(bytes.try_into().unwrap())).unwrap();
+        let v2 = v1.checked_add(num).unwrap();
         self.val.set(v2);
         assert_eq!(8, bytes.len());
         Ok(Ok(8))