Give access to file flags in read file_operations callback (#215)

Author: alex

build.rs

@@ -44,6 +44,7 @@ const INCLUDED_VARS: &[&str] = &[
     "SEEK_SET",
     "SEEK_CUR",
     "SEEK_END",
+    "O_NONBLOCK",
 ];
 const OPAQUE_TYPES: &[&str] = &[
     // These need to be opaque because they're both packed and aligned, which rustc

src/file_operations.rs

@@ -8,6 +8,12 @@ use crate::c_types;
 use crate::error::{Error, KernelResult};
 use crate::user_ptr::{UserSlicePtr, UserSlicePtrReader, UserSlicePtrWriter};
 
+bitflags::bitflags! {
+    pub struct FileFlags: c_types::c_uint {
+        const NONBLOCK = bindings::O_NONBLOCK;
+    }
+}
+
 pub struct File {
     ptr: *const bindings::file,
 }
@@ -20,6 +26,10 @@ impl File {
     pub fn pos(&self) -> u64 {
         unsafe { (*self.ptr).f_pos as u64 }
     }
+
+    pub fn flags(&self) -> FileFlags {
+        FileFlags::from_bits_truncate(unsafe { (*self.ptr).f_flags })
+    }
 }
 
 // Matches std::io::SeekFrom in the Rust stdlib
@@ -60,7 +70,7 @@ unsafe extern "C" fn read_callback<T: Read>(
         Ok(v) => v,
         Err(_) => return Error::EINVAL.to_kernel_errno().try_into().unwrap(),
     };
-    match f.read(&mut data, positive_offset) {
+    match f.read(&File::from_ptr(file), &mut data, positive_offset) {
         Ok(()) => {
             let written = len - data.len();
             (*offset) += bindings::loff_t::try_from(written).unwrap();
@@ -230,7 +240,7 @@ pub trait FileOperations: Sync + Sized {
 pub trait Read {
     /// Reads data from this file to userspace. Corresponds to the `read`
     /// function pointer in `struct file_operations`.
-    fn read(&self, buf: &mut UserSlicePtrWriter, offset: u64) -> KernelResult<()>;
+    fn read(&self, file: &File, buf: &mut UserSlicePtrWriter, offset: u64) -> KernelResult<()>;
 }
 
 pub trait Write {

tests/chrdev/src/lib.rs

@@ -22,6 +22,7 @@ impl linux_kernel_module::file_operations::FileOperations for CycleFile {
 impl linux_kernel_module::file_operations::Read for CycleFile {
     fn read(
         &self,
+        _file: &linux_kernel_module::file_operations::File,
         buf: &mut linux_kernel_module::user_ptr::UserSlicePtrWriter,
         offset: u64,
     ) -> linux_kernel_module::KernelResult<()> {
@@ -81,6 +82,7 @@ impl linux_kernel_module::file_operations::FileOperations for WriteFile {
 impl linux_kernel_module::file_operations::Read for WriteFile {
     fn read(
         &self,
+        _file: &linux_kernel_module::file_operations::File,
         buf: &mut linux_kernel_module::user_ptr::UserSlicePtrWriter,
         _offset: u64,
     ) -> linux_kernel_module::KernelResult<()> {