Merge pull request #220 from wedsonaf/sample

Add `rust_random` sample that uses `module_misc_device`.

Author: ojeda

samples/rust/Kconfig

@@ -100,4 +100,14 @@ config SAMPLE_RUST_SEMAPHORE_C
 
 	  If unsure, say N.
 
+config SAMPLE_RUST_RANDOM
+	tristate "Random"
+	help
+	  This option builds the Rust random sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_random.
+
+	  If unsure, say N.
+
 endif # SAMPLES_RUST

samples/rust/Makefile

@@ -9,3 +9,4 @@ obj-$(CONFIG_SAMPLE_RUST_MISCDEV)		+= rust_miscdev.o
 obj-$(CONFIG_SAMPLE_RUST_STACK_PROBING)		+= rust_stack_probing.o
 obj-$(CONFIG_SAMPLE_RUST_SEMAPHORE)		+= rust_semaphore.o
 obj-$(CONFIG_SAMPLE_RUST_SEMAPHORE_C)		+= rust_semaphore_c.o
+obj-$(CONFIG_SAMPLE_RUST_RANDOM)		+= rust_random.o

samples/rust/rust_random.rs

@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust random device
+//!
+//! Adapted from Alex Gaynor's original available at
+//! <https://github.com/alex/just-use/blob/master/src/lib.rs>.
+
+#![no_std]
+#![feature(allocator_api, global_asm)]
+
+use kernel::{
+    file_operations::{File, FileOperations},
+    prelude::*,
+    user_ptr::{UserSlicePtrReader, UserSlicePtrWriter},
+};
+
+#[derive(Default)]
+struct RandomFile;
+
+impl FileOperations for RandomFile {
+    kernel::declare_file_operations!(read, write);
+
+    fn read(&self, file: &File, buf: &mut UserSlicePtrWriter, _offset: u64) -> KernelResult<usize> {
+        let total_len = buf.len();
+        let mut chunkbuf = [0; 256];
+
+        while !buf.is_empty() {
+            let len = chunkbuf.len().min(buf.len());
+            let chunk = &mut chunkbuf[0..len];
+
+            if file.is_blocking() {
+                kernel::random::getrandom(chunk)?;
+            } else {
+                kernel::random::getrandom_nonblock(chunk)?;
+            }
+            buf.write_slice(chunk)?;
+        }
+        Ok(total_len)
+    }
+
+    fn write(&self, buf: &mut UserSlicePtrReader, _offset: u64) -> KernelResult<usize> {
+        let total_len = buf.len();
+        let mut chunkbuf = [0; 256];
+        while !buf.is_empty() {
+            let len = chunkbuf.len().min(buf.len());
+            let chunk = &mut chunkbuf[0..len];
+            buf.read_slice(chunk)?;
+            kernel::random::add_randomness(chunk);
+        }
+        Ok(total_len)
+    }
+}
+
+module_misc_device! {
+    type: RandomFile,
+    name: b"rust_random",
+    author: b"Rust for Linux Contributors",
+    description: b"Just use /dev/urandom: Now with early-boot safety",
+    license: b"GPL v2",
+}