rust: devcoredump: Add devcoredump abstraction

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: hoshinolina

rust/bindings/bindings_helper.h

@@ -22,6 +22,7 @@
 #include <linux/blkdev.h>
 #include <linux/cred.h>
 #include <linux/delay.h>
+#include <linux/devcoredump.h>
 #include <linux/dma-fence.h>
 #include <linux/dma-fence-chain.h>
 #include <linux/dma-mapping.h>

rust/kernel/devcoredump.rs

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+
+//! Device coredump support.
+//!
+//! C header: [`include/linux/devcoredump.h`](../../../../include/linux/devcoredump.h)
+
+use crate::{
+    alloc, bindings, device, error::from_result, prelude::Result, time::Jiffies,
+    types::ForeignOwnable, ThisModule,
+};
+
+use core::ops::Deref;
+
+/// The default timeout for device coredumps.
+pub const DEFAULT_TIMEOUT: Jiffies = bindings::DEVCD_TIMEOUT as Jiffies;
+
+/// Trait to implement reading from a device coredump.
+///
+/// Users must implement this trait to provide device coredump support.
+pub trait DevCoreDump {
+    /// Returns the IOVA (virtual address) of the buffer from RTKit's point of view, or an error if
+    /// unavailable.
+    fn read(&self, buf: &mut [u8], offset: usize) -> Result<usize>;
+}
+
+unsafe extern "C" fn read_callback<
+    'a,
+    T: ForeignOwnable<Borrowed<'a>: Deref<Target = D>>,
+    D: DevCoreDump,
+>(
+    buffer: *mut crate::ffi::c_char,
+    offset: bindings::loff_t,
+    count: usize,
+    data: *mut crate::ffi::c_void,
+    _datalen: usize,
+) -> isize {
+    // SAFETY: This pointer came from into_foreign() below.
+    let coredump = unsafe { T::borrow(data) };
+    // SAFETY: The caller guarantees `buffer` points to at least `count` bytes.
+    let buf = unsafe { core::slice::from_raw_parts_mut(buffer, count) };
+
+    from_result(|| Ok(coredump.read(buf, offset.try_into()?)?.try_into()?))
+}
+
+unsafe extern "C" fn free_callback<
+    'a,
+    T: ForeignOwnable<Borrowed<'a>: Deref<Target = D>>,
+    D: DevCoreDump,
+>(
+    data: *mut crate::ffi::c_void,
+) {
+    // SAFETY: This pointer came from into_foreign() below.
+    unsafe {
+        T::from_foreign(data);
+    }
+}
+
+/// Registers a coredump for the given device.
+pub fn dev_coredump<'a, T: ForeignOwnable<Borrowed<'a>: Deref<Target = D>>, D: DevCoreDump>(
+    dev: &device::Device,
+    module: &'static ThisModule,
+    coredump: T,
+    gfp: alloc::Flags,
+    timeout: Jiffies,
+) {
+    // SAFETY: Call upholds dev_coredumpm lifetime requirements.
+    unsafe {
+        bindings::dev_coredumpm_timeout(
+            dev.as_raw(),
+            module.0,
+            coredump.into_foreign() as *mut _,
+            0,
+            gfp.as_raw(),
+            Some(read_callback::<'a, T, D>),
+            Some(free_callback::<'a, T, D>),
+            timeout,
+        )
+    }
+}

rust/kernel/lib.rs

@@ -50,6 +50,7 @@ pub mod block;
 pub mod build_assert;
 pub mod cred;
 pub mod delay;
+pub mod devcoredump;
 pub mod device;
 pub mod device_id;
 pub mod devres;