Commit fc2f191f authored by Alice Ryhl's avatar Alice Ryhl Committed by Miguel Ojeda
Browse files

panic_qr: use new #[export] macro 



This validates at compile time that the signatures match what is in the
header file. It highlights one annoyance with the compile-time check,
which is that it can only be used with functions marked unsafe.

If the function is not unsafe, then this error is emitted:

error[E0308]: `if` and `else` have incompatible types
   --> <linux>/drivers/gpu/drm/drm_panic_qr.rs:987:19
    |
986 | #[export]
    | --------- expected because of this
987 | pub extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^ expected unsafe fn, found safe fn
    |
    = note: expected fn item `unsafe extern "C" fn(_, _) -> _ {kernel::bindings::drm_panic_qr_max_data_size}`
               found fn item `extern "C" fn(_, _) -> _ {drm_panic_qr_max_data_size}`

The signature declarations are moved to a header file so it can be
included in the Rust bindings helper, and the extern keyword is removed
as it is unnecessary.

Reviewed-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: default avatarTamir Duberstein <tamird@gmail.com>
Acked-by: default avatarSimona Vetter <simona.vetter@ffwll.ch>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarJocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250303-export-macro-v3-5-41fbad85a27f@google.com


[ Fixed `rustfmt`. Moved on top the unsafe requirement comment to follow
  the usual style, and slightly reworded it for clarity. Formatted
  bindings helper comment. - Miguel ]
Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 92d2873b

drivers/gpu/drm/drm_panic.c

+0 −5
Original line number Diff line number Diff line
@@ -486,11 +486,6 @@ static void drm_panic_qr_exit(void) 
	stream.workspace = NULL;

}



extern size_t drm_panic_qr_max_data_size(u8 version, size_t url_len);



extern u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size,

				u8 *tmp, size_t tmp_size);



static int drm_panic_get_qr_code_url(u8 **qr_image)

{

	struct kmsg_dump_iter iter;

drivers/gpu/drm/drm_panic_qr.rs

+9 −4
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ 
//! * <https://github.com/bjguillot/qr>



use core::cmp;

use kernel::str::CStr;

use kernel::{prelude::*, str::CStr};



#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd)]

struct Version(usize);
@@ -929,7 +929,7 @@ fn draw_all(&mut self, data: impl Iterator<Item = u8>) { 
/// * `tmp` must be valid for reading and writing for `tmp_size` bytes.

///

/// They must remain valid for the duration of the function call.

#[no_mangle]

#[export]

pub unsafe extern "C" fn drm_panic_qr_generate(

    url: *const kernel::ffi::c_char,

    data: *mut u8,
@@ -980,8 +980,13 @@ fn draw_all(&mut self, data: impl Iterator<Item = u8>) { 
/// * If `url_len` > 0, remove the 2 segments header/length and also count the

///   conversion to numeric segments.

/// * If `url_len` = 0, only removes 3 bytes for 1 binary segment.

#[no_mangle]

pub extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {

///

/// # Safety

///

/// Always safe to call.

// Required to be unsafe due to the `#[export]` annotation.

#[export]

pub unsafe extern "C" fn drm_panic_qr_max_data_size(version: u8, url_len: usize) -> usize {

    #[expect(clippy::manual_range_contains)]

    if version < 1 || version > 40 {

        return 0;

include/drm/drm_panic.h

+7 −0
Original line number Diff line number Diff line
@@ -163,4 +163,11 @@ static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) 


#endif



#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)

size_t drm_panic_qr_max_data_size(u8 version, size_t url_len);



u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size,

			 u8 *tmp, size_t tmp_size);

#endif



#endif /* __DRM_PANIC_H__ */

rust/bindings/bindings_helper.h

+5 −0
Original line number Diff line number Diff line
@@ -37,6 +37,11 @@ 
#include <linux/workqueue.h>

#include <trace/events/rust_sample.h>



#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)

// Used by `#[export]` in `drivers/gpu/drm/drm_panic_qr.rs`.

#include <drm/drm_panic.h>

#endif



/* `bindgen` gets confused at certain things. */

const size_t RUST_CONST_HELPER_ARCH_SLAB_MINALIGN = ARCH_SLAB_MINALIGN;

const size_t RUST_CONST_HELPER_PAGE_SIZE = PAGE_SIZE;