kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 274 insertions, 0 deletions

diff --git a/include/drm/drm_rect.h b/include/drm/drm_rect.h
new file mode 100644
index 000000000..46f09cf68
--- /dev/null
+++ b/include/drm/drm_rect.h
@@ -0,0 +1,274 @@
+/*
+ * Copyright (C) 2011-2013 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef DRM_RECT_H
+#define DRM_RECT_H
+
+#include <linux/types.h>
+
+/**
+ * DOC: rect utils
+ *
+ * Utility functions to help manage rectangular areas for
+ * clipping, scaling, etc. calculations.
+ */
+
+/**
+ * struct drm_rect - two dimensional rectangle
+ * @x1: horizontal starting coordinate (inclusive)
+ * @x2: horizontal ending coordinate (exclusive)
+ * @y1: vertical starting coordinate (inclusive)
+ * @y2: vertical ending coordinate (exclusive)
+ *
+ * Note that this must match the layout of struct drm_mode_rect or the damage
+ * helpers like drm_atomic_helper_damage_iter_init() break.
+ */
+struct drm_rect {
+	int x1, y1, x2, y2;
+};
+
+/**
+ * DRM_RECT_INIT - initialize a rectangle from x/y/w/h
+ * @x: x coordinate
+ * @y: y coordinate
+ * @w: width
+ * @h: height
+ *
+ * RETURNS:
+ * A new rectangle of the specified size.
+ */
+#define DRM_RECT_INIT(x, y, w, h) ((struct drm_rect){ \
+		.x1 = (x), \
+		.y1 = (y), \
+		.x2 = (x) + (w), \
+		.y2 = (y) + (h) })
+
+/**
+ * DRM_RECT_FMT - printf string for &struct drm_rect
+ */
+#define DRM_RECT_FMT    "%dx%d%+d%+d"
+/**
+ * DRM_RECT_ARG - printf arguments for &struct drm_rect
+ * @r: rectangle struct
+ */
+#define DRM_RECT_ARG(r) drm_rect_width(r), drm_rect_height(r), (r)->x1, (r)->y1
+
+/**
+ * DRM_RECT_FP_FMT - printf string for &struct drm_rect in 16.16 fixed point
+ */
+#define DRM_RECT_FP_FMT "%d.%06ux%d.%06u%+d.%06u%+d.%06u"
+/**
+ * DRM_RECT_FP_ARG - printf arguments for &struct drm_rect in 16.16 fixed point
+ * @r: rectangle struct
+ *
+ * This is useful for e.g. printing plane source rectangles, which are in 16.16
+ * fixed point.
+ */
+#define DRM_RECT_FP_ARG(r) \
+		drm_rect_width(r) >> 16, ((drm_rect_width(r) & 0xffff) * 15625) >> 10, \
+		drm_rect_height(r) >> 16, ((drm_rect_height(r) & 0xffff) * 15625) >> 10, \
+		(r)->x1 >> 16, (((r)->x1 & 0xffff) * 15625) >> 10, \
+		(r)->y1 >> 16, (((r)->y1 & 0xffff) * 15625) >> 10
+
+/**
+ * drm_rect_init - initialize the rectangle from x/y/w/h
+ * @r: rectangle
+ * @x: x coordinate
+ * @y: y coordinate
+ * @width: width
+ * @height: height
+ */
+static inline void drm_rect_init(struct drm_rect *r, int x, int y,
+				 int width, int height)
+{
+	r->x1 = x;
+	r->y1 = y;
+	r->x2 = x + width;
+	r->y2 = y + height;
+}
+
+/**
+ * drm_rect_adjust_size - adjust the size of the rectangle
+ * @r: rectangle to be adjusted
+ * @dw: horizontal adjustment
+ * @dh: vertical adjustment
+ *
+ * Change the size of rectangle @r by @dw in the horizontal direction,
+ * and by @dh in the vertical direction, while keeping the center
+ * of @r stationary.
+ *
+ * Positive @dw and @dh increase the size, negative values decrease it.
+ */
+static inline void drm_rect_adjust_size(struct drm_rect *r, int dw, int dh)
+{
+	r->x1 -= dw >> 1;
+	r->y1 -= dh >> 1;
+	r->x2 += (dw + 1) >> 1;
+	r->y2 += (dh + 1) >> 1;
+}
+
+/**
+ * drm_rect_translate - translate the rectangle
+ * @r: rectangle to be translated
+ * @dx: horizontal translation
+ * @dy: vertical translation
+ *
+ * Move rectangle @r by @dx in the horizontal direction,
+ * and by @dy in the vertical direction.
+ */
+static inline void drm_rect_translate(struct drm_rect *r, int dx, int dy)
+{
+	r->x1 += dx;
+	r->y1 += dy;
+	r->x2 += dx;
+	r->y2 += dy;
+}
+
+/**
+ * drm_rect_translate_to - translate the rectangle to an absolute position
+ * @r: rectangle to be translated
+ * @x: horizontal position
+ * @y: vertical position
+ *
+ * Move rectangle @r to @x in the horizontal direction,
+ * and to @y in the vertical direction.
+ */
+static inline void drm_rect_translate_to(struct drm_rect *r, int x, int y)
+{
+	drm_rect_translate(r, x - r->x1, y - r->y1);
+}
+
+/**
+ * drm_rect_downscale - downscale a rectangle
+ * @r: rectangle to be downscaled
+ * @horz: horizontal downscale factor
+ * @vert: vertical downscale factor
+ *
+ * Divide the coordinates of rectangle @r by @horz and @vert.
+ */
+static inline void drm_rect_downscale(struct drm_rect *r, int horz, int vert)
+{
+	r->x1 /= horz;
+	r->y1 /= vert;
+	r->x2 /= horz;
+	r->y2 /= vert;
+}
+
+/**
+ * drm_rect_width - determine the rectangle width
+ * @r: rectangle whose width is returned
+ *
+ * RETURNS:
+ * The width of the rectangle.
+ */
+static inline int drm_rect_width(const struct drm_rect *r)
+{
+	return r->x2 - r->x1;
+}
+
+/**
+ * drm_rect_height - determine the rectangle height
+ * @r: rectangle whose height is returned
+ *
+ * RETURNS:
+ * The height of the rectangle.
+ */
+static inline int drm_rect_height(const struct drm_rect *r)
+{
+	return r->y2 - r->y1;
+}
+
+/**
+ * drm_rect_visible - determine if the rectangle is visible
+ * @r: rectangle whose visibility is returned
+ *
+ * RETURNS:
+ * %true if the rectangle is visible, %false otherwise.
+ */
+static inline bool drm_rect_visible(const struct drm_rect *r)
+{
+	return drm_rect_width(r) > 0 && drm_rect_height(r) > 0;
+}
+
+/**
+ * drm_rect_equals - determine if two rectangles are equal
+ * @r1: first rectangle
+ * @r2: second rectangle
+ *
+ * RETURNS:
+ * %true if the rectangles are equal, %false otherwise.
+ */
+static inline bool drm_rect_equals(const struct drm_rect *r1,
+				   const struct drm_rect *r2)
+{
+	return r1->x1 == r2->x1 && r1->x2 == r2->x2 &&
+		r1->y1 == r2->y1 && r1->y2 == r2->y2;
+}
+
+/**
+ * drm_rect_fp_to_int - Convert a rect in 16.16 fixed point form to int form.
+ * @dst: rect to be stored the converted value
+ * @src: rect in 16.16 fixed point form
+ */
+static inline void drm_rect_fp_to_int(struct drm_rect *dst,
+				      const struct drm_rect *src)
+{
+	drm_rect_init(dst, src->x1 >> 16, src->y1 >> 16,
+		      drm_rect_width(src) >> 16,
+		      drm_rect_height(src) >> 16);
+}
+
+/**
+ * drm_rect_overlap - Check if two rectangles overlap
+ * @a: first rectangle
+ * @b: second rectangle
+ *
+ * RETURNS:
+ * %true if the rectangles overlap, %false otherwise.
+ */
+static inline bool drm_rect_overlap(const struct drm_rect *a,
+				    const struct drm_rect *b)
+{
+	return (a->x2 > b->x1 && b->x2 > a->x1 &&
+		a->y2 > b->y1 && b->y2 > a->y1);
+}
+
+bool drm_rect_intersect(struct drm_rect *r, const struct drm_rect *clip);
+bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
+			  const struct drm_rect *clip);
+int drm_rect_calc_hscale(const struct drm_rect *src,
+			 const struct drm_rect *dst,
+			 int min_hscale, int max_hscale);
+int drm_rect_calc_vscale(const struct drm_rect *src,
+			 const struct drm_rect *dst,
+			 int min_vscale, int max_vscale);
+void drm_rect_debug_print(const char *prefix,
+			  const struct drm_rect *r, bool fixed_point);
+void drm_rect_rotate(struct drm_rect *r,
+		     int width, int height,
+		     unsigned int rotation);
+void drm_rect_rotate_inv(struct drm_rect *r,
+			 int width, int height,
+			 unsigned int rotation);
+
+#endif