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, 79 insertions, 0 deletions

diff --git a/include/video/kyro.h b/include/video/kyro.h
new file mode 100644
index 000000000..418eef6c5
--- /dev/null
+++ b/include/video/kyro.h
@@ -0,0 +1,79 @@
+/*
+ *  linux/drivers/video/kyro/kryo.h
+ *
+ *  Copyright (C) 2002 STMicroelectronics
+ *  Copyright (C) 2004 Paul Mundt
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+ */
+
+#ifndef _KYRO_H
+#define _KYRO_H
+
+struct kyrofb_info {
+	void __iomem *regbase;
+
+	u32 palette[16];
+	u32 HTot;	/* Hor Total Time    */
+	u32 HFP;	/* Hor Front Porch   */
+	u32 HST;	/* Hor Sync Time     */
+	u32 HBP;	/* Hor Back Porch    */
+	s32 HSP;		/* Hor Sync Polarity */
+	u32 VTot;	/* Ver Total Time    */
+	u32 VFP;	/* Ver Front Porch   */
+	u32 VST;	/* Ver Sync Time     */
+	u32 VBP;	/* Ver Back Porch    */
+	s32 VSP;		/* Ver Sync Polarity */
+	u32 XRES;	/* X Resolution      */
+	u32 YRES;	/* Y Resolution      */
+	u32 VFREQ;	/* Ver Frequency     */
+	u32 PIXCLK;	/* Pixel Clock       */
+	u32 HCLK;	/* Hor Clock         */
+
+	/* Useful to hold depth here for Linux */
+	u8 PIXDEPTH;
+
+	int wc_cookie;
+};
+
+/*
+ * benedict.gaster@superh.com
+ * Added the follow IOCTLS for the creation of overlay services...
+ */
+#define KYRO_IOC_MAGIC 'k'
+
+#define KYRO_IOCTL_OVERLAY_CREATE       _IO(KYRO_IOC_MAGIC, 0)
+#define KYRO_IOCTL_OVERLAY_VIEWPORT_SET _IO(KYRO_IOC_MAGIC, 1)
+#define KYRO_IOCTL_SET_VIDEO_MODE       _IO(KYRO_IOC_MAGIC, 2)
+#define KYRO_IOCTL_UVSTRIDE             _IO(KYRO_IOC_MAGIC, 3)
+#define KYRO_IOCTL_OVERLAY_OFFSET       _IO(KYRO_IOC_MAGIC, 4)
+#define KYRO_IOCTL_STRIDE               _IO(KYRO_IOC_MAGIC, 5)
+
+/*
+ * The follow 3 structures are used to pass data from user space into the kernel
+ * for the creation of overlay surfaces and setting the video mode.
+ */
+typedef struct _OVERLAY_CREATE {
+	u32 ulWidth;
+	u32 ulHeight;
+	int bLinear;
+} overlay_create;
+
+typedef struct _OVERLAY_VIEWPORT_SET {
+	u32 xOrgin;
+	u32 yOrgin;
+	u32 xSize;
+	u32 ySize;
+} overlay_viewport_set;
+
+typedef struct _SET_VIDEO_MODE {
+	u32 ulWidth;
+	u32 ulHeight;
+	u32 ulScan;
+	u8 displayDepth;
+	int bLinear;
+} set_video_mode;
+
+#endif /* _KYRO_H */