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, 120 insertions, 0 deletions

diff --git a/include/video/pxa168fb.h b/include/video/pxa168fb.h
new file mode 100644
index 000000000..6e278248d
--- /dev/null
+++ b/include/video/pxa168fb.h
@@ -0,0 +1,120 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  Copyright (C) 2009 Marvell International Ltd.
+ */
+
+#ifndef __ASM_MACH_PXA168FB_H
+#define __ASM_MACH_PXA168FB_H
+
+#include <linux/fb.h>
+#include <linux/interrupt.h>
+
+/* Dumb interface */
+#define PIN_MODE_DUMB_24		0
+#define PIN_MODE_DUMB_18_SPI		1
+#define PIN_MODE_DUMB_18_GPIO		2
+#define PIN_MODE_DUMB_16_SPI		3
+#define PIN_MODE_DUMB_16_GPIO		4
+#define PIN_MODE_DUMB_12_SPI_GPIO	5
+#define PIN_MODE_SMART_18_SPI		6
+#define PIN_MODE_SMART_16_SPI		7
+#define PIN_MODE_SMART_8_SPI_GPIO	8
+
+/* Dumb interface pin allocation */
+#define DUMB_MODE_RGB565		0
+#define DUMB_MODE_RGB565_UPPER		1
+#define DUMB_MODE_RGB666		2
+#define DUMB_MODE_RGB666_UPPER		3
+#define DUMB_MODE_RGB444		4
+#define DUMB_MODE_RGB444_UPPER		5
+#define DUMB_MODE_RGB888		6
+
+/* default fb buffer size WVGA-32bits */
+#define DEFAULT_FB_SIZE	(800 * 480 * 4)
+
+/*
+ * Buffer pixel format
+ * bit0 is for rb swap.
+ * bit12 is for Y UorV swap
+ */
+#define PIX_FMT_RGB565		0
+#define PIX_FMT_BGR565		1
+#define PIX_FMT_RGB1555		2
+#define PIX_FMT_BGR1555		3
+#define PIX_FMT_RGB888PACK	4
+#define PIX_FMT_BGR888PACK	5
+#define PIX_FMT_RGB888UNPACK	6
+#define PIX_FMT_BGR888UNPACK	7
+#define PIX_FMT_RGBA888		8
+#define PIX_FMT_BGRA888		9
+#define PIX_FMT_YUV422PACK	10
+#define PIX_FMT_YVU422PACK	11
+#define PIX_FMT_YUV422PLANAR	12
+#define PIX_FMT_YVU422PLANAR	13
+#define PIX_FMT_YUV420PLANAR	14
+#define PIX_FMT_YVU420PLANAR	15
+#define PIX_FMT_PSEUDOCOLOR	20
+#define PIX_FMT_UYVY422PACK	(0x1000|PIX_FMT_YUV422PACK)
+
+/*
+ * PXA LCD controller private state.
+ */
+struct pxa168fb_info {
+	struct device		*dev;
+	struct clk		*clk;
+	struct fb_info		*info;
+
+	void __iomem		*reg_base;
+	dma_addr_t		fb_start_dma;
+	u32			pseudo_palette[16];
+
+	int			pix_fmt;
+	unsigned		is_blanked:1;
+	unsigned		panel_rbswap:1;
+	unsigned		active:1;
+};
+
+/*
+ * PXA fb machine information
+ */
+struct pxa168fb_mach_info {
+	char	id[16];
+
+	int		num_modes;
+	struct fb_videomode *modes;
+
+	/*
+	 * Pix_fmt
+	 */
+	unsigned	pix_fmt;
+
+	/*
+	 * I/O pin allocation.
+	 */
+	unsigned	io_pin_allocation_mode:4;
+
+	/*
+	 * Dumb panel -- assignment of R/G/B component info to the 24
+	 * available external data lanes.
+	 */
+	unsigned	dumb_mode:4;
+	unsigned	panel_rgb_reverse_lanes:1;
+
+	/*
+	 * Dumb panel -- GPIO output data.
+	 */
+	unsigned	gpio_output_mask:8;
+	unsigned	gpio_output_data:8;
+
+	/*
+	 * Dumb panel -- configurable output signal polarity.
+	 */
+	unsigned	invert_composite_blank:1;
+	unsigned	invert_pix_val_ena:1;
+	unsigned	invert_pixclock:1;
+	unsigned	panel_rbswap:1;
+	unsigned	active:1;
+	unsigned	enable_lcd:1;
+};
+
+#endif /* __ASM_MACH_PXA168FB_H */