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, 488 insertions, 0 deletions

diff --git a/include/video/vga.h b/include/video/vga.h
new file mode 100644
index 000000000..2f13c3718
--- /dev/null
+++ b/include/video/vga.h
@@ -0,0 +1,488 @@
+/*
+ * linux/include/video/vga.h -- standard VGA chipset interaction
+ *
+ * Copyright 1999 Jeff Garzik <jgarzik@pobox.com>
+ *
+ * Copyright history from vga16fb.c:
+ *	Copyright 1999 Ben Pfaff and Petr Vandrovec
+ *	Based on VGA info at http://www.osdever.net/FreeVGA/home.htm
+ *	Based on VESA framebuffer (c) 1998 Gerd Knorr
+ *
+ * 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 __linux_video_vga_h__
+#define __linux_video_vga_h__
+
+#include <linux/types.h>
+#include <linux/io.h>
+#include <asm/vga.h>
+#include <asm/byteorder.h>
+
+#define VGA_FB_PHYS_BASE	0xA0000 /* VGA framebuffer I/O base */
+#define VGA_FB_PHYS_SIZE	65536	/* VGA framebuffer I/O size */
+
+/* Some of the code below is taken from SVGAlib.  The original,
+   unmodified copyright notice for that code is below. */
+/* VGAlib version 1.2 - (c) 1993 Tommy Frandsen                    */
+/*                                                                 */
+/* This library is free software; you can redistribute it and/or   */
+/* modify it without any restrictions. This library is distributed */
+/* in the hope that it will be useful, but without any warranty.   */
+
+/* Multi-chipset support Copyright 1993 Harm Hanemaayer */
+/* partially copyrighted (C) 1993 by Hartmut Schirmer */
+
+/* VGA data register ports */
+#define VGA_CRT_DC  	0x3D5	/* CRT Controller Data Register - color emulation */
+#define VGA_CRT_DM  	0x3B5	/* CRT Controller Data Register - mono emulation */
+#define VGA_ATT_R   	0x3C1	/* Attribute Controller Data Read Register */
+#define VGA_ATT_W   	0x3C0	/* Attribute Controller Data Write Register */
+#define VGA_GFX_D   	0x3CF	/* Graphics Controller Data Register */
+#define VGA_SEQ_D   	0x3C5	/* Sequencer Data Register */
+#define VGA_MIS_R   	0x3CC	/* Misc Output Read Register */
+#define VGA_MIS_W   	0x3C2	/* Misc Output Write Register */
+#define VGA_FTC_R	0x3CA	/* Feature Control Read Register */
+#define VGA_IS0_R	0x3C2	/* Input Status Register 0 */
+#define VGA_IS1_RC  	0x3DA	/* Input Status Register 1 - color emulation */
+#define VGA_IS1_RM  	0x3BA	/* Input Status Register 1 - mono emulation */
+#define VGA_PEL_D   	0x3C9	/* PEL Data Register */
+#define VGA_PEL_MSK 	0x3C6	/* PEL mask register */
+
+/* EGA-specific registers */
+#define EGA_GFX_E0	0x3CC	/* Graphics enable processor 0 */
+#define EGA_GFX_E1	0x3CA	/* Graphics enable processor 1 */
+
+/* VGA index register ports */
+#define VGA_CRT_IC  	0x3D4	/* CRT Controller Index - color emulation */
+#define VGA_CRT_IM  	0x3B4	/* CRT Controller Index - mono emulation */
+#define VGA_ATT_IW  	0x3C0	/* Attribute Controller Index & Data Write Register */
+#define VGA_GFX_I   	0x3CE	/* Graphics Controller Index */
+#define VGA_SEQ_I   	0x3C4	/* Sequencer Index */
+#define VGA_PEL_IW  	0x3C8	/* PEL Write Index */
+#define VGA_PEL_IR  	0x3C7	/* PEL Read Index */
+
+/* standard VGA indexes max counts */
+#define VGA_CRT_C   	0x19	/* Number of CRT Controller Registers */
+#define VGA_ATT_C   	0x15	/* Number of Attribute Controller Registers */
+#define VGA_GFX_C   	0x09	/* Number of Graphics Controller Registers */
+#define VGA_SEQ_C   	0x05	/* Number of Sequencer Registers */
+#define VGA_MIS_C   	0x01	/* Number of Misc Output Register */
+
+/* VGA misc register bit masks */
+#define VGA_MIS_COLOR		0x01
+#define VGA_MIS_ENB_MEM_ACCESS	0x02
+#define VGA_MIS_DCLK_28322_720	0x04
+#define VGA_MIS_ENB_PLL_LOAD	(0x04 | 0x08)
+#define VGA_MIS_SEL_HIGH_PAGE	0x20
+
+/* VGA CRT controller register indices */
+#define VGA_CRTC_H_TOTAL	0
+#define VGA_CRTC_H_DISP		1
+#define VGA_CRTC_H_BLANK_START	2
+#define VGA_CRTC_H_BLANK_END	3
+#define VGA_CRTC_H_SYNC_START	4
+#define VGA_CRTC_H_SYNC_END	5
+#define VGA_CRTC_V_TOTAL	6
+#define VGA_CRTC_OVERFLOW	7
+#define VGA_CRTC_PRESET_ROW	8
+#define VGA_CRTC_MAX_SCAN	9
+#define VGA_CRTC_CURSOR_START	0x0A
+#define VGA_CRTC_CURSOR_END	0x0B
+#define VGA_CRTC_START_HI	0x0C
+#define VGA_CRTC_START_LO	0x0D
+#define VGA_CRTC_CURSOR_HI	0x0E
+#define VGA_CRTC_CURSOR_LO	0x0F
+#define VGA_CRTC_V_SYNC_START	0x10
+#define VGA_CRTC_V_SYNC_END	0x11
+#define VGA_CRTC_V_DISP_END	0x12
+#define VGA_CRTC_OFFSET		0x13
+#define VGA_CRTC_UNDERLINE	0x14
+#define VGA_CRTC_V_BLANK_START	0x15
+#define VGA_CRTC_V_BLANK_END	0x16
+#define VGA_CRTC_MODE		0x17
+#define VGA_CRTC_LINE_COMPARE	0x18
+#define VGA_CRTC_REGS		VGA_CRT_C
+
+/* VGA CRT controller bit masks */
+#define VGA_CR11_LOCK_CR0_CR7	0x80 /* lock writes to CR0 - CR7 */
+#define VGA_CR17_H_V_SIGNALS_ENABLED 0x80
+
+/* VGA attribute controller register indices */
+#define VGA_ATC_PALETTE0	0x00
+#define VGA_ATC_PALETTE1	0x01
+#define VGA_ATC_PALETTE2	0x02
+#define VGA_ATC_PALETTE3	0x03
+#define VGA_ATC_PALETTE4	0x04
+#define VGA_ATC_PALETTE5	0x05
+#define VGA_ATC_PALETTE6	0x06
+#define VGA_ATC_PALETTE7	0x07
+#define VGA_ATC_PALETTE8	0x08
+#define VGA_ATC_PALETTE9	0x09
+#define VGA_ATC_PALETTEA	0x0A
+#define VGA_ATC_PALETTEB	0x0B
+#define VGA_ATC_PALETTEC	0x0C
+#define VGA_ATC_PALETTED	0x0D
+#define VGA_ATC_PALETTEE	0x0E
+#define VGA_ATC_PALETTEF	0x0F
+#define VGA_ATC_MODE		0x10
+#define VGA_ATC_OVERSCAN	0x11
+#define VGA_ATC_PLANE_ENABLE	0x12
+#define VGA_ATC_PEL		0x13
+#define VGA_ATC_COLOR_PAGE	0x14
+
+#define VGA_AR_ENABLE_DISPLAY	0x20
+
+/* VGA sequencer register indices */
+#define VGA_SEQ_RESET		0x00
+#define VGA_SEQ_CLOCK_MODE	0x01
+#define VGA_SEQ_PLANE_WRITE	0x02
+#define VGA_SEQ_CHARACTER_MAP	0x03
+#define VGA_SEQ_MEMORY_MODE	0x04
+
+/* VGA sequencer register bit masks */
+#define VGA_SR01_CHAR_CLK_8DOTS	0x01 /* bit 0: character clocks 8 dots wide are generated */
+#define VGA_SR01_SCREEN_OFF	0x20 /* bit 5: Screen is off */
+#define VGA_SR02_ALL_PLANES	0x0F /* bits 3-0: enable access to all planes */
+#define VGA_SR04_EXT_MEM	0x02 /* bit 1: allows complete mem access to 256K */
+#define VGA_SR04_SEQ_MODE	0x04 /* bit 2: directs system to use a sequential addressing mode */
+#define VGA_SR04_CHN_4M		0x08 /* bit 3: selects modulo 4 addressing for CPU access to display memory */
+
+/* VGA graphics controller register indices */
+#define VGA_GFX_SR_VALUE	0x00
+#define VGA_GFX_SR_ENABLE	0x01
+#define VGA_GFX_COMPARE_VALUE	0x02
+#define VGA_GFX_DATA_ROTATE	0x03
+#define VGA_GFX_PLANE_READ	0x04
+#define VGA_GFX_MODE		0x05
+#define VGA_GFX_MISC		0x06
+#define VGA_GFX_COMPARE_MASK	0x07
+#define VGA_GFX_BIT_MASK	0x08
+
+/* VGA graphics controller bit masks */
+#define VGA_GR06_GRAPHICS_MODE	0x01
+
+/* macro for composing an 8-bit VGA register index and value
+ * into a single 16-bit quantity */
+#define VGA_OUT16VAL(v, r)       (((v) << 8) | (r))
+
+/* decide whether we should enable the faster 16-bit VGA register writes */
+#ifdef __LITTLE_ENDIAN
+#define VGA_OUTW_WRITE
+#endif
+
+/* VGA State Save and Restore */
+#define VGA_SAVE_FONT0 1  /* save/restore plane 2 fonts	  */
+#define VGA_SAVE_FONT1 2  /* save/restore plane 3 fonts   */
+#define VGA_SAVE_TEXT  4  /* save/restore plane 0/1 fonts */
+#define VGA_SAVE_FONTS 7  /* save/restore all fonts	  */
+#define VGA_SAVE_MODE  8  /* save/restore video mode 	  */
+#define VGA_SAVE_CMAP  16 /* save/restore color map/DAC   */
+
+struct vgastate {
+	void __iomem *vgabase;	/* mmio base, if supported 		   */
+	unsigned long membase;	/* VGA window base, 0 for default - 0xA000 */
+	__u32 memsize;		/* VGA window size, 0 for default 64K	   */
+	__u32 flags;		/* what state[s] to save (see VGA_SAVE_*)  */
+	__u32 depth;		/* current fb depth, not important	   */
+	__u32 num_attr;		/* number of att registers, 0 for default  */
+	__u32 num_crtc;		/* number of crt registers, 0 for default  */
+	__u32 num_gfx;		/* number of gfx registers, 0 for default  */
+	__u32 num_seq;		/* number of seq registers, 0 for default  */
+	void *vidstate;
+};
+
+extern int save_vga(struct vgastate *state);
+extern int restore_vga(struct vgastate *state);
+
+static inline unsigned char vga_mm_r (void __iomem *regbase, unsigned short port)
+{
+	return readb (regbase + port);
+}
+
+static inline void vga_mm_w (void __iomem *regbase, unsigned short port, unsigned char val)
+{
+	writeb (val, regbase + port);
+}
+
+static inline void vga_mm_w_fast (void __iomem *regbase, unsigned short port,
+				  unsigned char reg, unsigned char val)
+{
+	writew (VGA_OUT16VAL (val, reg), regbase + port);
+}
+
+/*
+ * generic VGA port read/write
+ */
+#ifdef CONFIG_HAS_IOPORT
+
+static inline unsigned char vga_io_r (unsigned short port)
+{
+	return inb_p(port);
+}
+
+static inline void vga_io_w (unsigned short port, unsigned char val)
+{
+	outb_p(val, port);
+}
+
+static inline void vga_io_w_fast (unsigned short port, unsigned char reg,
+				  unsigned char val)
+{
+	outw(VGA_OUT16VAL (val, reg), port);
+}
+
+static inline unsigned char vga_r (void __iomem *regbase, unsigned short port)
+{
+	if (regbase)
+		return vga_mm_r (regbase, port);
+	else
+		return vga_io_r (port);
+}
+
+static inline void vga_w (void __iomem *regbase, unsigned short port, unsigned char val)
+{
+	if (regbase)
+		vga_mm_w (regbase, port, val);
+	else
+		vga_io_w (port, val);
+}
+
+
+static inline void vga_w_fast (void __iomem *regbase, unsigned short port,
+			       unsigned char reg, unsigned char val)
+{
+	if (regbase)
+		vga_mm_w_fast (regbase, port, reg, val);
+	else
+		vga_io_w_fast (port, reg, val);
+}
+#else /* CONFIG_HAS_IOPORT */
+static inline unsigned char vga_r (void __iomem *regbase, unsigned short port)
+{
+	return vga_mm_r (regbase, port);
+}
+
+static inline void vga_w (void __iomem *regbase, unsigned short port, unsigned char val)
+{
+	vga_mm_w (regbase, port, val);
+}
+
+
+static inline void vga_w_fast (void __iomem *regbase, unsigned short port,
+			       unsigned char reg, unsigned char val)
+{
+	vga_mm_w_fast (regbase, port, reg, val);
+}
+#endif /* CONFIG_HAS_IOPORT */
+
+/*
+ * VGA CRTC register read/write
+ */
+
+static inline unsigned char vga_rcrt (void __iomem *regbase, unsigned char reg)
+{
+        vga_w (regbase, VGA_CRT_IC, reg);
+        return vga_r (regbase, VGA_CRT_DC);
+}
+
+static inline void vga_wcrt (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_w_fast (regbase, VGA_CRT_IC, reg, val);
+#else
+        vga_w (regbase, VGA_CRT_IC, reg);
+        vga_w (regbase, VGA_CRT_DC, val);
+#endif /* VGA_OUTW_WRITE */
+}
+
+#ifdef CONFIG_HAS_IOPORT
+static inline unsigned char vga_io_rcrt (unsigned char reg)
+{
+        vga_io_w (VGA_CRT_IC, reg);
+        return vga_io_r (VGA_CRT_DC);
+}
+
+static inline void vga_io_wcrt (unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_io_w_fast (VGA_CRT_IC, reg, val);
+#else
+        vga_io_w (VGA_CRT_IC, reg);
+        vga_io_w (VGA_CRT_DC, val);
+#endif /* VGA_OUTW_WRITE */
+}
+#endif /* CONFIG_HAS_IOPORT */
+
+static inline unsigned char vga_mm_rcrt (void __iomem *regbase, unsigned char reg)
+{
+        vga_mm_w (regbase, VGA_CRT_IC, reg);
+        return vga_mm_r (regbase, VGA_CRT_DC);
+}
+
+static inline void vga_mm_wcrt (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_mm_w_fast (regbase, VGA_CRT_IC, reg, val);
+#else
+        vga_mm_w (regbase, VGA_CRT_IC, reg);
+        vga_mm_w (regbase, VGA_CRT_DC, val);
+#endif /* VGA_OUTW_WRITE */
+}
+
+
+/*
+ * VGA sequencer register read/write
+ */
+
+static inline unsigned char vga_rseq (void __iomem *regbase, unsigned char reg)
+{
+        vga_w (regbase, VGA_SEQ_I, reg);
+        return vga_r (regbase, VGA_SEQ_D);
+}
+
+static inline void vga_wseq (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_w_fast (regbase, VGA_SEQ_I, reg, val);
+#else
+        vga_w (regbase, VGA_SEQ_I, reg);
+        vga_w (regbase, VGA_SEQ_D, val);
+#endif /* VGA_OUTW_WRITE */
+}
+
+#ifdef CONFIG_HAS_IOPORT
+static inline unsigned char vga_io_rseq (unsigned char reg)
+{
+        vga_io_w (VGA_SEQ_I, reg);
+        return vga_io_r (VGA_SEQ_D);
+}
+
+static inline void vga_io_wseq (unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_io_w_fast (VGA_SEQ_I, reg, val);
+#else
+        vga_io_w (VGA_SEQ_I, reg);
+        vga_io_w (VGA_SEQ_D, val);
+#endif /* VGA_OUTW_WRITE */
+}
+#endif /* CONFIG_HAS_IOPORT */
+
+static inline unsigned char vga_mm_rseq (void __iomem *regbase, unsigned char reg)
+{
+        vga_mm_w (regbase, VGA_SEQ_I, reg);
+        return vga_mm_r (regbase, VGA_SEQ_D);
+}
+
+static inline void vga_mm_wseq (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_mm_w_fast (regbase, VGA_SEQ_I, reg, val);
+#else
+        vga_mm_w (regbase, VGA_SEQ_I, reg);
+        vga_mm_w (regbase, VGA_SEQ_D, val);
+#endif /* VGA_OUTW_WRITE */
+}
+
+/*
+ * VGA graphics controller register read/write
+ */
+
+static inline unsigned char vga_rgfx (void __iomem *regbase, unsigned char reg)
+{
+        vga_w (regbase, VGA_GFX_I, reg);
+        return vga_r (regbase, VGA_GFX_D);
+}
+
+static inline void vga_wgfx (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_w_fast (regbase, VGA_GFX_I, reg, val);
+#else
+        vga_w (regbase, VGA_GFX_I, reg);
+        vga_w (regbase, VGA_GFX_D, val);
+#endif /* VGA_OUTW_WRITE */
+}
+
+#ifdef CONFIG_HAS_IOPORT
+static inline unsigned char vga_io_rgfx (unsigned char reg)
+{
+        vga_io_w (VGA_GFX_I, reg);
+        return vga_io_r (VGA_GFX_D);
+}
+
+static inline void vga_io_wgfx (unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_io_w_fast (VGA_GFX_I, reg, val);
+#else
+        vga_io_w (VGA_GFX_I, reg);
+        vga_io_w (VGA_GFX_D, val);
+#endif /* VGA_OUTW_WRITE */
+}
+#endif /* CONFIG_HAS_IOPORT */
+
+static inline unsigned char vga_mm_rgfx (void __iomem *regbase, unsigned char reg)
+{
+        vga_mm_w (regbase, VGA_GFX_I, reg);
+        return vga_mm_r (regbase, VGA_GFX_D);
+}
+
+static inline void vga_mm_wgfx (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+#ifdef VGA_OUTW_WRITE
+	vga_mm_w_fast (regbase, VGA_GFX_I, reg, val);
+#else
+        vga_mm_w (regbase, VGA_GFX_I, reg);
+        vga_mm_w (regbase, VGA_GFX_D, val);
+#endif /* VGA_OUTW_WRITE */
+}
+
+
+/*
+ * VGA attribute controller register read/write
+ */
+
+static inline unsigned char vga_rattr (void __iomem *regbase, unsigned char reg)
+{
+        vga_w (regbase, VGA_ATT_IW, reg);
+        return vga_r (regbase, VGA_ATT_R);
+}
+
+static inline void vga_wattr (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+        vga_w (regbase, VGA_ATT_IW, reg);
+        vga_w (regbase, VGA_ATT_W, val);
+}
+
+#ifdef CONFIG_HAS_IOPORT
+static inline unsigned char vga_io_rattr (unsigned char reg)
+{
+        vga_io_w (VGA_ATT_IW, reg);
+        return vga_io_r (VGA_ATT_R);
+}
+
+static inline void vga_io_wattr (unsigned char reg, unsigned char val)
+{
+        vga_io_w (VGA_ATT_IW, reg);
+        vga_io_w (VGA_ATT_W, val);
+}
+#endif /* CONFIG_HAS_IOPORT */
+
+static inline unsigned char vga_mm_rattr (void __iomem *regbase, unsigned char reg)
+{
+        vga_mm_w (regbase, VGA_ATT_IW, reg);
+        return vga_mm_r (regbase, VGA_ATT_R);
+}
+
+static inline void vga_mm_wattr (void __iomem *regbase, unsigned char reg, unsigned char val)
+{
+        vga_mm_w (regbase, VGA_ATT_IW, reg);
+        vga_mm_w (regbase, VGA_ATT_W, val);
+}
+
+#endif /* __linux_video_vga_h__ */