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, 368 insertions, 0 deletions

diff --git a/drivers/video/fbdev/platinumfb.h b/drivers/video/fbdev/platinumfb.h
new file mode 100644
index 000000000..f6bd77caf
--- /dev/null
+++ b/drivers/video/fbdev/platinumfb.h
@@ -0,0 +1,368 @@
+/*
+ * linux/drivers/video/platinumfb-hw.c -- Frame buffer device for the
+ * Platinum on-board video in PowerMac 7200s (and some clones based
+ * on the same motherboard.)
+ *
+ *  Created 09 Feb 1998 by Jon Howell <jonh@cs.dartmouth.edu>
+ *
+ * Copyright (C) 1998 Jon Howell
+ *
+ *  based on drivers/macintosh/platinum.c: Console support
+ * 	for PowerMac "platinum" display adaptor.
+ *  Copyright (C) 1996 Paul Mackerras and Mark Abene.
+ *
+ *  based on skeletonfb.c:
+ *  Created 28 Dec 1997 by Geert Uytterhoeven
+ *
+ * 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.
+ */
+
+/*
+ * Structure of the registers for the DACula colormap device.
+ */
+struct cmap_regs {
+	unsigned char addr;
+	char pad1[15];
+	unsigned char d1;
+	char pad2[15];
+	unsigned char d2;
+	char pad3[15];
+	unsigned char lut;
+	char pad4[15];
+};
+
+/*
+ * Structure of the registers for the "platinum" display adaptor".
+ */
+struct preg {			/* padded register */
+	unsigned r;			/* notice this is 32 bits. */
+	char pad[12];
+};
+
+struct platinum_regs {
+	struct preg reg[128];
+};
+
+/*
+ * Register initialization tables for the platinum display.
+ *
+ * It seems that there are two different types of platinum display
+ * out there.  Older ones use the values in clocksel[1], for which
+ * the formula for the clock frequency seems to be
+ *	F = 14.3MHz * c0 / (c1 & 0x1f) / (1 << (c1 >> 5))
+ * Newer ones use the values in clocksel[0], for which the formula
+ * seems to be
+ *	F = 15MHz * c0 / ((c1 & 0x1f) + 2) / (1 << (c1 >> 5))
+ */
+struct platinum_regvals {
+	int	fb_offset;
+	int	pitch[3];
+	unsigned regs[26];
+	unsigned char offset[3];
+	unsigned char mode[3];
+	unsigned char dacula_ctrl[3];
+	unsigned char clock_params[2][2];
+};
+
+#define DIV2	0x20
+#define DIV4	0x40
+#define DIV8	0x60
+#define DIV16	0x80
+
+/* 1280x1024, 75Hz (20) */
+static struct platinum_regvals platinum_reg_init_20 = {
+	0x5c00,
+	{ 1312, 2592, 2592 },
+	{ 0xffc, 4, 0, 0, 0, 0, 0x428, 0,
+	  0, 0xb3, 0xd3, 0x12, 0x1a5, 0x23, 0x28, 0x2d,
+	  0x5e, 0x19e, 0x1a4, 0x854, 0x852, 4, 9, 0x50,
+	  0x850, 0x851 }, { 0x58, 0x5d, 0x5d },
+	{ 0, 0xff, 0xff }, { 0x51, 0x55, 0x55 },
+	{{ 45, 3 }, { 66, 7 }}
+};
+
+/* 1280x960, 75Hz (19) */
+static struct platinum_regvals platinum_reg_init_19 = {
+	0x5c00,
+	{ 1312, 2592, 2592 },
+	{ 0xffc, 4, 0, 0, 0, 0, 0x428, 0,
+	  0, 0xb2, 0xd2, 0x12, 0x1a3, 0x23, 0x28, 0x2d,
+	  0x5c, 0x19c, 0x1a2, 0x7d0, 0x7ce, 4, 9, 0x4c,
+	  0x7cc, 0x7cd }, { 0x56, 0x5b, 0x5b },
+	{ 0, 0xff, 0xff }, { 0x51, 0x55, 0x55 },
+	{{ 42, 3 }, { 44, 5 }}
+};
+
+/* 1152x870, 75Hz (18) */
+static struct platinum_regvals platinum_reg_init_18 = {
+	0x11b0,
+	{ 1184, 2336, 4640 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x38f, 0,
+	  0, 0x294, 0x16c, 0x20, 0x2d7, 0x3f, 0x49, 0x53,
+	  0x82, 0x2c2, 0x2d6, 0x726, 0x724, 4, 9, 0x52,
+	  0x71e, 0x722 }, { 0x74, 0x7c, 0x81 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 26, 0 + DIV2 }, { 42, 6 }}
+};
+
+/* 1024x768, 75Hz (17) */
+static struct platinum_regvals platinum_reg_init_17 = {
+	0x10b0,
+	{ 1056, 2080, 4128 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x254, 0x14b, 0x18, 0x295, 0x2f, 0x32, 0x3b,
+	  0x80, 0x280, 0x296, 0x648, 0x646, 4, 9, 0x40,
+	  0x640, 0x644 }, { 0x72, 0x7a, 0x7f },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 54, 3 + DIV2 }, { 67, 12 }}
+};
+
+/* 1024x768, 75Hz (16) */
+static struct platinum_regvals platinum_reg_init_16 = {
+	0x10b0,
+	{ 1056, 2080, 4128 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x250, 0x147, 0x17, 0x28f, 0x2f, 0x35, 0x47,
+	  0x82, 0x282, 0x28e, 0x640, 0x63e, 4, 9, 0x3c,
+	  0x63c, 0x63d }, { 0x74, 0x7c, 0x81 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 20, 0 + DIV2 }, { 11, 2 }}
+};
+
+/* 1024x768, 70Hz (15) */
+static struct platinum_regvals platinum_reg_init_15 = {
+	0x10b0,
+	{ 1056, 2080, 4128 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x254, 0x14b, 0x22, 0x297, 0x43, 0x49, 0x5b,
+	  0x86, 0x286, 0x296, 0x64c, 0x64a, 0xa, 0xf, 0x44,
+	  0x644, 0x646 }, { 0x78, 0x80, 0x85 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 19, 0 + DIV2 }, { 110, 21 }}
+};
+
+/* 1024x768, 60Hz (14) */
+static struct platinum_regvals platinum_reg_init_14 = {
+	0x10b0,
+	{ 1056, 2080, 4128 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x25a, 0x14f, 0x22, 0x29f, 0x43, 0x49, 0x5b,
+	  0x8e, 0x28e, 0x29e, 0x64c, 0x64a, 0xa, 0xf, 0x44,
+	  0x644, 0x646 }, { 0x80, 0x88, 0x8d },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 71, 6 + DIV2 }, { 118, 13 + DIV2 }}
+};
+
+/* 832x624, 75Hz (13) */
+static struct platinum_regvals platinum_reg_init_13 = {
+	0x70,
+	{ 864, 1680, 3344 },	/* MacOS does 1680 instead of 1696 to fit 16bpp in 1MB,
+				 * and we use 3344 instead of 3360 to fit in 2Mb
+				 */
+	{ 0xff0, 4, 0, 0, 0, 0, 0x299, 0,
+	  0, 0x21e, 0x120, 0x10, 0x23f, 0x1f, 0x25, 0x37,
+	  0x8a, 0x22a, 0x23e, 0x536, 0x534, 4, 9, 0x52,
+	  0x532, 0x533 }, { 0x7c, 0x84, 0x89 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 30, 0 + DIV4 }, { 56, 7 + DIV2 }}
+};
+
+/* 800x600, 75Hz (12) */
+static struct platinum_regvals platinum_reg_init_12 = {
+	0x1010,
+	{ 832, 1632, 3232 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x1ce, 0x108, 0x14, 0x20f, 0x27, 0x30, 0x39,
+	  0x72, 0x202, 0x20e, 0x4e2, 0x4e0, 4, 9, 0x2e,
+	  0x4de, 0x4df }, { 0x64, 0x6c, 0x71 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 122, 7 + DIV4 }, { 62, 9 + DIV2 }}
+};
+
+/* 800x600, 72Hz (11) */
+static struct platinum_regvals platinum_reg_init_11 = {
+	0x1010,
+	{ 832, 1632, 3232 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x1ca, 0x104, 0x1e, 0x207, 0x3b, 0x44, 0x4d,
+	  0x56, 0x1e6, 0x206, 0x534, 0x532, 0xa, 0xe, 0x38,
+	  0x4e8, 0x4ec }, { 0x48, 0x50, 0x55 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 26, 0 + DIV4 }, { 42, 6 + DIV2 }}
+};
+
+/* 800x600, 60Hz (10) */
+static struct platinum_regvals platinum_reg_init_10 = {
+	0x1010,
+	{ 832, 1632, 3232 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x1ce, 0x108, 0x20, 0x20f, 0x3f, 0x45, 0x5d,
+	  0x66, 0x1f6, 0x20e, 0x4e8, 0x4e6, 6, 0xa, 0x34,
+	  0x4e4, 0x4e5 }, { 0x58, 0x60, 0x65 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 54, 3 + DIV4 }, { 95, 1 + DIV8 }}
+};
+
+/* 800x600, 56Hz (9) --unsupported? copy of mode 10 for now... */
+static struct platinum_regvals platinum_reg_init_9 = {
+	0x1010,
+	{ 832, 1632, 3232 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x1ce, 0x108, 0x20, 0x20f, 0x3f, 0x45, 0x5d,
+	  0x66, 0x1f6, 0x20e, 0x4e8, 0x4e6, 6, 0xa, 0x34,
+	  0x4e4, 0x4e5 }, { 0x58, 0x60, 0x65 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 54, 3 + DIV4 }, { 88, 1 + DIV8 }}
+};
+
+/* 768x576, 50Hz Interlaced-PAL (8) */
+static struct platinum_regvals platinum_reg_init_8 = {
+	0x1010,
+	{ 800, 1568, 3104 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0xc8, 0xec, 0x11, 0x1d7, 0x22, 0x25, 0x36,
+	  0x47, 0x1c7, 0x1d6, 0x271, 0x270, 4, 9, 0x27,
+	  0x267, 0x26b }, { 0x39, 0x41, 0x46 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 31, 0 + DIV16 }, { 74, 9 + DIV8 }}
+};
+
+/* 640x870, 75Hz Portrait (7) */
+static struct platinum_regvals platinum_reg_init_7 = {
+	0xb10,
+	{ 672, 1312, 2592 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x176, 0xd0, 0x14, 0x19f, 0x27, 0x2d, 0x3f,
+	  0x4a, 0x18a, 0x19e, 0x72c, 0x72a, 4, 9, 0x58,
+	  0x724, 0x72a }, { 0x3c, 0x44, 0x49 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 30, 0 + DIV4 }, { 56, 7 + DIV2 }}
+};
+
+/* 640x480, 67Hz (6) */
+static struct platinum_regvals platinum_reg_init_6 = {
+	0x1010,
+	{ 672, 1312, 2592 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x209, 0,
+	  0, 0x18e, 0xd8, 0x10, 0x1af, 0x1f, 0x25, 0x37,
+	  0x4a, 0x18a, 0x1ae, 0x41a, 0x418, 4, 9, 0x52,
+	  0x412, 0x416 }, { 0x3c, 0x44, 0x49 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 99, 4 + DIV8 }, { 42, 5 + DIV4 }}
+};
+
+/* 640x480, 60Hz (5) */
+static struct platinum_regvals platinum_reg_init_5 = {
+	0x1010,
+	{ 672, 1312, 2592 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x15e, 0xc8, 0x18, 0x18f, 0x2f, 0x35, 0x3e,
+	  0x42, 0x182, 0x18e, 0x41a, 0x418, 2, 7, 0x44,
+	  0x404, 0x408 }, { 0x34, 0x3c, 0x41 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 26, 0 + DIV8 }, { 14, 2 + DIV4 }}
+};
+
+/* 640x480, 60Hz Interlaced-NTSC (4) */
+static struct platinum_regvals platinum_reg_init_4 = {
+	0x1010,
+	{ 672, 1312, 2592 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0xa5, 0xc3, 0xe, 0x185, 0x1c, 0x1f, 0x30,
+	  0x37, 0x177, 0x184, 0x20d, 0x20c, 5, 0xb, 0x23,
+	  0x203, 0x206 }, { 0x29, 0x31, 0x36 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 94, 5 + DIV16 }, { 48, 7 + DIV8 }}
+};
+
+/* 640x480, 50Hz Interlaced-PAL (3) */
+static struct platinum_regvals platinum_reg_init_3 = {
+	0x1010,
+	{ 672, 1312, 2592 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0xc8, 0xec, 0x11, 0x1d7, 0x22, 0x25, 0x36,
+	  0x67, 0x1a7, 0x1d6, 0x271, 0x270, 4, 9, 0x57,
+	  0x237, 0x26b }, { 0x59, 0x61, 0x66 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 31, 0 + DIV16 }, { 74, 9 + DIV8 }}
+};
+
+/* 512x384, 60Hz (2) */
+static struct platinum_regvals platinum_reg_init_2 = {
+	0x1010,
+	{ 544, 1056, 2080 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0x25c, 0x140, 0x10, 0x27f, 0x1f, 0x2b, 0x4f,
+	  0x68, 0x268, 0x27e, 0x32e, 0x32c, 4, 9, 0x2a,
+	  0x32a, 0x32b }, { 0x5a, 0x62, 0x67 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 33, 2 + DIV8 }, { 79, 9 + DIV8 }}
+};
+
+/* 512x384, 60Hz Interlaced-NTSC (1) */
+static struct platinum_regvals platinum_reg_init_1 = {
+	0x1010,
+	{ 544, 1056, 2080 },
+	{ 0xff0, 4, 0, 0, 0, 0, 0x320, 0,
+	  0, 0xa5, 0xc3, 0xe, 0x185, 0x1c, 0x1f, 0x30,
+	  0x57, 0x157, 0x184, 0x20d, 0x20c, 5, 0xb, 0x53,
+	  0x1d3, 0x206 }, { 0x49, 0x51, 0x56 },
+	{ 2, 0, 0xff }, { 0x11, 0x15, 0x19 },
+	{{ 94, 5 + DIV16 }, { 48, 7 + DIV8 }}
+};
+
+static struct platinum_regvals *platinum_reg_init[VMODE_MAX] = {
+	&platinum_reg_init_1,
+	&platinum_reg_init_2,
+	&platinum_reg_init_3,
+	&platinum_reg_init_4,
+	&platinum_reg_init_5,
+	&platinum_reg_init_6,
+	&platinum_reg_init_7,
+	&platinum_reg_init_8,
+	&platinum_reg_init_9,
+	&platinum_reg_init_10,
+	&platinum_reg_init_11,
+	&platinum_reg_init_12,
+	&platinum_reg_init_13,
+	&platinum_reg_init_14,
+	&platinum_reg_init_15,
+	&platinum_reg_init_16,
+	&platinum_reg_init_17,
+	&platinum_reg_init_18,
+	&platinum_reg_init_19,
+	&platinum_reg_init_20
+};
+
+struct vmode_attr {
+	int hres;
+	int vres;
+	int vfreq;
+	int interlaced;
+};
+
+struct vmode_attr vmode_attrs[VMODE_MAX] = {
+	{512, 384, 60, 1},
+	{512, 384, 60},
+	{640, 480, 50, 1},
+	{640, 480, 60, 1},
+	{640, 480, 60},
+	{640, 480, 67},
+	{640, 870, 75},
+	{768, 576, 50, 1},
+	{800, 600, 56},
+	{800, 600, 60},
+	{800, 600, 72},
+	{800, 600, 75},
+	{832, 624, 75},
+	{1024, 768, 60},
+	{1024, 768, 72},
+	{1024, 768, 75},
+	{1024, 768, 75},
+	{1152, 870, 75},
+	{1280, 960, 75},
+	{1280, 1024, 75}
+};
+