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, 416 insertions, 0 deletions

diff --git a/drivers/video/fbdev/macmodes.c b/drivers/video/fbdev/macmodes.c
new file mode 100644
index 000000000..b16a9d9be
--- /dev/null
+++ b/drivers/video/fbdev/macmodes.c
@@ -0,0 +1,416 @@
+/*
+ *  linux/drivers/video/macmodes.c -- Standard MacOS video modes
+ *
+ *	Copyright (C) 1998 Geert Uytterhoeven
+ *
+ *      2000 - Removal of OpenFirmware dependencies by:
+ *      - Ani Joshi
+ *      - Brad Douglas <brad@neruo.com>
+ *
+ *	2001 - Documented with DocBook
+ *	- Brad Douglas <brad@neruo.com>
+ *
+ *  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.
+ */
+
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/fb.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+#include "macmodes.h"
+
+    /*
+     *  MacOS video mode definitions
+     *
+     *  Order IS important! If you change these, don't forget to update
+     *  mac_modes[] below!
+     */
+
+#define DEFAULT_MODEDB_INDEX	0
+
+static const struct fb_videomode mac_modedb[] = {
+    {
+	/* 512x384, 60Hz, Non-Interlaced (15.67 MHz dot clock) */
+	"mac2", 60, 512, 384, 63828, 80, 16, 19, 1, 32, 3,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 640x480, 60 Hz, Non-Interlaced (25.175 MHz dotclock) */
+	"mac5", 60, 640, 480, 39722, 32, 32, 33, 10, 96, 2,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 640x480, 67Hz, Non-Interlaced (30.0 MHz dotclock) */
+	"mac6", 67, 640, 480, 33334, 80, 80, 39, 3, 64, 3,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 640x870, 75Hz (portrait), Non-Interlaced (57.28 MHz dot clock) */
+	"mac7", 75, 640, 870, 17457, 80, 32, 42, 3, 80, 3,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 800x600, 56 Hz, Non-Interlaced (36.00 MHz dotclock) */
+	"mac9", 56, 800, 600, 27778, 112, 40, 22, 1, 72, 2,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 800x600, 60 Hz, Non-Interlaced (40.00 MHz dotclock) */
+	"mac10", 60, 800, 600, 25000, 72, 56, 23, 1, 128, 4,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 800x600, 72 Hz, Non-Interlaced (50.00 MHz dotclock) */
+	"mac11", 72, 800, 600, 20000, 48, 72, 23, 37, 120, 6,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 800x600, 75 Hz, Non-Interlaced (49.50 MHz dotclock) */
+	"mac12", 75, 800, 600, 20203, 144, 32, 21, 1, 80, 3,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 832x624, 75Hz, Non-Interlaced (57.6 MHz dotclock) */
+	"mac13", 75, 832, 624, 17362, 208, 48, 39, 1, 64, 3,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1024x768, 60 Hz, Non-Interlaced (65.00 MHz dotclock) */
+	"mac14", 60, 1024, 768, 15385, 144, 40, 29, 3, 136, 6,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1024x768, 72 Hz, Non-Interlaced (75.00 MHz dotclock) */
+	"mac15", 72, 1024, 768, 13334, 128, 40, 29, 3, 136, 6,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1024x768, 75 Hz, Non-Interlaced (78.75 MHz dotclock) */
+	"mac16", 75, 1024, 768, 12699, 176, 16, 28, 1, 96, 3,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1024x768, 75 Hz, Non-Interlaced (78.75 MHz dotclock) */
+	"mac17", 75, 1024, 768, 12699, 160, 32, 28, 1, 96, 3,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1152x870, 75 Hz, Non-Interlaced (100.0 MHz dotclock) */
+	"mac18", 75, 1152, 870, 10000, 128, 48, 39, 3, 128, 3,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1280x960, 75 Hz, Non-Interlaced (126.00 MHz dotclock) */
+	"mac19", 75, 1280, 960, 7937, 224, 32, 36, 1, 144, 3,
+	0, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1280x1024, 75 Hz, Non-Interlaced (135.00 MHz dotclock) */
+	"mac20", 75, 1280, 1024, 7408, 232, 64, 38, 1, 112, 3,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1152x768, 60 Hz, Titanium PowerBook */
+	"mac21", 60, 1152, 768, 15386, 158, 26, 29, 3, 136, 6,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }, {
+	/* 1600x1024, 60 Hz, Non-Interlaced (112.27 MHz dotclock) */
+	"mac22", 60, 1600, 1024, 8908, 88, 104, 1, 10, 16, 1,
+	FB_SYNC_HOR_HIGH_ACT|FB_SYNC_VERT_HIGH_ACT, FB_VMODE_NONINTERLACED
+    }
+
+#if 0
+    /* Anyone who has timings for these? */
+    {
+	/* VMODE_512_384_60I: 512x384, 60Hz, Interlaced (NTSC) */
+	"mac1", 60, 512, 384, pixclock, left, right, upper, lower, hslen, vslen,
+	sync, FB_VMODE_INTERLACED
+    }, {
+	/* VMODE_640_480_50I: 640x480, 50Hz, Interlaced (PAL) */
+	"mac3", 50, 640, 480, pixclock, left, right, upper, lower, hslen, vslen,
+	sync, FB_VMODE_INTERLACED
+    }, {
+	/* VMODE_640_480_60I: 640x480, 60Hz, Interlaced (NTSC) */
+	"mac4", 60, 640, 480, pixclock, left, right, upper, lower, hslen, vslen,
+	sync, FB_VMODE_INTERLACED
+    }, {
+	/* VMODE_768_576_50I: 768x576, 50Hz (PAL full frame), Interlaced */
+	"mac8", 50, 768, 576, pixclock, left, right, upper, lower, hslen, vslen,
+	sync, FB_VMODE_INTERLACED
+    },
+#endif
+};
+
+
+    /*
+     *  Mapping between MacOS video mode numbers and video mode definitions
+     *
+     *  These MUST be ordered in
+     *    - increasing resolution
+     *    - decreasing pixel clock period
+     */
+
+static const struct mode_map {
+    int vmode;
+    const struct fb_videomode *mode;
+} mac_modes[] = {
+    /* 512x384 */
+    { VMODE_512_384_60, &mac_modedb[0] },
+    /* 640x480 */
+    { VMODE_640_480_60, &mac_modedb[1] },
+    { VMODE_640_480_67, &mac_modedb[2] },
+    /* 640x870 */
+    { VMODE_640_870_75P, &mac_modedb[3] },
+    /* 800x600 */
+    { VMODE_800_600_56, &mac_modedb[4] },
+    { VMODE_800_600_60, &mac_modedb[5] },
+    { VMODE_800_600_75, &mac_modedb[7] },
+    { VMODE_800_600_72, &mac_modedb[6] },
+    /* 832x624 */
+    { VMODE_832_624_75, &mac_modedb[8] },
+    /* 1024x768 */
+    { VMODE_1024_768_60, &mac_modedb[9] },
+    { VMODE_1024_768_70, &mac_modedb[10] },
+    { VMODE_1024_768_75V, &mac_modedb[11] },
+    { VMODE_1024_768_75, &mac_modedb[12] },
+    /* 1152x768 */
+    { VMODE_1152_768_60, &mac_modedb[16] },
+    /* 1152x870 */
+    { VMODE_1152_870_75, &mac_modedb[13] },
+    /* 1280x960 */
+    { VMODE_1280_960_75, &mac_modedb[14] },
+    /* 1280x1024 */
+    { VMODE_1280_1024_75, &mac_modedb[15] },
+    /* 1600x1024 */
+    { VMODE_1600_1024_60, &mac_modedb[17] },
+    { -1, NULL }
+};
+
+
+    /*
+     *  Mapping between monitor sense values and MacOS video mode numbers
+     */
+
+static const struct monitor_map {
+    int sense;
+    int vmode;
+} mac_monitors[] = {
+    { 0x000, VMODE_1280_1024_75 },	/* 21" RGB */
+    { 0x114, VMODE_640_870_75P },	/* Portrait Monochrome */
+    { 0x221, VMODE_512_384_60 },	/* 12" RGB*/
+    { 0x331, VMODE_1280_1024_75 },	/* 21" RGB (Radius) */
+    { 0x334, VMODE_1280_1024_75 },	/* 21" mono (Radius) */
+    { 0x335, VMODE_1280_1024_75 },	/* 21" mono */
+    { 0x40A, VMODE_640_480_60I },	/* NTSC */
+    { 0x51E, VMODE_640_870_75P },	/* Portrait RGB */
+    { 0x603, VMODE_832_624_75 },	/* 12"-16" multiscan */
+    { 0x60b, VMODE_1024_768_70 },	/* 13"-19" multiscan */
+    { 0x623, VMODE_1152_870_75 },	/* 13"-21" multiscan */
+    { 0x62b, VMODE_640_480_67 },	/* 13"/14" RGB */
+    { 0x700, VMODE_640_480_50I },	/* PAL */
+    { 0x714, VMODE_640_480_60I },	/* NTSC */
+    { 0x717, VMODE_800_600_75 },	/* VGA */
+    { 0x72d, VMODE_832_624_75 },	/* 16" RGB (Goldfish) */
+    { 0x730, VMODE_768_576_50I },	/* PAL (Alternate) */
+    { 0x73a, VMODE_1152_870_75 },	/* 3rd party 19" */
+    { 0x73f, VMODE_640_480_67 },	/* no sense lines connected at all */
+    { 0xBEEF, VMODE_1600_1024_60 },	/* 22" Apple Cinema Display */
+    { -1,    VMODE_640_480_60 },	/* catch-all, must be last */
+};
+
+/**
+ *	mac_vmode_to_var - converts vmode/cmode pair to var structure
+ *	@vmode: MacOS video mode
+ *	@cmode: MacOS color mode
+ *	@var: frame buffer video mode structure
+ *
+ *	Converts a MacOS vmode/cmode pair to a frame buffer video
+ *	mode structure.
+ *
+ *	Returns negative errno on error, or zero for success.
+ *
+ */
+
+int mac_vmode_to_var(int vmode, int cmode, struct fb_var_screeninfo *var)
+{
+    const struct fb_videomode *mode = NULL;
+    const struct mode_map *map;
+
+    for (map = mac_modes; map->vmode != -1; map++)
+	if (map->vmode == vmode) {
+	    mode = map->mode;
+	    break;
+	}
+    if (!mode)
+	return -EINVAL;
+
+    memset(var, 0, sizeof(struct fb_var_screeninfo));
+    switch (cmode) {
+	case CMODE_8:
+	    var->bits_per_pixel = 8;
+	    var->red.offset = 0;
+	    var->red.length = 8;
+	    var->green.offset = 0;
+	    var->green.length = 8;
+	    var->blue.offset = 0;
+	    var->blue.length = 8;
+	    break;
+
+	case CMODE_16:
+	    var->bits_per_pixel = 16;
+	    var->red.offset = 10;
+	    var->red.length = 5;
+	    var->green.offset = 5;
+	    var->green.length = 5;
+	    var->blue.offset = 0;
+	    var->blue.length = 5;
+	    break;
+
+	case CMODE_32:
+	    var->bits_per_pixel = 32;
+	    var->red.offset = 16;
+	    var->red.length = 8;
+	    var->green.offset = 8;
+	    var->green.length = 8;
+	    var->blue.offset = 0;
+	    var->blue.length = 8;
+	    var->transp.offset = 24;
+	    var->transp.length = 8;
+	    break;
+
+	default:
+	    return -EINVAL;
+    }
+    var->xres = mode->xres;
+    var->yres = mode->yres;
+    var->xres_virtual = mode->xres;
+    var->yres_virtual = mode->yres;
+    var->height = -1;
+    var->width = -1;
+    var->pixclock = mode->pixclock;
+    var->left_margin = mode->left_margin;
+    var->right_margin = mode->right_margin;
+    var->upper_margin = mode->upper_margin;
+    var->lower_margin = mode->lower_margin;
+    var->hsync_len = mode->hsync_len;
+    var->vsync_len = mode->vsync_len;
+    var->sync = mode->sync;
+    var->vmode = mode->vmode;
+    return 0;
+}
+EXPORT_SYMBOL(mac_vmode_to_var);
+
+/**
+ *	mac_var_to_vmode - convert var structure to MacOS vmode/cmode pair
+ *	@var: frame buffer video mode structure
+ *	@vmode: MacOS video mode
+ *	@cmode: MacOS color mode
+ *
+ *	Converts a frame buffer video mode structure to a MacOS
+ *	vmode/cmode pair.
+ *
+ *	Returns negative errno on error, or zero for success.
+ *
+ */
+
+int mac_var_to_vmode(const struct fb_var_screeninfo *var, int *vmode,
+		     int *cmode)
+{
+    const struct mode_map *map;
+
+    if (var->bits_per_pixel <= 8)
+	*cmode = CMODE_8;
+    else if (var->bits_per_pixel <= 16)
+	*cmode = CMODE_16;
+    else if (var->bits_per_pixel <= 32)
+	*cmode = CMODE_32;
+    else
+	return -EINVAL;
+
+    /*
+     * Find the mac_mode with a matching resolution or failing that, the
+     * closest larger resolution. Skip modes with a shorter pixel clock period.
+     */
+    for (map = mac_modes; map->vmode != -1; map++) {
+	const struct fb_videomode *mode = map->mode;
+
+	if (var->xres > mode->xres || var->yres > mode->yres)
+	    continue;
+	if (var->xres_virtual > mode->xres || var->yres_virtual > mode->yres)
+	    continue;
+	if (var->pixclock > mode->pixclock)
+	    continue;
+	if ((var->vmode & FB_VMODE_MASK) != mode->vmode)
+	    continue;
+	*vmode = map->vmode;
+
+	/*
+	 * Having found a good resolution, find the matching pixel clock
+	 * or failing that, the closest longer pixel clock period.
+	 */
+	map++;
+	while (map->vmode != -1) {
+	    const struct fb_videomode *clk_mode = map->mode;
+
+	    if (mode->xres != clk_mode->xres || mode->yres != clk_mode->yres)
+		break;
+	    if (var->pixclock > mode->pixclock)
+	        break;
+	    if (mode->vmode != clk_mode->vmode)
+		continue;
+	    *vmode = map->vmode;
+	    map++;
+	}
+	return 0;
+    }
+    return -EINVAL;
+}
+
+/**
+ *	mac_map_monitor_sense - Convert monitor sense to vmode
+ *	@sense: Macintosh monitor sense number
+ *
+ *	Converts a Macintosh monitor sense number to a MacOS
+ *	vmode number.
+ *
+ *	Returns MacOS vmode video mode number.
+ *
+ */
+
+int mac_map_monitor_sense(int sense)
+{
+    const struct monitor_map *map;
+
+    for (map = mac_monitors; map->sense != -1; map++)
+	if (map->sense == sense)
+	    break;
+    return map->vmode;
+}
+EXPORT_SYMBOL(mac_map_monitor_sense);
+
+/**
+ *	mac_find_mode - find a video mode
+ *	@var: frame buffer user defined part of display
+ *	@info: frame buffer info structure
+ *	@mode_option: video mode name (see mac_modedb[])
+ *	@default_bpp: default color depth in bits per pixel
+ *
+ *	Finds a suitable video mode.  Tries to set mode specified
+ *	by @mode_option.  If the name of the wanted mode begins with
+ *	'mac', the Mac video mode database will be used, otherwise it
+ *	will fall back to the standard video mode database.
+ *
+ *	Note: Function marked as __init and can only be used during
+ *	system boot.
+ *
+ *	Returns error code from fb_find_mode (see fb_find_mode
+ *	function).
+ *
+ */
+
+int mac_find_mode(struct fb_var_screeninfo *var, struct fb_info *info,
+		  const char *mode_option, unsigned int default_bpp)
+{
+    const struct fb_videomode *db = NULL;
+    unsigned int dbsize = 0;
+
+    if (mode_option && !strncmp(mode_option, "mac", 3)) {
+	mode_option += 3;
+	db = mac_modedb;
+	dbsize = ARRAY_SIZE(mac_modedb);
+    }
+    return fb_find_mode(var, info, mode_option, db, dbsize,
+			&mac_modedb[DEFAULT_MODEDB_INDEX], default_bpp);
+}
+EXPORT_SYMBOL(mac_find_mode);
+
+MODULE_DESCRIPTION("MacOS video mode library");
+MODULE_LICENSE("GPL");