From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers 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 Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- samples/vfio-mdev/mdpy-fb.c | 233 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 233 insertions(+) create mode 100644 samples/vfio-mdev/mdpy-fb.c (limited to 'samples/vfio-mdev/mdpy-fb.c') diff --git a/samples/vfio-mdev/mdpy-fb.c b/samples/vfio-mdev/mdpy-fb.c new file mode 100644 index 000000000..149af7f59 --- /dev/null +++ b/samples/vfio-mdev/mdpy-fb.c @@ -0,0 +1,233 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Framebuffer driver for mdpy (mediated virtual pci display device). + * + * See mdpy-defs.h for device specs + * + * (c) Gerd Hoffmann + * + * Using some code snippets from simplefb and cirrusfb. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms and conditions of the GNU General Public License, + * version 2, as published by the Free Software Foundation. + * + * This program is distributed in the hope it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for + * more details. + */ +#include +#include +#include +#include +#include +#include +#include "mdpy-defs.h" + +static const struct fb_fix_screeninfo mdpy_fb_fix = { + .id = "mdpy-fb", + .type = FB_TYPE_PACKED_PIXELS, + .visual = FB_VISUAL_TRUECOLOR, + .accel = FB_ACCEL_NONE, +}; + +static const struct fb_var_screeninfo mdpy_fb_var = { + .height = -1, + .width = -1, + .activate = FB_ACTIVATE_NOW, + .vmode = FB_VMODE_NONINTERLACED, + + .bits_per_pixel = 32, + .transp.offset = 24, + .red.offset = 16, + .green.offset = 8, + .blue.offset = 0, + .transp.length = 8, + .red.length = 8, + .green.length = 8, + .blue.length = 8, +}; + +#define PSEUDO_PALETTE_SIZE 16 + +struct mdpy_fb_par { + u32 palette[PSEUDO_PALETTE_SIZE]; +}; + +static int mdpy_fb_setcolreg(u_int regno, u_int red, u_int green, u_int blue, + u_int transp, struct fb_info *info) +{ + u32 *pal = info->pseudo_palette; + u32 cr = red >> (16 - info->var.red.length); + u32 cg = green >> (16 - info->var.green.length); + u32 cb = blue >> (16 - info->var.blue.length); + u32 value, mask; + + if (regno >= PSEUDO_PALETTE_SIZE) + return -EINVAL; + + value = (cr << info->var.red.offset) | + (cg << info->var.green.offset) | + (cb << info->var.blue.offset); + if (info->var.transp.length > 0) { + mask = (1 << info->var.transp.length) - 1; + mask <<= info->var.transp.offset; + value |= mask; + } + pal[regno] = value; + + return 0; +} + +static void mdpy_fb_destroy(struct fb_info *info) +{ + if (info->screen_base) + iounmap(info->screen_base); +} + +static const struct fb_ops mdpy_fb_ops = { + .owner = THIS_MODULE, + FB_DEFAULT_IOMEM_OPS, + .fb_destroy = mdpy_fb_destroy, + .fb_setcolreg = mdpy_fb_setcolreg, +}; + +static int mdpy_fb_probe(struct pci_dev *pdev, + const struct pci_device_id *ent) +{ + struct fb_info *info; + struct mdpy_fb_par *par; + u32 format, width, height; + int ret; + + ret = pci_enable_device(pdev); + if (ret < 0) + return ret; + + ret = pci_request_regions(pdev, "mdpy-fb"); + if (ret < 0) + goto err_disable_dev; + + pci_read_config_dword(pdev, MDPY_FORMAT_OFFSET, &format); + pci_read_config_dword(pdev, MDPY_WIDTH_OFFSET, &width); + pci_read_config_dword(pdev, MDPY_HEIGHT_OFFSET, &height); + if (format != DRM_FORMAT_XRGB8888) { + pci_err(pdev, "format mismatch (0x%x != 0x%x)\n", + format, DRM_FORMAT_XRGB8888); + ret = -EINVAL; + goto err_release_regions; + } + if (width < 100 || width > 10000) { + pci_err(pdev, "width (%d) out of range\n", width); + ret = -EINVAL; + goto err_release_regions; + } + if (height < 100 || height > 10000) { + pci_err(pdev, "height (%d) out of range\n", height); + ret = -EINVAL; + goto err_release_regions; + } + pci_info(pdev, "mdpy found: %dx%d framebuffer\n", + width, height); + + info = framebuffer_alloc(sizeof(struct mdpy_fb_par), &pdev->dev); + if (!info) { + ret = -ENOMEM; + goto err_release_regions; + } + pci_set_drvdata(pdev, info); + par = info->par; + + info->fix = mdpy_fb_fix; + info->fix.smem_start = pci_resource_start(pdev, 0); + info->fix.smem_len = pci_resource_len(pdev, 0); + info->fix.line_length = width * 4; + + info->var = mdpy_fb_var; + info->var.xres = width; + info->var.yres = height; + info->var.xres_virtual = width; + info->var.yres_virtual = height; + + info->screen_size = info->fix.smem_len; + info->screen_base = ioremap(info->fix.smem_start, + info->screen_size); + if (!info->screen_base) { + pci_err(pdev, "ioremap(pcibar) failed\n"); + ret = -EIO; + goto err_release_fb; + } + + info->fbops = &mdpy_fb_ops; + info->pseudo_palette = par->palette; + + ret = register_framebuffer(info); + if (ret < 0) { + pci_err(pdev, "mdpy-fb device register failed: %d\n", ret); + goto err_unmap; + } + + pci_info(pdev, "fb%d registered\n", info->node); + return 0; + +err_unmap: + iounmap(info->screen_base); + +err_release_fb: + framebuffer_release(info); + +err_release_regions: + pci_release_regions(pdev); + +err_disable_dev: + pci_disable_device(pdev); + + return ret; +} + +static void mdpy_fb_remove(struct pci_dev *pdev) +{ + struct fb_info *info = pci_get_drvdata(pdev); + + unregister_framebuffer(info); + iounmap(info->screen_base); + framebuffer_release(info); + pci_release_regions(pdev); + pci_disable_device(pdev); +} + +static struct pci_device_id mdpy_fb_pci_table[] = { + { + .vendor = MDPY_PCI_VENDOR_ID, + .device = MDPY_PCI_DEVICE_ID, + .subvendor = MDPY_PCI_SUBVENDOR_ID, + .subdevice = MDPY_PCI_SUBDEVICE_ID, + }, { + /* end of list */ + } +}; + +static struct pci_driver mdpy_fb_pci_driver = { + .name = "mdpy-fb", + .id_table = mdpy_fb_pci_table, + .probe = mdpy_fb_probe, + .remove = mdpy_fb_remove, +}; + +static int __init mdpy_fb_init(void) +{ + int ret; + + ret = pci_register_driver(&mdpy_fb_pci_driver); + if (ret) + return ret; + + return 0; +} + +module_init(mdpy_fb_init); + +MODULE_DEVICE_TABLE(pci, mdpy_fb_pci_table); +MODULE_DESCRIPTION("Framebuffer driver for mdpy (mediated virtual pci display device)"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1