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 --- include/asm-generic/fixmap.h | 101 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 include/asm-generic/fixmap.h (limited to 'include/asm-generic/fixmap.h') diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h new file mode 100644 index 000000000..29cab7947 --- /dev/null +++ b/include/asm-generic/fixmap.h @@ -0,0 +1,101 @@ +/* + * fixmap.h: compile-time virtual memory allocation + * + * 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. + * + * Copyright (C) 1998 Ingo Molnar + * + * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999 + * x86_32 and x86_64 integration by Gustavo F. Padovan, February 2009 + * Break out common bits to asm-generic by Mark Salter, November 2013 + */ + +#ifndef __ASM_GENERIC_FIXMAP_H +#define __ASM_GENERIC_FIXMAP_H + +#include +#include + +#define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT)) +#define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT) + +#ifndef __ASSEMBLY__ +/* + * 'index to address' translation. If anyone tries to use the idx + * directly without translation, we catch the bug with a NULL-deference + * kernel oops. Illegal ranges of incoming indices are caught too. + */ +static __always_inline unsigned long fix_to_virt(const unsigned int idx) +{ + BUILD_BUG_ON(idx >= __end_of_fixed_addresses); + return __fix_to_virt(idx); +} + +static inline unsigned long virt_to_fix(const unsigned long vaddr) +{ + BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START); + return __virt_to_fix(vaddr); +} + +/* + * Provide some reasonable defaults for page flags. + * Not all architectures use all of these different types and some + * architectures use different names. + */ +#ifndef FIXMAP_PAGE_NORMAL +#define FIXMAP_PAGE_NORMAL PAGE_KERNEL +#endif +#if !defined(FIXMAP_PAGE_RO) && defined(PAGE_KERNEL_RO) +#define FIXMAP_PAGE_RO PAGE_KERNEL_RO +#endif +#ifndef FIXMAP_PAGE_NOCACHE +#define FIXMAP_PAGE_NOCACHE PAGE_KERNEL_NOCACHE +#endif +#ifndef FIXMAP_PAGE_IO +#define FIXMAP_PAGE_IO PAGE_KERNEL_IO +#endif +#ifndef FIXMAP_PAGE_CLEAR +#define FIXMAP_PAGE_CLEAR __pgprot(0) +#endif + +#ifndef set_fixmap +#define set_fixmap(idx, phys) \ + __set_fixmap(idx, phys, FIXMAP_PAGE_NORMAL) +#endif + +#ifndef clear_fixmap +#define clear_fixmap(idx) \ + __set_fixmap(idx, 0, FIXMAP_PAGE_CLEAR) +#endif + +/* Return a pointer with offset calculated */ +#define __set_fixmap_offset(idx, phys, flags) \ +({ \ + unsigned long ________addr; \ + __set_fixmap(idx, phys, flags); \ + ________addr = fix_to_virt(idx) + ((phys) & (PAGE_SIZE - 1)); \ + ________addr; \ +}) + +#define set_fixmap_offset(idx, phys) \ + __set_fixmap_offset(idx, phys, FIXMAP_PAGE_NORMAL) + +/* + * Some hardware wants to get fixmapped without caching. + */ +#define set_fixmap_nocache(idx, phys) \ + __set_fixmap(idx, phys, FIXMAP_PAGE_NOCACHE) + +#define set_fixmap_offset_nocache(idx, phys) \ + __set_fixmap_offset(idx, phys, FIXMAP_PAGE_NOCACHE) + +/* + * Some fixmaps are for IO + */ +#define set_fixmap_io(idx, phys) \ + __set_fixmap(idx, phys, FIXMAP_PAGE_IO) + +#endif /* __ASSEMBLY__ */ +#endif /* __ASM_GENERIC_FIXMAP_H */ -- cgit v1.3.1