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/cacheflush.h | 127 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 127 insertions(+) create mode 100644 include/asm-generic/cacheflush.h (limited to 'include/asm-generic/cacheflush.h') diff --git a/include/asm-generic/cacheflush.h b/include/asm-generic/cacheflush.h new file mode 100644 index 000000000..7ee8a179d --- /dev/null +++ b/include/asm-generic/cacheflush.h @@ -0,0 +1,127 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_CACHEFLUSH_H +#define _ASM_GENERIC_CACHEFLUSH_H + +#include + +struct mm_struct; +struct vm_area_struct; +struct page; +struct address_space; + +/* + * The cache doesn't need to be flushed when TLB entries change when + * the cache is mapped to physical memory, not virtual memory + */ +#ifndef flush_cache_all +static inline void flush_cache_all(void) +{ +} +#endif + +#ifndef flush_cache_mm +static inline void flush_cache_mm(struct mm_struct *mm) +{ +} +#endif + +#ifndef flush_cache_dup_mm +static inline void flush_cache_dup_mm(struct mm_struct *mm) +{ +} +#endif + +#ifndef flush_cache_range +static inline void flush_cache_range(struct vm_area_struct *vma, + unsigned long start, + unsigned long end) +{ +} +#endif + +#ifndef flush_cache_page +static inline void flush_cache_page(struct vm_area_struct *vma, + unsigned long vmaddr, + unsigned long pfn) +{ +} +#endif + +#ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE +static inline void flush_dcache_page(struct page *page) +{ +} + +#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0 +#endif + +#ifndef flush_dcache_mmap_lock +static inline void flush_dcache_mmap_lock(struct address_space *mapping) +{ +} +#endif + +#ifndef flush_dcache_mmap_unlock +static inline void flush_dcache_mmap_unlock(struct address_space *mapping) +{ +} +#endif + +#ifndef flush_icache_range +static inline void flush_icache_range(unsigned long start, unsigned long end) +{ +} +#endif + +#ifndef flush_icache_user_range +#define flush_icache_user_range flush_icache_range +#endif + +#ifndef flush_icache_user_page +static inline void flush_icache_user_page(struct vm_area_struct *vma, + struct page *page, + unsigned long addr, int len) +{ +} +#endif + +#ifndef flush_cache_vmap +static inline void flush_cache_vmap(unsigned long start, unsigned long end) +{ +} +#endif + +#ifndef flush_cache_vmap_early +static inline void flush_cache_vmap_early(unsigned long start, unsigned long end) +{ +} +#endif + +#ifndef flush_cache_vunmap +static inline void flush_cache_vunmap(unsigned long start, unsigned long end) +{ +} +#endif + +#ifndef copy_to_user_page +#define copy_to_user_page(vma, page, vaddr, dst, src, len) \ + do { \ + instrument_copy_to_user((void __user *)dst, src, len); \ + memcpy(dst, src, len); \ + flush_icache_user_page(vma, page, vaddr, len); \ + } while (0) +#endif + + +#ifndef copy_from_user_page +#define copy_from_user_page(vma, page, vaddr, dst, src, len) \ + do { \ + instrument_copy_from_user_before(dst, (void __user *)src, \ + len); \ + memcpy(dst, src, len); \ + instrument_copy_from_user_after(dst, (void __user *)src, len, \ + 0); \ + } while (0) +#endif + +#endif /* _ASM_GENERIC_CACHEFLUSH_H */ -- cgit v1.3.1