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Wed, 01 Jul 2026 05:51:54 -0700 (PDT) Received: from voyt-laptop-dell.fritz.box ([2001:9e8:bd55:a800:14a4:886c:f7de:bb03]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-475671d0403sm17665051f8f.29.2026.07.01.05.51.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jul 2026 05:51:54 -0700 (PDT) From: Dmitry Voytik To: Alexander Potapenko , Borislav Petkov , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Dave Hansen , Josh Poimboeuf Cc: Dmitry Vyukov , Andrew Morton , Ankur Arora , "H . Peter Anvin" , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Marco Elver , x86@kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, llvm@lists.linux.dev, Dmitry Voytik Subject: [PATCH] x86/mm: fix objtool failure with KMSAN enabled Date: Wed, 1 Jul 2026 14:51:51 +0200 Message-ID: <20260701125151.352632-1-voytikd@gmail.com> X-Mailer: git-send-email 2.54.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5F794160003 X-Rspam-User: X-Stat-Signature: daiq6rsiwu8339ih9fgee4ycb1gtzkis X-HE-Tag: 1782910316-967223 X-HE-Meta: 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 L5Mwu+1S 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This patch fixes broken builds with defconfig + CONFIG_KMSAN + CONFIG_DEBUG_INFO_*. To reproduce the issue before the fix: make mrproper make LLVM=1 defconfig ./scripts/config -e CONFIG_KMSAN \ -e CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT make LLVM=1 olddefconfig make LLVM=1 -j(nproc) vmlinux ... LD vmlinux.o vmlinux.o: warning: objtool: folio_zero_user+0x801: undefined stack state vmlinux.o: error: objtool: folio_zero_user+0x801: unknown CFA base reg -1 make[2]: *** [scripts/Makefile.vmlinux_o:76: vmlinux.o] Error 255 objtool in verbose mode shows how the frame pointer is omitted: make LLVM=1 OBJTOOL_VERBOSE=1 -j(nproc) vmlinux ... b15a2c: folio_zero_user+0x7fc xor %eax,%eax b15a2e: folio_zero_user+0x7fe mov %rcx,%rsp b15a31: folio_zero_user+0x801 mov %r14,%rdi b15a34: folio_zero_user+0x804 mov %rbx,%rcx b15a37: folio_zero_user+0x807 call 0xb15a3c <__clear_pages_unrol After the fix, the frame pointer is back: b15a37: 31 c0 xor %eax,%eax b15a39: 48 89 ec mov %rbp,%rsp b15a3c: 4c 89 f7 mov %r14,%rdi b15a3f: 48 89 d9 mov %rbx,%rcx b15a42: e8 00 00 00 00 call b15a47 It seems the issue was introduced by commit 54a6b89a3db2 ("x86/mm: simplify clear_page_*") The actual fix is to revert the change how ASM_CALL_CONSTRAINT is positioned. Additionally, reintroduce asm_inline to prevent potential compiler rejection of inlining. Link: https://lore.kernel.org/CAAX90H2_RPnZL_dFYN7cQF6yt-wAweKKSx2=6e2aZ0kv+Pm+NQ@mail.gmail.com Signed-off-by: Dmitry Voytik --- arch/x86/include/asm/page_64.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h index 1895c207f629..de8604f0a3a1 100644 --- a/arch/x86/include/asm/page_64.h +++ b/arch/x86/include/asm/page_64.h @@ -100,12 +100,13 @@ static inline void clear_pages(void *addr, unsigned int npages) * __clear_pages_unrolled() are part of the inline asm register * specification. */ - asm volatile(ALTERNATIVE_2("call __clear_pages_unrolled", - "shrq $3, %%rcx; rep stosq", X86_FEATURE_REP_GOOD, - "rep stosb", X86_FEATURE_ERMS) - : "+c" (len), "+D" (addr), ASM_CALL_CONSTRAINT - : "a" (0) - : "cc", "memory"); + asm_inline volatile( + ALTERNATIVE_2("call __clear_pages_unrolled", + "shrq $3, %%rcx; rep stosq", X86_FEATURE_REP_GOOD, + "rep stosb", X86_FEATURE_ERMS) + : ASM_CALL_CONSTRAINT, "+c"(len), "+D"(addr) + : "a"(0) + : "cc", "memory"); } #define clear_pages clear_pages -- 2.54.0