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Tue, 18 Aug 2026 18:05:14 +0000 (GMT) Received: from [0.0.0.0] (unknown [9.87.142.99]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 18 Aug 2026 18:05:14 +0000 (GMT) Message-ID: <605d3468-4b2f-4bde-b5cb-07619462dd51@linux.ibm.com> Date: Tue, 18 Aug 2026 20:05:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] x86/mm: fix objtool failure with KMSAN enabled To: Dmitry Voytik , 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 References: <20260701125151.352632-1-voytikd@gmail.com> Content-Language: en-US From: Ilya Leoshkevich In-Reply-To: <20260701125151.352632-1-voytikd@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE4MDEzMyBTYWx0ZWRfXykfSQBA7Lksw W1dXri9x8UBF8W1c6VbZZlrXsRErJTWfLUbOX41paanvjh6j6ymjP4Dh4mafxLiOvxJXrBQDu0J Y3kLSLZN4F9X6zeuMRGKBMzfcfkZsjeiJT7Mg1mvrNmreNc4BMY3gG73ReSV243MT+GwKvZaonc wUBE5MqAxEeSE4ZpOHTVmLj+R1m+ZNZXJClb+qAbfyvTvNiNfUxeTBzNBGcRxmuMytAWGIMFDtH Uf29UesSk3Izv9VLmMyNmzHRw7gYAaq8XpwTIfjeRwRHoPwflOwMTMIXinuEuOvinJFp7bm5ImB CGbMb9E/+V/eeFnHidZ2loILu4d1gQ1UsroMd0ggsuHyZZ0JysSLsMPmYjqpbfjRndlk1Fz5TWk 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/1/26 14:51, Dmitry Voytik wrote: > 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(-) FWIW I just bumped into this build issue; this patch helped and the resulting kernel booted. Config: https://pastebin.com/B6GedVDL Tested-by: Ilya Leoshkevich