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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 Subject: Re: [PATCH] x86/mm: fix objtool failure with KMSAN enabled In-Reply-To: <87se61npie.ffs@fw13> References: <20260701125151.352632-1-voytikd@gmail.com> <20260702025342.GJakXStrsCmIRnEwFD@fat_crate.local> <20260702111550.GH751831@noisy.programming.kicks-ass.net> <87se61npie.ffs@fw13> Date: Thu, 02 Jul 2026 22:05:03 +0200 Message-ID: <87mrw9nonk.ffs@fw13> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: 8rumsnxqrzbm8xibnk3jfjhz69gp4c1q X-Rspamd-Queue-Id: E427580004 X-HE-Tag: 1783022708-645296 X-HE-Meta: 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 TfhYqtB7 TEKbhOW0wjCnbPguaF5PvfRRbAgaMzBDzU8Ip0brCu9QLckbyTeogdPMn3rV9CHy3Aje7t4PYW4Q6EQOw+FYvgLuU6iiAw545nW9cMSi/284wOnTqTz3svEasShJ6o25fznQOM40TxrAisDzs86+durFYbN0FqBQFMOMhI1mtYEe3cw5FoJ7/zdhHs/4YlziAZwaWQ6zx5bS62c47hqNO0LR/0EsyEZExlAEtgbBs6zJVEM+f3U83Z/iqaWWNcVbALTyxeyfmi6M59CfQD9jv35Da+gOLW8jk4CTJmJliaxq8uPeP+ihTM9oIitDr00r/MfZRPPkemsFKpGImKaIl9dex8cMU7qAYvlrn Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 02 2026 at 21:46, Thomas Gleixner wrote: > On Thu, Jul 02 2026 at 13:15, Peter Zijlstra wrote: >> A quick test with folio_zero_user() seems to suggest the >> ASM_CALL_CONSTRAINT movement (your patch) generates the same code for >> defconfg as does the unmodified code. The change from the thread linked >> above (input constraint on __builtin_frame_address(0)) generates >> different code. >> >> A third option is to force FRAME_POINTER=y for KMSAN builds -- for now, >> until clang is taught to be less insane. > > With FRAME_POINTER=y I get now with clang-22 > > vmlinux.o: warning: objtool: folio_zero_user+0xa7b: stack state mismatch: reg1[4]=-1+0 reg2[4]=-2-336 > vmlinux.o: warning: objtool: set_ftrace_ops_ro+0x64: relocation to !ENDBR: machine_kexec_prepare+0x8f0 > > That's with your objtool patch applied. When I remove that then the > folio_zero_user one goes away. The relocation to !ENDBR stays. > > Oh well... And none of this boots when KMSAN=y ....