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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: <20260702111550.GH751831@noisy.programming.kicks-ass.net> References: <20260701125151.352632-1-voytikd@gmail.com> <20260702025342.GJakXStrsCmIRnEwFD@fat_crate.local> <20260702111550.GH751831@noisy.programming.kicks-ass.net> Date: Thu, 02 Jul 2026 21:46:33 +0200 Message-ID: <87se61npie.ffs@fw13> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 00EAA40011 X-Stat-Signature: 7m46hhq1tye1hhetn3qx6sab3tubtwtq X-Rspam-User: X-HE-Tag: 1783021597-558452 X-HE-Meta: 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 IS+F+DHU iHVifS99dhJhs2HGDwaCH2QdmMmXgULRIWdgm4Fk1Nk7YItXwVOlg2tiGPan9ZzBqLGQSUNyLm+11D8ktmFzxnpNECuYW3f/gYv5BPk1xSjBFQdHfomMvqqaIm604yxI83U+/hsLtxuJ7KEr9F95YPT+ZNvfGH/FFxImu2Z5vRiIkCFql3XVWh9tNA5K3n/PT8sjxDlodvDOifg+A02T+1/7NgVr5gy3nEz2v2m7OeANClP+zWAmU6Ez4GlSTj7eKzAFgAEo1/lGhd02tn8HqthXPsL4pERidIFp35yBcJ+XkW245D6sV48+WojNRhb/8hYoM7kVKHwryIU0ToahnQafoYZhcoq7rxMcl 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 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...