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Shutemov" To: Sohil Mehta Cc: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Peter Zijlstra , Ard Biesheuvel , "Paul E. McKenney" , Josh Poimboeuf , Xiongwei Song , Xin Li , "Mike Rapoport (IBM)" , Brijesh Singh , Michael Roth , Tony Luck , Alexey Kardashevskiy , Alexander Shishkin , Jonathan Corbet , Ingo Molnar , Pawan Gupta , Daniel Sneddon , Kai Huang , Sandipan Das , Breno Leitao , Rick Edgecombe , Alexei Starovoitov , Hou Tao , Juergen Gross , Vegard Nossum , Kees Cook , Eric Biggers , Jason Gunthorpe , "Masami Hiramatsu (Google)" , Andrew Morton , Luis Chamberlain , Yuntao Wang , Rasmus Villemoes , Christophe Leroy , Tejun Heo , Changbin Du , Huang Shijie , Geert Uytterhoeven , Namhyung Kim , Arnaldo Carvalho de Melo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv9 02/16] x86/alternatives: Disable LASS when patching kernel alternatives Message-ID: References: <20250707080317.3791624-1-kirill.shutemov@linux.intel.com> <20250707080317.3791624-3-kirill.shutemov@linux.intel.com> <53b8d516-5d19-4b3b-b7fa-99f1066f79fe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53b8d516-5d19-4b3b-b7fa-99f1066f79fe@intel.com> X-Rspamd-Queue-Id: 1C8141A0007 X-Stat-Signature: af3e7tk1dmynftf8ww8mtgiuw4kq5pwt X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1752053771-689281 X-HE-Meta: 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 JQYIr+BP HPSmztaZaPfbaeByn1k2Gy9NdJP1kOLUKwfe/WmYq+N/EIw088slbCNHjOhCLKJMRI53aU2w4DcOQTGrpNQx7fWu7WNvffwgkB9f7EVMxbeVEm3BnVcHz0HxN9X6/hVJX9BKMHiw9Z1LygXvY5GU1qEYCL+40WnZya1h3vNUwWI5xxvujX/Ee12W61qNpnXSXv12hFU4h+4T03sHnL0zTS28NiiBbw5sdTv3q1K4Wn9ErSKMiJuz8q1PCN7DBr6uxaPLVoNKiQQQDgkN0Fe2WM4BFlaT960wgZb2VS2aE4IyDZLEWqf767IvELwPbr3HnZIKX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jul 08, 2025 at 06:08:18PM -0700, Sohil Mehta wrote: > On 7/7/2025 1:03 AM, Kirill A. Shutemov wrote: > > From: Sohil Mehta > > > > For patching, the kernel initializes a temporary mm area in the lower > > half of the address range. See commit 4fc19708b165 ("x86/alternatives: > > Initialize temporary mm for patching"). > > > > Disable LASS enforcement during patching to avoid triggering a #GP > > fault. > > > > The objtool warns due to a call to a non-allowed function that exists > > outside of the stac/clac guard, or references to any function with a > > dynamic function pointer inside the guard. See the Objtool warnings > > section #9 in the document tools/objtool/Documentation/objtool.txt. > > > > Considering that patching is usually small, replace the memcpy() and > > memset() functions in the text poking functions with their open coded > > versions. > > > > Signed-off-by: Sohil Mehta > > Signed-off-by: Alexander Shishkin > > Signed-off-by: Kirill A. Shutemov > > Kirill, it might be worth adding your co-developed-by tag. The patch has > more changes than I can claim credit for. Okay. Will do. -- Kiryl Shutsemau / Kirill A. Shutemov