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Shutemov" To: Xin Li 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 , Sohil Mehta , 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: [PATCHv6 13/16] x86/traps: Handle LASS thrown #SS Message-ID: References: <20250620135325.3300848-1-kirill.shutemov@linux.intel.com> <20250620135325.3300848-14-kirill.shutemov@linux.intel.com> <08758240-fd38-4d90-9efa-354274e8bb8e@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <08758240-fd38-4d90-9efa-354274e8bb8e@zytor.com> X-Rspamd-Queue-Id: 236AF4000B X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: rgfq8fxjjrqojbpcsz7sfhbadtrj97bg X-HE-Tag: 1750442029-236761 X-HE-Meta: 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 xE4ZDuPR dMuFaLNm0PAQcsBDvOrq2xNyfvU4iuTZLXq8LPHYuGoNXHDKvJ2TAY/gBPn5t79yg3DDdjcXb80s1hnamzsovP97IpC1cFmA0MyDLNgLfvAFyKb4SgjvuT8yAaS97H5QKEIJ/4AoFA0AsFhqq/UECBYTKHZHSoryO5SY80gnkcclCv7DdfuThNLm4viJVXFW5AaI0SynViIjEsYz5HO0fH3KGpWEywbHIVz61Kd2mgXGulP+8lomENqlf2T2ACnqjwkbqPoXNaaXxvuH8DmmPhe0jxIxwmfOKhtkDKSNerDhzD/qajZzbadPhPw== 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 Fri, Jun 20, 2025 at 08:20:12AM -0700, Xin Li wrote: > On 6/20/2025 6:53 AM, Kirill A. Shutemov wrote: > > From: Alexander Shishkin > > > > LASS throws a #GP for any violations except for stack register accesses, > > in which case it throws a #SS instead. Handle this similarly to how other > > LASS violations are handled. > > > > Signed-off-by: Alexander Shishkin > > Signed-off-by: Kirill A. Shutemov > > --- > > arch/x86/kernel/traps.c | 34 ++++++++++++++++++++++++++++------ > > 1 file changed, 28 insertions(+), 6 deletions(-) > > > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > > index 0f558d3369a3..bd8f7e72b238 100644 > > --- a/arch/x86/kernel/traps.c > > +++ b/arch/x86/kernel/traps.c > > @@ -866,6 +860,34 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) > > cond_local_irq_disable(regs); > > } > > +DEFINE_IDTENTRY_ERRORCODE(exc_stack_segment) > > +{ > > + if (cpu_feature_enabled(X86_FEATURE_LASS)) { > > + enum kernel_gp_hint hint = GP_NO_HINT; > > + unsigned long gp_addr; > > + > > + if (user_mode(regs)) { > > + gp_user_force_sig_segv(regs, X86_TRAP_GP, error_code, GPFSTR); > > + return; > > + } > > Please add the following FRED code: > > if (cpu_feature_enabled(X86_FEATURE_FRED) && > fixup_exception(regs, X86_TRAP_SS, error_code, 0)) > return; > > Because the following FRED fixup > > https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5105e7687ad3dffde77f6e4393b5530e83d672dc > > is otherwise skipped, it is interpreted as a LASS #SS before reaching > the FRED fixup (which is indeed a userspace fault but triggered from > a specific kernel IP as described in the commit changelog). > > The x86 selftest sigreturn_64 fails w/o the above fix. Okay, will do. > > + > > + hint = get_kernel_gp_address(regs, &gp_addr); > > + if (hint != GP_NO_HINT) { > > + printk(GPFSTR ", %s 0x%lx", kernel_gp_hint_help[hint], > > GPFSTR? > > #define GPFSTR "general protection fault" > > It is misleading here, you need something like SSFSTR which tells > exactly which exception caused it. Yep, thanks for catching that! -- Kiryl Shutsemau / Kirill A. Shutemov