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Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, Yu-cheng Yu Subject: Re: [PATCH v4 03/39] x86/cpufeatures: Add CPU feature flags for shadow stacks Message-ID: References: <20221203003606.6838-1-rick.p.edgecombe@intel.com> <20221203003606.6838-4-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20221203003606.6838-4-rick.p.edgecombe@intel.com> X-Spamd-Result: default: False [-4.70 / 9.00]; BAYES_HAM(-6.00)[99.99%]; SUSPICIOUS_RECIPS(1.50)[]; R_SPF_ALLOW(-0.20)[+a:mail.skyhub.de]; MIME_GOOD(-0.10)[text/plain]; RCVD_NO_TLS_LAST(0.10)[]; RCPT_COUNT_TWELVE(0.00)[39]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; MIME_TRACE(0.00)[0:+]; DMARC_DNSFAIL(0.00)[alien8.de : server fail]; DKIM_TRACE(0.00)[alien8.de:?]; ARC_SIGNED(0.00)[hostedemail.com:s=arc-20220608:i=1]; ARC_NA(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; FROM_HAS_DN(0.00)[]; TAGGED_RCPT(0.00)[]; TO_DN_SOME(0.00)[]; R_DKIM_TEMPFAIL(0.00)[alien8.de:s=dkim] X-Rspamd-Queue-Id: 1A8F6140011 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: oxjemksuwu9x3uu5xuu5wzx4dsorjty8 X-HE-Tag: 1670410861-971877 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: On Fri, Dec 02, 2022 at 04:35:30PM -0800, Rick Edgecombe wrote: > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h > index 11a0e06362e4..aab7fa4104d7 100644 > --- a/arch/x86/include/asm/cpufeatures.h > +++ b/arch/x86/include/asm/cpufeatures.h > @@ -307,6 +307,7 @@ > #define X86_FEATURE_SGX_EDECCSSA (11*32+18) /* "" SGX EDECCSSA user leaf function */ > #define X86_FEATURE_CALL_DEPTH (11*32+19) /* "" Call depth tracking for RSB stuffing */ > #define X86_FEATURE_MSR_TSX_CTRL (11*32+20) /* "" MSR IA32_TSX_CTRL (Intel) implemented */ > +#define X86_FEATURE_USER_SHSTK (11*32+21) /* Shadow stack support for user mode applications */ > > /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */ > #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */ > @@ -369,6 +370,7 @@ > #define X86_FEATURE_OSPKE (16*32+ 4) /* OS Protection Keys Enable */ > #define X86_FEATURE_WAITPKG (16*32+ 5) /* UMONITOR/UMWAIT/TPAUSE Instructions */ > #define X86_FEATURE_AVX512_VBMI2 (16*32+ 6) /* Additional AVX512 Vector Bit Manipulation Instructions */ > +#define X86_FEATURE_SHSTK (16*32+ 7) /* Shadow Stack */ > #define X86_FEATURE_GFNI (16*32+ 8) /* Galois Field New Instructions */ > #define X86_FEATURE_VAES (16*32+ 9) /* Vector AES */ > #define X86_FEATURE_VPCLMULQDQ (16*32+10) /* Carry-Less Multiplication Double Quadword */ What is the end goal here? To have X86_FEATURE_KERNEL_SHSTK or so someday too? If so, then the hardware bit X86_FEATURE_SHSTK should be hidden in /proc/cpuinfo, i.e., #define X86_FEATURE_SHSTK (16*32+ 7) /* "" Shadow Stack hardware support */ note the "", otherwise you'll have people go: "hey, I have "shstk" in /proc/cpuinfo on my machine. Why doesn't it do anything?" Or am I misreading where this is headed? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette