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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id i65-20020a626d44000000b0055f1db26b3csm5611281pfc.37.2022.10.03.10.25.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Oct 2022 10:25:29 -0700 (PDT) Date: Mon, 3 Oct 2022 10:25:28 -0700 From: Kees Cook To: Rick Edgecombe Cc: x86@kernel.org, "H . 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 , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V . Shankar" , Weijiang Yang , "Kirill A . Shutemov" , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, Yu-cheng Yu Subject: Re: [PATCH v2 02/39] x86/cet/shstk: Add Kconfig option for Shadow Stack Message-ID: <202210031020.0E93C75F9@keescook> References: <20220929222936.14584-1-rick.p.edgecombe@intel.com> <20220929222936.14584-3-rick.p.edgecombe@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220929222936.14584-3-rick.p.edgecombe@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu, Sep 29, 2022 at 03:28:59PM -0700, Rick Edgecombe wrote: > From: Yu-cheng Yu > > Shadow Stack provides protection against function return address > corruption. It is active when the processor supports it, the kernel has > CONFIG_X86_SHADOW_STACK enabled, and the application is built for the > feature. This is only implemented for the 64-bit kernel. When it is > enabled, legacy non-Shadow Stack applications continue to work, but without > protection. > > Signed-off-by: Yu-cheng Yu > Co-developed-by: Rick Edgecombe > Signed-off-by: Rick Edgecombe > Cc: Kees Cook > > --- > > v2: > - Remove already wrong kernel size increase info (tlgx) > - Change prompt to remove "Intel" (tglx) > - Update line about what CPUs are supported (Dave) > > Yu-cheng v25: > - Remove X86_CET and use X86_SHADOW_STACK directly. > > Yu-cheng v24: > - Update for the splitting X86_CET to X86_SHADOW_STACK and X86_IBT. > > arch/x86/Kconfig | 18 ++++++++++++++++++ > arch/x86/Kconfig.assembler | 5 +++++ > 2 files changed, 23 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index f9920f1341c8..b68eb75887b8 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -26,6 +26,7 @@ config X86_64 > depends on 64BIT > # Options that are inherently 64-bit kernel only: > select ARCH_HAS_GIGANTIC_PAGE > + select ARCH_HAS_SHADOW_STACK > select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 > select ARCH_USE_CMPXCHG_LOCKREF > select HAVE_ARCH_SOFT_DIRTY > @@ -1936,6 +1937,23 @@ config X86_SGX > > If unsure, say N. > > +config ARCH_HAS_SHADOW_STACK > + def_bool n > + > +config X86_SHADOW_STACK > + prompt "X86 Shadow Stack" > + def_bool n I hope we can switch this to "default y" soon, given it's a hardware feature that is disabled at runtime when not available. > + depends on ARCH_HAS_SHADOW_STACK Doesn't this depend on AS_WRUSS too? > + select ARCH_USES_HIGH_VMA_FLAGS > + help > + Shadow Stack protection is a hardware feature that detects function > + return address corruption. Today the kernel's support is limited to > + virtualizing it in KVM guests. > + > + CPUs supporting shadow stacks were first released in 2020. > + > + If unsure, say N. > + > config EFI > bool "EFI runtime service support" > depends on ACPI > diff --git a/arch/x86/Kconfig.assembler b/arch/x86/Kconfig.assembler > index 26b8c08e2fc4..00c79dd93651 100644 > --- a/arch/x86/Kconfig.assembler > +++ b/arch/x86/Kconfig.assembler > @@ -19,3 +19,8 @@ config AS_TPAUSE > def_bool $(as-instr,tpause %ecx) > help > Supported by binutils >= 2.31.1 and LLVM integrated assembler >= V7 > + > +config AS_WRUSS > + def_bool $(as-instr,wrussq %rax$(comma)(%rbx)) > + help > + Supported by binutils >= 2.31 and LLVM integrated assembler Otherwise, I don't see anything else using OCNFIG_AS_WRUSS: $ git grep AS_WRUSS arch/x86/Kconfig.assembler:config AS_WRUSS -Kees -- Kees Cook