On Wed, Feb 03, 2021 at 02:55:24PM -0800, Yu-cheng Yu wrote: > Shadow Stack provides protection against function return address > corruption. It is active when the processor supports it, the kernel has > CONFIG_X86_CET 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 <yu-cheng.yu@xxxxxxxxx> > --- > arch/x86/Kconfig | 22 ++++++++++++++++++++++ > arch/x86/Kconfig.assembler | 5 +++++ > 2 files changed, 27 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 21f851179ff0..074b3c0e6bf6 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1951,6 +1951,28 @@ config X86_SGX > > If unsure, say N. > > +config ARCH_HAS_SHADOW_STACK > + def_bool n > + > +config X86_CET > + prompt "Intel Control-flow protection for user-mode" > + def_bool n > + depends on X86_64 > + depends on AS_WRUSS > + select ARCH_USES_HIGH_VMA_FLAGS > + select ARCH_HAS_SHADOW_STACK This seems backwards to me? Shouldn't 'config X86_64' do the 'select ARCH_HAS_SHADOW_STACK' and 'config X86_CET' do a 'depends on ARCH_HAS_SHADOW_STACK' instead? > + help > + Control-flow protection is a set of hardware features which place > + additional restrictions on indirect branches. These help > + mitigate ROP attacks. Applications must be enabled to use it, > + and old userspace does not get protection "for free". > + Support for this feature is present on Tiger Lake family of > + processors released in 2020 or later. Enabling this feature > + increases kernel text size by 3.7 KB. > + See Documentation/x86/intel_cet.rst for more information. > + > + 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 > -- > 2.21.0 > -- Kees Cook
