diff mbox series

[v5,02/39] x86/shstk: Add Kconfig option for shadow stack

Message ID 20230119212317.8324-3-rick.p.edgecombe@intel.com (mailing list archive)
State New
Headers show
Series Shadow stacks for userspace | expand

Commit Message

Rick Edgecombe Jan. 19, 2023, 9:22 p.m. UTC 
From: Yu-cheng Yu <yu-cheng.yu@intel.com>

Shadow stack provides protection for applications 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.

Since there is another feature that utilizes CET (Kernel IBT) that will
share implementation with shadow stacks, create CONFIG_CET to signify
that at least one CET feature is configured.

Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: John Allen <john.allen@amd.com>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Co-developed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Kees Cook <keescook@chromium.org>
---

v5:
 - Remove capitalization of shadow stack (Boris)

v3:
 - Add X86_CET (Kees)
 - Add back WRUSS dependency (Kees)
 - Fix verbiage (Dave)
 - Change from promt to bool (Kirill)
 - Add more to commit log

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.

 arch/x86/Kconfig           | 24 ++++++++++++++++++++++++
 arch/x86/Kconfig.assembler |  5 +++++
 2 files changed, 29 insertions(+)

Comments

Kees Cook Jan. 20, 2023, 12:40 a.m. UTC | #1 
On Thu, Jan 19, 2023 at 01:22:40PM -0800, Rick Edgecombe wrote:
> From: Yu-cheng Yu <yu-cheng.yu@intel.com>
> 
> Shadow stack provides protection for applications 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.
> 
> Since there is another feature that utilizes CET (Kernel IBT) that will
> share implementation with shadow stacks, create CONFIG_CET to signify
> that at least one CET feature is configured.
> 
> Tested-by: Pengfei Xu <pengfei.xu@intel.com>
> Tested-by: John Allen <john.allen@amd.com>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>

Reviewed-by: Kees Cook <keescook@chromium.org>
diff mbox series

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 3604074a878b..d0037181bc15 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1851,6 +1851,11 @@  config CC_HAS_IBT
 		  (CC_IS_CLANG && CLANG_VERSION >= 140000)) && \
 		  $(as-instr,endbr64)
 
+config X86_CET
+	def_bool n
+	help
+	  CET features configured (Shadow stack or IBT)
+
 config X86_KERNEL_IBT
 	prompt "Indirect Branch Tracking"
 	def_bool y
@@ -1858,6 +1863,7 @@  config X86_KERNEL_IBT
 	# https://github.com/llvm/llvm-project/commit/9d7001eba9c4cb311e03cd8cdc231f9e579f2d0f
 	depends on !LD_IS_LLD || LLD_VERSION >= 140000
 	select OBJTOOL
+	select X86_CET
 	help
 	  Build the kernel with support for Indirect Branch Tracking, a
 	  hardware support course-grain forward-edge Control Flow Integrity
@@ -1952,6 +1958,24 @@  config X86_SGX
 
 	  If unsure, say N.
 
+config X86_USER_SHADOW_STACK
+	bool "X86 userspace shadow stack"
+	depends on AS_WRUSS
+	depends on X86_64
+	select ARCH_USES_HIGH_VMA_FLAGS
+	select X86_CET
+	help
+	  Shadow stack protection is a hardware feature that detects function
+	  return address corruption.  This helps mitigate ROP attacks.
+	  Applications must be enabled to use it, and old userspace does not
+	  get protection "for free".
+
+	  CPUs supporting shadow stacks were first released in 2020.
+
+	  See Documentation/x86/shstk.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