On Tue, Feb 18, 2020 at 8:20 PM Randy Dunlap [off-list ref] wrote:

Hi Sami,

a couple of minor tweaks:

On 2/18/20 4:08 PM, Sami Tolvanen wrote:

quoted

diff --git a/arch/Kconfig b/arch/Kconfig
index 98de654b79b3..66b34fd0df54 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig

@@ -526,6 +526,40 @@ config STACKPROTECTOR_STRONG
        about 20% of all kernel functions, which increases the kernel code
        size by about 2%.

+config ARCH_SUPPORTS_SHADOW_CALL_STACK
+     bool
+     help
+       An architecture should select this if it supports Clang's Shadow
+       Call Stack, has asm/scs.h, and implements runtime support for shadow
+       stack switching.
+
+config SHADOW_CALL_STACK
+     bool "Clang Shadow Call Stack"
+     depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
+     help
+       This option enables Clang's Shadow Call Stack, which uses a
+       shadow stack to protect function return addresses from being
+       overwritten by an attacker. More information can be found from

                                                              found in

quoted

+       Clang's documentation:
+
+         https://clang.llvm.org/docs/ShadowCallStack.html
+
+       Note that security guarantees in the kernel differ from the ones
+       documented for user space. The kernel must store addresses of shadow
+       stacks used by other tasks and interrupt handlers in memory, which
+       means an attacker capable reading and writing arbitrary memory may

                            capable of

Thanks, Randy! I'll fix these in the next version.

Sami

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