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arm64: Add gcc Shadow Call Stack support

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Shadow call stacks will be available in GCC >= 12, this patch makes
the corresponding kernel configuration available when compiling
the kernel with the gcc.

Note that the implementation in GCC is slightly different from Clang.
With SCS enabled, functions will only pop x30 once in the epilogue,
like:

   str     x30, [x18], #8
   stp     x29, x30, [sp, #-16]!
   ......
-  ldp     x29, x30, [sp], #16	  //clang
+  ldr     x29, [sp], #16	  //GCC
   ldr     x30, [x18, #-8]!

Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=ce09ab17ddd21f73ff2caf6eec3b0ee9b0e1a11e

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Dan Li <ashimida@linux.alibaba.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220303074323.86282-1-ashimida@linux.alibaba.com
This commit is contained in:
Dan Li 2022-03-02 23:43:23 -08:00 committed by Kees Cook
parent 575d6b77fa
commit afcf5441b9
3 changed files with 15 additions and 10 deletions
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19
arch/Kconfig
View File

@ -599,21 +599,22 @@ config STACKPROTECTOR_STRONG
config ARCH_SUPPORTS_SHADOW_CALL_STACK
bool
help
An architecture should select this if it supports Clang's Shadow
Call Stack and implements runtime support for shadow stack
An architecture should select this if it supports the compiler's
Shadow Call Stack and implements runtime support for shadow stack
switching.
config SHADOW_CALL_STACK
bool "Clang Shadow Call Stack"
depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK
bool "Shadow Call Stack"
depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
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 in
Clang's documentation:
This option enables the compiler'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
in the compiler's documentation:
https://clang.llvm.org/docs/ShadowCallStack.html
- Clang: https://clang.llvm.org/docs/ShadowCallStack.html
- GCC: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options
Note that security guarantees in the kernel differ from the
ones documented for user space. The kernel must store addresses

2
arch/arm64/Kconfig
View File

@ -1239,7 +1239,7 @@ config HW_PERF_EVENTS
config ARCH_HAS_FILTER_PGPROT
def_bool y
# Supported by clang >= 7.0
# Supported by clang >= 7.0 or GCC >= 12.0.0
config CC_HAVE_SHADOW_CALL_STACK
def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)

4
include/linux/compiler-gcc.h
View File

@ -97,6 +97,10 @@
#define KASAN_ABI_VERSION 4
#endif
#ifdef CONFIG_SHADOW_CALL_STACK
#define __noscs __attribute__((__no_sanitize__("shadow-call-stack")))
#endif
#if __has_attribute(__no_sanitize_address__)
#define __no_sanitize_address __attribute__((no_sanitize_address))
#else