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Date: Tue, 2 Nov 2021 00:58:12 -0700
From: Dan Li <ashimida@...ux.alibaba.com>
To: catalin.marinas@....com, will@...nel.org, nathan@...nel.org,
ndesaulniers@...gle.com, keescook@...omium.org, tglx@...utronix.de,
akpm@...ux-foundation.org, peterz@...radead.org,
samitolvanen@...gle.com, masahiroy@...nel.org, rppt@...nel.org,
mark.rutland@....com, frederic@...nel.org, yifeifz2@...inois.edu,
rostedt@...dmis.org, viresh.kumar@...aro.org, andreyknvl@...il.com,
colin.king@...onical.com, ojeda@...nel.org, arnd@...db.de,
luc.vanoostenryck@...il.com, nivedita@...m.mit.edu,
elver@...gle.com
Cc: linux-hardening@...r.kernel.org,
Dan Li <ashimida@...ux.alibaba.com>
Subject: [PATCH] [RFC/RFT] AARCH64: Add gcc Shadow Call Stack support
I tried to submit a patch[1] to add compiler's SCS support on gcc-11.1.0.
Kernel can enable SCS under gcc based on this patch, commands as follows:
make ARCH=arm64 defconfig
./scripts/config -e CONFIG_SHADOW_CALL_STACK
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
[1] https://gcc.gnu.org/pipermail/gcc-patches/2021-November/583062.html
Signed-off-by: Dan Li <ashimida@...ux.alibaba.com>
---
This function can be used to test whether the shadow stack is effective:
//noinline void __noscs scs_test(void)
noinline void scs_test(void)
{
register unsigned long *sp asm("sp");
unsigned long * lr = sp + 1;
asm volatile("":::"x30");
*lr = 0;
}
ffff800010012710 <scs_test>:
ffff800010012710: d503245f bti c
ffff800010012714: d503233f paciasp
ffff800010012718: a9bf7bfd stp x29, x30, [sp, #-16]!
ffff80001001271c: 910003fd mov x29, sp
ffff800010012720: 910003e0 mov x0, sp
ffff800010012724: f900041f str xzr, [x0, #8]
ffff800010012728: a8c17bfd ldp x29, x30, [sp], #16
ffff80001001272c: d50323bf autiasp
ffff800010012730: d65f03c0 ret
arch/Kconfig | 6 +++---
arch/arm64/Kconfig | 2 +-
include/linux/compiler-gcc.h | 6 ++++++
3 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index 98db63496bab..35b27be0d7ee 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -593,11 +593,11 @@ config ARCH_SUPPORTS_SHADOW_CALL_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
+ This option enables Clang/GCC'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:
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 62c3c1d2190f..5d49c0c89645 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1062,7 +1062,7 @@ config ARCH_HAS_FILTER_PGPROT
# Supported by clang >= 7.0
config CC_HAVE_SHADOW_CALL_STACK
- def_bool $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
+ def_bool CC_IS_CLANG || $(cc-option, -fsanitize=shadow-call-stack -ffixed-x18)
config PARAVIRT
bool "Enable paravirtualization code"
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index cb9217fc60af..917c3bb6aa43 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -104,6 +104,12 @@
#define KASAN_ABI_VERSION 3
#endif
+#if __has_attribute(__no_sanitize_shadow_call_stack__)
+#define __noscs __attribute__((no_sanitize_shadow_call_stack))
+#else
+#define __noscs
+#endif
+
#if __has_attribute(__no_sanitize_address__)
#define __no_sanitize_address __attribute__((no_sanitize_address))
#else
--
2.17.1
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