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arm64: Add ARM64_PTR_AUTH_KERNEL config option 

This patch add the ARM64_PTR_AUTH_KERNEL config and deals with the
build aspect of it.

Userspace support has no dependency on the toolchain therefore all
toolchain checks and build flags are controlled the new config
option.
The default config behavior will not be changed.

Signed-off-by: Daniel Kiss <daniel.kiss@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20210613092632.93591-2-daniel.kiss@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Daniel Kiss 2021-06-13 11:26:31 +02:00 committed by Will Deacon
parent c4681547bc
commit b27a9f4119
4 changed files with 25 additions and 18 deletions
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33
arch/arm64/Kconfig
View File

@ -1481,12 +1481,6 @@ menu "ARMv8.3 architectural features"
config ARM64_PTR_AUTH
bool "Enable support for pointer authentication"
default y
depends on (CC_HAS_SIGN_RETURN_ADDRESS || CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC
# Modern compilers insert a .note.gnu.property section note for PAC
# which is only understood by binutils starting with version 2.33.1.
depends on LD_IS_LLD || LD_VERSION >= 23301 || (CC_IS_GCC && GCC_VERSION < 90100)
depends on !CC_IS_CLANG || AS_HAS_CFI_NEGATE_RA_STATE
depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_REGS)
help
Pointer authentication (part of the ARMv8.3 Extensions) provides
instructions for signing and authenticating pointers against secret
@ -1498,13 +1492,6 @@ config ARM64_PTR_AUTH
for each process at exec() time, with these keys being
context-switched along with the process.
If the compiler supports the -mbranch-protection or
-msign-return-address flag (e.g. GCC 7 or later), then this option
will also cause the kernel itself to be compiled with return address
protection. In this case, and if the target hardware is known to
support pointer authentication, then CONFIG_STACKPROTECTOR can be
disabled with minimal loss of protection.
The feature is detected at runtime. If the feature is not present in
hardware it will not be advertised to userspace/KVM guest nor will it
be enabled.
@ -1515,6 +1502,24 @@ config ARM64_PTR_AUTH
but with the feature disabled. On such a system, this option should
not be selected.
config ARM64_PTR_AUTH_KERNEL
bool
default y
depends on ARM64_PTR_AUTH
depends on (CC_HAS_SIGN_RETURN_ADDRESS || CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC
# Modern compilers insert a .note.gnu.property section note for PAC
# which is only understood by binutils starting with version 2.33.1.
depends on LD_IS_LLD || LD_VERSION >= 23301 || (CC_IS_GCC && GCC_VERSION < 90100)
depends on !CC_IS_CLANG || AS_HAS_CFI_NEGATE_RA_STATE
depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_REGS)
help
If the compiler supports the -mbranch-protection or
-msign-return-address flag (e.g. GCC 7 or later), then this option
will cause the kernel itself to be compiled with return address
protection. In this case, and if the target hardware is known to
support pointer authentication, then CONFIG_STACKPROTECTOR can be
disabled with minimal loss of protection.
This feature works with FUNCTION_GRAPH_TRACER option only if
DYNAMIC_FTRACE_WITH_REGS is enabled.
@ -1606,7 +1611,7 @@ config ARM64_BTI_KERNEL
bool "Use Branch Target Identification for kernel"
default y
depends on ARM64_BTI
depends on ARM64_PTR_AUTH
depends on ARM64_PTR_AUTH_KERNEL
depends on CC_HAS_BRANCH_PROT_PAC_RET_BTI
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94697
depends on !CC_IS_GCC || GCC_VERSION >= 100100

2
arch/arm64/Makefile
View File

@ -70,7 +70,7 @@ endif
# off, this will be overridden if we are using branch protection.
branch-prot-flags-y += $(call cc-option,-mbranch-protection=none)
ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
ifeq ($(CONFIG_ARM64_PTR_AUTH_KERNEL),y)
branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
# We enable additional protection for leaf functions as there is some
# narrow potential for ROP protection benefits and no substantial

2
arch/arm64/kernel/asm-offsets.c
View File

@ -46,6 +46,8 @@ int main(void)
DEFINE(THREAD_SCTLR_USER, offsetof(struct task_struct, thread.sctlr_user));
#ifdef CONFIG_ARM64_PTR_AUTH
DEFINE(THREAD_KEYS_USER, offsetof(struct task_struct, thread.keys_user));
#endif
#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
DEFINE(THREAD_KEYS_KERNEL, offsetof(struct task_struct, thread.keys_kernel));
#endif
#ifdef CONFIG_ARM64_MTE

6
drivers/misc/lkdtm/bugs.c
View File

@ -463,7 +463,7 @@ void lkdtm_DOUBLE_FAULT(void)
#ifdef CONFIG_ARM64
static noinline void change_pac_parameters(void)
{
if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH)) {
if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL)) {
/* Reset the keys of current task */
ptrauth_thread_init_kernel(current);
ptrauth_thread_switch_kernel(current);
@ -477,8 +477,8 @@ noinline void lkdtm_CORRUPT_PAC(void)
#define CORRUPT_PAC_ITERATE 10
int i;
if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH))
pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH\n");
if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH_KERNEL))
pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH_KERNEL\n");
if (!system_supports_address_auth()) {
pr_err("FAIL: CPU lacks pointer authentication feature\n");