* [PATCH v6 1/2] arm64: Add ARM64_PTR_AUTH_KERNEL config option
2021-06-13 9:26 [PATCH v6 0/2] arm64: split ARM64_PTR_AUTH option to userspace and kernel Daniel Kiss
@ 2021-06-13 9:26 ` Daniel Kiss
2021-06-13 9:26 ` [PATCH v6 2/2] arm64: Conditionally configure PTR_AUTH key of the kernel Daniel Kiss
2021-06-15 12:06 ` [PATCH v6 0/2] arm64: split ARM64_PTR_AUTH option to userspace and kernel Will Deacon
2 siblings, 0 replies; 4+ messages in thread
From: Daniel Kiss @ 2021-06-13 9:26 UTC (permalink / raw)
To: will, Catalin.Marinas
Cc: Ard.Biesheuvel, daniel.kiss, linux-arm-kernel, pcc, Catalin Marinas
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>
---
arch/arm64/Kconfig | 33 +++++++++++++++++++--------------
arch/arm64/Makefile | 2 +-
arch/arm64/kernel/asm-offsets.c | 2 ++
drivers/misc/lkdtm/bugs.c | 6 +++---
4 files changed, 25 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9f1d8566bbf9..489e3e42320f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -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
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b52481f0605d..3b5b1c480449 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -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
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 0cb34ccb6e73..03420b89c602 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -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
diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index 0e8254d0cf0b..a164896dc6d4 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -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");
--
2.25.1
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^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v6 2/2] arm64: Conditionally configure PTR_AUTH key of the kernel.
2021-06-13 9:26 [PATCH v6 0/2] arm64: split ARM64_PTR_AUTH option to userspace and kernel Daniel Kiss
2021-06-13 9:26 ` [PATCH v6 1/2] arm64: Add ARM64_PTR_AUTH_KERNEL config option Daniel Kiss
@ 2021-06-13 9:26 ` Daniel Kiss
2021-06-15 12:06 ` [PATCH v6 0/2] arm64: split ARM64_PTR_AUTH option to userspace and kernel Will Deacon
2 siblings, 0 replies; 4+ messages in thread
From: Daniel Kiss @ 2021-06-13 9:26 UTC (permalink / raw)
To: will, Catalin.Marinas
Cc: Ard.Biesheuvel, daniel.kiss, linux-arm-kernel, pcc, Catalin Marinas
If the kernel is not compiled with CONFIG_ARM64_PTR_AUTH_KERNEL=y,
then no PACI/AUTI instructions are expected while the kernel is running
so the kernel's key will not be used. Write of a system registers
is expensive therefore avoid if not required.
Signed-off-by: Daniel Kiss <daniel.kiss@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/Kconfig | 2 +-
arch/arm64/include/asm/asm_pointer_auth.h | 49 +++++++++++--------
arch/arm64/include/asm/pointer_auth.h | 59 +++++++++++++----------
arch/arm64/include/asm/processor.h | 2 +
arch/arm64/kernel/asm-offsets.c | 2 +
5 files changed, 67 insertions(+), 47 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 489e3e42320f..dabe9b81012f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1503,7 +1503,7 @@ config ARM64_PTR_AUTH
not be selected.
config ARM64_PTR_AUTH_KERNEL
- bool
+ bool "Use pointer authentication for kernel"
default y
depends on ARM64_PTR_AUTH
depends on (CC_HAS_SIGN_RETURN_ADDRESS || CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC
diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h
index 8ca2dc0661ee..f1bba5fc61c4 100644
--- a/arch/arm64/include/asm/asm_pointer_auth.h
+++ b/arch/arm64/include/asm/asm_pointer_auth.h
@@ -7,19 +7,7 @@
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
-#ifdef CONFIG_ARM64_PTR_AUTH
-/*
- * thread.keys_user.ap* as offset exceeds the #imm offset range
- * so use the base value of ldp as thread.keys_user and offset as
- * thread.keys_user.ap*.
- */
- .macro __ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
- mov \tmp1, #THREAD_KEYS_USER
- add \tmp1, \tsk, \tmp1
- ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIA]
- msr_s SYS_APIAKEYLO_EL1, \tmp2
- msr_s SYS_APIAKEYHI_EL1, \tmp3
- .endm
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
.macro __ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
mov \tmp1, #THREAD_KEYS_KERNEL
@@ -42,6 +30,33 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
alternative_else_nop_endif
.endm
+#else /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
+ .macro __ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
+ .endm
+
+ .macro ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
+ .endm
+
+ .macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3
+ .endm
+
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
+#ifdef CONFIG_ARM64_PTR_AUTH
+/*
+ * thread.keys_user.ap* as offset exceeds the #imm offset range
+ * so use the base value of ldp as thread.keys_user and offset as
+ * thread.keys_user.ap*.
+ */
+ .macro __ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
+ mov \tmp1, #THREAD_KEYS_USER
+ add \tmp1, \tsk, \tmp1
+ ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIA]
+ msr_s SYS_APIAKEYLO_EL1, \tmp2
+ msr_s SYS_APIAKEYHI_EL1, \tmp3
+ .endm
+
.macro __ptrauth_keys_init_cpu tsk, tmp1, tmp2, tmp3
mrs \tmp1, id_aa64isar1_el1
ubfx \tmp1, \tmp1, #ID_AA64ISAR1_APA_SHIFT, #8
@@ -64,17 +79,11 @@ alternative_else_nop_endif
.Lno_addr_auth\@:
.endm
-#else /* CONFIG_ARM64_PTR_AUTH */
+#else /* !CONFIG_ARM64_PTR_AUTH */
.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
.endm
- .macro ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
- .endm
-
- .macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3
- .endm
-
#endif /* CONFIG_ARM64_PTR_AUTH */
#endif /* __ASM_ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index d50416be99be..28a78b67d9b4 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -31,10 +31,6 @@ struct ptrauth_keys_user {
struct ptrauth_key apga;
};
-struct ptrauth_keys_kernel {
- struct ptrauth_key apia;
-};
-
#define __ptrauth_key_install_nosync(k, v) \
do { \
struct ptrauth_key __pki_v = (v); \
@@ -42,6 +38,29 @@ do { \
write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \
} while (0)
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
+
+struct ptrauth_keys_kernel {
+ struct ptrauth_key apia;
+};
+
+static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
+{
+ if (system_supports_address_auth())
+ get_random_bytes(&keys->apia, sizeof(keys->apia));
+}
+
+static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
+{
+ if (!system_supports_address_auth())
+ return;
+
+ __ptrauth_key_install_nosync(APIA, keys->apia);
+ isb();
+}
+
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
static inline void ptrauth_keys_install_user(struct ptrauth_keys_user *keys)
{
if (system_supports_address_auth()) {
@@ -69,21 +88,6 @@ static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
ptrauth_keys_install_user(keys);
}
-static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
-{
- if (system_supports_address_auth())
- get_random_bytes(&keys->apia, sizeof(keys->apia));
-}
-
-static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
-{
- if (!system_supports_address_auth())
- return;
-
- __ptrauth_key_install_nosync(APIA, keys->apia);
- isb();
-}
-
extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
extern int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys,
@@ -121,11 +125,6 @@ static __always_inline void ptrauth_enable(void)
#define ptrauth_thread_switch_user(tsk) \
ptrauth_keys_install_user(&(tsk)->thread.keys_user)
-#define ptrauth_thread_init_kernel(tsk) \
- ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel)
-#define ptrauth_thread_switch_kernel(tsk) \
- ptrauth_keys_switch_kernel(&(tsk)->thread.keys_kernel)
-
#else /* CONFIG_ARM64_PTR_AUTH */
#define ptrauth_enable()
#define ptrauth_prctl_reset_keys(tsk, arg) (-EINVAL)
@@ -134,11 +133,19 @@ static __always_inline void ptrauth_enable(void)
#define ptrauth_strip_insn_pac(lr) (lr)
#define ptrauth_suspend_exit()
#define ptrauth_thread_init_user()
-#define ptrauth_thread_init_kernel(tsk)
#define ptrauth_thread_switch_user(tsk)
-#define ptrauth_thread_switch_kernel(tsk)
#endif /* CONFIG_ARM64_PTR_AUTH */
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
+#define ptrauth_thread_init_kernel(tsk) \
+ ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel)
+#define ptrauth_thread_switch_kernel(tsk) \
+ ptrauth_keys_switch_kernel(&(tsk)->thread.keys_kernel)
+#else
+#define ptrauth_thread_init_kernel(tsk)
+#define ptrauth_thread_switch_kernel(tsk)
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
#define PR_PAC_ENABLED_KEYS_MASK \
(PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY | PR_PAC_APDBKEY)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 9df3feeee890..e7d50c6f700d 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -148,8 +148,10 @@ struct thread_struct {
struct debug_info debug; /* debugging */
#ifdef CONFIG_ARM64_PTR_AUTH
struct ptrauth_keys_user keys_user;
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
struct ptrauth_keys_kernel keys_kernel;
#endif
+#endif
#ifdef CONFIG_ARM64_MTE
u64 gcr_user_excl;
#endif
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 03420b89c602..c9e72d92606f 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -155,7 +155,9 @@ int main(void)
#endif
#ifdef CONFIG_ARM64_PTR_AUTH
DEFINE(PTRAUTH_USER_KEY_APIA, offsetof(struct ptrauth_keys_user, apia));
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
DEFINE(PTRAUTH_KERNEL_KEY_APIA, offsetof(struct ptrauth_keys_kernel, apia));
+#endif
BLANK();
#endif
return 0;
--
2.25.1
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^ permalink raw reply related [flat|nested] 4+ messages in thread