* [PATCH v3 1/2] arm64: Add ARM64_PTR_AUTH_KERNEL config option
2021-02-08 14:55 [PATCH v3 0/2] arm64: split ARM64_PTR_AUTH option to userspace and kernel Daniel Kiss
@ 2021-02-08 14:55 ` Daniel Kiss
2021-03-29 14:51 ` Will Deacon
2021-02-08 14:55 ` [PATCH v3 2/2] arm64: Conditionally configure PTR_AUTH key of the kernel Daniel Kiss
1 sibling, 1 reply; 6+ messages in thread
From: Daniel Kiss @ 2021-02-08 14:55 UTC (permalink / raw)
To: linux-arm-kernel, will; +Cc: Catalin.Marinas, pcc, Ard.Biesheuvel, Daniel Kiss
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>
---
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 f39568b28ec1..c1268cdd6964 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1474,12 +1474,6 @@ 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 >= 233010000 || (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
@@ -1491,13 +1485,6 @@ 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.
@@ -1508,6 +1495,24 @@ 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 "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
+ # 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 >= 233010000 || (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.
@@ -1599,7 +1604,7 @@ 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 90309208bb28..a50b5e8231a7 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 301784463587..21c9f98f868d 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -45,6 +45,8 @@ int main(void)
DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_context));
#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 110f5a8538e9..b5b809b3e1ef 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -446,7 +446,7 @@ 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);
@@ -460,8 +460,8 @@ 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] 6+ messages in thread* [PATCH v3 2/2] arm64: Conditionally configure PTR_AUTH key of the kernel.
2021-02-08 14:55 [PATCH v3 0/2] arm64: split ARM64_PTR_AUTH option to userspace and kernel Daniel Kiss
2021-02-08 14:55 ` [PATCH v3 1/2] arm64: Add ARM64_PTR_AUTH_KERNEL config option Daniel Kiss
@ 2021-02-08 14:55 ` Daniel Kiss
2021-03-29 14:51 ` Will Deacon
1 sibling, 1 reply; 6+ messages in thread
From: Daniel Kiss @ 2021-02-08 14:55 UTC (permalink / raw)
To: linux-arm-kernel, will; +Cc: Catalin.Marinas, pcc, Ard.Biesheuvel, Daniel Kiss
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 regiters
is expensive therefore avoid it not required.
Signed-off-by: Daniel Kiss <daniel.kiss@arm.com>
---
arch/arm64/include/asm/asm_pointer_auth.h | 63 +++++++++++++----------
arch/arm64/include/asm/pointer_auth.h | 20 +++++--
arch/arm64/include/asm/processor.h | 2 +
arch/arm64/kernel/asm-offsets.c | 2 +
4 files changed, 54 insertions(+), 33 deletions(-)
diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h
index 52dead2a8640..413cc36fdd5c 100644
--- a/arch/arm64/include/asm/asm_pointer_auth.h
+++ b/arch/arm64/include/asm/asm_pointer_auth.h
@@ -7,6 +7,38 @@
#include <asm/cpufeature.h>
#include <asm/sysreg.h>
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
+ .macro __ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
+ mov \tmp1, #THREAD_KEYS_KERNEL
+ add \tmp1, \tsk, \tmp1
+ ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_KERNEL_KEY_APIA]
+ msr_s SYS_APIAKEYLO_EL1, \tmp2
+ msr_s SYS_APIAKEYHI_EL1, \tmp3
+ .endm
+
+ .macro ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
+alternative_if ARM64_HAS_ADDRESS_AUTH
+ __ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
+alternative_else_nop_endif
+ .endm
+
+ .macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3
+alternative_if ARM64_HAS_ADDRESS_AUTH
+ __ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
+ isb
+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 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
@@ -39,27 +71,6 @@ alternative_if ARM64_HAS_GENERIC_AUTH
alternative_else_nop_endif
.endm
- .macro __ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
- mov \tmp1, #THREAD_KEYS_KERNEL
- add \tmp1, \tsk, \tmp1
- ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_KERNEL_KEY_APIA]
- msr_s SYS_APIAKEYLO_EL1, \tmp2
- msr_s SYS_APIAKEYHI_EL1, \tmp3
- .endm
-
- .macro ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
-alternative_if ARM64_HAS_ADDRESS_AUTH
- __ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
-alternative_else_nop_endif
- .endm
-
- .macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3
-alternative_if ARM64_HAS_ADDRESS_AUTH
- __ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
- isb
-alternative_else_nop_endif
- .endm
-
.macro __ptrauth_keys_init_cpu tsk, tmp1, tmp2, tmp3
mrs \tmp1, id_aa64isar1_el1
ubfx \tmp1, \tmp1, #ID_AA64ISAR1_APA_SHIFT, #8
@@ -69,7 +80,9 @@ alternative_else_nop_endif
mrs \tmp2, sctlr_el1
orr \tmp2, \tmp2, \tmp1
msr sctlr_el1, \tmp2
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
__ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
+#endif
isb
.Lno_addr_auth\@:
.endm
@@ -82,17 +95,11 @@ 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 c6b4f0603024..b34aebb95757 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -30,9 +30,11 @@ struct ptrauth_keys_user {
struct ptrauth_key apga;
};
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
struct ptrauth_keys_kernel {
struct ptrauth_key apia;
};
+#endif
static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
{
@@ -54,6 +56,8 @@ do { \
write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \
} while (0)
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
+
static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
{
if (system_supports_address_auth())
@@ -69,6 +73,8 @@ static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kerne
isb();
}
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
@@ -78,17 +84,21 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
#define ptrauth_thread_init_user(tsk) \
ptrauth_keys_init_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_prctl_reset_keys(tsk, arg) (-EINVAL)
#define ptrauth_strip_insn_pac(lr) (lr)
#define ptrauth_thread_init_user(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 */
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
#endif /* __ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index ca2cd75d3286..318e0e7cf9e1 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 sctlr_tcf0;
u64 gcr_user_excl;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 21c9f98f868d..3b58804e4224 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -150,7 +150,9 @@ int main(void)
DEFINE(PTRAUTH_USER_KEY_APDA, offsetof(struct ptrauth_keys_user, apda));
DEFINE(PTRAUTH_USER_KEY_APDB, offsetof(struct ptrauth_keys_user, apdb));
DEFINE(PTRAUTH_USER_KEY_APGA, offsetof(struct ptrauth_keys_user, apga));
+#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] 6+ messages in thread