[PATCH v4 2/2] arm64: Conditionally configure PTR_AUTH key of the kernel.
Daniel Kiss
daniel.kiss at arm.com
Fri Apr 16 13:50:15 BST 2021
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 at arm.com>
---
arch/arm64/include/asm/asm_pointer_auth.h | 63 +++++++++++++----------
arch/arm64/include/asm/pointer_auth.h | 44 +++++++++-------
arch/arm64/include/asm/processor.h | 2 +
arch/arm64/kernel/asm-offsets.c | 2 +
4 files changed, 65 insertions(+), 46 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 b112a11e9302..32e540e3042f 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -30,23 +30,12 @@ struct ptrauth_keys_user {
struct ptrauth_key apga;
};
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
+
struct ptrauth_keys_kernel {
struct ptrauth_key apia;
};
-static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
-{
- if (system_supports_address_auth()) {
- get_random_bytes(&keys->apia, sizeof(keys->apia));
- get_random_bytes(&keys->apib, sizeof(keys->apib));
- get_random_bytes(&keys->apda, sizeof(keys->apda));
- get_random_bytes(&keys->apdb, sizeof(keys->apdb));
- }
-
- if (system_supports_generic_auth())
- get_random_bytes(&keys->apga, sizeof(keys->apga));
-}
-
#define __ptrauth_key_install_nosync(k, v) \
do { \
struct ptrauth_key __pki_v = (v); \
@@ -69,6 +58,21 @@ static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kerne
isb();
}
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
+static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
+{
+ if (system_supports_address_auth()) {
+ get_random_bytes(&keys->apia, sizeof(keys->apia));
+ get_random_bytes(&keys->apib, sizeof(keys->apib));
+ get_random_bytes(&keys->apda, sizeof(keys->apda));
+ get_random_bytes(&keys->apdb, sizeof(keys->apdb));
+ }
+
+ if (system_supports_generic_auth())
+ get_random_bytes(&keys->apga, sizeof(keys->apga));
+}
+
extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
@@ -87,18 +91,22 @@ static __always_inline void ptrauth_enable(void)
#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_enable()
#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 efc10e9041a0..9392c0dc2eeb 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 e4c6585909ed..443ec8b7622b 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -153,7 +153,9 @@ 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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