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arm64: Conditionally configure PTR_AUTH key of the kernel. 

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>
Link: https://lore.kernel.org/r/20210613092632.93591-3-daniel.kiss@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Daniel Kiss 2021-06-13 11:26:32 +02:00 committed by Will Deacon
parent b27a9f4119
commit d053e71ac8
5 changed files with 67 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm64/Kconfig
View File

@ -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

49
arch/arm64/include/asm/asm_pointer_auth.h
View File

@ -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 */

59
arch/arm64/include/asm/pointer_auth.h
View File

@ -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)

2
arch/arm64/include/asm/processor.h
View File

@ -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

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

@ -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;