[PATCH v6 20/21] arm64: Defer enabling pointer authentication on boot core

[Marc Zyngier]

From: Srinivas Ramana <sramana@xxxxxxxxxxxxxx>

Defer enabling pointer authentication on boot core until
after its required to be enabled by cpufeature framework.
This will help in controlling the feature dynamically
with a boot parameter.

Signed-off-by: Ajay Patil <pajay@xxxxxxxxxxxxxxxx>
Signed-off-by: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
Signed-off-by: Srinivas Ramana <sramana@xxxxxxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/1610152163-16554-2-git-send-email-sramana@xxxxxxxxxxxxxx
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Acked-by: David Brazdil <dbrazdil@xxxxxxxxxx>
---
 arch/arm64/include/asm/pointer_auth.h   | 10 ++++++++++
 arch/arm64/include/asm/stackprotector.h |  1 +
 arch/arm64/kernel/head.S                |  4 ----
 3 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index c6b4f0603024..b112a11e9302 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -76,6 +76,15 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 	return ptrauth_clear_pac(ptr);
 }
 
+static __always_inline void ptrauth_enable(void)
+{
+	if (!system_supports_address_auth())
+		return;
+	sysreg_clear_set(sctlr_el1, 0, (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB |
+					SCTLR_ELx_ENDA | SCTLR_ELx_ENDB));
+	isb();
+}
+
 #define ptrauth_thread_init_user(tsk)					\
 	ptrauth_keys_init_user(&(tsk)->thread.keys_user)
 #define ptrauth_thread_init_kernel(tsk)					\
@@ -84,6 +93,7 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 	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)
diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h
index 7263e0bac680..33f1bb453150 100644
--- a/arch/arm64/include/asm/stackprotector.h
+++ b/arch/arm64/include/asm/stackprotector.h
@@ -41,6 +41,7 @@ static __always_inline void boot_init_stack_canary(void)
 #endif
 	ptrauth_thread_init_kernel(current);
 	ptrauth_thread_switch_kernel(current);
+	ptrauth_enable();
 }
 
 #endif	/* _ASM_STACKPROTECTOR_H */
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 3243e3ae9bd8..2e116ef255e1 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -404,10 +404,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	adr_l	x5, init_task
 	msr	sp_el0, x5			// Save thread_info
 
-#ifdef CONFIG_ARM64_PTR_AUTH
-	__ptrauth_keys_init_cpu	x5, x6, x7, x8
-#endif
-
 	adr_l	x8, vectors			// load VBAR_EL1 with virtual
 	msr	vbar_el1, x8			// vector table address
 	isb
-- 
2.29.2