[PATCH 2/2] arm64: Configure kernel's PTR_AUTH key when it is built with PTR_AUTH.

[Daniel Kiss]

If the kernel is not compiled with CONFIG_ARM64_PTR_AUTH_KERNEL,
then the kernel does not need a key and kernel's key could be disabled.

Signed-off-by: Daniel Kiss <daniel.kiss at arm.com>
---
 arch/arm64/include/asm/asm_pointer_auth.h | 68 ++++++++++++++++-------
 arch/arm64/include/asm/processor.h        |  2 +
 arch/arm64/kernel/asm-offsets.c           |  4 ++
 3 files changed, 55 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h
index 52dead2a8640..af3d16027e8f 100644
--- a/arch/arm64/include/asm/asm_pointer_auth.h
+++ b/arch/arm64/include/asm/asm_pointer_auth.h
@@ -14,6 +14,12 @@
  * thread.keys_user.ap*.
  */
 	.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
+#ifndef CONFIG_ARM64_PTR_AUTH_KERNEL
+	/* Reenable A key */
+	mrs	\tmp1, sctlr_el1
+	orr	\tmp1, \tmp1, SCTLR_ELx_ENIA
+	msr	sctlr_el1, \tmp1
+#endif
 	mov	\tmp1, #THREAD_KEYS_USER
 	add	\tmp1, \tsk, \tmp1
 alternative_if_not ARM64_HAS_ADDRESS_AUTH
@@ -39,6 +45,36 @@ alternative_if ARM64_HAS_GENERIC_AUTH
 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
+	cbz	\tmp1, .Lno_addr_auth\@
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
+	mov_q	\tmp1, (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
+			SCTLR_ELx_ENDA | SCTLR_ELx_ENDB)
+#else
+	mov_q	\tmp1, (SCTLR_ELx_ENIB | \
+			SCTLR_ELx_ENDA | SCTLR_ELx_ENDB)
+#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
+
+	.macro ptrauth_keys_init_cpu tsk, tmp1, tmp2, tmp3
+alternative_if_not ARM64_HAS_ADDRESS_AUTH
+	b	.Lno_addr_auth\@
+alternative_else_nop_endif
+	__ptrauth_keys_init_cpu \tsk, \tmp1, \tmp2, \tmp3
+.Lno_addr_auth\@:
+	.endm
+
+#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
@@ -60,29 +96,23 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
 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
-	cbz	\tmp1, .Lno_addr_auth\@
-	mov_q	\tmp1, (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
-			SCTLR_ELx_ENDA | SCTLR_ELx_ENDB)
-	mrs	\tmp2, sctlr_el1
-	orr	\tmp2, \tmp2, \tmp1
-	msr	sctlr_el1, \tmp2
-	__ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
-	isb
-.Lno_addr_auth\@:
+#else /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
+	.macro ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3
+	mrs	\tmp1, sctlr_el1
+	and	\tmp1, \tmp1, ~SCTLR_ELx_ENIA
+	msr	sctlr_el1, \tmp1
 	.endm
 
-	.macro ptrauth_keys_init_cpu tsk, tmp1, tmp2, tmp3
-alternative_if_not ARM64_HAS_ADDRESS_AUTH
-	b	.Lno_addr_auth\@
-alternative_else_nop_endif
-	__ptrauth_keys_init_cpu \tsk, \tmp1, \tmp2, \tmp3
-.Lno_addr_auth\@:
+	.macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3
+	mrs	\tmp1, sctlr_el1
+	and	\tmp1, \tmp1, ~SCTLR_ELx_ENIA
+	msr	sctlr_el1, \tmp1
 	.endm
 
-#else /* CONFIG_ARM64_PTR_AUTH */
+#endif /* CONFIG_ARM64_PTR_AUTH_KERNEL */
+
+#else /* !CONFIG_ARM64_PTR_AUTH */
 
 	.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
 	.endm
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index fce8cbecd6bc..e20888b321e3 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -150,8 +150,10 @@ 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_incl;
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 7d32fc959b1a..cb7965a9f505 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -46,7 +46,9 @@ 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));
+#ifdef CONFIG_ARM64_PTR_AUTH_KERNEL
   DEFINE(THREAD_KEYS_KERNEL,	offsetof(struct task_struct, thread.keys_kernel));
+#endif
 #endif
   BLANK();
   DEFINE(S_X0,			offsetof(struct pt_regs, regs[0]));
@@ -141,7 +143,9 @@ 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;
-- 
2.17.1