Merge branch 'for-next/ptrauth' into for-next/core

Allow Pointer Authentication to be configured independently for kernel
and userspace.

* for-next/ptrauth:
  arm64: Conditionally configure PTR_AUTH key of the kernel.
  arm64: Add ARM64_PTR_AUTH_KERNEL config option

Author: willdeacon

arch/arm64/Kconfig

@@ -1481,12 +1481,6 @@ 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 >= 23301 || (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
@@ -1498,13 +1492,6 @@ 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.
@@ -1515,6 +1502,24 @@ 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 >= 23301 || (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.
 
@@ -1606,7 +1611,7 @@ 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

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

arch/arm64/include/asm/asm_pointer_auth.h

@@ -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 */

arch/arm64/include/asm/pointer_auth.h

@@ -31,17 +31,36 @@ 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);			\
 	write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1);	\
 	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)
 

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			gcr_user_excl;
 #endif

arch/arm64/kernel/asm-offsets.c

@@ -47,6 +47,8 @@ int main(void)
   DEFINE(THREAD_SCTLR_USER,	offsetof(struct task_struct, thread.sctlr_user));
 #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
@@ -153,7 +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;

drivers/misc/lkdtm/bugs.c

@@ -463,7 +463,7 @@ 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);
@@ -477,8 +477,8 @@ 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");