arm64: add ptrace regsets for ptrauth key management

Add two new ptrace regsets, which can be used to request and change the
pointer authentication keys of a thread. NT_ARM_PACA_KEYS gives access
to the instruction/data address keys, and NT_ARM_PACG_KEYS to the
generic authentication key. The keys are also part of the core dump file
of the process.

The regsets are only exposed if the kernel is compiled with
CONFIG_CHECKPOINT_RESTORE=y, as the only intended use case is
checkpointing and restoring processes that are using pointer
authentication. (This can be changed later if there are other use
cases.)

Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/ptrace.c

@@ -979,6 +979,131 @@ static int pac_mask_get(struct task_struct *target,
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &uregs, 0, -1);
 }
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static __uint128_t pac_key_to_user(const struct ptrauth_key *key)
+{
+	return (__uint128_t)key->hi << 64 | key->lo;
+}
+
+static struct ptrauth_key pac_key_from_user(__uint128_t ukey)
+{
+	struct ptrauth_key key = {
+		.lo = (unsigned long)ukey,
+		.hi = (unsigned long)(ukey >> 64),
+	};
+
+	return key;
+}
+
+static void pac_address_keys_to_user(struct user_pac_address_keys *ukeys,
+				     const struct ptrauth_keys *keys)
+{
+	ukeys->apiakey = pac_key_to_user(&keys->apia);
+	ukeys->apibkey = pac_key_to_user(&keys->apib);
+	ukeys->apdakey = pac_key_to_user(&keys->apda);
+	ukeys->apdbkey = pac_key_to_user(&keys->apdb);
+}
+
+static void pac_address_keys_from_user(struct ptrauth_keys *keys,
+				       const struct user_pac_address_keys *ukeys)
+{
+	keys->apia = pac_key_from_user(ukeys->apiakey);
+	keys->apib = pac_key_from_user(ukeys->apibkey);
+	keys->apda = pac_key_from_user(ukeys->apdakey);
+	keys->apdb = pac_key_from_user(ukeys->apdbkey);
+}
+
+static int pac_address_keys_get(struct task_struct *target,
+				const struct user_regset *regset,
+				unsigned int pos, unsigned int count,
+				void *kbuf, void __user *ubuf)
+{
+	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct user_pac_address_keys user_keys;
+
+	if (!system_supports_address_auth())
+		return -EINVAL;
+
+	pac_address_keys_to_user(&user_keys, keys);
+
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+				   &user_keys, 0, -1);
+}
+
+static int pac_address_keys_set(struct task_struct *target,
+				const struct user_regset *regset,
+				unsigned int pos, unsigned int count,
+				const void *kbuf, const void __user *ubuf)
+{
+	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct user_pac_address_keys user_keys;
+	int ret;
+
+	if (!system_supports_address_auth())
+		return -EINVAL;
+
+	pac_address_keys_to_user(&user_keys, keys);
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				 &user_keys, 0, -1);
+	if (ret)
+		return ret;
+	pac_address_keys_from_user(keys, &user_keys);
+
+	return 0;
+}
+
+static void pac_generic_keys_to_user(struct user_pac_generic_keys *ukeys,
+				     const struct ptrauth_keys *keys)
+{
+	ukeys->apgakey = pac_key_to_user(&keys->apga);
+}
+
+static void pac_generic_keys_from_user(struct ptrauth_keys *keys,
+				       const struct user_pac_generic_keys *ukeys)
+{
+	keys->apga = pac_key_from_user(ukeys->apgakey);
+}
+
+static int pac_generic_keys_get(struct task_struct *target,
+				const struct user_regset *regset,
+				unsigned int pos, unsigned int count,
+				void *kbuf, void __user *ubuf)
+{
+	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct user_pac_generic_keys user_keys;
+
+	if (!system_supports_generic_auth())
+		return -EINVAL;
+
+	pac_generic_keys_to_user(&user_keys, keys);
+
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+				   &user_keys, 0, -1);
+}
+
+static int pac_generic_keys_set(struct task_struct *target,
+				const struct user_regset *regset,
+				unsigned int pos, unsigned int count,
+				const void *kbuf, const void __user *ubuf)
+{
+	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct user_pac_generic_keys user_keys;
+	int ret;
+
+	if (!system_supports_generic_auth())
+		return -EINVAL;
+
+	pac_generic_keys_to_user(&user_keys, keys);
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+				 &user_keys, 0, -1);
+	if (ret)
+		return ret;
+	pac_generic_keys_from_user(keys, &user_keys);
+
+	return 0;
+}
+#endif /* CONFIG_CHECKPOINT_RESTORE */
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 enum aarch64_regset {
@@ -995,6 +1120,10 @@ enum aarch64_regset {
 #endif
 #ifdef CONFIG_ARM64_PTR_AUTH
 	REGSET_PAC_MASK,
+#ifdef CONFIG_CHECKPOINT_RESTORE
+	REGSET_PACA_KEYS,
+	REGSET_PACG_KEYS,
+#endif
 #endif
 };
 
@@ -1074,6 +1203,24 @@ static const struct user_regset aarch64_regsets[] = {
 		.get = pac_mask_get,
 		/* this cannot be set dynamically */
 	},
+#ifdef CONFIG_CHECKPOINT_RESTORE
+	[REGSET_PACA_KEYS] = {
+		.core_note_type = NT_ARM_PACA_KEYS,
+		.n = sizeof(struct user_pac_address_keys) / sizeof(__uint128_t),
+		.size = sizeof(__uint128_t),
+		.align = sizeof(__uint128_t),
+		.get = pac_address_keys_get,
+		.set = pac_address_keys_set,
+	},
+	[REGSET_PACG_KEYS] = {
+		.core_note_type = NT_ARM_PACG_KEYS,
+		.n = sizeof(struct user_pac_generic_keys) / sizeof(__uint128_t),
+		.size = sizeof(__uint128_t),
+		.align = sizeof(__uint128_t),
+		.get = pac_generic_keys_get,
+		.set = pac_generic_keys_set,
+	},
+#endif
 #endif
 };