arm64: ptr auth: Move per-thread keys from thread_info to thread_struct

We don't need to get at the per-thread keys from assembly at all, so
they can live alongside the rest of the per-thread register state in
thread_struct instead of thread_info.

This will also allow straighforward whitelisting of the keys for
hardened usercopy should we expose them via a ptrace request later on.
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/pointer_auth.h

@@ -80,12 +80,12 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 #define ptrauth_thread_init_user(tsk)					\
 do {									\
 	struct task_struct *__ptiu_tsk = (tsk);				\
-	ptrauth_keys_init(&__ptiu_tsk->thread_info.keys_user);		\
-	ptrauth_keys_switch(&__ptiu_tsk->thread_info.keys_user);	\
+	ptrauth_keys_init(&__ptiu_tsk->thread.keys_user);		\
+	ptrauth_keys_switch(&__ptiu_tsk->thread.keys_user);		\
 } while (0)
 
 #define ptrauth_thread_switch(tsk)	\
-	ptrauth_keys_switch(&(tsk)->thread_info.keys_user)
+	ptrauth_keys_switch(&(tsk)->thread.keys_user)
 
 #else /* CONFIG_ARM64_PTR_AUTH */
 #define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)

arch/arm64/include/asm/processor.h

@@ -147,6 +147,9 @@ struct thread_struct {
 	unsigned long		fault_address;	/* fault info */
 	unsigned long		fault_code;	/* ESR_EL1 value */
 	struct debug_info	debug;		/* debugging */
+#ifdef CONFIG_ARM64_PTR_AUTH
+	struct ptrauth_keys	keys_user;
+#endif
 };
 
 static inline void arch_thread_struct_whitelist(unsigned long *offset,

arch/arm64/include/asm/thread_info.h

@@ -28,7 +28,6 @@
 struct task_struct;
 
 #include <asm/memory.h>
-#include <asm/pointer_auth.h>
 #include <asm/stack_pointer.h>
 #include <asm/types.h>
 
@@ -55,9 +54,6 @@ struct thread_info {
 #endif
 		} preempt;
 	};
-#ifdef CONFIG_ARM64_PTR_AUTH
-	struct ptrauth_keys	keys_user;
-#endif
 };
 
 #define thread_saved_pc(tsk)	\

arch/arm64/kernel/pointer_auth.c

@@ -9,7 +9,7 @@
 
 int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
 {
-	struct ptrauth_keys *keys = &tsk->thread_info.keys_user;
+	struct ptrauth_keys *keys = &tsk->thread.keys_user;
 	unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |
 				      PR_PAC_APDAKEY | PR_PAC_APDBKEY;
 	unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;