arm64: Remove the get_thread_info() function

This function was introduced by previous commits implementing UAO.
However, it can be replaced with task_thread_info() in
uao_thread_switch() or get_fs() in do_page_fault() (the latter being
called only on the current context, so no need for using the saved
pt_regs).
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/thread_info.h

@@ -85,12 +85,6 @@ static inline struct thread_info *current_thread_info(void)
 	return (struct thread_info *)sp_el0;
 }
 
-/* Access struct thread_info of another thread */
-static inline struct thread_info *get_thread_info(unsigned long thread_stack)
-{
-	return (struct thread_info *)(thread_stack & ~(THREAD_SIZE - 1));
-}
-
 #define thread_saved_pc(tsk)	\
 	((unsigned long)(tsk->thread.cpu_context.pc))
 #define thread_saved_sp(tsk)	\

arch/arm64/kernel/process.c

@@ -315,15 +315,12 @@ static void tls_thread_switch(struct task_struct *next)
 /* Restore the UAO state depending on next's addr_limit */
 static void uao_thread_switch(struct task_struct *next)
 {
-	unsigned long next_sp = next->thread.cpu_context.sp;
-
-	if (IS_ENABLED(CONFIG_ARM64_UAO) &&
-	    get_thread_info(next_sp)->addr_limit == KERNEL_DS)
-		asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO,
-			        CONFIG_ARM64_UAO));
-	else
-		asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO,
-				CONFIG_ARM64_UAO));
+	if (IS_ENABLED(CONFIG_ARM64_UAO)) {
+		if (task_thread_info(next)->addr_limit == KERNEL_DS)
+			asm(ALTERNATIVE("nop", SET_PSTATE_UAO(1), ARM64_HAS_UAO));
+		else
+			asm(ALTERNATIVE("nop", SET_PSTATE_UAO(0), ARM64_HAS_UAO));
+	}
 }
 
 /*

arch/arm64/mm/fault.c

@@ -234,7 +234,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 	}
 
 	if (permission_fault(esr) && (addr < USER_DS)) {
-		if (get_thread_info(regs->sp)->addr_limit == KERNEL_DS)
+		if (get_fs() == KERNEL_DS)
 			panic("Accessing user space memory with fs=KERNEL_DS");
 
 		if (!search_exception_tables(regs->pc))