1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Copyright (C) 2013 Linaro Limited 4 * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> 5 * Copyright (C) 2017 Andes Technology Corporation 6 */ 7 8 #include <linux/ftrace.h> 9 10 /* 11 * Most of this file is copied from arm64. 12 */ 13 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, 14 unsigned long frame_pointer) 15 { 16 unsigned long return_hooker = (unsigned long)&return_to_handler; 17 unsigned long old; 18 struct ftrace_graph_ent trace; 19 int err; 20 21 if (unlikely(atomic_read(¤t->tracing_graph_pause))) 22 return; 23 24 /* 25 * We don't suffer access faults, so no extra fault-recovery assembly 26 * is needed here. 27 */ 28 old = *parent; 29 30 trace.func = self_addr; 31 trace.depth = current->curr_ret_stack + 1; 32 33 if (!ftrace_graph_entry(&trace)) 34 return; 35 36 err = ftrace_push_return_trace(old, self_addr, &trace.depth, 37 frame_pointer, NULL); 38 if (err == -EBUSY) 39 return; 40 *parent = return_hooker; 41 } 42