// SPDX-License-Identifier: GPL-2.0/* Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. */ #include <linux/sched/debug.h>#include <linux/sched/task_stack.h>#include <linux/stacktrace.h>#include <linux/ftrace.h> void save_stack_trace(struct stack_trace *trace){	save_stack_trace_tsk(current, trace);}EXPORT_SYMBOL_GPL(save_stack_trace); void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace){	unsigned long *fp, *stack_start, *stack_end;	unsigned long addr;	int skip = trace->skip;	int savesched;	int graph_idx = 0; 	if (tsk == current) {		asm volatile("mov %0, r8\n":"=r"(fp));		savesched = 1;	} else {		fp = (unsigned long *)thread_saved_fp(tsk);		savesched = 0;	} 	addr = (unsigned long) fp & THREAD_MASK;	stack_start = (unsigned long *) addr;	stack_end = (unsigned long *) (addr + THREAD_SIZE); 	while (fp > stack_start && fp < stack_end) {		unsigned long lpp, fpp; 		fpp = fp[0];		lpp = fp[1];		if (!__kernel_text_address(lpp))			break;		else			lpp = ftrace_graph_ret_addr(tsk, &graph_idx, lpp, NULL); 		if (savesched || !in_sched_functions(lpp)) {			if (skip) {				skip--;			} else {				trace->entries[trace->nr_entries++] = lpp;				if (trace->nr_entries >= trace->max_entries)					break;			}		}		fp = (unsigned long *)fpp;	}}EXPORT_SYMBOL_GPL(save_stack_trace_tsk);