/* * Stack tracing support * * Copyright (C) 2012 ARM Ltd. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program.  If not, see <http://www.gnu.org/licenses/>. */#include <linux/kernel.h>#include <linux/export.h>#include <linux/sched.h>#include <linux/stacktrace.h> #include <asm/stacktrace.h> /* * AArch64 PCS assigns the frame pointer to x29. * * A simple function prologue looks like this: * 	sub	sp, sp, #0x10 *   	stp	x29, x30, [sp] *	mov	x29, sp * * A simple function epilogue looks like this: *	mov	sp, x29 *	ldp	x29, x30, [sp] *	add	sp, sp, #0x10 */int notrace unwind_frame(struct stackframe *frame){	unsigned long high, low;	unsigned long fp = frame->fp; 	low  = frame->sp;	high = ALIGN(low, THREAD_SIZE); 	if (fp < low || fp > high - 0x18 || fp & 0xf)		return -EINVAL; 	frame->sp = fp + 0x10;	frame->fp = *(unsigned long *)(fp);	/*	 * -4 here because we care about the PC at time of bl,	 * not where the return will go.	 */	frame->pc = *(unsigned long *)(fp + 8) - 4; 	return 0;} void notrace walk_stackframe(struct stackframe *frame,		     int (*fn)(struct stackframe *, void *), void *data){	while (1) {		int ret; 		if (fn(frame, data))			break;		ret = unwind_frame(frame);		if (ret < 0)			break;	}}EXPORT_SYMBOL(walk_stackframe); #ifdef CONFIG_STACKTRACEstruct stack_trace_data {	struct stack_trace *trace;	unsigned int no_sched_functions;	unsigned int skip;}; static int save_trace(struct stackframe *frame, void *d){	struct stack_trace_data *data = d;	struct stack_trace *trace = data->trace;	unsigned long addr = frame->pc; 	if (data->no_sched_functions && in_sched_functions(addr))		return 0;	if (data->skip) {		data->skip--;		return 0;	} 	trace->entries[trace->nr_entries++] = addr; 	return trace->nr_entries >= trace->max_entries;} void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace){	struct stack_trace_data data;	struct stackframe frame; 	data.trace = trace;	data.skip = trace->skip; 	if (tsk != current) {		data.no_sched_functions = 1;		frame.fp = thread_saved_fp(tsk);		frame.sp = thread_saved_sp(tsk);		frame.pc = thread_saved_pc(tsk);	} else {		data.no_sched_functions = 0;		frame.fp = (unsigned long)__builtin_frame_address(0);		frame.sp = current_stack_pointer;		frame.pc = (unsigned long)save_stack_trace_tsk;	} 	walk_stackframe(&frame, save_trace, &data);	if (trace->nr_entries < trace->max_entries)		trace->entries[trace->nr_entries++] = ULONG_MAX;} void save_stack_trace(struct stack_trace *trace){	save_stack_trace_tsk(current, trace);}EXPORT_SYMBOL_GPL(save_stack_trace);#endif