/* * 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/ftrace.h>#include <linux/sched.h>#include <linux/sched/debug.h>#include <linux/sched/task_stack.h>#include <linux/stacktrace.h> #include <asm/irq.h>#include <asm/stack_pointer.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 task_struct *tsk, struct stackframe *frame){	unsigned long high, low;	unsigned long fp = frame->fp;	unsigned long irq_stack_ptr; 	if (!tsk)		tsk = current; 	/*	 * Switching between stacks is valid when tracing current and in	 * non-preemptible context.	 */	if (tsk == current && !preemptible())		irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());	else		irq_stack_ptr = 0; 	low  = frame->sp;	/* irq stacks are not THREAD_SIZE aligned */	if (on_irq_stack(frame->sp, raw_smp_processor_id()))		high = irq_stack_ptr;	else		high = ALIGN(low, THREAD_SIZE) - 0x20; 	if (fp < low || fp > high || fp & 0xf)		return -EINVAL; 	frame->sp = fp + 0x10;	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); #ifdef CONFIG_FUNCTION_GRAPH_TRACER	if (tsk->ret_stack &&			(frame->pc == (unsigned long)return_to_handler)) {		/*		 * This is a case where function graph tracer has		 * modified a return address (LR) in a stack frame		 * to hook a function return.		 * So replace it to an original value.		 */		frame->pc = tsk->ret_stack[frame->graph--].ret;	}#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 	/*	 * Check whether we are going to walk through from interrupt stack	 * to task stack.	 * If we reach the end of the stack - and its an interrupt stack,	 * unpack the dummy frame to find the original elr.	 *	 * Check the frame->fp we read from the bottom of the irq_stack,	 * and the original task stack pointer are both in current->stack.	 */	if (frame->sp == irq_stack_ptr) {		struct pt_regs *irq_args;		unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr); 		if (object_is_on_stack((void *)orig_sp) &&		   object_is_on_stack((void *)frame->fp)) {			frame->sp = orig_sp; 			/* orig_sp is the saved pt_regs, find the elr */			irq_args = (struct pt_regs *)orig_sp;			frame->pc = irq_args->pc;		} else {			/*			 * This frame has a non-standard format, and we			 * didn't fix it, because the data looked wrong.			 * Refuse to output this frame.			 */			return -EINVAL;		}	} 	return 0;} void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,		     int (*fn)(struct stackframe *, void *), void *data){	while (1) {		int ret; 		if (fn(frame, data))			break;		ret = unwind_frame(tsk, frame);		if (ret < 0)			break;	}} #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_regs(struct pt_regs *regs, struct stack_trace *trace){	struct stack_trace_data data;	struct stackframe frame; 	data.trace = trace;	data.skip = trace->skip;	data.no_sched_functions = 0; 	frame.fp = regs->regs[29];	frame.sp = regs->sp;	frame.pc = regs->pc;#ifdef CONFIG_FUNCTION_GRAPH_TRACER	frame.graph = current->curr_ret_stack;#endif 	walk_stackframe(current, &frame, save_trace, &data);	if (trace->nr_entries < trace->max_entries)		trace->entries[trace->nr_entries++] = ULONG_MAX;} void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace){	struct stack_trace_data data;	struct stackframe frame; 	if (!try_get_task_stack(tsk))		return; 	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;	}#ifdef CONFIG_FUNCTION_GRAPH_TRACER	frame.graph = tsk->curr_ret_stack;#endif 	walk_stackframe(tsk, &frame, save_trace, &data);	if (trace->nr_entries < trace->max_entries)		trace->entries[trace->nr_entries++] = ULONG_MAX; 	put_task_stack(tsk);}EXPORT_SYMBOL_GPL(save_stack_trace_tsk); void save_stack_trace(struct stack_trace *trace){	save_stack_trace_tsk(current, trace);}EXPORT_SYMBOL_GPL(save_stack_trace);#endif