21  * AArch64 PCS assigns the frame pointer to x29.
35  * Unwind from one frame record (A) to the next frame record (B).
37  * We terminate early if the location of B indicates a malformed chain of frame
41 int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)  in unwind_frame()  argument
43 	unsigned long fp = frame->fp;  in unwind_frame()
55 	if (test_bit(info.type, frame->stacks_done))  in unwind_frame()
71 	if (info.type == frame->prev_type) {  in unwind_frame()
72 		if (fp <= frame->prev_fp)  in unwind_frame()
75 		set_bit(frame->prev_type, frame->stacks_done);  in unwind_frame()
79 	 * Record this frame record's values and location. The prev_fp and  in unwind_frame()
82 	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));  in unwind_frame()
83 	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));  in unwind_frame()
84 	frame->prev_fp = fp;  in unwind_frame()
85 	frame->prev_type = info.type;  in unwind_frame()
89 			(frame->pc == (unsigned long)return_to_handler)) {  in unwind_frame()
93 		 * modified a return address (LR) in a stack frame  in unwind_frame()
97 		ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);  in unwind_frame()
100 		frame->pc = ret_stack->ret;  in unwind_frame()
110 	if (!frame->fp && !frame->pc)  in unwind_frame()
117 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,  in walk_stackframe()  argument
123 		if (fn(frame, data))  in walk_stackframe()
125 		ret = unwind_frame(tsk, frame);  in walk_stackframe()
139 static int save_trace(struct stackframe *frame, void *d)  in save_trace()  argument
143 	unsigned long addr = frame->pc;  in save_trace()
160 	struct stackframe frame;  in save_stack_trace_regs()  local
166 	start_backtrace(&frame, regs->regs[29], regs->pc);  in save_stack_trace_regs()
167 	walk_stackframe(current, &frame, save_trace, &data);  in save_stack_trace_regs()
175 	struct stackframe frame;  in __save_stack_trace()  local
185 		start_backtrace(&frame, thread_saved_fp(tsk),  in __save_stack_trace()
190 		start_backtrace(&frame,  in __save_stack_trace()
195 	walk_stackframe(tsk, &frame, save_trace, &data);  in __save_stack_trace()