void notrace walk_stackframe()

in kernel/stacktrace.c [21:66]

• 38 lines of code
• 12 McCabe index (conditional complexity)

void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
			     bool (*fn)(void *, unsigned long), void *arg)
{
	unsigned long fp, sp, pc;

	if (regs) {
		fp = frame_pointer(regs);
		sp = user_stack_pointer(regs);
		pc = instruction_pointer(regs);
	} else if (task == NULL || task == current) {
		fp = (unsigned long)__builtin_frame_address(1);
		sp = (unsigned long)__builtin_frame_address(0);
		pc = (unsigned long)__builtin_return_address(0);
	} else {
		/* task blocked in __switch_to */
		fp = task->thread.s[0];
		sp = task->thread.sp;
		pc = task->thread.ra;
	}

	for (;;) {
		unsigned long low, high;
		struct stackframe *frame;

		if (unlikely(!__kernel_text_address(pc) || !fn(arg, pc)))
			break;

		/* Validate frame pointer */
		low = sp + sizeof(struct stackframe);
		high = ALIGN(sp, THREAD_SIZE);
		if (unlikely(fp < low || fp > high || fp & 0x7))
			break;
		/* Unwind stack frame */
		frame = (struct stackframe *)fp - 1;
		sp = fp;
		if (regs && (regs->epc == pc) && (frame->fp & 0x7)) {
			fp = frame->ra;
			pc = regs->ra;
		} else {
			fp = frame->fp;
			pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
						   (unsigned long *)(fp - 8));
		}

	}
}