// SPDX-License-Identifier: GPL-2.0-only/* * Stack tracing support * * Copyright (C) 2012 ARM Ltd. */#include <linux/kernel.h>#include <linux/export.h>#include <linux/ftrace.h>#include <linux/kprobes.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/pointer_auth.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 */  void start_backtrace(struct stackframe *frame, unsigned long fp,		     unsigned long pc){	frame->fp = fp;	frame->pc = pc;#ifdef CONFIG_FUNCTION_GRAPH_TRACER	frame->graph = 0;#endif 	/*	 * Prime the first unwind.	 *	 * In unwind_frame() we'll check that the FP points to a valid stack,	 * which can't be STACK_TYPE_UNKNOWN, and the first unwind will be	 * treated as a transition to whichever stack that happens to be. The	 * prev_fp value won't be used, but we set it to 0 such that it is	 * definitely not an accessible stack address.	 */	bitmap_zero(frame->stacks_done, __NR_STACK_TYPES);	frame->prev_fp = 0;	frame->prev_type = STACK_TYPE_UNKNOWN;} /* * Unwind from one frame record (A) to the next frame record (B). * * We terminate early if the location of B indicates a malformed chain of frame * records (e.g. a cycle), determined based on the location and fp value of A * and the location (but not the fp value) of B. */int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame){	unsigned long fp = frame->fp;	struct stack_info info; 	if (fp & 0xf)		return -EINVAL; 	if (!tsk)		tsk = current; 	if (!on_accessible_stack(tsk, fp, &info))		return -EINVAL; 	if (test_bit(info.type, frame->stacks_done))		return -EINVAL; 	/*	 * As stacks grow downward, any valid record on the same stack must be	 * at a strictly higher address than the prior record.	 *	 * Stacks can nest in several valid orders, e.g.	 *	 * TASK -> IRQ -> OVERFLOW -> SDEI_NORMAL	 * TASK -> SDEI_NORMAL -> SDEI_CRITICAL -> OVERFLOW	 *	 * ... but the nesting itself is strict. Once we transition from one	 * stack to another, it's never valid to unwind back to that first	 * stack.	 */	if (info.type == frame->prev_type) {		if (fp <= frame->prev_fp)			return -EINVAL;	} else {		set_bit(frame->prev_type, frame->stacks_done);	} 	/*	 * Record this frame record's values and location. The prev_fp and	 * prev_type are only meaningful to the next unwind_frame() invocation.	 */	frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));	frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));	frame->prev_fp = fp;	frame->prev_type = info.type; #ifdef CONFIG_FUNCTION_GRAPH_TRACER	if (tsk->ret_stack &&		(ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) {		struct ftrace_ret_stack *ret_stack;		/*		 * 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.		 */		ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++);		if (WARN_ON_ONCE(!ret_stack))			return -EINVAL;		frame->pc = ret_stack->ret;	}#endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 	frame->pc = ptrauth_strip_insn_pac(frame->pc); 	/*	 * This is a terminal record, so we have finished unwinding.	 */	if (!frame->fp && !frame->pc)		return -ENOENT; 	return 0;}NOKPROBE_SYMBOL(unwind_frame); void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,			     bool (*fn)(void *, unsigned long), void *data){	while (1) {		int ret; 		if (!fn(data, frame->pc))			break;		ret = unwind_frame(tsk, frame);		if (ret < 0)			break;	}}NOKPROBE_SYMBOL(walk_stackframe); static void dump_backtrace_entry(unsigned long where, const char *loglvl){	printk("%s %pS\n", loglvl, (void *)where);} void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,		    const char *loglvl){	struct stackframe frame;	int skip = 0; 	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 	if (regs) {		if (user_mode(regs))			return;		skip = 1;	} 	if (!tsk)		tsk = current; 	if (!try_get_task_stack(tsk))		return; 	if (tsk == current) {		start_backtrace(&frame,				(unsigned long)__builtin_frame_address(0),				(unsigned long)dump_backtrace);	} else {		/*		 * task blocked in __switch_to		 */		start_backtrace(&frame,				thread_saved_fp(tsk),				thread_saved_pc(tsk));	} 	printk("%sCall trace:\n", loglvl);	do {		/* skip until specified stack frame */		if (!skip) {			dump_backtrace_entry(frame.pc, loglvl);		} else if (frame.fp == regs->regs[29]) {			skip = 0;			/*			 * Mostly, this is the case where this function is			 * called in panic/abort. As exception handler's			 * stack frame does not contain the corresponding pc			 * at which an exception has taken place, use regs->pc			 * instead.			 */			dump_backtrace_entry(regs->pc, loglvl);		}	} while (!unwind_frame(tsk, &frame)); 	put_task_stack(tsk);} void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl){	dump_backtrace(NULL, tsk, loglvl);	barrier();} #ifdef CONFIG_STACKTRACE noinline void arch_stack_walk(stack_trace_consume_fn consume_entry,			      void *cookie, struct task_struct *task,			      struct pt_regs *regs){	struct stackframe frame; 	if (regs)		start_backtrace(&frame, regs->regs[29], regs->pc);	else if (task == current)		start_backtrace(&frame,				(unsigned long)__builtin_frame_address(1),				(unsigned long)__builtin_return_address(0));	else		start_backtrace(&frame, thread_saved_fp(task),				thread_saved_pc(task)); 	walk_stackframe(task, &frame, consume_entry, cookie);} #endif