// 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 */ /* * 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); 	/*	 * Frames created upon entry from EL0 have NULL FP and PC values, so	 * don't bother reporting these. Frames created by __noreturn functions	 * might have a valid FP even if PC is bogus, so only terminate where	 * both are NULL.	 */	if (!frame->fp && !frame->pc)		return -EINVAL; 	return 0;}NOKPROBE_SYMBOL(unwind_frame); 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;	}}NOKPROBE_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_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; 	start_backtrace(&frame, regs->regs[29], regs->pc);	walk_stackframe(current, &frame, save_trace, &data);}EXPORT_SYMBOL_GPL(save_stack_trace_regs); static noinline void __save_stack_trace(struct task_struct *tsk,	struct stack_trace *trace, unsigned int nosched){	struct stack_trace_data data;	struct stackframe frame; 	if (!try_get_task_stack(tsk))		return; 	data.trace = trace;	data.skip = trace->skip;	data.no_sched_functions = nosched; 	if (tsk != current) {		start_backtrace(&frame, thread_saved_fp(tsk),				thread_saved_pc(tsk));	} else {		/* We don't want this function nor the caller */		data.skip += 2;		start_backtrace(&frame,				(unsigned long)__builtin_frame_address(0),				(unsigned long)__save_stack_trace);	} 	walk_stackframe(tsk, &frame, save_trace, &data); 	put_task_stack(tsk);} void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace){	__save_stack_trace(tsk, trace, 1);}EXPORT_SYMBOL_GPL(save_stack_trace_tsk); void save_stack_trace(struct stack_trace *trace){	__save_stack_trace(current, trace, 0);} EXPORT_SYMBOL_GPL(save_stack_trace);#endif