// 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> /* * A snapshot of a frame record or fp/lr register values, along with some * accounting information necessary for robust unwinding. * * @fp:          The fp value in the frame record (or the real fp) * @pc:          The lr value in the frame record (or the real lr) * * @stacks_done: Stacks which have been entirely unwound, for which it is no *               longer valid to unwind to. * * @prev_fp:     The fp that pointed to this frame record, or a synthetic value *               of 0. This is used to ensure that within a stack, each *               subsequent frame record is at an increasing address. * @prev_type:   The type of stack this frame record was on, or a synthetic *               value of STACK_TYPE_UNKNOWN. This is used to detect a *               transition from one stack to another. * * @kr_cur:      When KRETPROBES is selected, holds the kretprobe instance *               associated with the most recently encountered replacement lr *               value. */struct unwind_state {	unsigned long fp;	unsigned long pc;	DECLARE_BITMAP(stacks_done, __NR_STACK_TYPES);	unsigned long prev_fp;	enum stack_type prev_type;#ifdef CONFIG_KRETPROBES	struct llist_node *kr_cur;#endif}; static notrace void unwind_init(struct unwind_state *state, unsigned long fp,				unsigned long pc){	state->fp = fp;	state->pc = pc;#ifdef CONFIG_KRETPROBES	state->kr_cur = NULL;#endif 	/*	 * Prime the first unwind.	 *	 * In unwind_next() 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(state->stacks_done, __NR_STACK_TYPES);	state->prev_fp = 0;	state->prev_type = STACK_TYPE_UNKNOWN;}NOKPROBE_SYMBOL(unwind_init); /* * 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. */static int notrace unwind_next(struct task_struct *tsk,			       struct unwind_state *state){	unsigned long fp = state->fp;	struct stack_info info; 	/* Final frame; nothing to unwind */	if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)		return -ENOENT; 	if (fp & 0x7)		return -EINVAL; 	if (!on_accessible_stack(tsk, fp, 16, &info))		return -EINVAL; 	if (test_bit(info.type, state->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 == state->prev_type) {		if (fp <= state->prev_fp)			return -EINVAL;	} else {		set_bit(state->prev_type, state->stacks_done);	} 	/*	 * Record this frame record's values and location. The prev_fp and	 * prev_type are only meaningful to the next unwind_next() invocation.	 */	state->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));	state->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));	state->prev_fp = fp;	state->prev_type = info.type; 	state->pc = ptrauth_strip_insn_pac(state->pc); #ifdef CONFIG_FUNCTION_GRAPH_TRACER	if (tsk->ret_stack &&		(state->pc == (unsigned long)return_to_handler)) {		unsigned long orig_pc;		/*		 * 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.		 */		orig_pc = ftrace_graph_ret_addr(tsk, NULL, state->pc,						(void *)state->fp);		if (WARN_ON_ONCE(state->pc == orig_pc))			return -EINVAL;		state->pc = orig_pc;	}#endif /* CONFIG_FUNCTION_GRAPH_TRACER */#ifdef CONFIG_KRETPROBES	if (is_kretprobe_trampoline(state->pc))		state->pc = kretprobe_find_ret_addr(tsk, (void *)state->fp, &state->kr_cur);#endif 	return 0;}NOKPROBE_SYMBOL(unwind_next); static void notrace unwind(struct task_struct *tsk,			   struct unwind_state *state,			   stack_trace_consume_fn consume_entry, void *cookie){	while (1) {		int ret; 		if (!consume_entry(cookie, state->pc))			break;		ret = unwind_next(tsk, state);		if (ret < 0)			break;	}}NOKPROBE_SYMBOL(unwind); static bool dump_backtrace_entry(void *arg, unsigned long where){	char *loglvl = arg;	printk("%s %pSb\n", loglvl, (void *)where);	return true;} void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,		    const char *loglvl){	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); 	if (regs && user_mode(regs))		return; 	if (!tsk)		tsk = current; 	if (!try_get_task_stack(tsk))		return; 	printk("%sCall trace:\n", loglvl);	arch_stack_walk(dump_backtrace_entry, (void *)loglvl, tsk, regs); 	put_task_stack(tsk);} void show_stack(struct task_struct *tsk, unsigned long *sp, const char *loglvl){	dump_backtrace(NULL, tsk, loglvl);	barrier();} noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry,			      void *cookie, struct task_struct *task,			      struct pt_regs *regs){	struct unwind_state state; 	if (regs)		unwind_init(&state, regs->regs[29], regs->pc);	else if (task == current)		unwind_init(&state,				(unsigned long)__builtin_frame_address(1),				(unsigned long)__builtin_return_address(0));	else		unwind_init(&state, thread_saved_fp(task),				thread_saved_pc(task)); 	unwind(task, &state, consume_entry, cookie);}