// 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/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>

#include <asm/irq.h>
#include <asm/stack_pointer.h>
#include <asm/stacktrace.h>

/*
 * Start an unwind from a pt_regs.
 *
 * The unwind will begin at the PC within the regs.
 *
 * The regs must be on a stack currently owned by the calling task.
 */
static inline void unwind_init_from_regs(struct unwind_state *state,
					 struct pt_regs *regs)
{
	unwind_init_common(state, current);

	state->fp = regs->regs[29];
	state->pc = regs->pc;
}

/*
 * Start an unwind from a caller.
 *
 * The unwind will begin at the caller of whichever function this is inlined
 * into.
 *
 * The function which invokes this must be noinline.
 */
static __always_inline void unwind_init_from_caller(struct unwind_state *state)
{
	unwind_init_common(state, current);

	state->fp = (unsigned long)__builtin_frame_address(1);
	state->pc = (unsigned long)__builtin_return_address(0);
}

/*
 * Start an unwind from a blocked task.
 *
 * The unwind will begin at the blocked tasks saved PC (i.e. the caller of
 * cpu_switch_to()).
 *
 * The caller should ensure the task is blocked in cpu_switch_to() for the
 * duration of the unwind, or the unwind will be bogus. It is never valid to
 * call this for the current task.
 */
static inline void unwind_init_from_task(struct unwind_state *state,
					 struct task_struct *task)
{
	unwind_init_common(state, task);

	state->fp = thread_saved_fp(task);
	state->pc = thread_saved_pc(task);
}

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) {
		if (task != current)
			return;
		unwind_init_from_regs(&state, regs);
	} else if (task == current) {
		unwind_init_from_caller(&state);
	} else {
		unwind_init_from_task(&state, task);
	}

	unwind(&state, consume_entry, cookie);
}