// 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);
}

/*
 * We can only safely access per-cpu stacks from current in a non-preemptible
 * context.
 */
static bool on_accessible_stack(const struct task_struct *tsk,
                                unsigned long sp, unsigned long size,
                                struct stack_info *info)
{
        if (info)
                info->type = STACK_TYPE_UNKNOWN;

        if (on_task_stack(tsk, sp, size, info))
                return true;
        if (tsk != current || preemptible())
                return false;
        if (on_irq_stack(sp, size, info))
                return true;
        if (on_overflow_stack(sp, size, info))
                return true;
        if (on_sdei_stack(sp, size, info))
                return true;

        return false;
}

/*
 * 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 unwind_state *state)
{
        struct task_struct *tsk = state->task;
        unsigned long fp = state->fp;
        struct stack_info info;
        int err;

        /* Final frame; nothing to unwind */
        if (fp == (unsigned long)task_pt_regs(tsk)->stackframe)
                return -ENOENT;

        err = unwind_next_common(state, &info, on_accessible_stack, NULL);
        if (err)
                return err;

        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 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(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) {
                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);
}