// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2008 ARM Limited
 * Copyright (C) 2014 Regents of the University of California
 */

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

#include <asm/stacktrace.h>

#ifdef CONFIG_FRAME_POINTER

/*
 * This disables KASAN checking when reading a value from another task's stack,
 * since the other task could be running on another CPU and could have poisoned
 * the stack in the meantime.
 */
#define READ_ONCE_TASK_STACK(task, x)                   \
({                                                      \
        unsigned long val;                              \
        unsigned long addr = x;                         \
        if ((task) == current)                          \
                val = READ_ONCE(addr);                  \
        else                                            \
                val = READ_ONCE_NOCHECK(addr);          \
        val;                                            \
})

extern asmlinkage void handle_exception(void);
extern unsigned long ret_from_exception_end;

static inline int fp_is_valid(unsigned long fp, unsigned long sp)
{
        unsigned long low, high;

        low = sp + sizeof(struct stackframe);
        high = ALIGN(sp, THREAD_SIZE);

        return !(fp < low || fp > high || fp & 0x07);
}

void notrace walk_stackframe(struct task_struct *task, struct pt_regs *regs,
                             bool (*fn)(void *, unsigned long), void *arg)
{
        unsigned long fp, sp, pc;
        int graph_idx = 0;
        int level = 0;

        if (regs) {
                fp = frame_pointer(regs);
                sp = user_stack_pointer(regs);
                pc = instruction_pointer(regs);
        } else if (task == NULL || task == current) {
                fp = (unsigned long)__builtin_frame_address(0);
                sp = current_stack_pointer;
                pc = (unsigned long)walk_stackframe;
                level = -1;
        } else {
                /* task blocked in __switch_to */
                fp = task->thread.s[0];
                sp = task->thread.sp;
                pc = task->thread.ra;
        }

        for (;;) {
                struct stackframe *frame;

                if (unlikely(!__kernel_text_address(pc) || (level++ >= 0 && !fn(arg, pc))))
                        break;

                if (unlikely(!fp_is_valid(fp, sp)))
                        break;

                /* Unwind stack frame */
                frame = (struct stackframe *)fp - 1;
                sp = fp;
                if (regs && (regs->epc == pc) && fp_is_valid(frame->ra, sp)) {
                        /* We hit function where ra is not saved on the stack */
                        fp = frame->ra;
                        pc = regs->ra;
                } else {
                        fp = READ_ONCE_TASK_STACK(task, frame->fp);
                        pc = READ_ONCE_TASK_STACK(task, frame->ra);
                        pc = ftrace_graph_ret_addr(current, &graph_idx, pc,
                                                   &frame->ra);
                        if (pc >= (unsigned long)handle_exception &&
                            pc < (unsigned long)&ret_from_exception_end) {
                                if (unlikely(!fn(arg, pc)))
                                        break;

                                pc = ((struct pt_regs *)sp)->epc;
                                fp = ((struct pt_regs *)sp)->s0;
                        }
                }

        }
}

#else /* !CONFIG_FRAME_POINTER */

void notrace walk_stackframe(struct task_struct *task,
        struct pt_regs *regs, bool (*fn)(void *, unsigned long), void *arg)
{
        unsigned long sp, pc;
        unsigned long *ksp;

        if (regs) {
                sp = user_stack_pointer(regs);
                pc = instruction_pointer(regs);
        } else if (task == NULL || task == current) {
                sp = current_stack_pointer;
                pc = (unsigned long)walk_stackframe;
        } else {
                /* task blocked in __switch_to */
                sp = task->thread.sp;
                pc = task->thread.ra;
        }

        if (unlikely(sp & 0x7))
                return;

        ksp = (unsigned long *)sp;
        while (!kstack_end(ksp)) {
                if (__kernel_text_address(pc) && unlikely(!fn(arg, pc)))
                        break;
                pc = READ_ONCE_NOCHECK(*ksp++) - 0x4;
        }
}

#endif /* CONFIG_FRAME_POINTER */

static bool print_trace_address(void *arg, unsigned long pc)
{
        const char *loglvl = arg;

        print_ip_sym(loglvl, pc);
        return true;
}

noinline void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
                    const char *loglvl)
{
        walk_stackframe(task, regs, print_trace_address, (void *)loglvl);
}

void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
{
        pr_cont("%sCall Trace:\n", loglvl);
        dump_backtrace(NULL, task, loglvl);
}

static bool save_wchan(void *arg, unsigned long pc)
{
        if (!in_sched_functions(pc)) {
                unsigned long *p = arg;
                *p = pc;
                return false;
        }
        return true;
}

unsigned long __get_wchan(struct task_struct *task)
{
        unsigned long pc = 0;

        if (!try_get_task_stack(task))
                return 0;
        walk_stackframe(task, NULL, save_wchan, &pc);
        put_task_stack(task);
        return pc;
}

noinline noinstr void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
                     struct task_struct *task, struct pt_regs *regs)
{
        walk_stackframe(task, regs, consume_entry, cookie);
}

/*
 * Get the return address for a single stackframe and return a pointer to the
 * next frame tail.
 */
static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry,
                                       void *cookie, unsigned long fp,
                                       unsigned long reg_ra)
{
        struct stackframe buftail;
        unsigned long ra = 0;
        unsigned long __user *user_frame_tail =
                (unsigned long __user *)(fp - sizeof(struct stackframe));

        /* Check accessibility of one struct frame_tail beyond */
        if (!access_ok(user_frame_tail, sizeof(buftail)))
                return 0;
        if (__copy_from_user_inatomic(&buftail, user_frame_tail,
                                      sizeof(buftail)))
                return 0;

        ra = reg_ra ? : buftail.ra;

        fp = buftail.fp;
        if (!ra || !consume_entry(cookie, ra))
                return 0;

        return fp;
}

void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
                          const struct pt_regs *regs)
{
        unsigned long fp = 0;

        fp = regs->s0;
        if (!consume_entry(cookie, regs->epc))
                return;

        fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra);
        while (fp && !(fp & 0x7))
                fp = unwind_user_frame(consume_entry, cookie, fp, 0);
}