// SPDX-License-Identifier: GPL-2.0
/*
 * Stack trace management functions
 *
 * Copyright (C) 2022 Loongson Technology Corporation Limited
 */
#include <linux/sched.h>
#include <linux/stacktrace.h>
#include <linux/uaccess.h>

#include <asm/stacktrace.h>
#include <asm/unwind.h>

void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
                     struct task_struct *task, struct pt_regs *regs)
{
        unsigned long addr;
        struct pt_regs dummyregs;
        struct unwind_state state;

        if (!regs) {
                regs = &dummyregs;

                if (task == current) {
                        regs->regs[3] = (unsigned long)__builtin_frame_address(0);
                        regs->csr_era = (unsigned long)__builtin_return_address(0);
                } else {
                        regs->regs[3] = thread_saved_fp(task);
                        regs->csr_era = thread_saved_ra(task);
                }
                regs->regs[1] = 0;
                regs->regs[22] = 0;
        }

        for (unwind_start(&state, task, regs);
             !unwind_done(&state); unwind_next_frame(&state)) {
                addr = unwind_get_return_address(&state);
                if (!addr || !consume_entry(cookie, addr))
                        break;
        }
}

int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
                             void *cookie, struct task_struct *task)
{
        unsigned long addr;
        struct pt_regs dummyregs;
        struct pt_regs *regs = &dummyregs;
        struct unwind_state state;

        if (task == current) {
                regs->regs[3] = (unsigned long)__builtin_frame_address(0);
                regs->csr_era = (unsigned long)__builtin_return_address(0);
                regs->regs[22] = 0;
        } else {
                regs->regs[3] = thread_saved_fp(task);
                regs->csr_era = thread_saved_ra(task);
                regs->regs[22] = task->thread.reg22;
        }
        regs->regs[1] = 0;

        for (unwind_start(&state, task, regs);
             !unwind_done(&state) && !unwind_error(&state); unwind_next_frame(&state)) {
                addr = unwind_get_return_address(&state);

                /*
                 * A NULL or invalid return address probably means there's some
                 * generated code which __kernel_text_address() doesn't know about.
                 */
                if (!addr)
                        return -EINVAL;

                if (!consume_entry(cookie, addr))
                        return -EINVAL;
        }

        /* Check for stack corruption */
        if (unwind_error(&state))
                return -EINVAL;

        return 0;
}

static int
copy_stack_frame(unsigned long fp, struct stack_frame *frame)
{
        int ret = 1;
        unsigned long err;
        unsigned long __user *user_frame_tail;

        user_frame_tail = (unsigned long *)(fp - sizeof(struct stack_frame));
        if (!access_ok(user_frame_tail, sizeof(*frame)))
                return 0;

        pagefault_disable();
        err = (__copy_from_user_inatomic(frame, user_frame_tail, sizeof(*frame)));
        if (err || (unsigned long)user_frame_tail >= frame->fp)
                ret = 0;
        pagefault_enable();

        return ret;
}

void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
                          const struct pt_regs *regs)
{
        unsigned long fp = regs->regs[22];

        while (fp && !((unsigned long)fp & 0xf)) {
                struct stack_frame frame;

                frame.fp = 0;
                frame.ra = 0;
                if (!copy_stack_frame(fp, &frame))
                        break;
                if (!frame.ra)
                        break;
                if (!consume_entry(cookie, frame.ra))
                        break;
                fp = frame.fp;
        }
}