// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2022 Loongson Technology Corporation Limited
 */

#include <linux/init.h>
#include <linux/ftrace.h>
#include <linux/syscalls.h>
#include <linux/uaccess.h>

#include <asm/asm.h>
#include <asm/asm-offsets.h>
#include <asm/cacheflush.h>
#include <asm/inst.h>
#include <asm/loongarch.h>
#include <asm/syscall.h>

#include <asm-generic/sections.h>

#ifdef CONFIG_FUNCTION_GRAPH_TRACER

/*
 * As `call _mcount` follows LoongArch psABI, ra-saved operation and
 * stack operation can be found before this insn.
 */

static int ftrace_get_parent_ra_addr(unsigned long insn_addr, int *ra_off)
{
        int limit = 32;
        union loongarch_instruction *insn;

        insn = (union loongarch_instruction *)insn_addr;

        do {
                insn--;
                limit--;

                if (is_ra_save_ins(insn))
                        *ra_off = -((1 << 12) - insn->reg2i12_format.immediate);

        } while (!is_stack_alloc_ins(insn) && limit);

        if (!limit)
                return -EINVAL;

        return 0;
}

void prepare_ftrace_return(unsigned long self_addr,
                unsigned long callsite_sp, unsigned long old)
{
        int ra_off;
        unsigned long return_hooker = (unsigned long)&return_to_handler;

        if (unlikely(ftrace_graph_is_dead()))
                return;

        if (unlikely(atomic_read(&current->tracing_graph_pause)))
                return;

        if (ftrace_get_parent_ra_addr(self_addr, &ra_off))
                goto out;

        if (!function_graph_enter(old, self_addr, 0, NULL))
                *(unsigned long *)(callsite_sp + ra_off) = return_hooker;

        return;

out:
        ftrace_graph_stop();
        WARN_ON(1);
}
#endif  /* CONFIG_FUNCTION_GRAPH_TRACER */