/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (C) 2017 Andes Technology Corporation */

#ifndef _ASM_RISCV_MODULE_H
#define _ASM_RISCV_MODULE_H

#include <asm-generic/module.h>
#include <linux/elf.h>

struct module;
unsigned long module_emit_got_entry(struct module *mod, unsigned long val);
unsigned long module_emit_plt_entry(struct module *mod, unsigned long val);

#ifdef CONFIG_MODULE_SECTIONS
struct mod_section {
        Elf_Shdr *shdr;
        int num_entries;
        int max_entries;
};

struct mod_arch_specific {
        struct mod_section got;
        struct mod_section plt;
        struct mod_section got_plt;
};

struct got_entry {
        unsigned long symbol_addr;      /* the real variable address */
};

static inline struct got_entry emit_got_entry(unsigned long val)
{
        return (struct got_entry) {val};
}

static inline struct got_entry *get_got_entry(unsigned long val,
                                              const struct mod_section *sec)
{
        struct got_entry *got = (struct got_entry *)(sec->shdr->sh_addr);
        int i;
        for (i = 0; i < sec->num_entries; i++) {
                if (got[i].symbol_addr == val)
                        return &got[i];
        }
        return NULL;
}

struct plt_entry {
        /*
         * Trampoline code to real target address. The return address
         * should be the original (pc+4) before entring plt entry.
         */
        u32 insn_auipc;         /* auipc t0, 0x0                       */
        u32 insn_ld;            /* ld    t1, 0x10(t0)                  */
        u32 insn_jr;            /* jr    t1                            */
};

#define OPC_AUIPC  0x0017
#define OPC_LD     0x3003
#define OPC_JALR   0x0067
#define REG_T0     0x5
#define REG_T1     0x6

static inline struct plt_entry emit_plt_entry(unsigned long val,
                                              unsigned long plt,
                                              unsigned long got_plt)
{
        /*
         * U-Type encoding:
         * +------------+----------+----------+
         * | imm[31:12] | rd[11:7] | opc[6:0] |
         * +------------+----------+----------+
         *
         * I-Type encoding:
         * +------------+------------+--------+----------+----------+
         * | imm[31:20] | rs1[19:15] | funct3 | rd[11:7] | opc[6:0] |
         * +------------+------------+--------+----------+----------+
         *
         */
        unsigned long offset = got_plt - plt;
        u32 hi20 = (offset + 0x800) & 0xfffff000;
        u32 lo12 = (offset - hi20);
        return (struct plt_entry) {
                OPC_AUIPC | (REG_T0 << 7) | hi20,
                OPC_LD | (lo12 << 20) | (REG_T0 << 15) | (REG_T1 << 7),
                OPC_JALR | (REG_T1 << 15)
        };
}

static inline int get_got_plt_idx(unsigned long val, const struct mod_section *sec)
{
        struct got_entry *got_plt = (struct got_entry *)sec->shdr->sh_addr;
        int i;
        for (i = 0; i < sec->num_entries; i++) {
                if (got_plt[i].symbol_addr == val)
                        return i;
        }
        return -1;
}

static inline struct plt_entry *get_plt_entry(unsigned long val,
                                              const struct mod_section *sec_plt,
                                              const struct mod_section *sec_got_plt)
{
        struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr;
        int got_plt_idx = get_got_plt_idx(val, sec_got_plt);
        if (got_plt_idx >= 0)
                return plt + got_plt_idx;
        else
                return NULL;
}

#endif /* CONFIG_MODULE_SECTIONS */

static inline const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
                                           const Elf_Shdr *sechdrs,
                                           const char *name)
{
        const Elf_Shdr *s, *se;
        const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

        for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
                if (strcmp(name, secstrs + s->sh_name) == 0)
                        return s;
        }

        return NULL;
}

#endif /* _ASM_RISCV_MODULE_H */