linux/arch/riscv/include/asm/module.h
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   1/* SPDX-License-Identifier: GPL-2.0 */
   2/* Copyright (C) 2017 Andes Technology Corporation */
   3
   4#ifndef _ASM_RISCV_MODULE_H
   5#define _ASM_RISCV_MODULE_H
   6
   7#include <asm-generic/module.h>
   8
   9struct module;
  10unsigned long module_emit_got_entry(struct module *mod, unsigned long val);
  11unsigned long module_emit_plt_entry(struct module *mod, unsigned long val);
  12
  13#ifdef CONFIG_MODULE_SECTIONS
  14struct mod_section {
  15        Elf_Shdr *shdr;
  16        int num_entries;
  17        int max_entries;
  18};
  19
  20struct mod_arch_specific {
  21        struct mod_section got;
  22        struct mod_section plt;
  23        struct mod_section got_plt;
  24};
  25
  26struct got_entry {
  27        unsigned long symbol_addr;      /* the real variable address */
  28};
  29
  30static inline struct got_entry emit_got_entry(unsigned long val)
  31{
  32        return (struct got_entry) {val};
  33}
  34
  35static inline struct got_entry *get_got_entry(unsigned long val,
  36                                              const struct mod_section *sec)
  37{
  38        struct got_entry *got = (struct got_entry *)(sec->shdr->sh_addr);
  39        int i;
  40        for (i = 0; i < sec->num_entries; i++) {
  41                if (got[i].symbol_addr == val)
  42                        return &got[i];
  43        }
  44        return NULL;
  45}
  46
  47struct plt_entry {
  48        /*
  49         * Trampoline code to real target address. The return address
  50         * should be the original (pc+4) before entring plt entry.
  51         */
  52        u32 insn_auipc;         /* auipc t0, 0x0                       */
  53        u32 insn_ld;            /* ld    t1, 0x10(t0)                  */
  54        u32 insn_jr;            /* jr    t1                            */
  55};
  56
  57#define OPC_AUIPC  0x0017
  58#define OPC_LD     0x3003
  59#define OPC_JALR   0x0067
  60#define REG_T0     0x5
  61#define REG_T1     0x6
  62
  63static inline struct plt_entry emit_plt_entry(unsigned long val,
  64                                              unsigned long plt,
  65                                              unsigned long got_plt)
  66{
  67        /*
  68         * U-Type encoding:
  69         * +------------+----------+----------+
  70         * | imm[31:12] | rd[11:7] | opc[6:0] |
  71         * +------------+----------+----------+
  72         *
  73         * I-Type encoding:
  74         * +------------+------------+--------+----------+----------+
  75         * | imm[31:20] | rs1[19:15] | funct3 | rd[11:7] | opc[6:0] |
  76         * +------------+------------+--------+----------+----------+
  77         *
  78         */
  79        unsigned long offset = got_plt - plt;
  80        u32 hi20 = (offset + 0x800) & 0xfffff000;
  81        u32 lo12 = (offset - hi20);
  82        return (struct plt_entry) {
  83                OPC_AUIPC | (REG_T0 << 7) | hi20,
  84                OPC_LD | (lo12 << 20) | (REG_T0 << 15) | (REG_T1 << 7),
  85                OPC_JALR | (REG_T1 << 15)
  86        };
  87}
  88
  89static inline int get_got_plt_idx(unsigned long val, const struct mod_section *sec)
  90{
  91        struct got_entry *got_plt = (struct got_entry *)sec->shdr->sh_addr;
  92        int i;
  93        for (i = 0; i < sec->num_entries; i++) {
  94                if (got_plt[i].symbol_addr == val)
  95                        return i;
  96        }
  97        return -1;
  98}
  99
 100static inline struct plt_entry *get_plt_entry(unsigned long val,
 101                                              const struct mod_section *sec_plt,
 102                                              const struct mod_section *sec_got_plt)
 103{
 104        struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr;
 105        int got_plt_idx = get_got_plt_idx(val, sec_got_plt);
 106        if (got_plt_idx >= 0)
 107                return plt + got_plt_idx;
 108        else
 109                return NULL;
 110}
 111
 112#endif /* CONFIG_MODULE_SECTIONS */
 113
 114#endif /* _ASM_RISCV_MODULE_H */
 115
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