arch/riscv/kernel/module.c

   1 /*
   2  *  This program is free software; you can redistribute it and/or modify
   3  *  it under the terms of the GNU General Public License as published by
   4  *  the Free Software Foundation; either version 2 of the License, or
   5  *  (at your option) any later version.
   6  *
   7  *  This program is distributed in the hope that it will be useful,
   8  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *  GNU General Public License for more details.
  11  *
  12  *  Copyright (C) 2017 Zihao Yu
  13  */
  14
  15 #include <linux/elf.h>
  16 #include <linux/err.h>
  17 #include <linux/errno.h>
  18 #include <linux/moduleloader.h>
  19
  20 static int apply_r_riscv_64_rela(struct module *me, u32 *location, Elf_Addr v)
  21 {
  22         *(u64 *)location = v;
  23         return 0;
  24 }
  25
  26 static int apply_r_riscv_branch_rela(struct module *me, u32 *location,
  27                                      Elf_Addr v)
  28 {
  29         s64 offset = (void *)v - (void *)location;
  30         u32 imm12 = (offset & 0x1000) << (31 - 12);
  31         u32 imm11 = (offset & 0x800) >> (11 - 7);
  32         u32 imm10_5 = (offset & 0x7e0) << (30 - 10);
  33         u32 imm4_1 = (offset & 0x1e) << (11 - 4);
  34
  35         *location = (*location & 0x1fff07f) | imm12 | imm11 | imm10_5 | imm4_1;
  36         return 0;
  37 }
  38
  39 static int apply_r_riscv_jal_rela(struct module *me, u32 *location,
  40                                   Elf_Addr v)
  41 {
  42         s64 offset = (void *)v - (void *)location;
  43         u32 imm20 = (offset & 0x100000) << (31 - 20);
  44         u32 imm19_12 = (offset & 0xff000);
  45         u32 imm11 = (offset & 0x800) << (20 - 11);
  46         u32 imm10_1 = (offset & 0x7fe) << (30 - 10);
  47
  48         *location = (*location & 0xfff) | imm20 | imm19_12 | imm11 | imm10_1;
  49         return 0;
  50 }
  51
  52 static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
  53                                          Elf_Addr v)
  54 {
  55         s64 offset = (void *)v - (void *)location;
  56         s32 hi20;
  57
  58         if (offset != (s32)offset) {
  59                 pr_err(
  60                   "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
  61                   me->name, v, location);
  62                 return -EINVAL;
  63         }
  64
  65         hi20 = (offset + 0x800) & 0xfffff000;
  66         *location = (*location & 0xfff) | hi20;
  67         return 0;
  68 }
  69
  70 static int apply_r_riscv_pcrel_lo12_i_rela(struct module *me, u32 *location,
  71                                            Elf_Addr v)
  72 {
  73         /*
  74          * v is the lo12 value to fill. It is calculated before calling this
  75          * handler.
  76          */
  77         *location = (*location & 0xfffff) | ((v & 0xfff) << 20);
  78         return 0;
  79 }
  80
  81 static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
  82                                            Elf_Addr v)
  83 {
  84         /*
  85          * v is the lo12 value to fill. It is calculated before calling this
  86          * handler.
  87          */
  88         u32 imm11_5 = (v & 0xfe0) << (31 - 11);
  89         u32 imm4_0 = (v & 0x1f) << (11 - 4);
  90
  91         *location = (*location & 0x1fff07f) | imm11_5 | imm4_0;
  92         return 0;
  93 }
  94
  95 static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
  96                                        Elf_Addr v)
  97 {
  98         s64 offset = (void *)v - (void *)location;
  99         s32 fill_v = offset;
 100         u32 hi20, lo12;
 101
 102         if (offset != fill_v) {
 103                 pr_err(
 104                   "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
 105                   me->name, v, location);
 106                 return -EINVAL;
 107         }
 108
 109         hi20 = (offset + 0x800) & 0xfffff000;
 110         lo12 = (offset - hi20) & 0xfff;
 111         *location = (*location & 0xfff) | hi20;
 112         *(location + 1) = (*(location + 1) & 0xfffff) | (lo12 << 20);
 113         return 0;
 114 }
 115
 116 static int apply_r_riscv_relax_rela(struct module *me, u32 *location,
 117                                     Elf_Addr v)
 118 {
 119         return 0;
 120 }
 121
 122 static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
 123                                 Elf_Addr v) = {
 124         [R_RISCV_64]                    = apply_r_riscv_64_rela,
 125         [R_RISCV_BRANCH]                = apply_r_riscv_branch_rela,
 126         [R_RISCV_JAL]                   = apply_r_riscv_jal_rela,
 127         [R_RISCV_PCREL_HI20]            = apply_r_riscv_pcrel_hi20_rela,
 128         [R_RISCV_PCREL_LO12_I]          = apply_r_riscv_pcrel_lo12_i_rela,
 129         [R_RISCV_PCREL_LO12_S]          = apply_r_riscv_pcrel_lo12_s_rela,
 130         [R_RISCV_CALL_PLT]              = apply_r_riscv_call_plt_rela,
 131         [R_RISCV_RELAX]                 = apply_r_riscv_relax_rela,
 132 };
 133
 134 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 135                        unsigned int symindex, unsigned int relsec,
 136                        struct module *me)
 137 {
 138         Elf_Rela *rel = (void *) sechdrs[relsec].sh_addr;
 139         int (*handler)(struct module *me, u32 *location, Elf_Addr v);
 140         Elf_Sym *sym;
 141         u32 *location;
 142         unsigned int i, type;
 143         Elf_Addr v;
 144         int res;
 145
 146         pr_debug("Applying relocate section %u to %u\n", relsec,
 147                sechdrs[relsec].sh_info);
 148
 149         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 150                 /* This is where to make the change */
 151                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 152                         + rel[i].r_offset;
 153                 /* This is the symbol it is referring to */
 154                 sym = (Elf_Sym *)sechdrs[symindex].sh_addr
 155                         + ELF_RISCV_R_SYM(rel[i].r_info);
 156                 if (IS_ERR_VALUE(sym->st_value)) {
 157                         /* Ignore unresolved weak symbol */
 158                         if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
 159                                 continue;
 160                         pr_warning("%s: Unknown symbol %s\n",
 161                                    me->name, strtab + sym->st_name);
 162                         return -ENOENT;
 163                 }
 164
 165                 type = ELF_RISCV_R_TYPE(rel[i].r_info);
 166
 167                 if (type < ARRAY_SIZE(reloc_handlers_rela))
 168                         handler = reloc_handlers_rela[type];
 169                 else
 170                         handler = NULL;
 171
 172                 if (!handler) {
 173                         pr_err("%s: Unknown relocation type %u\n",
 174                                me->name, type);
 175                         return -EINVAL;
 176                 }
 177
 178                 v = sym->st_value + rel[i].r_addend;
 179
 180                 if (type == R_RISCV_PCREL_LO12_I || type == R_RISCV_PCREL_LO12_S) {
 181                         unsigned int j;
 182
 183                         for (j = 0; j < sechdrs[relsec].sh_size / sizeof(*rel); j++) {
 184                                 u64 hi20_loc =
 185                                         sechdrs[sechdrs[relsec].sh_info].sh_addr
 186                                         + rel[j].r_offset;
 187                                 /* Find the corresponding HI20 PC-relative relocation entry */
 188                                 if (hi20_loc == sym->st_value) {
 189                                         Elf_Sym *hi20_sym =
 190                                                 (Elf_Sym *)sechdrs[symindex].sh_addr
 191                                                 + ELF_RISCV_R_SYM(rel[j].r_info);
 192                                         u64 hi20_sym_val =
 193                                                 hi20_sym->st_value
 194                                                 + rel[j].r_addend;
 195                                         /* Calculate lo12 */
 196                                         s64 offset = hi20_sym_val - hi20_loc;
 197                                         s32 hi20 = (offset + 0x800) & 0xfffff000;
 198                                         s32 lo12 = offset - hi20;
 199                                         v = lo12;
 200                                         break;
 201                                 }
 202                         }
 203                         if (j == sechdrs[relsec].sh_size / sizeof(*rel)) {
 204                                 pr_err(
 205                                   "%s: Can not find HI20 PC-relative relocation information\n",
 206                                   me->name);
 207                                 return -EINVAL;
 208                         }
 209                 }
 210
 211                 res = handler(me, location, v);
 212                 if (res)
 213                         return res;
 214         }
 215
 216         return 0;
 217 }