1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited 4 */ 5 6 #include <linux/elf.h> 7 #include <linux/kernel.h> 8 #include <linux/module.h> 9 10 Elf_Addr module_emit_got_entry(struct module *mod, Elf_Addr val) 11 { 12 struct mod_section *got_sec = &mod->arch.got; 13 int i = got_sec->num_entries; 14 struct got_entry *got = get_got_entry(val, got_sec); 15 16 if (got) 17 return (Elf_Addr)got; 18 19 /* There is no GOT entry for val yet, create a new one. */ 20 got = (struct got_entry *)got_sec->shdr->sh_addr; 21 got[i] = emit_got_entry(val); 22 23 got_sec->num_entries++; 24 if (got_sec->num_entries > got_sec->max_entries) { 25 /* 26 * This may happen when the module contains a GOT_HI20 without 27 * a paired GOT_LO12. Such a module is broken, reject it. 28 */ 29 pr_err("%s: module contains bad GOT relocation\n", mod->name); 30 return 0; 31 } 32 33 return (Elf_Addr)&got[i]; 34 } 35 36 Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Addr val) 37 { 38 int nr; 39 struct mod_section *plt_sec = &mod->arch.plt; 40 struct mod_section *plt_idx_sec = &mod->arch.plt_idx; 41 struct plt_entry *plt = get_plt_entry(val, plt_sec, plt_idx_sec); 42 struct plt_idx_entry *plt_idx; 43 44 if (plt) 45 return (Elf_Addr)plt; 46 47 nr = plt_sec->num_entries; 48 49 /* There is no duplicate entry, create a new one */ 50 plt = (struct plt_entry *)plt_sec->shdr->sh_addr; 51 plt[nr] = emit_plt_entry(val); 52 plt_idx = (struct plt_idx_entry *)plt_idx_sec->shdr->sh_addr; 53 plt_idx[nr] = emit_plt_idx_entry(val); 54 55 plt_sec->num_entries++; 56 plt_idx_sec->num_entries++; 57 BUG_ON(plt_sec->num_entries > plt_sec->max_entries); 58 59 return (Elf_Addr)&plt[nr]; 60 } 61 62 static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y) 63 { 64 return x->r_info == y->r_info && x->r_addend == y->r_addend; 65 } 66 67 static bool duplicate_rela(const Elf_Rela *rela, int idx) 68 { 69 int i; 70 71 for (i = 0; i < idx; i++) { 72 if (is_rela_equal(&rela[i], &rela[idx])) 73 return true; 74 } 75 76 return false; 77 } 78 79 static void count_max_entries(Elf_Rela *relas, int num, 80 unsigned int *plts, unsigned int *gots) 81 { 82 unsigned int i, type; 83 84 for (i = 0; i < num; i++) { 85 type = ELF_R_TYPE(relas[i].r_info); 86 switch (type) { 87 case R_LARCH_SOP_PUSH_PLT_PCREL: 88 case R_LARCH_B26: 89 if (!duplicate_rela(relas, i)) 90 (*plts)++; 91 break; 92 case R_LARCH_GOT_PC_HI20: 93 if (!duplicate_rela(relas, i)) 94 (*gots)++; 95 break; 96 default: 97 break; /* Do nothing. */ 98 } 99 } 100 } 101 102 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, 103 char *secstrings, struct module *mod) 104 { 105 unsigned int i, num_plts = 0, num_gots = 0; 106 107 /* 108 * Find the empty .plt sections. 109 */ 110 for (i = 0; i < ehdr->e_shnum; i++) { 111 if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) 112 mod->arch.got.shdr = sechdrs + i; 113 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) 114 mod->arch.plt.shdr = sechdrs + i; 115 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx")) 116 mod->arch.plt_idx.shdr = sechdrs + i; 117 } 118 119 if (!mod->arch.got.shdr) { 120 pr_err("%s: module GOT section(s) missing\n", mod->name); 121 return -ENOEXEC; 122 } 123 if (!mod->arch.plt.shdr) { 124 pr_err("%s: module PLT section(s) missing\n", mod->name); 125 return -ENOEXEC; 126 } 127 if (!mod->arch.plt_idx.shdr) { 128 pr_err("%s: module PLT.IDX section(s) missing\n", mod->name); 129 return -ENOEXEC; 130 } 131 132 /* Calculate the maxinum number of entries */ 133 for (i = 0; i < ehdr->e_shnum; i++) { 134 int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela); 135 Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset; 136 Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info; 137 138 if (sechdrs[i].sh_type != SHT_RELA) 139 continue; 140 141 /* ignore relocations that operate on non-exec sections */ 142 if (!(dst_sec->sh_flags & SHF_EXECINSTR)) 143 continue; 144 145 count_max_entries(relas, num_rela, &num_plts, &num_gots); 146 } 147 148 mod->arch.got.shdr->sh_type = SHT_NOBITS; 149 mod->arch.got.shdr->sh_flags = SHF_ALLOC; 150 mod->arch.got.shdr->sh_addralign = L1_CACHE_BYTES; 151 mod->arch.got.shdr->sh_size = (num_gots + 1) * sizeof(struct got_entry); 152 mod->arch.got.num_entries = 0; 153 mod->arch.got.max_entries = num_gots; 154 155 mod->arch.plt.shdr->sh_type = SHT_NOBITS; 156 mod->arch.plt.shdr->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 157 mod->arch.plt.shdr->sh_addralign = L1_CACHE_BYTES; 158 mod->arch.plt.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_entry); 159 mod->arch.plt.num_entries = 0; 160 mod->arch.plt.max_entries = num_plts; 161 162 mod->arch.plt_idx.shdr->sh_type = SHT_NOBITS; 163 mod->arch.plt_idx.shdr->sh_flags = SHF_ALLOC; 164 mod->arch.plt_idx.shdr->sh_addralign = L1_CACHE_BYTES; 165 mod->arch.plt_idx.shdr->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry); 166 mod->arch.plt_idx.num_entries = 0; 167 mod->arch.plt_idx.max_entries = num_plts; 168 169 return 0; 170 } 171