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 #include <linux/moduleloader.h> 10 #include <linux/ftrace.h> 11 12 Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) 13 { 14 struct mod_section *got_sec = &mod->arch.got; 15 int i = got_sec->num_entries; 16 struct got_entry *got = get_got_entry(val, sechdrs, got_sec); 17 18 if (got) 19 return (Elf_Addr)got; 20 21 /* There is no GOT entry for val yet, create a new one. */ 22 got = (struct got_entry *)sechdrs[got_sec->shndx].sh_addr; 23 got[i] = emit_got_entry(val); 24 25 got_sec->num_entries++; 26 if (got_sec->num_entries > got_sec->max_entries) { 27 /* 28 * This may happen when the module contains a GOT_HI20 without 29 * a paired GOT_LO12. Such a module is broken, reject it. 30 */ 31 pr_err("%s: module contains bad GOT relocation\n", mod->name); 32 return 0; 33 } 34 35 return (Elf_Addr)&got[i]; 36 } 37 38 Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) 39 { 40 int nr; 41 struct mod_section *plt_sec = &mod->arch.plt; 42 struct mod_section *plt_idx_sec = &mod->arch.plt_idx; 43 struct plt_entry *plt = get_plt_entry(val, sechdrs, plt_sec, plt_idx_sec); 44 struct plt_idx_entry *plt_idx; 45 46 if (plt) 47 return (Elf_Addr)plt; 48 49 nr = plt_sec->num_entries; 50 51 /* There is no duplicate entry, create a new one */ 52 plt = (struct plt_entry *)sechdrs[plt_sec->shndx].sh_addr; 53 plt[nr] = emit_plt_entry(val); 54 plt_idx = (struct plt_idx_entry *)sechdrs[plt_idx_sec->shndx].sh_addr; 55 plt_idx[nr] = emit_plt_idx_entry(val); 56 57 plt_sec->num_entries++; 58 plt_idx_sec->num_entries++; 59 BUG_ON(plt_sec->num_entries > plt_sec->max_entries); 60 61 return (Elf_Addr)&plt[nr]; 62 } 63 64 static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y) 65 { 66 return x->r_info == y->r_info && x->r_addend == y->r_addend; 67 } 68 69 static bool duplicate_rela(const Elf_Rela *rela, int idx) 70 { 71 int i; 72 73 for (i = 0; i < idx; i++) { 74 if (is_rela_equal(&rela[i], &rela[idx])) 75 return true; 76 } 77 78 return false; 79 } 80 81 static void count_max_entries(Elf_Rela *relas, int num, 82 unsigned int *plts, unsigned int *gots) 83 { 84 unsigned int i, type; 85 86 for (i = 0; i < num; i++) { 87 type = ELF_R_TYPE(relas[i].r_info); 88 switch (type) { 89 case R_LARCH_SOP_PUSH_PLT_PCREL: 90 case R_LARCH_B26: 91 if (!duplicate_rela(relas, i)) 92 (*plts)++; 93 break; 94 case R_LARCH_GOT_PC_HI20: 95 if (!duplicate_rela(relas, i)) 96 (*gots)++; 97 break; 98 default: 99 break; /* Do nothing. */ 100 } 101 } 102 } 103 104 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, 105 char *secstrings, struct module *mod) 106 { 107 unsigned int i, num_plts = 0, num_gots = 0; 108 Elf_Shdr *got_sec, *plt_sec, *plt_idx_sec, *tramp = NULL; 109 110 /* 111 * Find the empty .plt sections. 112 */ 113 for (i = 0; i < ehdr->e_shnum; i++) { 114 if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) 115 mod->arch.got.shndx = i; 116 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) 117 mod->arch.plt.shndx = i; 118 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx")) 119 mod->arch.plt_idx.shndx = i; 120 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".ftrace_trampoline")) 121 tramp = sechdrs + i; 122 } 123 124 if (!mod->arch.got.shndx) { 125 pr_err("%s: module GOT section(s) missing\n", mod->name); 126 return -ENOEXEC; 127 } 128 if (!mod->arch.plt.shndx) { 129 pr_err("%s: module PLT section(s) missing\n", mod->name); 130 return -ENOEXEC; 131 } 132 if (!mod->arch.plt_idx.shndx) { 133 pr_err("%s: module PLT.IDX section(s) missing\n", mod->name); 134 return -ENOEXEC; 135 } 136 137 /* Calculate the maxinum number of entries */ 138 for (i = 0; i < ehdr->e_shnum; i++) { 139 int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela); 140 Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset; 141 Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info; 142 143 if (sechdrs[i].sh_type != SHT_RELA) 144 continue; 145 146 /* ignore relocations that operate on non-exec sections */ 147 if (!(dst_sec->sh_flags & SHF_EXECINSTR)) 148 continue; 149 150 count_max_entries(relas, num_rela, &num_plts, &num_gots); 151 } 152 153 got_sec = sechdrs + mod->arch.got.shndx; 154 got_sec->sh_type = SHT_NOBITS; 155 got_sec->sh_flags = SHF_ALLOC; 156 got_sec->sh_addralign = L1_CACHE_BYTES; 157 got_sec->sh_size = (num_gots + 1) * sizeof(struct got_entry); 158 mod->arch.got.num_entries = 0; 159 mod->arch.got.max_entries = num_gots; 160 161 plt_sec = sechdrs + mod->arch.plt.shndx; 162 plt_sec->sh_type = SHT_NOBITS; 163 plt_sec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 164 plt_sec->sh_addralign = L1_CACHE_BYTES; 165 plt_sec->sh_size = (num_plts + 1) * sizeof(struct plt_entry); 166 mod->arch.plt.num_entries = 0; 167 mod->arch.plt.max_entries = num_plts; 168 169 plt_idx_sec = sechdrs + mod->arch.plt_idx.shndx; 170 plt_idx_sec->sh_type = SHT_NOBITS; 171 plt_idx_sec->sh_flags = SHF_ALLOC; 172 plt_idx_sec->sh_addralign = L1_CACHE_BYTES; 173 plt_idx_sec->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry); 174 mod->arch.plt_idx.num_entries = 0; 175 mod->arch.plt_idx.max_entries = num_plts; 176 177 if (tramp) { 178 tramp->sh_type = SHT_NOBITS; 179 tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 180 tramp->sh_addralign = __alignof__(struct plt_entry); 181 tramp->sh_size = NR_FTRACE_PLTS * sizeof(struct plt_entry); 182 } 183 184 return 0; 185 } 186