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