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 #include <linux/sort.h> 12 13 Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) 14 { 15 struct mod_section *got_sec = &mod->arch.got; 16 int i = got_sec->num_entries; 17 struct got_entry *got = get_got_entry(val, sechdrs, got_sec); 18 19 if (got) 20 return (Elf_Addr)got; 21 22 /* There is no GOT entry for val yet, create a new one. */ 23 got = (struct got_entry *)sechdrs[got_sec->shndx].sh_addr; 24 got[i] = emit_got_entry(val); 25 26 got_sec->num_entries++; 27 if (got_sec->num_entries > got_sec->max_entries) { 28 /* 29 * This may happen when the module contains a GOT_HI20 without 30 * a paired GOT_LO12. Such a module is broken, reject it. 31 */ 32 pr_err("%s: module contains bad GOT relocation\n", mod->name); 33 return 0; 34 } 35 36 return (Elf_Addr)&got[i]; 37 } 38 39 Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val) 40 { 41 int nr; 42 struct mod_section *plt_sec = &mod->arch.plt; 43 struct mod_section *plt_idx_sec = &mod->arch.plt_idx; 44 struct plt_entry *plt = get_plt_entry(val, sechdrs, plt_sec, plt_idx_sec); 45 struct plt_idx_entry *plt_idx; 46 47 if (plt) 48 return (Elf_Addr)plt; 49 50 nr = plt_sec->num_entries; 51 52 /* There is no duplicate entry, create a new one */ 53 plt = (struct plt_entry *)sechdrs[plt_sec->shndx].sh_addr; 54 plt[nr] = emit_plt_entry(val); 55 plt_idx = (struct plt_idx_entry *)sechdrs[plt_idx_sec->shndx].sh_addr; 56 plt_idx[nr] = emit_plt_idx_entry(val); 57 58 plt_sec->num_entries++; 59 plt_idx_sec->num_entries++; 60 BUG_ON(plt_sec->num_entries > plt_sec->max_entries); 61 62 return (Elf_Addr)&plt[nr]; 63 } 64 65 #define cmp_3way(a, b) ((a) < (b) ? -1 : (a) > (b)) 66 67 static int compare_rela(const void *x, const void *y) 68 { 69 int ret; 70 const Elf_Rela *rela_x = x, *rela_y = y; 71 72 ret = cmp_3way(rela_x->r_info, rela_y->r_info); 73 if (ret == 0) 74 ret = cmp_3way(rela_x->r_addend, rela_y->r_addend); 75 76 return ret; 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; 83 84 sort(relas, num, sizeof(Elf_Rela), compare_rela, NULL); 85 86 for (i = 0; i < num; i++) { 87 if (i && !compare_rela(&relas[i-1], &relas[i])) 88 continue; 89 90 switch (ELF_R_TYPE(relas[i].r_info)) { 91 case R_LARCH_SOP_PUSH_PLT_PCREL: 92 case R_LARCH_B26: 93 (*plts)++; 94 break; 95 case R_LARCH_GOT_PC_HI20: 96 case R_LARCH_GOT_PCADD_HI20: 97 (*gots)++; 98 break; 99 default: 100 break; /* Do nothing. */ 101 } 102 } 103 } 104 105 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, 106 char *secstrings, struct module *mod) 107 { 108 unsigned int i, num_plts = 0, num_gots = 0; 109 Elf_Shdr *got_sec, *plt_sec, *plt_idx_sec, *tramp = NULL; 110 111 /* 112 * Find the empty .plt sections. 113 */ 114 for (i = 0; i < ehdr->e_shnum; i++) { 115 if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) 116 mod->arch.got.shndx = i; 117 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt")) 118 mod->arch.plt.shndx = i; 119 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx")) 120 mod->arch.plt_idx.shndx = i; 121 else if (!strcmp(secstrings + sechdrs[i].sh_name, ".ftrace_trampoline")) 122 tramp = sechdrs + i; 123 } 124 125 if (!mod->arch.got.shndx) { 126 pr_err("%s: module GOT section(s) missing\n", mod->name); 127 return -ENOEXEC; 128 } 129 if (!mod->arch.plt.shndx) { 130 pr_err("%s: module PLT section(s) missing\n", mod->name); 131 return -ENOEXEC; 132 } 133 if (!mod->arch.plt_idx.shndx) { 134 pr_err("%s: module PLT.IDX section(s) missing\n", mod->name); 135 return -ENOEXEC; 136 } 137 138 /* Calculate the maxinum number of entries */ 139 for (i = 0; i < ehdr->e_shnum; i++) { 140 int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela); 141 Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset; 142 Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info; 143 144 if (sechdrs[i].sh_type != SHT_RELA) 145 continue; 146 147 /* ignore relocations that operate on non-exec sections */ 148 if (!(dst_sec->sh_flags & SHF_EXECINSTR)) 149 continue; 150 151 count_max_entries(relas, num_rela, &num_plts, &num_gots); 152 } 153 154 got_sec = sechdrs + mod->arch.got.shndx; 155 got_sec->sh_type = SHT_NOBITS; 156 got_sec->sh_flags = SHF_ALLOC; 157 got_sec->sh_addralign = L1_CACHE_BYTES; 158 got_sec->sh_size = (num_gots + 1) * sizeof(struct got_entry); 159 mod->arch.got.num_entries = 0; 160 mod->arch.got.max_entries = num_gots; 161 162 plt_sec = sechdrs + mod->arch.plt.shndx; 163 plt_sec->sh_type = SHT_NOBITS; 164 plt_sec->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 165 plt_sec->sh_addralign = L1_CACHE_BYTES; 166 plt_sec->sh_size = (num_plts + 1) * sizeof(struct plt_entry); 167 mod->arch.plt.num_entries = 0; 168 mod->arch.plt.max_entries = num_plts; 169 170 plt_idx_sec = sechdrs + mod->arch.plt_idx.shndx; 171 plt_idx_sec->sh_type = SHT_NOBITS; 172 plt_idx_sec->sh_flags = SHF_ALLOC; 173 plt_idx_sec->sh_addralign = L1_CACHE_BYTES; 174 plt_idx_sec->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry); 175 mod->arch.plt_idx.num_entries = 0; 176 mod->arch.plt_idx.max_entries = num_plts; 177 178 if (tramp) { 179 tramp->sh_type = SHT_NOBITS; 180 tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC; 181 tramp->sh_addralign = __alignof__(struct plt_entry); 182 tramp->sh_size = NR_FTRACE_PLTS * sizeof(struct plt_entry); 183 } 184 185 return 0; 186 } 187