1 /* 2 * Copyright (C) 2015 Imagination Technologies 3 * Author: Alex Smith <alex.smith@imgtec.com> 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License as published by the 7 * Free Software Foundation; either version 2 of the License, or (at your 8 * option) any later version. 9 */ 10 11 static inline bool FUNC(patch_vdso)(const char *path, void *vdso) 12 { 13 const ELF(Ehdr) *ehdr = vdso; 14 void *shdrs; 15 ELF(Shdr) *shdr; 16 char *shstrtab, *name; 17 uint16_t sh_count, sh_entsize, i; 18 unsigned int local_gotno, symtabno, gotsym; 19 ELF(Dyn) *dyn = NULL; 20 21 shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff); 22 sh_count = swap_uint16(ehdr->e_shnum); 23 sh_entsize = swap_uint16(ehdr->e_shentsize); 24 25 shdr = shdrs + (sh_entsize * swap_uint16(ehdr->e_shstrndx)); 26 shstrtab = vdso + FUNC(swap_uint)(shdr->sh_offset); 27 28 for (i = 0; i < sh_count; i++) { 29 shdr = shdrs + (i * sh_entsize); 30 name = shstrtab + swap_uint32(shdr->sh_name); 31 32 /* 33 * Ensure there are no relocation sections - ld.so does not 34 * relocate the VDSO so if there are relocations things will 35 * break. 36 */ 37 switch (swap_uint32(shdr->sh_type)) { 38 case SHT_REL: 39 case SHT_RELA: 40 fprintf(stderr, 41 "%s: '%s' contains relocation sections\n", 42 program_name, path); 43 return false; 44 case SHT_DYNAMIC: 45 dyn = vdso + FUNC(swap_uint)(shdr->sh_offset); 46 break; 47 } 48 49 /* Check for existing sections. */ 50 if (strcmp(name, ".MIPS.abiflags") == 0) { 51 fprintf(stderr, 52 "%s: '%s' already contains a '.MIPS.abiflags' section\n", 53 program_name, path); 54 return false; 55 } 56 57 if (strcmp(name, ".mips_abiflags") == 0) { 58 strcpy(name, ".MIPS.abiflags"); 59 shdr->sh_type = swap_uint32(SHT_MIPS_ABIFLAGS); 60 shdr->sh_entsize = shdr->sh_size; 61 } 62 } 63 64 /* 65 * Ensure the GOT has no entries other than the standard 2, for the same 66 * reason we check that there's no relocation sections above. 67 * The standard two entries are: 68 * - Lazy resolver 69 * - Module pointer 70 */ 71 if (dyn) { 72 local_gotno = symtabno = gotsym = 0; 73 74 while (FUNC(swap_uint)(dyn->d_tag) != DT_NULL) { 75 switch (FUNC(swap_uint)(dyn->d_tag)) { 76 /* 77 * This member holds the number of local GOT entries. 78 */ 79 case DT_MIPS_LOCAL_GOTNO: 80 local_gotno = FUNC(swap_uint)(dyn->d_un.d_val); 81 break; 82 /* 83 * This member holds the number of entries in the 84 * .dynsym section. 85 */ 86 case DT_MIPS_SYMTABNO: 87 symtabno = FUNC(swap_uint)(dyn->d_un.d_val); 88 break; 89 /* 90 * This member holds the index of the first dynamic 91 * symbol table entry that corresponds to an entry in 92 * the GOT. 93 */ 94 case DT_MIPS_GOTSYM: 95 gotsym = FUNC(swap_uint)(dyn->d_un.d_val); 96 break; 97 } 98 99 dyn++; 100 } 101 102 if (local_gotno > 2 || symtabno - gotsym) { 103 fprintf(stderr, 104 "%s: '%s' contains unexpected GOT entries\n", 105 program_name, path); 106 return false; 107 } 108 } 109 110 return true; 111 } 112 113 static inline bool FUNC(get_symbols)(const char *path, void *vdso) 114 { 115 const ELF(Ehdr) *ehdr = vdso; 116 void *shdrs, *symtab; 117 ELF(Shdr) *shdr; 118 const ELF(Sym) *sym; 119 char *strtab, *name; 120 uint16_t sh_count, sh_entsize, st_count, st_entsize, i, j; 121 uint64_t offset; 122 uint32_t flags; 123 124 shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff); 125 sh_count = swap_uint16(ehdr->e_shnum); 126 sh_entsize = swap_uint16(ehdr->e_shentsize); 127 128 for (i = 0; i < sh_count; i++) { 129 shdr = shdrs + (i * sh_entsize); 130 131 if (swap_uint32(shdr->sh_type) == SHT_SYMTAB) 132 break; 133 } 134 135 if (i == sh_count) { 136 fprintf(stderr, "%s: '%s' has no symbol table\n", program_name, 137 path); 138 return false; 139 } 140 141 /* Get flags */ 142 flags = swap_uint32(ehdr->e_flags); 143 if (elf_class == ELFCLASS64) 144 elf_abi = ABI_N64; 145 else if (flags & EF_MIPS_ABI2) 146 elf_abi = ABI_N32; 147 else 148 elf_abi = ABI_O32; 149 150 /* Get symbol table. */ 151 symtab = vdso + FUNC(swap_uint)(shdr->sh_offset); 152 st_entsize = FUNC(swap_uint)(shdr->sh_entsize); 153 st_count = FUNC(swap_uint)(shdr->sh_size) / st_entsize; 154 155 /* Get string table. */ 156 shdr = shdrs + (swap_uint32(shdr->sh_link) * sh_entsize); 157 strtab = vdso + FUNC(swap_uint)(shdr->sh_offset); 158 159 /* Write offsets for symbols needed by the kernel. */ 160 for (i = 0; vdso_symbols[i].name; i++) { 161 if (!(vdso_symbols[i].abis & elf_abi)) 162 continue; 163 164 for (j = 0; j < st_count; j++) { 165 sym = symtab + (j * st_entsize); 166 name = strtab + swap_uint32(sym->st_name); 167 168 if (!strcmp(name, vdso_symbols[i].name)) { 169 offset = FUNC(swap_uint)(sym->st_value); 170 171 fprintf(out_file, 172 "\t.%s = 0x%" PRIx64 ",\n", 173 vdso_symbols[i].offset_name, offset); 174 break; 175 } 176 } 177 178 if (j == st_count) { 179 fprintf(stderr, 180 "%s: '%s' is missing required symbol '%s'\n", 181 program_name, path, vdso_symbols[i].name); 182 return false; 183 } 184 } 185 186 return true; 187 } 188