1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Kernel module help for Alpha. 3 Copyright (C) 2002 Richard Henderson. 4 5 */ 6 #include <linux/moduleloader.h> 7 #include <linux/elf.h> 8 #include <linux/vmalloc.h> 9 #include <linux/fs.h> 10 #include <linux/string.h> 11 #include <linux/kernel.h> 12 #include <linux/slab.h> 13 14 #if 0 15 #define DEBUGP printk 16 #else 17 #define DEBUGP(fmt...) 18 #endif 19 20 /* Allocate the GOT at the end of the core sections. */ 21 22 struct got_entry { 23 struct got_entry *next; 24 Elf64_Sxword r_addend; 25 int got_offset; 26 }; 27 28 static inline void 29 process_reloc_for_got(Elf64_Rela *rela, 30 struct got_entry *chains, Elf64_Xword *poffset) 31 { 32 unsigned long r_sym = ELF64_R_SYM (rela->r_info); 33 unsigned long r_type = ELF64_R_TYPE (rela->r_info); 34 Elf64_Sxword r_addend = rela->r_addend; 35 struct got_entry *g; 36 37 if (r_type != R_ALPHA_LITERAL) 38 return; 39 40 for (g = chains + r_sym; g ; g = g->next) 41 if (g->r_addend == r_addend) { 42 if (g->got_offset == 0) { 43 g->got_offset = *poffset; 44 *poffset += 8; 45 } 46 goto found_entry; 47 } 48 49 g = kmalloc (sizeof (*g), GFP_KERNEL); 50 g->next = chains[r_sym].next; 51 g->r_addend = r_addend; 52 g->got_offset = *poffset; 53 *poffset += 8; 54 chains[r_sym].next = g; 55 56 found_entry: 57 /* Trick: most of the ELF64_R_TYPE field is unused. There are 58 42 valid relocation types, and a 32-bit field. Co-opt the 59 bits above 256 to store the got offset for this reloc. */ 60 rela->r_info |= g->got_offset << 8; 61 } 62 63 int 64 module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs, 65 char *secstrings, struct module *me) 66 { 67 struct got_entry *chains; 68 Elf64_Rela *rela; 69 Elf64_Shdr *esechdrs, *symtab, *s, *got; 70 unsigned long nsyms, nrela, i; 71 72 esechdrs = sechdrs + hdr->e_shnum; 73 symtab = got = NULL; 74 75 /* Find out how large the symbol table is. Allocate one got_entry 76 head per symbol. Normally this will be enough, but not always. 77 We'll chain different offsets for the symbol down each head. */ 78 for (s = sechdrs; s < esechdrs; ++s) 79 if (s->sh_type == SHT_SYMTAB) 80 symtab = s; 81 else if (!strcmp(".got", secstrings + s->sh_name)) { 82 got = s; 83 me->arch.gotsecindex = s - sechdrs; 84 } 85 86 if (!symtab) { 87 printk(KERN_ERR "module %s: no symbol table\n", me->name); 88 return -ENOEXEC; 89 } 90 if (!got) { 91 printk(KERN_ERR "module %s: no got section\n", me->name); 92 return -ENOEXEC; 93 } 94 95 nsyms = symtab->sh_size / sizeof(Elf64_Sym); 96 chains = kcalloc(nsyms, sizeof(struct got_entry), GFP_KERNEL); 97 if (!chains) { 98 printk(KERN_ERR 99 "module %s: no memory for symbol chain buffer\n", 100 me->name); 101 return -ENOMEM; 102 } 103 104 got->sh_size = 0; 105 got->sh_addralign = 8; 106 got->sh_type = SHT_NOBITS; 107 108 /* Examine all LITERAL relocations to find out what GOT entries 109 are required. This sizes the GOT section as well. */ 110 for (s = sechdrs; s < esechdrs; ++s) 111 if (s->sh_type == SHT_RELA) { 112 nrela = s->sh_size / sizeof(Elf64_Rela); 113 rela = (void *)hdr + s->sh_offset; 114 for (i = 0; i < nrela; ++i) 115 process_reloc_for_got(rela+i, chains, 116 &got->sh_size); 117 } 118 119 /* Free the memory we allocated. */ 120 for (i = 0; i < nsyms; ++i) { 121 struct got_entry *g, *n; 122 for (g = chains[i].next; g ; g = n) { 123 n = g->next; 124 kfree(g); 125 } 126 } 127 kfree(chains); 128 129 return 0; 130 } 131 132 int 133 apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab, 134 unsigned int symindex, unsigned int relsec, 135 struct module *me) 136 { 137 Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr; 138 unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela); 139 Elf64_Sym *symtab, *sym; 140 void *base, *location; 141 unsigned long got, gp; 142 143 DEBUGP("Applying relocate section %u to %u\n", relsec, 144 sechdrs[relsec].sh_info); 145 146 base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr; 147 symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr; 148 149 /* The small sections were sorted to the end of the segment. 150 The following should definitely cover them. */ 151 gp = (u64)me->core_layout.base + me->core_layout.size - 0x8000; 152 got = sechdrs[me->arch.gotsecindex].sh_addr; 153 154 for (i = 0; i < n; i++) { 155 unsigned long r_sym = ELF64_R_SYM (rela[i].r_info); 156 unsigned long r_type = ELF64_R_TYPE (rela[i].r_info); 157 unsigned long r_got_offset = r_type >> 8; 158 unsigned long value, hi, lo; 159 r_type &= 0xff; 160 161 /* This is where to make the change. */ 162 location = base + rela[i].r_offset; 163 164 /* This is the symbol it is referring to. Note that all 165 unresolved symbols have been resolved. */ 166 sym = symtab + r_sym; 167 value = sym->st_value + rela[i].r_addend; 168 169 switch (r_type) { 170 case R_ALPHA_NONE: 171 break; 172 case R_ALPHA_REFLONG: 173 *(u32 *)location = value; 174 break; 175 case R_ALPHA_REFQUAD: 176 /* BUG() can produce misaligned relocations. */ 177 ((u32 *)location)[0] = value; 178 ((u32 *)location)[1] = value >> 32; 179 break; 180 case R_ALPHA_GPREL32: 181 value -= gp; 182 if ((int)value != value) 183 goto reloc_overflow; 184 *(u32 *)location = value; 185 break; 186 case R_ALPHA_LITERAL: 187 hi = got + r_got_offset; 188 lo = hi - gp; 189 if ((short)lo != lo) 190 goto reloc_overflow; 191 *(u16 *)location = lo; 192 *(u64 *)hi = value; 193 break; 194 case R_ALPHA_LITUSE: 195 break; 196 case R_ALPHA_GPDISP: 197 value = gp - (u64)location; 198 lo = (short)value; 199 hi = (int)(value - lo); 200 if (hi + lo != value) 201 goto reloc_overflow; 202 *(u16 *)location = hi >> 16; 203 *(u16 *)(location + rela[i].r_addend) = lo; 204 break; 205 case R_ALPHA_BRSGP: 206 /* BRSGP is only allowed to bind to local symbols. 207 If the section is undef, this means that the 208 value was resolved from somewhere else. */ 209 if (sym->st_shndx == SHN_UNDEF) 210 goto reloc_overflow; 211 if ((sym->st_other & STO_ALPHA_STD_GPLOAD) == 212 STO_ALPHA_STD_GPLOAD) 213 /* Omit the prologue. */ 214 value += 8; 215 fallthrough; 216 case R_ALPHA_BRADDR: 217 value -= (u64)location + 4; 218 if (value & 3) 219 goto reloc_overflow; 220 value = (long)value >> 2; 221 if (value + (1<<21) >= 1<<22) 222 goto reloc_overflow; 223 value &= 0x1fffff; 224 value |= *(u32 *)location & ~0x1fffff; 225 *(u32 *)location = value; 226 break; 227 case R_ALPHA_HINT: 228 break; 229 case R_ALPHA_SREL32: 230 value -= (u64)location; 231 if ((int)value != value) 232 goto reloc_overflow; 233 *(u32 *)location = value; 234 break; 235 case R_ALPHA_SREL64: 236 value -= (u64)location; 237 *(u64 *)location = value; 238 break; 239 case R_ALPHA_GPRELHIGH: 240 value = (long)(value - gp + 0x8000) >> 16; 241 if ((short) value != value) 242 goto reloc_overflow; 243 *(u16 *)location = value; 244 break; 245 case R_ALPHA_GPRELLOW: 246 value -= gp; 247 *(u16 *)location = value; 248 break; 249 case R_ALPHA_GPREL16: 250 value -= gp; 251 if ((short) value != value) 252 goto reloc_overflow; 253 *(u16 *)location = value; 254 break; 255 default: 256 printk(KERN_ERR "module %s: Unknown relocation: %lu\n", 257 me->name, r_type); 258 return -ENOEXEC; 259 reloc_overflow: 260 if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION) 261 printk(KERN_ERR 262 "module %s: Relocation (type %lu) overflow vs section %d\n", 263 me->name, r_type, sym->st_shndx); 264 else 265 printk(KERN_ERR 266 "module %s: Relocation (type %lu) overflow vs %s\n", 267 me->name, r_type, strtab + sym->st_name); 268 return -ENOEXEC; 269 } 270 } 271 272 return 0; 273 } 274