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 got = sechdrs[me->arch.gotsecindex].sh_addr; 150 gp = got + 0x8000; 151 152 for (i = 0; i < n; i++) { 153 unsigned long r_sym = ELF64_R_SYM (rela[i].r_info); 154 unsigned long r_type = ELF64_R_TYPE (rela[i].r_info); 155 unsigned long r_got_offset = r_type >> 8; 156 unsigned long value, hi, lo; 157 r_type &= 0xff; 158 159 /* This is where to make the change. */ 160 location = base + rela[i].r_offset; 161 162 /* This is the symbol it is referring to. Note that all 163 unresolved symbols have been resolved. */ 164 sym = symtab + r_sym; 165 value = sym->st_value + rela[i].r_addend; 166 167 switch (r_type) { 168 case R_ALPHA_NONE: 169 break; 170 case R_ALPHA_REFLONG: 171 *(u32 *)location = value; 172 break; 173 case R_ALPHA_REFQUAD: 174 /* BUG() can produce misaligned relocations. */ 175 ((u32 *)location)[0] = value; 176 ((u32 *)location)[1] = value >> 32; 177 break; 178 case R_ALPHA_GPREL32: 179 value -= gp; 180 if ((int)value != value) 181 goto reloc_overflow; 182 *(u32 *)location = value; 183 break; 184 case R_ALPHA_LITERAL: 185 hi = got + r_got_offset; 186 lo = hi - gp; 187 if ((short)lo != lo) 188 goto reloc_overflow; 189 *(u16 *)location = lo; 190 *(u64 *)hi = value; 191 break; 192 case R_ALPHA_LITUSE: 193 break; 194 case R_ALPHA_GPDISP: 195 value = gp - (u64)location; 196 lo = (short)value; 197 hi = (int)(value - lo); 198 if (hi + lo != value) 199 goto reloc_overflow; 200 *(u16 *)location = hi >> 16; 201 *(u16 *)(location + rela[i].r_addend) = lo; 202 break; 203 case R_ALPHA_BRSGP: 204 /* BRSGP is only allowed to bind to local symbols. 205 If the section is undef, this means that the 206 value was resolved from somewhere else. */ 207 if (sym->st_shndx == SHN_UNDEF) 208 goto reloc_overflow; 209 if ((sym->st_other & STO_ALPHA_STD_GPLOAD) == 210 STO_ALPHA_STD_GPLOAD) 211 /* Omit the prologue. */ 212 value += 8; 213 fallthrough; 214 case R_ALPHA_BRADDR: 215 value -= (u64)location + 4; 216 if (value & 3) 217 goto reloc_overflow; 218 value = (long)value >> 2; 219 if (value + (1<<21) >= 1<<22) 220 goto reloc_overflow; 221 value &= 0x1fffff; 222 value |= *(u32 *)location & ~0x1fffff; 223 *(u32 *)location = value; 224 break; 225 case R_ALPHA_HINT: 226 break; 227 case R_ALPHA_SREL32: 228 value -= (u64)location; 229 if ((int)value != value) 230 goto reloc_overflow; 231 *(u32 *)location = value; 232 break; 233 case R_ALPHA_SREL64: 234 value -= (u64)location; 235 *(u64 *)location = value; 236 break; 237 case R_ALPHA_GPRELHIGH: 238 value = (long)(value - gp + 0x8000) >> 16; 239 if ((short) value != value) 240 goto reloc_overflow; 241 *(u16 *)location = value; 242 break; 243 case R_ALPHA_GPRELLOW: 244 value -= gp; 245 *(u16 *)location = value; 246 break; 247 case R_ALPHA_GPREL16: 248 value -= gp; 249 if ((short) value != value) 250 goto reloc_overflow; 251 *(u16 *)location = value; 252 break; 253 default: 254 printk(KERN_ERR "module %s: Unknown relocation: %lu\n", 255 me->name, r_type); 256 return -ENOEXEC; 257 reloc_overflow: 258 if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION) 259 printk(KERN_ERR 260 "module %s: Relocation (type %lu) overflow vs section %d\n", 261 me->name, r_type, sym->st_shndx); 262 else 263 printk(KERN_ERR 264 "module %s: Relocation (type %lu) overflow vs %s\n", 265 me->name, r_type, strtab + sym->st_name); 266 return -ENOEXEC; 267 } 268 } 269 270 return 0; 271 } 272