arch/alpha/kernel/module.c

   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 }