LXR linux/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
  22struct got_entry {
  23        struct got_entry *next;
  24        Elf64_Sxword r_addend;
  25        int got_offset;
  26};
  27
  28static inline void
  29process_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
  63int
  64module_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
 132int
 133apply_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