arm-link.c

   1 #ifdef TARGET_DEFS_ONLY
   2
   3 #define EM_TCC_TARGET EM_ARM
   4
   5 /* relocation type for 32 bit data relocation */
   6 #define R_DATA_32   R_ARM_ABS32
   7 #define R_DATA_PTR  R_ARM_ABS32
   8 #define R_JMP_SLOT  R_ARM_JUMP_SLOT
   9 #define R_GLOB_DAT  R_ARM_GLOB_DAT
  10 #define R_COPY      R_ARM_COPY
  11 #define R_RELATIVE  R_ARM_RELATIVE
  12
  13 #define R_NUM       R_ARM_NUM
  14
  15 #define ELF_START_ADDR 0x00008000
  16 #define ELF_PAGE_SIZE  0x1000
  17
  18 #define PCRELATIVE_DLLPLT 1
  19 #define RELOCATE_DLLPLT 1
  20
  21 enum float_abi {
  22     ARM_SOFTFP_FLOAT,
  23     ARM_HARD_FLOAT,
  24 };
  25
  26 #else /* !TARGET_DEFS_ONLY */
  27
  28 #include "tcc.h"
  29
  30 /* Returns 1 for a code relocation, 0 for a data relocation. For unknown
  31    relocations, returns -1. */
  32 int code_reloc (int reloc_type)
  33 {
  34     switch (reloc_type) {
  35         case R_ARM_MOVT_ABS:
  36         case R_ARM_MOVW_ABS_NC:
  37         case R_ARM_THM_MOVT_ABS:
  38         case R_ARM_THM_MOVW_ABS_NC:
  39         case R_ARM_ABS32:
  40         case R_ARM_REL32:
  41         case R_ARM_GOTPC:
  42         case R_ARM_GOTOFF:
  43         case R_ARM_GOT32:
  44         case R_ARM_GOT_PREL:
  45         case R_ARM_COPY:
  46         case R_ARM_GLOB_DAT:
  47         case R_ARM_NONE:
  48             return 0;
  49
  50         case R_ARM_PC24:
  51         case R_ARM_CALL:
  52         case R_ARM_JUMP24:
  53         case R_ARM_PLT32:
  54         case R_ARM_THM_PC22:
  55         case R_ARM_THM_JUMP24:
  56         case R_ARM_PREL31:
  57         case R_ARM_V4BX:
  58         case R_ARM_JUMP_SLOT:
  59             return 1;
  60     }
  61     return -1;
  62 }
  63
  64 /* Returns an enumerator to describe whether and when the relocation needs a
  65    GOT and/or PLT entry to be created. See tcc.h for a description of the
  66    different values. */
  67 int gotplt_entry_type (int reloc_type)
  68 {
  69     switch (reloc_type) {
  70         case R_ARM_NONE:
  71         case R_ARM_COPY:
  72         case R_ARM_GLOB_DAT:
  73         case R_ARM_JUMP_SLOT:
  74             return NO_GOTPLT_ENTRY;
  75
  76         case R_ARM_PC24:
  77         case R_ARM_CALL:
  78         case R_ARM_JUMP24:
  79         case R_ARM_PLT32:
  80         case R_ARM_THM_PC22:
  81         case R_ARM_THM_JUMP24:
  82         case R_ARM_MOVT_ABS:
  83         case R_ARM_MOVW_ABS_NC:
  84         case R_ARM_THM_MOVT_ABS:
  85         case R_ARM_THM_MOVW_ABS_NC:
  86         case R_ARM_PREL31:
  87         case R_ARM_ABS32:
  88         case R_ARM_REL32:
  89         case R_ARM_V4BX:
  90             return AUTO_GOTPLT_ENTRY;
  91
  92         case R_ARM_GOTPC:
  93         case R_ARM_GOTOFF:
  94             return BUILD_GOT_ONLY;
  95
  96         case R_ARM_GOT32:
  97         case R_ARM_GOT_PREL:
  98             return ALWAYS_GOTPLT_ENTRY;
  99     }
 100     return -1;
 101 }
 102
 103 #ifndef TCC_TARGET_PE
 104 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
 105 {
 106     Section *plt = s1->plt;
 107     uint8_t *p;
 108     unsigned plt_offset;
 109
 110     /* when building a DLL, GOT entry accesses must be done relative to
 111        start of GOT (see x86_64 example above)  */
 112
 113     /* empty PLT: create PLT0 entry that push address of call site and
 114        jump to ld.so resolution routine (GOT + 8) */
 115     if (plt->data_offset == 0) {
 116         p = section_ptr_add(plt, 20);
 117         write32le(p,    0xe52de004); /* push {lr}         */
 118         write32le(p+4,  0xe59fe004); /* ldr lr, [pc, #4] */
 119         write32le(p+8,  0xe08fe00e); /* add lr, pc, lr    */
 120         write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
 121         /* p+16 is set in relocate_plt */
 122     }
 123     plt_offset = plt->data_offset;
 124
 125     if (attr->plt_thumb_stub) {
 126         p = section_ptr_add(plt, 4);
 127         write32le(p,   0x4778); /* bx pc */
 128         write32le(p+2, 0x46c0); /* nop   */
 129     }
 130     p = section_ptr_add(plt, 12);
 131     /* save GOT offset for relocate_plt */
 132     write32le(p + 4, got_offset);
 133     return plt_offset;
 134 }
 135
 136 /* relocate the PLT: compute addresses and offsets in the PLT now that final
 137    address for PLT and GOT are known (see fill_program_header) */
 138 ST_FUNC void relocate_plt(TCCState *s1)
 139 {
 140     uint8_t *p, *p_end;
 141
 142     if (!s1->plt)
 143       return;
 144
 145     p = s1->plt->data;
 146     p_end = p + s1->plt->data_offset;
 147
 148     if (p < p_end) {
 149         int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
 150         write32le(s1->plt->data + 16, x - 4);
 151         p += 20;
 152         while (p < p_end) {
 153             unsigned off = x  + read32le(p + 4) + (s1->plt->data - p) + 4;
 154             if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
 155                 p += 4;
 156             write32le(p, 0xe28fc600 | ((off >> 20) & 0xff));     // add ip, pc, #0xNN00000
 157             write32le(p + 4, 0xe28cca00 | ((off >> 12) & 0xff)); // add ip, ip, #0xNN000
 158             write32le(p + 8, 0xe5bcf000 | (off & 0xfff));        // ldr pc, [ip, #0xNNN]!
 159             p += 12;
 160         }
 161     }
 162
 163     if (s1->got->relocplt) {
 164         int mem = s1->output_type == TCC_OUTPUT_MEMORY;
 165         ElfW_Rel *rel;
 166
 167         p = s1->got->data;
 168         for_each_elem(s1->got->relocplt, 0, rel, ElfW_Rel) {
 169             int sym_index = ELFW(R_SYM)(rel->r_info);
 170             ElfW(Sym) *sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 171             write32le(p + rel->r_offset, mem ? sym->st_value : s1->plt->sh_addr);
 172         }
 173     }
 174 }
 175 #endif
 176
 177 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 178 {
 179     ElfW(Sym) *sym;
 180     int sym_index, esym_index;
 181
 182     sym_index = ELFW(R_SYM)(rel->r_info);
 183     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 184
 185     switch(type) {
 186         case R_ARM_PC24:
 187         case R_ARM_CALL:
 188         case R_ARM_JUMP24:
 189         case R_ARM_PLT32:
 190             {
 191                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 192                 x = (*(int *) ptr) & 0xffffff;
 193 #ifdef DEBUG_RELOC
 194                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 195 #endif
 196                 (*(int *)ptr) &= 0xff000000;
 197                 if (x & 0x800000)
 198                     x -= 0x1000000;
 199                 x <<= 2;
 200                 blx_avail = (TCC_CPU_VERSION >= 5);
 201                 is_thumb = val & 1;
 202                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 203                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 204                 x += val - addr;
 205 #ifdef DEBUG_RELOC
 206                 printf (" newx=0x%x name=%s\n", x,
 207                         (char *) symtab_section->link->data + sym->st_name);
 208 #endif
 209                 h = x & 2;
 210                 th_ko = (x & 3) && (!blx_avail || !is_call);
 211                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 212                     tcc_error("can't relocate value at %x,%d",addr, type);
 213                 x >>= 2;
 214                 x &= 0xffffff;
 215                 /* Only reached if blx is avail and it is a call */
 216                 if (is_thumb) {
 217                     x |= h << 24;
 218                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 219                 }
 220                 (*(int *) ptr) |= x;
 221             }
 222             return;
 223         /* Since these relocations only concern Thumb-2 and blx instruction was
 224            introduced before Thumb-2, we can assume blx is available and not
 225            guard its use */
 226         case R_ARM_THM_PC22:
 227         case R_ARM_THM_JUMP24:
 228             {
 229                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 230                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 231                 Section *plt;
 232
 233                 /* weak reference */
 234                 if (sym->st_shndx == SHN_UNDEF &&
 235                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 236                     return;
 237
 238                 /* Get initial offset */
 239                 hi = (*(uint16_t *)ptr);
 240                 lo = (*(uint16_t *)(ptr+2));
 241                 s = (hi >> 10) & 1;
 242                 j1 = (lo >> 13) & 1;
 243                 j2 = (lo >> 11) & 1;
 244                 i1 = (j1 ^ s) ^ 1;
 245                 i2 = (j2 ^ s) ^ 1;
 246                 imm10 = hi & 0x3ff;
 247                 imm11 = lo & 0x7ff;
 248                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 249                     (imm10 << 12) | (imm11 << 1);
 250                 if (x & 0x01000000)
 251                     x -= 0x02000000;
 252
 253                 /* Relocation infos */
 254                 to_thumb = val & 1;
 255                 plt = s1->plt;
 256                 to_plt = (val >= plt->sh_addr) &&
 257                          (val < plt->sh_addr + plt->data_offset);
 258                 is_call = (type == R_ARM_THM_PC22);
 259
 260                 if (!to_thumb && !to_plt && !is_call) {
 261                     int index;
 262                     uint8_t *p;
 263                     char *name, buf[1024];
 264                     Section *text;
 265
 266                     name = (char *) symtab_section->link->data + sym->st_name;
 267                     text = s1->sections[sym->st_shndx];
 268                     /* Modify reloc to target a thumb stub to switch to ARM */
 269                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 270                     index = put_elf_sym(symtab_section,
 271                                         text->data_offset + 1,
 272                                         sym->st_size, sym->st_info, 0,
 273                                         sym->st_shndx, buf);
 274                     to_thumb = 1;
 275                     val = text->data_offset + 1;
 276                     rel->r_info = ELFW(R_INFO)(index, type);
 277                     /* Create a thumb stub function to switch to ARM mode */
 278                     put_elf_reloc(symtab_section, text,
 279                                   text->data_offset + 4, R_ARM_JUMP24,
 280                                   sym_index);
 281                     p = section_ptr_add(text, 8);
 282                     write32le(p,   0x4778); /* bx pc */
 283                     write32le(p+2, 0x46c0); /* nop   */
 284                     write32le(p+4, 0xeafffffe); /* b $sym */
 285                 }
 286
 287                 /* Compute final offset */
 288                 x += val - addr;
 289                 if (!to_thumb && is_call) {
 290                     blx_bit = 0; /* bl -> blx */
 291                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 292                 }
 293
 294                 /* Check that relocation is possible
 295                    * offset must not be out of range
 296                    * if target is to be entered in arm mode:
 297                      - bit 1 must not set
 298                      - instruction must be a call (bl) or a jump to PLT */
 299                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 300                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 301                         tcc_error("can't relocate value at %x,%d",addr, type);
 302
 303                 /* Compute and store final offset */
 304                 s = (x >> 24) & 1;
 305                 i1 = (x >> 23) & 1;
 306                 i2 = (x >> 22) & 1;
 307                 j1 = s ^ (i1 ^ 1);
 308                 j2 = s ^ (i2 ^ 1);
 309                 imm10 = (x >> 12) & 0x3ff;
 310                 imm11 = (x >> 1) & 0x7ff;
 311                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 312                                      (s << 10) | imm10);
 313                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 314                                 (j1 << 13) | blx_bit | (j2 << 11) |
 315                                 imm11);
 316             }
 317             return;
 318         case R_ARM_MOVT_ABS:
 319         case R_ARM_MOVW_ABS_NC:
 320             {
 321                 int x, imm4, imm12;
 322                 if (type == R_ARM_MOVT_ABS)
 323                     val >>= 16;
 324                 imm12 = val & 0xfff;
 325                 imm4 = (val >> 12) & 0xf;
 326                 x = (imm4 << 16) | imm12;
 327                 if (type == R_ARM_THM_MOVT_ABS)
 328                     *(int *)ptr |= x;
 329                 else
 330                     *(int *)ptr += x;
 331             }
 332             return;
 333         case R_ARM_THM_MOVT_ABS:
 334         case R_ARM_THM_MOVW_ABS_NC:
 335             {
 336                 int x, i, imm4, imm3, imm8;
 337                 if (type == R_ARM_THM_MOVT_ABS)
 338                     val >>= 16;
 339                 imm8 = val & 0xff;
 340                 imm3 = (val >> 8) & 0x7;
 341                 i = (val >> 11) & 1;
 342                 imm4 = (val >> 12) & 0xf;
 343                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 344                 if (type == R_ARM_THM_MOVT_ABS)
 345                     *(int *)ptr |= x;
 346                 else
 347                     *(int *)ptr += x;
 348             }
 349             return;
 350         case R_ARM_PREL31:
 351             {
 352                 int x;
 353                 x = (*(int *)ptr) & 0x7fffffff;
 354                 (*(int *)ptr) &= 0x80000000;
 355                 x = (x * 2) / 2;
 356                 x += val - addr;
 357                 if((x^(x>>1))&0x40000000)
 358                     tcc_error("can't relocate value at %x,%d",addr, type);
 359                 (*(int *)ptr) |= x & 0x7fffffff;
 360             }
 361         case R_ARM_ABS32:
 362             if (s1->output_type == TCC_OUTPUT_DLL) {
 363                 esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
 364                 qrel->r_offset = rel->r_offset;
 365                 if (esym_index) {
 366                     qrel->r_info = ELFW(R_INFO)(esym_index, R_ARM_ABS32);
 367                     qrel++;
 368                     return;
 369                 } else {
 370                     qrel->r_info = ELFW(R_INFO)(0, R_ARM_RELATIVE);
 371                     qrel++;
 372                 }
 373             }
 374             *(int *)ptr += val;
 375             return;
 376         case R_ARM_REL32:
 377             *(int *)ptr += val - addr;
 378             return;
 379         case R_ARM_GOTPC:
 380             *(int *)ptr += s1->got->sh_addr - addr;
 381             return;
 382         case R_ARM_GOTOFF:
 383             *(int *)ptr += val - s1->got->sh_addr;
 384             return;
 385         case R_ARM_GOT32:
 386             /* we load the got offset */
 387             *(int *)ptr += get_sym_attr(s1, sym_index, 0)->got_offset;
 388             return;
 389         case R_ARM_GOT_PREL:
 390             /* we load the pc relative got offset */
 391             *(int *)ptr += s1->got->sh_addr +
 392                            get_sym_attr(s1, sym_index, 0)->got_offset -
 393                            addr;
 394             return;
 395         case R_ARM_COPY:
 396             return;
 397         case R_ARM_V4BX:
 398             /* trade Thumb support for ARMv4 support */
 399             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 400                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 401             return;
 402         case R_ARM_GLOB_DAT:
 403         case R_ARM_JUMP_SLOT:
 404             *(addr_t *)ptr = val;
 405             return;
 406         case R_ARM_NONE:
 407             /* Nothing to do.  Normally used to indicate a dependency
 408                on a certain symbol (like for exception handling under EABI).  */
 409             return;
 410         case R_ARM_RELATIVE:
 411 #ifdef TCC_TARGET_PE
 412             add32le(ptr, val - s1->pe_imagebase);
 413 #endif
 414             /* do nothing */
 415             return;
 416         default:
 417             fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
 418                 type, (unsigned)addr, ptr, (unsigned)val);
 419             return;
 420     }
 421 }
 422
 423 #endif /* !TARGET_DEFS_ONLY */