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         case R_ARM_TARGET1:
  49             return 0;
  50
  51         case R_ARM_PC24:
  52         case R_ARM_CALL:
  53         case R_ARM_JUMP24:
  54         case R_ARM_PLT32:
  55         case R_ARM_THM_PC22:
  56         case R_ARM_THM_JUMP24:
  57         case R_ARM_PREL31:
  58         case R_ARM_V4BX:
  59         case R_ARM_JUMP_SLOT:
  60             return 1;
  61     }
  62     return -1;
  63 }
  64
  65 /* Returns an enumerator to describe whether and when the relocation needs a
  66    GOT and/or PLT entry to be created. See tcc.h for a description of the
  67    different values. */
  68 int gotplt_entry_type (int reloc_type)
  69 {
  70     switch (reloc_type) {
  71         case R_ARM_NONE:
  72         case R_ARM_COPY:
  73         case R_ARM_GLOB_DAT:
  74         case R_ARM_JUMP_SLOT:
  75             return NO_GOTPLT_ENTRY;
  76
  77         case R_ARM_PC24:
  78         case R_ARM_CALL:
  79         case R_ARM_JUMP24:
  80         case R_ARM_PLT32:
  81         case R_ARM_THM_PC22:
  82         case R_ARM_THM_JUMP24:
  83         case R_ARM_MOVT_ABS:
  84         case R_ARM_MOVW_ABS_NC:
  85         case R_ARM_THM_MOVT_ABS:
  86         case R_ARM_THM_MOVW_ABS_NC:
  87         case R_ARM_PREL31:
  88         case R_ARM_ABS32:
  89         case R_ARM_REL32:
  90         case R_ARM_V4BX:
  91         case R_ARM_TARGET1:
  92             return AUTO_GOTPLT_ENTRY;
  93
  94         case R_ARM_GOTPC:
  95         case R_ARM_GOTOFF:
  96             return BUILD_GOT_ONLY;
  97
  98         case R_ARM_GOT32:
  99         case R_ARM_GOT_PREL:
 100             return ALWAYS_GOTPLT_ENTRY;
 101     }
 102     return -1;
 103 }
 104
 105 #ifndef TCC_TARGET_PE
 106 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
 107 {
 108     Section *plt = s1->plt;
 109     uint8_t *p;
 110     unsigned plt_offset;
 111
 112     /* when building a DLL, GOT entry accesses must be done relative to
 113        start of GOT (see x86_64 example above)  */
 114
 115     /* empty PLT: create PLT0 entry that push address of call site and
 116        jump to ld.so resolution routine (GOT + 8) */
 117     if (plt->data_offset == 0) {
 118         p = section_ptr_add(plt, 20);
 119         write32le(p,    0xe52de004); /* push {lr}         */
 120         write32le(p+4,  0xe59fe004); /* ldr lr, [pc, #4] */
 121         write32le(p+8,  0xe08fe00e); /* add lr, pc, lr    */
 122         write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
 123         /* p+16 is set in relocate_plt */
 124     }
 125     plt_offset = plt->data_offset;
 126
 127     if (attr->plt_thumb_stub) {
 128         p = section_ptr_add(plt, 4);
 129         write32le(p,   0x4778); /* bx pc */
 130         write32le(p+2, 0x46c0); /* nop   */
 131     }
 132     p = section_ptr_add(plt, 12);
 133     /* save GOT offset for relocate_plt */
 134     write32le(p + 4, got_offset);
 135     return plt_offset;
 136 }
 137
 138 /* relocate the PLT: compute addresses and offsets in the PLT now that final
 139    address for PLT and GOT are known (see fill_program_header) */
 140 ST_FUNC void relocate_plt(TCCState *s1)
 141 {
 142     uint8_t *p, *p_end;
 143
 144     if (!s1->plt)
 145       return;
 146
 147     p = s1->plt->data;
 148     p_end = p + s1->plt->data_offset;
 149
 150     if (p < p_end) {
 151         int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
 152         write32le(s1->plt->data + 16, x - 4);
 153         p += 20;
 154         while (p < p_end) {
 155             unsigned off = x  + read32le(p + 4) + (s1->plt->data - p) + 4;
 156             if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
 157                 p += 4;
 158             write32le(p, 0xe28fc600 | ((off >> 20) & 0xff));     // add ip, pc, #0xNN00000
 159             write32le(p + 4, 0xe28cca00 | ((off >> 12) & 0xff)); // add ip, ip, #0xNN000
 160             write32le(p + 8, 0xe5bcf000 | (off & 0xfff));        // ldr pc, [ip, #0xNNN]!
 161             p += 12;
 162         }
 163     }
 164
 165     if (s1->got->relocplt) {
 166         int mem = s1->output_type == TCC_OUTPUT_MEMORY;
 167         ElfW_Rel *rel;
 168
 169         p = s1->got->data;
 170         for_each_elem(s1->got->relocplt, 0, rel, ElfW_Rel) {
 171             int sym_index = ELFW(R_SYM)(rel->r_info);
 172             ElfW(Sym) *sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 173             write32le(p + rel->r_offset, mem ? sym->st_value : s1->plt->sh_addr);
 174         }
 175     }
 176 }
 177 #endif
 178
 179 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 180 {
 181     ElfW(Sym) *sym;
 182     int sym_index, esym_index;
 183
 184     sym_index = ELFW(R_SYM)(rel->r_info);
 185     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 186
 187     switch(type) {
 188         case R_ARM_PC24:
 189         case R_ARM_CALL:
 190         case R_ARM_JUMP24:
 191         case R_ARM_PLT32:
 192             {
 193                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 194                 x = (*(int *) ptr) & 0xffffff;
 195 #ifdef DEBUG_RELOC
 196                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 197 #endif
 198                 (*(int *)ptr) &= 0xff000000;
 199                 if (x & 0x800000)
 200                     x -= 0x1000000;
 201                 x <<= 2;
 202                 blx_avail = (TCC_CPU_VERSION >= 5);
 203                 is_thumb = val & 1;
 204                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 205                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 206                 x += val - addr;
 207 #ifdef DEBUG_RELOC
 208                 printf (" newx=0x%x name=%s\n", x,
 209                         (char *) symtab_section->link->data + sym->st_name);
 210 #endif
 211                 h = x & 2;
 212                 th_ko = (x & 3) && (!blx_avail || !is_call);
 213                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 214                     tcc_error("can't relocate value at %x,%d",addr, type);
 215                 x >>= 2;
 216                 x &= 0xffffff;
 217                 /* Only reached if blx is avail and it is a call */
 218                 if (is_thumb) {
 219                     x |= h << 24;
 220                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 221                 }
 222                 (*(int *) ptr) |= x;
 223             }
 224             return;
 225         /* Since these relocations only concern Thumb-2 and blx instruction was
 226            introduced before Thumb-2, we can assume blx is available and not
 227            guard its use */
 228         case R_ARM_THM_PC22:
 229         case R_ARM_THM_JUMP24:
 230             {
 231                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 232                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 233                 Section *plt;
 234
 235                 /* weak reference */
 236                 if (sym->st_shndx == SHN_UNDEF &&
 237                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 238                     return;
 239
 240                 /* Get initial offset */
 241                 hi = (*(uint16_t *)ptr);
 242                 lo = (*(uint16_t *)(ptr+2));
 243                 s = (hi >> 10) & 1;
 244                 j1 = (lo >> 13) & 1;
 245                 j2 = (lo >> 11) & 1;
 246                 i1 = (j1 ^ s) ^ 1;
 247                 i2 = (j2 ^ s) ^ 1;
 248                 imm10 = hi & 0x3ff;
 249                 imm11 = lo & 0x7ff;
 250                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 251                     (imm10 << 12) | (imm11 << 1);
 252                 if (x & 0x01000000)
 253                     x -= 0x02000000;
 254
 255                 /* Relocation infos */
 256                 to_thumb = val & 1;
 257                 plt = s1->plt;
 258                 to_plt = (val >= plt->sh_addr) &&
 259                          (val < plt->sh_addr + plt->data_offset);
 260                 is_call = (type == R_ARM_THM_PC22);
 261
 262                 if (!to_thumb && !to_plt && !is_call) {
 263                     int index;
 264                     uint8_t *p;
 265                     char *name, buf[1024];
 266                     Section *text;
 267
 268                     name = (char *) symtab_section->link->data + sym->st_name;
 269                     text = s1->sections[sym->st_shndx];
 270                     /* Modify reloc to target a thumb stub to switch to ARM */
 271                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 272                     index = put_elf_sym(symtab_section,
 273                                         text->data_offset + 1,
 274                                         sym->st_size, sym->st_info, 0,
 275                                         sym->st_shndx, buf);
 276                     to_thumb = 1;
 277                     val = text->data_offset + 1;
 278                     rel->r_info = ELFW(R_INFO)(index, type);
 279                     /* Create a thumb stub function to switch to ARM mode */
 280                     put_elf_reloc(symtab_section, text,
 281                                   text->data_offset + 4, R_ARM_JUMP24,
 282                                   sym_index);
 283                     p = section_ptr_add(text, 8);
 284                     write32le(p,   0x4778); /* bx pc */
 285                     write32le(p+2, 0x46c0); /* nop   */
 286                     write32le(p+4, 0xeafffffe); /* b $sym */
 287                 }
 288
 289                 /* Compute final offset */
 290                 x += val - addr;
 291                 if (!to_thumb && is_call) {
 292                     blx_bit = 0; /* bl -> blx */
 293                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 294                 }
 295
 296                 /* Check that relocation is possible
 297                    * offset must not be out of range
 298                    * if target is to be entered in arm mode:
 299                      - bit 1 must not set
 300                      - instruction must be a call (bl) or a jump to PLT */
 301                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 302                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 303                         tcc_error("can't relocate value at %x,%d",addr, type);
 304
 305                 /* Compute and store final offset */
 306                 s = (x >> 24) & 1;
 307                 i1 = (x >> 23) & 1;
 308                 i2 = (x >> 22) & 1;
 309                 j1 = s ^ (i1 ^ 1);
 310                 j2 = s ^ (i2 ^ 1);
 311                 imm10 = (x >> 12) & 0x3ff;
 312                 imm11 = (x >> 1) & 0x7ff;
 313                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 314                                      (s << 10) | imm10);
 315                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 316                                 (j1 << 13) | blx_bit | (j2 << 11) |
 317                                 imm11);
 318             }
 319             return;
 320         case R_ARM_MOVT_ABS:
 321         case R_ARM_MOVW_ABS_NC:
 322             {
 323                 int x, imm4, imm12;
 324                 if (type == R_ARM_MOVT_ABS)
 325                     val >>= 16;
 326                 imm12 = val & 0xfff;
 327                 imm4 = (val >> 12) & 0xf;
 328                 x = (imm4 << 16) | imm12;
 329                 if (type == R_ARM_THM_MOVT_ABS)
 330                     *(int *)ptr |= x;
 331                 else
 332                     *(int *)ptr += x;
 333             }
 334             return;
 335         case R_ARM_THM_MOVT_ABS:
 336         case R_ARM_THM_MOVW_ABS_NC:
 337             {
 338                 int x, i, imm4, imm3, imm8;
 339                 if (type == R_ARM_THM_MOVT_ABS)
 340                     val >>= 16;
 341                 imm8 = val & 0xff;
 342                 imm3 = (val >> 8) & 0x7;
 343                 i = (val >> 11) & 1;
 344                 imm4 = (val >> 12) & 0xf;
 345                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 346                 if (type == R_ARM_THM_MOVT_ABS)
 347                     *(int *)ptr |= x;
 348                 else
 349                     *(int *)ptr += x;
 350             }
 351             return;
 352         case R_ARM_PREL31:
 353             {
 354                 int x;
 355                 x = (*(int *)ptr) & 0x7fffffff;
 356                 (*(int *)ptr) &= 0x80000000;
 357                 x = (x * 2) / 2;
 358                 x += val - addr;
 359                 if((x^(x>>1))&0x40000000)
 360                     tcc_error("can't relocate value at %x,%d",addr, type);
 361                 (*(int *)ptr) |= x & 0x7fffffff;
 362             }
 363         case R_ARM_ABS32:
 364      // case R_ARM_TARGET1: /* ??? as seen on NetBSD - FIXME! */
 365             if (s1->output_type == TCC_OUTPUT_DLL) {
 366                 esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
 367                 qrel->r_offset = rel->r_offset;
 368                 if (esym_index) {
 369                     qrel->r_info = ELFW(R_INFO)(esym_index, type);
 370                     qrel++;
 371                     return;
 372                 } else {
 373                     qrel->r_info = ELFW(R_INFO)(0, R_ARM_RELATIVE);
 374                     qrel++;
 375                 }
 376             }
 377             *(int *)ptr += val;
 378             return;
 379         case R_ARM_REL32:
 380             *(int *)ptr += val - addr;
 381             return;
 382         case R_ARM_GOTPC:
 383             *(int *)ptr += s1->got->sh_addr - addr;
 384             return;
 385         case R_ARM_GOTOFF:
 386             *(int *)ptr += val - s1->got->sh_addr;
 387             return;
 388         case R_ARM_GOT32:
 389             /* we load the got offset */
 390             *(int *)ptr += get_sym_attr(s1, sym_index, 0)->got_offset;
 391             return;
 392         case R_ARM_GOT_PREL:
 393             /* we load the pc relative got offset */
 394             *(int *)ptr += s1->got->sh_addr +
 395                            get_sym_attr(s1, sym_index, 0)->got_offset -
 396                            addr;
 397             return;
 398         case R_ARM_COPY:
 399             return;
 400         case R_ARM_V4BX:
 401             /* trade Thumb support for ARMv4 support */
 402             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 403                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 404             return;
 405         case R_ARM_GLOB_DAT:
 406         case R_ARM_JUMP_SLOT:
 407             *(addr_t *)ptr = val;
 408             return;
 409         case R_ARM_NONE:
 410             /* Nothing to do.  Normally used to indicate a dependency
 411                on a certain symbol (like for exception handling under EABI).  */
 412             return;
 413         case R_ARM_RELATIVE:
 414 #ifdef TCC_TARGET_PE
 415             add32le(ptr, val - s1->pe_imagebase);
 416 #endif
 417             /* do nothing */
 418             return;
 419         default:
 420             fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
 421                 type, (unsigned)addr, ptr, (unsigned)val);
 422             return;
 423     }
 424 }
 425
 426 #endif /* !TARGET_DEFS_ONLY */