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 0x00010000
  16 #define ELF_PAGE_SIZE  0x10000
  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 #ifdef NEED_RELOC_TYPE
  31 /* Returns 1 for a code relocation, 0 for a data relocation. For unknown
  32    relocations, returns -1. */
  33 int code_reloc (int reloc_type)
  34 {
  35     switch (reloc_type) {
  36         case R_ARM_MOVT_ABS:
  37         case R_ARM_MOVW_ABS_NC:
  38         case R_ARM_THM_MOVT_ABS:
  39         case R_ARM_THM_MOVW_ABS_NC:
  40         case R_ARM_ABS32:
  41         case R_ARM_REL32:
  42         case R_ARM_GOTPC:
  43         case R_ARM_GOTOFF:
  44         case R_ARM_GOT32:
  45         case R_ARM_GOT_PREL:
  46         case R_ARM_COPY:
  47         case R_ARM_GLOB_DAT:
  48         case R_ARM_NONE:
  49         case R_ARM_TARGET1:
  50         case R_ARM_MOVT_PREL:
  51         case R_ARM_MOVW_PREL_NC:
  52             return 0;
  53
  54         case R_ARM_PC24:
  55         case R_ARM_CALL:
  56         case R_ARM_JUMP24:
  57         case R_ARM_PLT32:
  58         case R_ARM_THM_PC22:
  59         case R_ARM_THM_JUMP24:
  60         case R_ARM_PREL31:
  61         case R_ARM_V4BX:
  62         case R_ARM_JUMP_SLOT:
  63             return 1;
  64     }
  65     return -1;
  66 }
  67
  68 /* Returns an enumerator to describe whether and when the relocation needs a
  69    GOT and/or PLT entry to be created. See tcc.h for a description of the
  70    different values. */
  71 int gotplt_entry_type (int reloc_type)
  72 {
  73     switch (reloc_type) {
  74         case R_ARM_NONE:
  75         case R_ARM_COPY:
  76         case R_ARM_GLOB_DAT:
  77         case R_ARM_JUMP_SLOT:
  78             return NO_GOTPLT_ENTRY;
  79
  80         case R_ARM_PC24:
  81         case R_ARM_CALL:
  82         case R_ARM_JUMP24:
  83         case R_ARM_PLT32:
  84         case R_ARM_THM_PC22:
  85         case R_ARM_THM_JUMP24:
  86         case R_ARM_MOVT_ABS:
  87         case R_ARM_MOVW_ABS_NC:
  88         case R_ARM_THM_MOVT_ABS:
  89         case R_ARM_THM_MOVW_ABS_NC:
  90         case R_ARM_PREL31:
  91         case R_ARM_ABS32:
  92         case R_ARM_REL32:
  93         case R_ARM_V4BX:
  94         case R_ARM_TARGET1:
  95         case R_ARM_MOVT_PREL:
  96         case R_ARM_MOVW_PREL_NC:
  97             return AUTO_GOTPLT_ENTRY;
  98
  99         case R_ARM_GOTPC:
 100         case R_ARM_GOTOFF:
 101             return BUILD_GOT_ONLY;
 102
 103         case R_ARM_GOT32:
 104         case R_ARM_GOT_PREL:
 105             return ALWAYS_GOTPLT_ENTRY;
 106     }
 107     return -1;
 108 }
 109
 110 #ifdef NEED_BUILD_GOT
 111 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
 112 {
 113     Section *plt = s1->plt;
 114     uint8_t *p;
 115     unsigned plt_offset;
 116
 117     /* when building a DLL, GOT entry accesses must be done relative to
 118        start of GOT (see x86_64 example above)  */
 119
 120     /* empty PLT: create PLT0 entry that push address of call site and
 121        jump to ld.so resolution routine (GOT + 8) */
 122     if (plt->data_offset == 0) {
 123         p = section_ptr_add(plt, 20);
 124         write32le(p,    0xe52de004); /* push {lr}         */
 125         write32le(p+4,  0xe59fe004); /* ldr lr, [pc, #4] */
 126         write32le(p+8,  0xe08fe00e); /* add lr, pc, lr    */
 127         write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
 128         /* p+16 is set in relocate_plt */
 129     }
 130     plt_offset = plt->data_offset;
 131
 132     if (attr->plt_thumb_stub) {
 133         p = section_ptr_add(plt, 4);
 134         write32le(p,   0x4778); /* bx pc */
 135         write32le(p+2, 0x46c0); /* nop   */
 136     }
 137     p = section_ptr_add(plt, 16);
 138     /* save GOT offset for relocate_plt */
 139     write32le(p + 4, got_offset);
 140     return plt_offset;
 141 }
 142
 143 /* relocate the PLT: compute addresses and offsets in the PLT now that final
 144    address for PLT and GOT are known (see fill_program_header) */
 145 ST_FUNC void relocate_plt(TCCState *s1)
 146 {
 147     uint8_t *p, *p_end;
 148
 149     if (!s1->plt)
 150       return;
 151
 152     p = s1->plt->data;
 153     p_end = p + s1->plt->data_offset;
 154
 155     if (p < p_end) {
 156         int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
 157         write32le(s1->plt->data + 16, x - 4);
 158         p += 20;
 159         while (p < p_end) {
 160             unsigned off = x  + read32le(p + 4) + (s1->plt->data - p) + 4;
 161             if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
 162                 p += 4;
 163             write32le(p, 0xe28fc200 | ((off >> 28) & 0xf));      // add ip, pc, #0xN0000000
 164             write32le(p + 4, 0xe28cc600 | ((off >> 20) & 0xff)); // add ip, pc, #0xNN00000
 165             write32le(p + 8, 0xe28cca00 | ((off >> 12) & 0xff)); // add ip, ip, #0xNN000
 166             write32le(p + 12, 0xe5bcf000 | (off & 0xfff));       // ldr pc, [ip, #0xNNN]!
 167             p += 16;
 168         }
 169     }
 170
 171     if (s1->plt->reloc) {
 172         ElfW_Rel *rel;
 173         p = s1->got->data;
 174         for_each_elem(s1->plt->reloc, 0, rel, ElfW_Rel) {
 175             write32le(p + rel->r_offset, s1->plt->sh_addr);
 176         }
 177     }
 178 }
 179 #endif
 180 #endif
 181
 182 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 183 {
 184     ElfW(Sym) *sym;
 185     int sym_index, esym_index;
 186
 187     sym_index = ELFW(R_SYM)(rel->r_info);
 188     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 189
 190     switch(type) {
 191         case R_ARM_PC24:
 192         case R_ARM_CALL:
 193         case R_ARM_JUMP24:
 194         case R_ARM_PLT32:
 195             {
 196                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 197                 x = (*(int *) ptr) & 0xffffff;
 198 #ifdef DEBUG_RELOC
 199                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 200 #endif
 201                 (*(int *)ptr) &= 0xff000000;
 202                 if (x & 0x800000)
 203                     x -= 0x1000000;
 204                 x <<= 2;
 205                 blx_avail = (TCC_CPU_VERSION >= 5);
 206                 is_thumb = val & 1;
 207                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 208                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 209                 x += val - addr;
 210 #ifdef DEBUG_RELOC
 211                 printf (" newx=0x%x name=%s\n", x,
 212                         (char *) symtab_section->link->data + sym->st_name);
 213 #endif
 214                 h = x & 2;
 215                 th_ko = (x & 3) && (!blx_avail || !is_call);
 216                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 217                     tcc_error("can't relocate value at %x,%d",addr, type);
 218                 x >>= 2;
 219                 x &= 0xffffff;
 220                 /* Only reached if blx is avail and it is a call */
 221                 if (is_thumb) {
 222                     x |= h << 24;
 223                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 224                 }
 225                 (*(int *) ptr) |= x;
 226             }
 227             return;
 228         /* Since these relocations only concern Thumb-2 and blx instruction was
 229            introduced before Thumb-2, we can assume blx is available and not
 230            guard its use */
 231         case R_ARM_THM_PC22:
 232         case R_ARM_THM_JUMP24:
 233             {
 234                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 235                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 236                 Section *plt;
 237
 238                 /* weak reference */
 239                 if (sym->st_shndx == SHN_UNDEF &&
 240                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 241                     return;
 242
 243                 /* Get initial offset */
 244                 hi = (*(uint16_t *)ptr);
 245                 lo = (*(uint16_t *)(ptr+2));
 246                 s = (hi >> 10) & 1;
 247                 j1 = (lo >> 13) & 1;
 248                 j2 = (lo >> 11) & 1;
 249                 i1 = (j1 ^ s) ^ 1;
 250                 i2 = (j2 ^ s) ^ 1;
 251                 imm10 = hi & 0x3ff;
 252                 imm11 = lo & 0x7ff;
 253                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 254                     (imm10 << 12) | (imm11 << 1);
 255                 if (x & 0x01000000)
 256                     x -= 0x02000000;
 257
 258                 /* Relocation infos */
 259                 to_thumb = val & 1;
 260                 plt = s1->plt;
 261                 to_plt = (val >= plt->sh_addr) &&
 262                          (val < plt->sh_addr + plt->data_offset);
 263                 is_call = (type == R_ARM_THM_PC22);
 264
 265                 if (!to_thumb && !to_plt && !is_call) {
 266                     int index;
 267                     uint8_t *p;
 268                     char *name, buf[1024];
 269                     Section *text;
 270
 271                     name = (char *) symtab_section->link->data + sym->st_name;
 272                     text = s1->sections[sym->st_shndx];
 273                     /* Modify reloc to target a thumb stub to switch to ARM */
 274                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 275                     index = put_elf_sym(symtab_section,
 276                                         text->data_offset + 1,
 277                                         sym->st_size, sym->st_info, 0,
 278                                         sym->st_shndx, buf);
 279                     to_thumb = 1;
 280                     val = text->data_offset + 1;
 281                     rel->r_info = ELFW(R_INFO)(index, type);
 282                     /* Create a thumb stub function to switch to ARM mode */
 283                     put_elf_reloc(symtab_section, text,
 284                                   text->data_offset + 4, R_ARM_JUMP24,
 285                                   sym_index);
 286                     p = section_ptr_add(text, 8);
 287                     write32le(p,   0x4778); /* bx pc */
 288                     write32le(p+2, 0x46c0); /* nop   */
 289                     write32le(p+4, 0xeafffffe); /* b $sym */
 290                 }
 291
 292                 /* Compute final offset */
 293                 x += val - addr;
 294                 if (!to_thumb && is_call) {
 295                     blx_bit = 0; /* bl -> blx */
 296                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 297                 }
 298
 299                 /* Check that relocation is possible
 300                    * offset must not be out of range
 301                    * if target is to be entered in arm mode:
 302                      - bit 1 must not set
 303                      - instruction must be a call (bl) or a jump to PLT */
 304                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 305                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 306                         tcc_error("can't relocate value at %x,%d",addr, type);
 307
 308                 /* Compute and store final offset */
 309                 s = (x >> 24) & 1;
 310                 i1 = (x >> 23) & 1;
 311                 i2 = (x >> 22) & 1;
 312                 j1 = s ^ (i1 ^ 1);
 313                 j2 = s ^ (i2 ^ 1);
 314                 imm10 = (x >> 12) & 0x3ff;
 315                 imm11 = (x >> 1) & 0x7ff;
 316                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 317                                      (s << 10) | imm10);
 318                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 319                                 (j1 << 13) | blx_bit | (j2 << 11) |
 320                                 imm11);
 321             }
 322             return;
 323         case R_ARM_MOVT_ABS:
 324         case R_ARM_MOVW_ABS_NC:
 325             {
 326                 int x, imm4, imm12;
 327                 if (type == R_ARM_MOVT_ABS)
 328                     val >>= 16;
 329                 imm12 = val & 0xfff;
 330                 imm4 = (val >> 12) & 0xf;
 331                 x = (imm4 << 16) | imm12;
 332                 if (type == R_ARM_THM_MOVT_ABS)
 333                     *(int *)ptr |= x;
 334                 else
 335                     *(int *)ptr += x;
 336             }
 337             return;
 338         case R_ARM_MOVT_PREL:
 339         case R_ARM_MOVW_PREL_NC:
 340             {
 341                 int insn = *(int *)ptr;
 342                 int addend = ((insn >> 4) & 0xf000) | (insn & 0xfff);
 343
 344                 addend = (addend ^ 0x8000) - 0x8000;
 345                 val += addend - addr;
 346                 if (type == R_ARM_MOVT_PREL)
 347                     val >>= 16;
 348                 *(int *)ptr = (insn & 0xfff0f000) |
 349                               ((val & 0xf000) << 4) | (val & 0xfff);
 350             }
 351             return;
 352         case R_ARM_THM_MOVT_ABS:
 353         case R_ARM_THM_MOVW_ABS_NC:
 354             {
 355                 int x, i, imm4, imm3, imm8;
 356                 if (type == R_ARM_THM_MOVT_ABS)
 357                     val >>= 16;
 358                 imm8 = val & 0xff;
 359                 imm3 = (val >> 8) & 0x7;
 360                 i = (val >> 11) & 1;
 361                 imm4 = (val >> 12) & 0xf;
 362                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 363                 if (type == R_ARM_THM_MOVT_ABS)
 364                     *(int *)ptr |= x;
 365                 else
 366                     *(int *)ptr += x;
 367             }
 368             return;
 369         case R_ARM_PREL31:
 370             {
 371                 int x;
 372                 x = (*(int *)ptr) & 0x7fffffff;
 373                 (*(int *)ptr) &= 0x80000000;
 374                 x = (x * 2) / 2;
 375                 x += val - addr;
 376                 if((x^(x>>1))&0x40000000)
 377                     tcc_error("can't relocate value at %x,%d",addr, type);
 378                 (*(int *)ptr) |= x & 0x7fffffff;
 379             }
 380             return;
 381         case R_ARM_ABS32:
 382         case R_ARM_TARGET1:
 383             if (s1->output_type & TCC_OUTPUT_DYN) {
 384                 esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
 385                 qrel->r_offset = rel->r_offset;
 386                 if (esym_index) {
 387                     qrel->r_info = ELFW(R_INFO)(esym_index, R_ARM_ABS32);
 388                     qrel++;
 389                     return;
 390                 } else {
 391                     qrel->r_info = ELFW(R_INFO)(0, R_ARM_RELATIVE);
 392                     qrel++;
 393                 }
 394             }
 395             *(int *)ptr += val;
 396             return;
 397         case R_ARM_REL32:
 398             *(int *)ptr += val - addr;
 399             return;
 400         case R_ARM_GOTPC:
 401             *(int *)ptr += s1->got->sh_addr - addr;
 402             return;
 403         case R_ARM_GOTOFF:
 404             *(int *)ptr += val - s1->got->sh_addr;
 405             return;
 406         case R_ARM_GOT32:
 407             /* we load the got offset */
 408             *(int *)ptr += get_sym_attr(s1, sym_index, 0)->got_offset;
 409             return;
 410         case R_ARM_GOT_PREL:
 411             /* we load the pc relative got offset */
 412             *(int *)ptr += s1->got->sh_addr +
 413                            get_sym_attr(s1, sym_index, 0)->got_offset -
 414                            addr;
 415             return;
 416         case R_ARM_COPY:
 417             return;
 418         case R_ARM_V4BX:
 419             /* trade Thumb support for ARMv4 support */
 420             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 421                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 422             return;
 423         case R_ARM_GLOB_DAT:
 424         case R_ARM_JUMP_SLOT:
 425             *(addr_t *)ptr = val;
 426             return;
 427         case R_ARM_NONE:
 428             /* Nothing to do.  Normally used to indicate a dependency
 429                on a certain symbol (like for exception handling under EABI).  */
 430             return;
 431         case R_ARM_RELATIVE:
 432 #ifdef TCC_TARGET_PE
 433             add32le(ptr, val - s1->pe_imagebase);
 434 #endif
 435             /* do nothing */
 436             return;
 437         default:
 438             fprintf(stderr,"FIXME: handle reloc type %d at %x [%p] to %x\n",
 439                 type, (unsigned)addr, ptr, (unsigned)val);
 440             return;
 441     }
 442 }
 443
 444 #endif /* !TARGET_DEFS_ONLY */