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 /* 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         case R_ARM_MOVT_PREL:
  50         case R_ARM_MOVW_PREL_NC:
  51             return 0;
  52
  53         case R_ARM_PC24:
  54         case R_ARM_CALL:
  55         case R_ARM_JUMP24:
  56         case R_ARM_PLT32:
  57         case R_ARM_THM_PC22:
  58         case R_ARM_THM_JUMP24:
  59         case R_ARM_PREL31:
  60         case R_ARM_V4BX:
  61         case R_ARM_JUMP_SLOT:
  62             return 1;
  63     }
  64     return -1;
  65 }
  66
  67 /* Returns an enumerator to describe whether and when the relocation needs a
  68    GOT and/or PLT entry to be created. See tcc.h for a description of the
  69    different values. */
  70 int gotplt_entry_type (int reloc_type)
  71 {
  72     switch (reloc_type) {
  73         case R_ARM_NONE:
  74         case R_ARM_COPY:
  75         case R_ARM_GLOB_DAT:
  76         case R_ARM_JUMP_SLOT:
  77             return NO_GOTPLT_ENTRY;
  78
  79         case R_ARM_PC24:
  80         case R_ARM_CALL:
  81         case R_ARM_JUMP24:
  82         case R_ARM_PLT32:
  83         case R_ARM_THM_PC22:
  84         case R_ARM_THM_JUMP24:
  85         case R_ARM_MOVT_ABS:
  86         case R_ARM_MOVW_ABS_NC:
  87         case R_ARM_THM_MOVT_ABS:
  88         case R_ARM_THM_MOVW_ABS_NC:
  89         case R_ARM_PREL31:
  90         case R_ARM_ABS32:
  91         case R_ARM_REL32:
  92         case R_ARM_V4BX:
  93         case R_ARM_TARGET1:
  94         case R_ARM_MOVT_PREL:
  95         case R_ARM_MOVW_PREL_NC:
  96             return AUTO_GOTPLT_ENTRY;
  97
  98         case R_ARM_GOTPC:
  99         case R_ARM_GOTOFF:
 100             return BUILD_GOT_ONLY;
 101
 102         case R_ARM_GOT32:
 103         case R_ARM_GOT_PREL:
 104             return ALWAYS_GOTPLT_ENTRY;
 105     }
 106     return -1;
 107 }
 108
 109 #ifndef TCC_TARGET_PE
 110 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
 111 {
 112     Section *plt = s1->plt;
 113     uint8_t *p;
 114     unsigned plt_offset;
 115
 116     /* when building a DLL, GOT entry accesses must be done relative to
 117        start of GOT (see x86_64 example above)  */
 118
 119     /* empty PLT: create PLT0 entry that push address of call site and
 120        jump to ld.so resolution routine (GOT + 8) */
 121     if (plt->data_offset == 0) {
 122         p = section_ptr_add(plt, 20);
 123         write32le(p,    0xe52de004); /* push {lr}         */
 124         write32le(p+4,  0xe59fe004); /* ldr lr, [pc, #4] */
 125         write32le(p+8,  0xe08fe00e); /* add lr, pc, lr    */
 126         write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
 127         /* p+16 is set in relocate_plt */
 128     }
 129     plt_offset = plt->data_offset;
 130
 131     if (attr->plt_thumb_stub) {
 132         p = section_ptr_add(plt, 4);
 133         write32le(p,   0x4778); /* bx pc */
 134         write32le(p+2, 0x46c0); /* nop   */
 135     }
 136     p = section_ptr_add(plt, 16);
 137     /* save GOT offset for relocate_plt */
 138     write32le(p + 4, got_offset);
 139     return plt_offset;
 140 }
 141
 142 /* relocate the PLT: compute addresses and offsets in the PLT now that final
 143    address for PLT and GOT are known (see fill_program_header) */
 144 ST_FUNC void relocate_plt(TCCState *s1)
 145 {
 146     uint8_t *p, *p_end;
 147
 148     if (!s1->plt)
 149       return;
 150
 151     p = s1->plt->data;
 152     p_end = p + s1->plt->data_offset;
 153
 154     if (p < p_end) {
 155         int x = s1->got->sh_addr - s1->plt->sh_addr - 12;
 156         write32le(s1->plt->data + 16, x - 4);
 157         p += 20;
 158         while (p < p_end) {
 159             unsigned off = x  + read32le(p + 4) + (s1->plt->data - p) + 4;
 160             if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
 161                 p += 4;
 162             write32le(p, 0xe28fc200 | ((off >> 28) & 0xf));      // add ip, pc, #0xN0000000
 163             write32le(p + 4, 0xe28cc600 | ((off >> 20) & 0xff)); // add ip, pc, #0xNN00000
 164             write32le(p + 8, 0xe28cca00 | ((off >> 12) & 0xff)); // add ip, ip, #0xNN000
 165             write32le(p + 12, 0xe5bcf000 | (off & 0xfff));       // ldr pc, [ip, #0xNNN]!
 166             p += 16;
 167         }
 168     }
 169
 170     if (s1->got->relocplt) {
 171         int mem = s1->output_type == TCC_OUTPUT_MEMORY;
 172         ElfW_Rel *rel;
 173
 174         p = s1->got->data;
 175         for_each_elem(s1->got->relocplt, 0, rel, ElfW_Rel) {
 176             int sym_index = ELFW(R_SYM)(rel->r_info);
 177             ElfW(Sym) *sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 178             write32le(p + rel->r_offset, mem ? sym->st_value : s1->plt->sh_addr);
 179         }
 180     }
 181 }
 182 #endif
 183
 184 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 185 {
 186     ElfW(Sym) *sym;
 187     int sym_index, esym_index;
 188
 189     sym_index = ELFW(R_SYM)(rel->r_info);
 190     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 191
 192     switch(type) {
 193         case R_ARM_PC24:
 194         case R_ARM_CALL:
 195         case R_ARM_JUMP24:
 196         case R_ARM_PLT32:
 197             {
 198                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 199                 x = (*(int *) ptr) & 0xffffff;
 200 #ifdef DEBUG_RELOC
 201                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 202 #endif
 203                 (*(int *)ptr) &= 0xff000000;
 204                 if (x & 0x800000)
 205                     x -= 0x1000000;
 206                 x <<= 2;
 207                 blx_avail = (TCC_CPU_VERSION >= 5);
 208                 is_thumb = val & 1;
 209                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 210                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 211                 x += val - addr;
 212 #ifdef DEBUG_RELOC
 213                 printf (" newx=0x%x name=%s\n", x,
 214                         (char *) symtab_section->link->data + sym->st_name);
 215 #endif
 216                 h = x & 2;
 217                 th_ko = (x & 3) && (!blx_avail || !is_call);
 218                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 219                     tcc_error("can't relocate value at %x,%d",addr, type);
 220                 x >>= 2;
 221                 x &= 0xffffff;
 222                 /* Only reached if blx is avail and it is a call */
 223                 if (is_thumb) {
 224                     x |= h << 24;
 225                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 226                 }
 227                 (*(int *) ptr) |= x;
 228             }
 229             return;
 230         /* Since these relocations only concern Thumb-2 and blx instruction was
 231            introduced before Thumb-2, we can assume blx is available and not
 232            guard its use */
 233         case R_ARM_THM_PC22:
 234         case R_ARM_THM_JUMP24:
 235             {
 236                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 237                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 238                 Section *plt;
 239
 240                 /* weak reference */
 241                 if (sym->st_shndx == SHN_UNDEF &&
 242                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 243                     return;
 244
 245                 /* Get initial offset */
 246                 hi = (*(uint16_t *)ptr);
 247                 lo = (*(uint16_t *)(ptr+2));
 248                 s = (hi >> 10) & 1;
 249                 j1 = (lo >> 13) & 1;
 250                 j2 = (lo >> 11) & 1;
 251                 i1 = (j1 ^ s) ^ 1;
 252                 i2 = (j2 ^ s) ^ 1;
 253                 imm10 = hi & 0x3ff;
 254                 imm11 = lo & 0x7ff;
 255                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 256                     (imm10 << 12) | (imm11 << 1);
 257                 if (x & 0x01000000)
 258                     x -= 0x02000000;
 259
 260                 /* Relocation infos */
 261                 to_thumb = val & 1;
 262                 plt = s1->plt;
 263                 to_plt = (val >= plt->sh_addr) &&
 264                          (val < plt->sh_addr + plt->data_offset);
 265                 is_call = (type == R_ARM_THM_PC22);
 266
 267                 if (!to_thumb && !to_plt && !is_call) {
 268                     int index;
 269                     uint8_t *p;
 270                     char *name, buf[1024];
 271                     Section *text;
 272
 273                     name = (char *) symtab_section->link->data + sym->st_name;
 274                     text = s1->sections[sym->st_shndx];
 275                     /* Modify reloc to target a thumb stub to switch to ARM */
 276                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 277                     index = put_elf_sym(symtab_section,
 278                                         text->data_offset + 1,
 279                                         sym->st_size, sym->st_info, 0,
 280                                         sym->st_shndx, buf);
 281                     to_thumb = 1;
 282                     val = text->data_offset + 1;
 283                     rel->r_info = ELFW(R_INFO)(index, type);
 284                     /* Create a thumb stub function to switch to ARM mode */
 285                     put_elf_reloc(symtab_section, text,
 286                                   text->data_offset + 4, R_ARM_JUMP24,
 287                                   sym_index);
 288                     p = section_ptr_add(text, 8);
 289                     write32le(p,   0x4778); /* bx pc */
 290                     write32le(p+2, 0x46c0); /* nop   */
 291                     write32le(p+4, 0xeafffffe); /* b $sym */
 292                 }
 293
 294                 /* Compute final offset */
 295                 x += val - addr;
 296                 if (!to_thumb && is_call) {
 297                     blx_bit = 0; /* bl -> blx */
 298                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 299                 }
 300
 301                 /* Check that relocation is possible
 302                    * offset must not be out of range
 303                    * if target is to be entered in arm mode:
 304                      - bit 1 must not set
 305                      - instruction must be a call (bl) or a jump to PLT */
 306                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 307                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 308                         tcc_error("can't relocate value at %x,%d",addr, type);
 309
 310                 /* Compute and store final offset */
 311                 s = (x >> 24) & 1;
 312                 i1 = (x >> 23) & 1;
 313                 i2 = (x >> 22) & 1;
 314                 j1 = s ^ (i1 ^ 1);
 315                 j2 = s ^ (i2 ^ 1);
 316                 imm10 = (x >> 12) & 0x3ff;
 317                 imm11 = (x >> 1) & 0x7ff;
 318                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 319                                      (s << 10) | imm10);
 320                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 321                                 (j1 << 13) | blx_bit | (j2 << 11) |
 322                                 imm11);
 323             }
 324             return;
 325         case R_ARM_MOVT_ABS:
 326         case R_ARM_MOVW_ABS_NC:
 327             {
 328                 int x, imm4, imm12;
 329                 if (type == R_ARM_MOVT_ABS)
 330                     val >>= 16;
 331                 imm12 = val & 0xfff;
 332                 imm4 = (val >> 12) & 0xf;
 333                 x = (imm4 << 16) | imm12;
 334                 if (type == R_ARM_THM_MOVT_ABS)
 335                     *(int *)ptr |= x;
 336                 else
 337                     *(int *)ptr += x;
 338             }
 339             return;
 340         case R_ARM_MOVT_PREL:
 341         case R_ARM_MOVW_PREL_NC:
 342             {
 343                 int insn = *(int *)ptr;
 344                 int addend = ((insn >> 4) & 0xf000) | (insn & 0xfff);
 345
 346                 addend = (addend ^ 0x8000) - 0x8000;
 347                 val += addend - addr;
 348                 if (type == R_ARM_MOVT_PREL)
 349                     val >>= 16;
 350                 *(int *)ptr = (insn & 0xfff0f000) |
 351                               ((val & 0xf000) << 4) | (val & 0xfff);
 352             }
 353             return;
 354         case R_ARM_THM_MOVT_ABS:
 355         case R_ARM_THM_MOVW_ABS_NC:
 356             {
 357                 int x, i, imm4, imm3, imm8;
 358                 if (type == R_ARM_THM_MOVT_ABS)
 359                     val >>= 16;
 360                 imm8 = val & 0xff;
 361                 imm3 = (val >> 8) & 0x7;
 362                 i = (val >> 11) & 1;
 363                 imm4 = (val >> 12) & 0xf;
 364                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 365                 if (type == R_ARM_THM_MOVT_ABS)
 366                     *(int *)ptr |= x;
 367                 else
 368                     *(int *)ptr += x;
 369             }
 370             return;
 371         case R_ARM_PREL31:
 372             {
 373                 int x;
 374                 x = (*(int *)ptr) & 0x7fffffff;
 375                 (*(int *)ptr) &= 0x80000000;
 376                 x = (x * 2) / 2;
 377                 x += val - addr;
 378                 if((x^(x>>1))&0x40000000)
 379                     tcc_error("can't relocate value at %x,%d",addr, type);
 380                 (*(int *)ptr) |= x & 0x7fffffff;
 381             }
 382             return;
 383         case R_ARM_ABS32:
 384         case R_ARM_TARGET1:
 385             if (s1->output_type == TCC_OUTPUT_DLL) {
 386                 esym_index = get_sym_attr(s1, sym_index, 0)->dyn_index;
 387                 qrel->r_offset = rel->r_offset;
 388                 if (esym_index) {
 389                     qrel->r_info = ELFW(R_INFO)(esym_index, R_ARM_ABS32);
 390                     qrel++;
 391                     return;
 392                 } else {
 393                     qrel->r_info = ELFW(R_INFO)(0, R_ARM_RELATIVE);
 394                     qrel++;
 395                 }
 396             }
 397             *(int *)ptr += val;
 398             return;
 399         case R_ARM_REL32:
 400             *(int *)ptr += val - addr;
 401             return;
 402         case R_ARM_GOTPC:
 403             *(int *)ptr += s1->got->sh_addr - addr;
 404             return;
 405         case R_ARM_GOTOFF:
 406             *(int *)ptr += val - s1->got->sh_addr;
 407             return;
 408         case R_ARM_GOT32:
 409             /* we load the got offset */
 410             *(int *)ptr += get_sym_attr(s1, sym_index, 0)->got_offset;
 411             return;
 412         case R_ARM_GOT_PREL:
 413             /* we load the pc relative got offset */
 414             *(int *)ptr += s1->got->sh_addr +
 415                            get_sym_attr(s1, sym_index, 0)->got_offset -
 416                            addr;
 417             return;
 418         case R_ARM_COPY:
 419             return;
 420         case R_ARM_V4BX:
 421             /* trade Thumb support for ARMv4 support */
 422             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 423                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 424             return;
 425         case R_ARM_GLOB_DAT:
 426         case R_ARM_JUMP_SLOT:
 427             *(addr_t *)ptr = val;
 428             return;
 429         case R_ARM_NONE:
 430             /* Nothing to do.  Normally used to indicate a dependency
 431                on a certain symbol (like for exception handling under EABI).  */
 432             return;
 433         case R_ARM_RELATIVE:
 434 #ifdef TCC_TARGET_PE
 435             add32le(ptr, val - s1->pe_imagebase);
 436 #endif
 437             /* do nothing */
 438             return;
 439         default:
 440             fprintf(stderr,"FIXME: handle reloc type %d at %x [%p] to %x\n",
 441                 type, (unsigned)addr, ptr, (unsigned)val);
 442             return;
 443     }
 444 }
 445
 446 #endif /* !TARGET_DEFS_ONLY */