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