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 0
  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
  61     tcc_error ("Unknown relocation type: %d", reloc_type);
  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             return AUTO_GOTPLT_ENTRY;
  92
  93         case R_ARM_GOTPC:
  94         case R_ARM_GOTOFF:
  95             return BUILD_GOT_ONLY;
  96
  97         case R_ARM_GOT32:
  98             return ALWAYS_GOTPLT_ENTRY;
  99     }
 100
 101     tcc_error ("Unknown relocation type: %d", reloc_type);
 102     return -1;
 103 }
 104
 105 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
 106 {
 107     Section *plt = s1->plt;
 108     uint8_t *p;
 109     unsigned plt_offset;
 110
 111     /* when building a DLL, GOT entry accesses must be done relative to
 112        start of GOT (see x86_64 example above)  */
 113     if (s1->output_type == TCC_OUTPUT_DLL)
 114         tcc_error("DLLs unimplemented!");
 115
 116     /* empty PLT: create PLT0 entry that push address of call site and
 117        jump to ld.so resolution routine (GOT + 8) */
 118     if (plt->data_offset == 0) {
 119         p = section_ptr_add(plt, 20);
 120         write32le(p,    0xe52de004); /* push {lr}         */
 121         write32le(p+4,  0xe59fe004); /* ldr lr, [pc, #4] */
 122         write32le(p+8,  0xe08fe00e); /* add lr, pc, lr    */
 123         write32le(p+12, 0xe5bef008); /* ldr pc, [lr, #8]! */
 124         /* p+16 is set in relocate_plt */
 125     }
 126     plt_offset = plt->data_offset;
 127
 128     if (attr->plt_thumb_stub) {
 129         p = section_ptr_add(plt, 4);
 130         write32le(p,   0x4778); /* bx pc */
 131         write32le(p+2, 0x46c0); /* nop   */
 132     }
 133     p = section_ptr_add(plt, 16);
 134     /* Jump to GOT entry where ld.so initially put address of PLT0 */
 135     write32le(p,   0xe59fc004); /* ldr ip, [pc, #4] */
 136     write32le(p+4, 0xe08fc00c); /* add ip, pc, ip */
 137     write32le(p+8, 0xe59cf000); /* ldr pc, [ip] */
 138     /* p + 12 contains offset to GOT entry once patched by relocate_plt */
 139     write32le(p+12, 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 - 16);
 158         p += 20;
 159         while (p < p_end) {
 160             if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
 161                 p += 4;
 162             add32le(p + 12, x + s1->plt->data - p);
 163             p += 16;
 164         }
 165     }
 166 }
 167
 168 void relocate_init(Section *sr) {}
 169 void relocate_fini(Section *sr) {}
 170
 171 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 172 {
 173     ElfW(Sym) *sym;
 174     int sym_index;
 175
 176     sym_index = ELFW(R_SYM)(rel->r_info);
 177     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 178
 179     switch(type) {
 180         case R_ARM_PC24:
 181         case R_ARM_CALL:
 182         case R_ARM_JUMP24:
 183         case R_ARM_PLT32:
 184             {
 185                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 186                 x = (*(int *) ptr) & 0xffffff;
 187 #ifdef DEBUG_RELOC
 188                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 189 #endif
 190                 (*(int *)ptr) &= 0xff000000;
 191                 if (x & 0x800000)
 192                     x -= 0x1000000;
 193                 x <<= 2;
 194                 blx_avail = (TCC_CPU_VERSION >= 5);
 195                 is_thumb = val & 1;
 196                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 197                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 198                 x += val - addr;
 199 #ifdef DEBUG_RELOC
 200                 printf (" newx=0x%x name=%s\n", x,
 201                         (char *) symtab_section->link->data + sym->st_name);
 202 #endif
 203                 h = x & 2;
 204                 th_ko = (x & 3) && (!blx_avail || !is_call);
 205                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 206                     tcc_error("can't relocate value at %x,%d",addr, type);
 207                 x >>= 2;
 208                 x &= 0xffffff;
 209                 /* Only reached if blx is avail and it is a call */
 210                 if (is_thumb) {
 211                     x |= h << 24;
 212                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 213                 }
 214                 (*(int *) ptr) |= x;
 215             }
 216             return;
 217         /* Since these relocations only concern Thumb-2 and blx instruction was
 218            introduced before Thumb-2, we can assume blx is available and not
 219            guard its use */
 220         case R_ARM_THM_PC22:
 221         case R_ARM_THM_JUMP24:
 222             {
 223                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 224                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 225                 Section *plt;
 226
 227                 /* weak reference */
 228                 if (sym->st_shndx == SHN_UNDEF &&
 229                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 230                     return;
 231
 232                 /* Get initial offset */
 233                 hi = (*(uint16_t *)ptr);
 234                 lo = (*(uint16_t *)(ptr+2));
 235                 s = (hi >> 10) & 1;
 236                 j1 = (lo >> 13) & 1;
 237                 j2 = (lo >> 11) & 1;
 238                 i1 = (j1 ^ s) ^ 1;
 239                 i2 = (j2 ^ s) ^ 1;
 240                 imm10 = hi & 0x3ff;
 241                 imm11 = lo & 0x7ff;
 242                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 243                     (imm10 << 12) | (imm11 << 1);
 244                 if (x & 0x01000000)
 245                     x -= 0x02000000;
 246
 247                 /* Relocation infos */
 248                 to_thumb = val & 1;
 249                 plt = s1->plt;
 250                 to_plt = (val >= plt->sh_addr) &&
 251                          (val < plt->sh_addr + plt->data_offset);
 252                 is_call = (type == R_ARM_THM_PC22);
 253
 254                 if (!to_thumb && !to_plt && !is_call) {
 255                     int index;
 256                     uint8_t *p;
 257                     char *name, buf[1024];
 258                     Section *text_section;
 259
 260                     name = (char *) symtab_section->link->data + sym->st_name;
 261                     text_section = s1->sections[sym->st_shndx];
 262                     /* Modify reloc to target a thumb stub to switch to ARM */
 263                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 264                     index = put_elf_sym(symtab_section,
 265                                         text_section->data_offset + 1,
 266                                         sym->st_size, sym->st_info, 0,
 267                                         sym->st_shndx, buf);
 268                     to_thumb = 1;
 269                     val = text_section->data_offset + 1;
 270                     rel->r_info = ELFW(R_INFO)(index, type);
 271                     /* Create a thumb stub function to switch to ARM mode */
 272                     put_elf_reloc(symtab_section, text_section,
 273                                   text_section->data_offset + 4, R_ARM_JUMP24,
 274                                   sym_index);
 275                     p = section_ptr_add(text_section, 8);
 276                     write32le(p,   0x4778); /* bx pc */
 277                     write32le(p+2, 0x46c0); /* nop   */
 278                     write32le(p+4, 0xeafffffe); /* b $sym */
 279                 }
 280
 281                 /* Compute final offset */
 282                 x += val - addr;
 283                 if (!to_thumb && is_call) {
 284                     blx_bit = 0; /* bl -> blx */
 285                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 286                 }
 287
 288                 /* Check that relocation is possible
 289                    * offset must not be out of range
 290                    * if target is to be entered in arm mode:
 291                      - bit 1 must not set
 292                      - instruction must be a call (bl) or a jump to PLT */
 293                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 294                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 295                         tcc_error("can't relocate value at %x,%d",addr, type);
 296
 297                 /* Compute and store final offset */
 298                 s = (x >> 24) & 1;
 299                 i1 = (x >> 23) & 1;
 300                 i2 = (x >> 22) & 1;
 301                 j1 = s ^ (i1 ^ 1);
 302                 j2 = s ^ (i2 ^ 1);
 303                 imm10 = (x >> 12) & 0x3ff;
 304                 imm11 = (x >> 1) & 0x7ff;
 305                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 306                                      (s << 10) | imm10);
 307                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 308                                 (j1 << 13) | blx_bit | (j2 << 11) |
 309                                 imm11);
 310             }
 311             return;
 312         case R_ARM_MOVT_ABS:
 313         case R_ARM_MOVW_ABS_NC:
 314             {
 315                 int x, imm4, imm12;
 316                 if (type == R_ARM_MOVT_ABS)
 317                     val >>= 16;
 318                 imm12 = val & 0xfff;
 319                 imm4 = (val >> 12) & 0xf;
 320                 x = (imm4 << 16) | imm12;
 321                 if (type == R_ARM_THM_MOVT_ABS)
 322                     *(int *)ptr |= x;
 323                 else
 324                     *(int *)ptr += x;
 325             }
 326             return;
 327         case R_ARM_THM_MOVT_ABS:
 328         case R_ARM_THM_MOVW_ABS_NC:
 329             {
 330                 int x, i, imm4, imm3, imm8;
 331                 if (type == R_ARM_THM_MOVT_ABS)
 332                     val >>= 16;
 333                 imm8 = val & 0xff;
 334                 imm3 = (val >> 8) & 0x7;
 335                 i = (val >> 11) & 1;
 336                 imm4 = (val >> 12) & 0xf;
 337                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 338                 if (type == R_ARM_THM_MOVT_ABS)
 339                     *(int *)ptr |= x;
 340                 else
 341                     *(int *)ptr += x;
 342             }
 343             return;
 344         case R_ARM_PREL31:
 345             {
 346                 int x;
 347                 x = (*(int *)ptr) & 0x7fffffff;
 348                 (*(int *)ptr) &= 0x80000000;
 349                 x = (x * 2) / 2;
 350                 x += val - addr;
 351                 if((x^(x>>1))&0x40000000)
 352                     tcc_error("can't relocate value at %x,%d",addr, type);
 353                 (*(int *)ptr) |= x & 0x7fffffff;
 354             }
 355         case R_ARM_ABS32:
 356             *(int *)ptr += val;
 357             return;
 358         case R_ARM_REL32:
 359             *(int *)ptr += val - addr;
 360             return;
 361         case R_ARM_GOTPC:
 362             *(int *)ptr += s1->got->sh_addr - addr;
 363             return;
 364         case R_ARM_GOTOFF:
 365             *(int *)ptr += val - s1->got->sh_addr;
 366             return;
 367         case R_ARM_GOT32:
 368             /* we load the got offset */
 369             *(int *)ptr += get_sym_attr(s1, sym_index, 0)->got_offset;
 370             return;
 371         case R_ARM_COPY:
 372             return;
 373         case R_ARM_V4BX:
 374             /* trade Thumb support for ARMv4 support */
 375             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 376                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 377             return;
 378         case R_ARM_GLOB_DAT:
 379         case R_ARM_JUMP_SLOT:
 380             *(addr_t *)ptr = val;
 381             return;
 382         case R_ARM_NONE:
 383             /* Nothing to do.  Normally used to indicate a dependency
 384                on a certain symbol (like for exception handling under EABI).  */
 385             return;
 386         case R_ARM_RELATIVE:
 387 #ifdef TCC_TARGET_PE
 388             add32le(ptr, val - s1->pe_imagebase);
 389 #endif
 390             /* do nothing */
 391             return;
 392         default:
 393             fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
 394                 type, (unsigned)addr, ptr, (unsigned)val);
 395             return;
 396     }
 397 }
 398
 399 #endif /* !TARGET_DEFS_ONLY */