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
  12 #define R_NUM       R_ARM_NUM
  13
  14 #define ELF_START_ADDR 0x00008000
  15 #define ELF_PAGE_SIZE  0x1000
  16
  17 #define PCRELATIVE_DLLPLT 1
  18 #define RELOCATE_DLLPLT 0
  19
  20 enum float_abi {
  21     ARM_SOFTFP_FLOAT,
  22     ARM_HARD_FLOAT,
  23 };
  24
  25 #else /* !TARGET_DEFS_ONLY */
  26
  27 #include "tcc.h"
  28
  29 /* Returns 1 for a code relocation, 0 for a data relocation. For unknown
  30    relocations, returns -1. */
  31 int code_reloc (int reloc_type)
  32 {
  33     switch (reloc_type) {
  34         case R_ARM_MOVT_ABS:
  35         case R_ARM_MOVW_ABS_NC:
  36         case R_ARM_THM_MOVT_ABS:
  37         case R_ARM_THM_MOVW_ABS_NC:
  38         case R_ARM_ABS32:
  39         case R_ARM_REL32:
  40         case R_ARM_GOTPC:
  41         case R_ARM_GOTOFF:
  42         case R_ARM_GOT32:
  43         case R_ARM_COPY:
  44         case R_ARM_GLOB_DAT:
  45         case R_ARM_NONE:
  46             return 0;
  47
  48         case R_ARM_PC24:
  49         case R_ARM_CALL:
  50         case R_ARM_JUMP24:
  51         case R_ARM_PLT32:
  52         case R_ARM_THM_PC22:
  53         case R_ARM_THM_JUMP24:
  54         case R_ARM_PREL31:
  55         case R_ARM_V4BX:
  56         case R_ARM_JUMP_SLOT:
  57             return 1;
  58     }
  59
  60     tcc_error ("Unknown relocation type: %d", reloc_type);
  61     return -1;
  62 }
  63
  64 /* Returns an enumerator to describe wether and when the relocation needs a
  65    GOT and/or PLT entry to be created. See tcc.h for a description of the
  66    different values. */
  67 int gotplt_entry_type (int reloc_type)
  68 {
  69     switch (reloc_type) {
  70         case R_ARM_NONE:
  71         case R_ARM_COPY:
  72         case R_ARM_GLOB_DAT:
  73         case R_ARM_JUMP_SLOT:
  74             return NO_GOTPLT_ENTRY;
  75
  76         case R_ARM_PC24:
  77         case R_ARM_CALL:
  78         case R_ARM_JUMP24:
  79         case R_ARM_PLT32:
  80         case R_ARM_THM_PC22:
  81         case R_ARM_THM_JUMP24:
  82         case R_ARM_MOVT_ABS:
  83         case R_ARM_MOVW_ABS_NC:
  84         case R_ARM_THM_MOVT_ABS:
  85         case R_ARM_THM_MOVW_ABS_NC:
  86         case R_ARM_PREL31:
  87         case R_ARM_ABS32:
  88         case R_ARM_REL32:
  89         case R_ARM_V4BX:
  90             return AUTO_GOTPLT_ENTRY;
  91
  92         case R_ARM_GOTPC:
  93         case R_ARM_GOTOFF:
  94             return BUILD_GOT_ONLY;
  95
  96         case R_ARM_GOT32:
  97             return ALWAYS_GOTPLT_ENTRY;
  98     }
  99
 100     tcc_error ("Unknown relocation type: %d", reloc_type);
 101     return -1;
 102 }
 103
 104 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
 105 {
 106     Section *plt = s1->plt;
 107     uint8_t *p;
 108     unsigned plt_offset;
 109
 110     /* when building a DLL, GOT entry accesses must be done relative to
 111        start of GOT (see x86_64 examble above)  */
 112     if (s1->output_type == TCC_OUTPUT_DLL)
 113         tcc_error("DLLs unimplemented!");
 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, 16);
 133     /* Jump to GOT entry where ld.so initially put address of PLT0 */
 134     write32le(p,   0xe59fc004); /* ldr ip, [pc, #4] */
 135     write32le(p+4, 0xe08fc00c); /* add ip, pc, ip */
 136     write32le(p+8, 0xe59cf000); /* ldr pc, [ip] */
 137     /* p + 12 contains offset to GOT entry once patched by relocate_plt */
 138     write32le(p+12, 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 - 16);
 157         p += 20;
 158         while (p < p_end) {
 159             if (read32le(p) == 0x46c04778) /* PLT Thumb stub present */
 160                 p += 4;
 161             add32le(p + 12, x + s1->plt->data - p);
 162             p += 16;
 163         }
 164     }
 165 }
 166
 167 void relocate_init(Section *sr) {}
 168
 169 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 170 {
 171     ElfW(Sym) *sym;
 172     int sym_index;
 173
 174     sym_index = ELFW(R_SYM)(rel->r_info);
 175     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 176
 177     switch(type) {
 178         case R_ARM_PC24:
 179         case R_ARM_CALL:
 180         case R_ARM_JUMP24:
 181         case R_ARM_PLT32:
 182             {
 183                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 184                 x = (*(int *) ptr) & 0xffffff;
 185 #ifdef DEBUG_RELOC
 186                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 187 #endif
 188                 (*(int *)ptr) &= 0xff000000;
 189                 if (x & 0x800000)
 190                     x -= 0x1000000;
 191                 x <<= 2;
 192                 blx_avail = (TCC_ARM_VERSION >= 5);
 193                 is_thumb = val & 1;
 194                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 195                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 196                 x += val - addr;
 197 #ifdef DEBUG_RELOC
 198                 printf (" newx=0x%x name=%s\n", x,
 199                         (char *) symtab_section->link->data + sym->st_name);
 200 #endif
 201                 h = x & 2;
 202                 th_ko = (x & 3) && (!blx_avail || !is_call);
 203                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 204                     tcc_error("can't relocate value at %x,%d",addr, type);
 205                 x >>= 2;
 206                 x &= 0xffffff;
 207                 /* Only reached if blx is avail and it is a call */
 208                 if (is_thumb) {
 209                     x |= h << 24;
 210                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 211                 }
 212                 (*(int *) ptr) |= x;
 213             }
 214             return;
 215         /* Since these relocations only concern Thumb-2 and blx instruction was
 216            introduced before Thumb-2, we can assume blx is available and not
 217            guard its use */
 218         case R_ARM_THM_PC22:
 219         case R_ARM_THM_JUMP24:
 220             {
 221                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 222                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 223                 Section *plt;
 224
 225                 /* weak reference */
 226                 if (sym->st_shndx == SHN_UNDEF &&
 227                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 228                     return;
 229
 230                 /* Get initial offset */
 231                 hi = (*(uint16_t *)ptr);
 232                 lo = (*(uint16_t *)(ptr+2));
 233                 s = (hi >> 10) & 1;
 234                 j1 = (lo >> 13) & 1;
 235                 j2 = (lo >> 11) & 1;
 236                 i1 = (j1 ^ s) ^ 1;
 237                 i2 = (j2 ^ s) ^ 1;
 238                 imm10 = hi & 0x3ff;
 239                 imm11 = lo & 0x7ff;
 240                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 241                     (imm10 << 12) | (imm11 << 1);
 242                 if (x & 0x01000000)
 243                     x -= 0x02000000;
 244
 245                 /* Relocation infos */
 246                 to_thumb = val & 1;
 247                 plt = s1->plt;
 248                 to_plt = (val >= plt->sh_addr) &&
 249                          (val < plt->sh_addr + plt->data_offset);
 250                 is_call = (type == R_ARM_THM_PC22);
 251
 252                 if (!to_thumb && !to_plt && !is_call) {
 253                     int index;
 254                     uint8_t *p;
 255                     char *name, buf[1024];
 256                     Section *text_section;
 257
 258                     name = (char *) symtab_section->link->data + sym->st_name;
 259                     text_section = s1->sections[sym->st_shndx];
 260                     /* Modify reloc to target a thumb stub to switch to ARM */
 261                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 262                     index = put_elf_sym(symtab_section,
 263                                         text_section->data_offset + 1,
 264                                         sym->st_size, sym->st_info, 0,
 265                                         sym->st_shndx, buf);
 266                     to_thumb = 1;
 267                     val = text_section->data_offset + 1;
 268                     rel->r_info = ELFW(R_INFO)(index, type);
 269                     /* Create a thumb stub function to switch to ARM mode */
 270                     put_elf_reloc(symtab_section, text_section,
 271                                   text_section->data_offset + 4, R_ARM_JUMP24,
 272                                   sym_index);
 273                     p = section_ptr_add(text_section, 8);
 274                     write32le(p,   0x4778); /* bx pc */
 275                     write32le(p+2, 0x46c0); /* nop   */
 276                     write32le(p+4, 0xeafffffe); /* b $sym */
 277                 }
 278
 279                 /* Compute final offset */
 280                 x += val - addr;
 281                 if (!to_thumb && is_call) {
 282                     blx_bit = 0; /* bl -> blx */
 283                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 284                 }
 285
 286                 /* Check that relocation is possible
 287                    * offset must not be out of range
 288                    * if target is to be entered in arm mode:
 289                      - bit 1 must not set
 290                      - instruction must be a call (bl) or a jump to PLT */
 291                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 292                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 293                         tcc_error("can't relocate value at %x,%d",addr, type);
 294
 295                 /* Compute and store final offset */
 296                 s = (x >> 24) & 1;
 297                 i1 = (x >> 23) & 1;
 298                 i2 = (x >> 22) & 1;
 299                 j1 = s ^ (i1 ^ 1);
 300                 j2 = s ^ (i2 ^ 1);
 301                 imm10 = (x >> 12) & 0x3ff;
 302                 imm11 = (x >> 1) & 0x7ff;
 303                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 304                                      (s << 10) | imm10);
 305                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 306                                 (j1 << 13) | blx_bit | (j2 << 11) |
 307                                 imm11);
 308             }
 309             return;
 310         case R_ARM_MOVT_ABS:
 311         case R_ARM_MOVW_ABS_NC:
 312             {
 313                 int x, imm4, imm12;
 314                 if (type == R_ARM_MOVT_ABS)
 315                     val >>= 16;
 316                 imm12 = val & 0xfff;
 317                 imm4 = (val >> 12) & 0xf;
 318                 x = (imm4 << 16) | imm12;
 319                 if (type == R_ARM_THM_MOVT_ABS)
 320                     *(int *)ptr |= x;
 321                 else
 322                     *(int *)ptr += x;
 323             }
 324             return;
 325         case R_ARM_THM_MOVT_ABS:
 326         case R_ARM_THM_MOVW_ABS_NC:
 327             {
 328                 int x, i, imm4, imm3, imm8;
 329                 if (type == R_ARM_THM_MOVT_ABS)
 330                     val >>= 16;
 331                 imm8 = val & 0xff;
 332                 imm3 = (val >> 8) & 0x7;
 333                 i = (val >> 11) & 1;
 334                 imm4 = (val >> 12) & 0xf;
 335                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 336                 if (type == R_ARM_THM_MOVT_ABS)
 337                     *(int *)ptr |= x;
 338                 else
 339                     *(int *)ptr += x;
 340             }
 341             return;
 342         case R_ARM_PREL31:
 343             {
 344                 int x;
 345                 x = (*(int *)ptr) & 0x7fffffff;
 346                 (*(int *)ptr) &= 0x80000000;
 347                 x = (x * 2) / 2;
 348                 x += val - addr;
 349                 if((x^(x>>1))&0x40000000)
 350                     tcc_error("can't relocate value at %x,%d",addr, type);
 351                 (*(int *)ptr) |= x & 0x7fffffff;
 352             }
 353         case R_ARM_ABS32:
 354             *(int *)ptr += val;
 355             return;
 356         case R_ARM_REL32:
 357             *(int *)ptr += val - addr;
 358             return;
 359         case R_ARM_GOTPC:
 360             *(int *)ptr += s1->got->sh_addr - addr;
 361             return;
 362         case R_ARM_GOTOFF:
 363             *(int *)ptr += val - s1->got->sh_addr;
 364             return;
 365         case R_ARM_GOT32:
 366             /* we load the got offset */
 367             *(int *)ptr += s1->sym_attrs[sym_index].got_offset;
 368             return;
 369         case R_ARM_COPY:
 370             return;
 371         case R_ARM_V4BX:
 372             /* trade Thumb support for ARMv4 support */
 373             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 374                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 375             return;
 376         case R_ARM_GLOB_DAT:
 377         case R_ARM_JUMP_SLOT:
 378             *(addr_t *)ptr = val;
 379             return;
 380         case R_ARM_NONE:
 381             /* Nothing to do.  Normally used to indicate a dependency
 382                on a certain symbol (like for exception handling under EABI).  */
 383             return;
 384         default:
 385             fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
 386                 type, (unsigned)addr, ptr, (unsigned)val);
 387             return;
 388     }
 389 }
 390
 391 #endif /* !TARGET_DEFS_ONLY */