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
 170 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 171 {
 172     ElfW(Sym) *sym;
 173     int sym_index;
 174
 175     sym_index = ELFW(R_SYM)(rel->r_info);
 176     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 177
 178     switch(type) {
 179         case R_ARM_PC24:
 180         case R_ARM_CALL:
 181         case R_ARM_JUMP24:
 182         case R_ARM_PLT32:
 183             {
 184                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 185                 x = (*(int *) ptr) & 0xffffff;
 186 #ifdef DEBUG_RELOC
 187                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 188 #endif
 189                 (*(int *)ptr) &= 0xff000000;
 190                 if (x & 0x800000)
 191                     x -= 0x1000000;
 192                 x <<= 2;
 193                 blx_avail = (TCC_CPU_VERSION >= 5);
 194                 is_thumb = val & 1;
 195                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 196                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 197                 x += val - addr;
 198 #ifdef DEBUG_RELOC
 199                 printf (" newx=0x%x name=%s\n", x,
 200                         (char *) symtab_section->link->data + sym->st_name);
 201 #endif
 202                 h = x & 2;
 203                 th_ko = (x & 3) && (!blx_avail || !is_call);
 204                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 205                     tcc_error("can't relocate value at %x,%d",addr, type);
 206                 x >>= 2;
 207                 x &= 0xffffff;
 208                 /* Only reached if blx is avail and it is a call */
 209                 if (is_thumb) {
 210                     x |= h << 24;
 211                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 212                 }
 213                 (*(int *) ptr) |= x;
 214             }
 215             return;
 216         /* Since these relocations only concern Thumb-2 and blx instruction was
 217            introduced before Thumb-2, we can assume blx is available and not
 218            guard its use */
 219         case R_ARM_THM_PC22:
 220         case R_ARM_THM_JUMP24:
 221             {
 222                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 223                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 224                 Section *plt;
 225
 226                 /* weak reference */
 227                 if (sym->st_shndx == SHN_UNDEF &&
 228                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 229                     return;
 230
 231                 /* Get initial offset */
 232                 hi = (*(uint16_t *)ptr);
 233                 lo = (*(uint16_t *)(ptr+2));
 234                 s = (hi >> 10) & 1;
 235                 j1 = (lo >> 13) & 1;
 236                 j2 = (lo >> 11) & 1;
 237                 i1 = (j1 ^ s) ^ 1;
 238                 i2 = (j2 ^ s) ^ 1;
 239                 imm10 = hi & 0x3ff;
 240                 imm11 = lo & 0x7ff;
 241                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 242                     (imm10 << 12) | (imm11 << 1);
 243                 if (x & 0x01000000)
 244                     x -= 0x02000000;
 245
 246                 /* Relocation infos */
 247                 to_thumb = val & 1;
 248                 plt = s1->plt;
 249                 to_plt = (val >= plt->sh_addr) &&
 250                          (val < plt->sh_addr + plt->data_offset);
 251                 is_call = (type == R_ARM_THM_PC22);
 252
 253                 if (!to_thumb && !to_plt && !is_call) {
 254                     int index;
 255                     uint8_t *p;
 256                     char *name, buf[1024];
 257                     Section *text_section;
 258
 259                     name = (char *) symtab_section->link->data + sym->st_name;
 260                     text_section = s1->sections[sym->st_shndx];
 261                     /* Modify reloc to target a thumb stub to switch to ARM */
 262                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 263                     index = put_elf_sym(symtab_section,
 264                                         text_section->data_offset + 1,
 265                                         sym->st_size, sym->st_info, 0,
 266                                         sym->st_shndx, buf);
 267                     to_thumb = 1;
 268                     val = text_section->data_offset + 1;
 269                     rel->r_info = ELFW(R_INFO)(index, type);
 270                     /* Create a thumb stub function to switch to ARM mode */
 271                     put_elf_reloc(symtab_section, text_section,
 272                                   text_section->data_offset + 4, R_ARM_JUMP24,
 273                                   sym_index);
 274                     p = section_ptr_add(text_section, 8);
 275                     write32le(p,   0x4778); /* bx pc */
 276                     write32le(p+2, 0x46c0); /* nop   */
 277                     write32le(p+4, 0xeafffffe); /* b $sym */
 278                 }
 279
 280                 /* Compute final offset */
 281                 x += val - addr;
 282                 if (!to_thumb && is_call) {
 283                     blx_bit = 0; /* bl -> blx */
 284                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 285                 }
 286
 287                 /* Check that relocation is possible
 288                    * offset must not be out of range
 289                    * if target is to be entered in arm mode:
 290                      - bit 1 must not set
 291                      - instruction must be a call (bl) or a jump to PLT */
 292                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 293                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 294                         tcc_error("can't relocate value at %x,%d",addr, type);
 295
 296                 /* Compute and store final offset */
 297                 s = (x >> 24) & 1;
 298                 i1 = (x >> 23) & 1;
 299                 i2 = (x >> 22) & 1;
 300                 j1 = s ^ (i1 ^ 1);
 301                 j2 = s ^ (i2 ^ 1);
 302                 imm10 = (x >> 12) & 0x3ff;
 303                 imm11 = (x >> 1) & 0x7ff;
 304                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 305                                      (s << 10) | imm10);
 306                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 307                                 (j1 << 13) | blx_bit | (j2 << 11) |
 308                                 imm11);
 309             }
 310             return;
 311         case R_ARM_MOVT_ABS:
 312         case R_ARM_MOVW_ABS_NC:
 313             {
 314                 int x, imm4, imm12;
 315                 if (type == R_ARM_MOVT_ABS)
 316                     val >>= 16;
 317                 imm12 = val & 0xfff;
 318                 imm4 = (val >> 12) & 0xf;
 319                 x = (imm4 << 16) | imm12;
 320                 if (type == R_ARM_THM_MOVT_ABS)
 321                     *(int *)ptr |= x;
 322                 else
 323                     *(int *)ptr += x;
 324             }
 325             return;
 326         case R_ARM_THM_MOVT_ABS:
 327         case R_ARM_THM_MOVW_ABS_NC:
 328             {
 329                 int x, i, imm4, imm3, imm8;
 330                 if (type == R_ARM_THM_MOVT_ABS)
 331                     val >>= 16;
 332                 imm8 = val & 0xff;
 333                 imm3 = (val >> 8) & 0x7;
 334                 i = (val >> 11) & 1;
 335                 imm4 = (val >> 12) & 0xf;
 336                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 337                 if (type == R_ARM_THM_MOVT_ABS)
 338                     *(int *)ptr |= x;
 339                 else
 340                     *(int *)ptr += x;
 341             }
 342             return;
 343         case R_ARM_PREL31:
 344             {
 345                 int x;
 346                 x = (*(int *)ptr) & 0x7fffffff;
 347                 (*(int *)ptr) &= 0x80000000;
 348                 x = (x * 2) / 2;
 349                 x += val - addr;
 350                 if((x^(x>>1))&0x40000000)
 351                     tcc_error("can't relocate value at %x,%d",addr, type);
 352                 (*(int *)ptr) |= x & 0x7fffffff;
 353             }
 354         case R_ARM_ABS32:
 355             *(int *)ptr += val;
 356             return;
 357         case R_ARM_REL32:
 358             *(int *)ptr += val - addr;
 359             return;
 360         case R_ARM_GOTPC:
 361             *(int *)ptr += s1->got->sh_addr - addr;
 362             return;
 363         case R_ARM_GOTOFF:
 364             *(int *)ptr += val - s1->got->sh_addr;
 365             return;
 366         case R_ARM_GOT32:
 367             /* we load the got offset */
 368             *(int *)ptr += s1->sym_attrs[sym_index].got_offset;
 369             return;
 370         case R_ARM_COPY:
 371             return;
 372         case R_ARM_V4BX:
 373             /* trade Thumb support for ARMv4 support */
 374             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 375                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 376             return;
 377         case R_ARM_GLOB_DAT:
 378         case R_ARM_JUMP_SLOT:
 379             *(addr_t *)ptr = val;
 380             return;
 381         case R_ARM_NONE:
 382             /* Nothing to do.  Normally used to indicate a dependency
 383                on a certain symbol (like for exception handling under EABI).  */
 384             return;
 385         default:
 386             fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
 387                 type, (unsigned)addr, ptr, (unsigned)val);
 388             return;
 389     }
 390 }
 391
 392 #endif /* !TARGET_DEFS_ONLY */