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 HAVE_SECTION_RELOC
  18 #define PCRELATIVE_DLLPLT 1
  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 void relocate_init(Section *sr) {}
 105
 106 void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, addr_t val)
 107 {
 108     ElfW(Sym) *sym;
 109     int sym_index;
 110
 111     sym_index = ELFW(R_SYM)(rel->r_info);
 112     sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
 113
 114     switch(type) {
 115         case R_ARM_PC24:
 116         case R_ARM_CALL:
 117         case R_ARM_JUMP24:
 118         case R_ARM_PLT32:
 119             {
 120                 int x, is_thumb, is_call, h, blx_avail, is_bl, th_ko;
 121                 x = (*(int *) ptr) & 0xffffff;
 122 #ifdef DEBUG_RELOC
 123                 printf ("reloc %d: x=0x%x val=0x%x ", type, x, val);
 124 #endif
 125                 (*(int *)ptr) &= 0xff000000;
 126                 if (x & 0x800000)
 127                     x -= 0x1000000;
 128                 x <<= 2;
 129                 blx_avail = (TCC_ARM_VERSION >= 5);
 130                 is_thumb = val & 1;
 131                 is_bl = (*(unsigned *) ptr) >> 24 == 0xeb;
 132                 is_call = (type == R_ARM_CALL || (type == R_ARM_PC24 && is_bl));
 133                 x += val - addr;
 134 #ifdef DEBUG_RELOC
 135                 printf (" newx=0x%x name=%s\n", x,
 136                         (char *) symtab_section->link->data + sym->st_name);
 137 #endif
 138                 h = x & 2;
 139                 th_ko = (x & 3) && (!blx_avail || !is_call);
 140                 if (th_ko || x >= 0x2000000 || x < -0x2000000)
 141                     tcc_error("can't relocate value at %x,%d",addr, type);
 142                 x >>= 2;
 143                 x &= 0xffffff;
 144                 /* Only reached if blx is avail and it is a call */
 145                 if (is_thumb) {
 146                     x |= h << 24;
 147                     (*(int *)ptr) = 0xfa << 24; /* bl -> blx */
 148                 }
 149                 (*(int *) ptr) |= x;
 150             }
 151             return;
 152         /* Since these relocations only concern Thumb-2 and blx instruction was
 153            introduced before Thumb-2, we can assume blx is available and not
 154            guard its use */
 155         case R_ARM_THM_PC22:
 156         case R_ARM_THM_JUMP24:
 157             {
 158                 int x, hi, lo, s, j1, j2, i1, i2, imm10, imm11;
 159                 int to_thumb, is_call, to_plt, blx_bit = 1 << 12;
 160                 Section *plt;
 161
 162                 /* weak reference */
 163                 if (sym->st_shndx == SHN_UNDEF &&
 164                     ELFW(ST_BIND)(sym->st_info) == STB_WEAK)
 165                     return;
 166
 167                 /* Get initial offset */
 168                 hi = (*(uint16_t *)ptr);
 169                 lo = (*(uint16_t *)(ptr+2));
 170                 s = (hi >> 10) & 1;
 171                 j1 = (lo >> 13) & 1;
 172                 j2 = (lo >> 11) & 1;
 173                 i1 = (j1 ^ s) ^ 1;
 174                 i2 = (j2 ^ s) ^ 1;
 175                 imm10 = hi & 0x3ff;
 176                 imm11 = lo & 0x7ff;
 177                 x = (s << 24) | (i1 << 23) | (i2 << 22) |
 178                     (imm10 << 12) | (imm11 << 1);
 179                 if (x & 0x01000000)
 180                     x -= 0x02000000;
 181
 182                 /* Relocation infos */
 183                 to_thumb = val & 1;
 184                 plt = s1->plt;
 185                 to_plt = (val >= plt->sh_addr) &&
 186                          (val < plt->sh_addr + plt->data_offset);
 187                 is_call = (type == R_ARM_THM_PC22);
 188
 189                 if (!to_thumb && !to_plt && !is_call) {
 190                     int index;
 191                     uint8_t *p;
 192                     char *name, buf[1024];
 193                     Section *text_section;
 194
 195                     name = (char *) symtab_section->link->data + sym->st_name;
 196                     text_section = s1->sections[sym->st_shndx];
 197                     /* Modify reloc to target a thumb stub to switch to ARM */
 198                     snprintf(buf, sizeof(buf), "%s_from_thumb", name);
 199                     index = put_elf_sym(symtab_section,
 200                                         text_section->data_offset + 1,
 201                                         sym->st_size, sym->st_info, 0,
 202                                         sym->st_shndx, buf);
 203                     to_thumb = 1;
 204                     val = text_section->data_offset + 1;
 205                     rel->r_info = ELFW(R_INFO)(index, type);
 206                     /* Create a thumb stub function to switch to ARM mode */
 207                     put_elf_reloc(symtab_section, text_section,
 208                                   text_section->data_offset + 4, R_ARM_JUMP24,
 209                                   sym_index);
 210                     p = section_ptr_add(text_section, 8);
 211                     write32le(p,   0x4778); /* bx pc */
 212                     write32le(p+2, 0x46c0); /* nop   */
 213                     write32le(p+4, 0xeafffffe); /* b $sym */
 214                 }
 215
 216                 /* Compute final offset */
 217                 x += val - addr;
 218                 if (!to_thumb && is_call) {
 219                     blx_bit = 0; /* bl -> blx */
 220                     x = (x + 3) & -4; /* Compute offset from aligned PC */
 221                 }
 222
 223                 /* Check that relocation is possible
 224                    * offset must not be out of range
 225                    * if target is to be entered in arm mode:
 226                      - bit 1 must not set
 227                      - instruction must be a call (bl) or a jump to PLT */
 228                 if (!to_thumb || x >= 0x1000000 || x < -0x1000000)
 229                     if (to_thumb || (val & 2) || (!is_call && !to_plt))
 230                         tcc_error("can't relocate value at %x,%d",addr, type);
 231
 232                 /* Compute and store final offset */
 233                 s = (x >> 24) & 1;
 234                 i1 = (x >> 23) & 1;
 235                 i2 = (x >> 22) & 1;
 236                 j1 = s ^ (i1 ^ 1);
 237                 j2 = s ^ (i2 ^ 1);
 238                 imm10 = (x >> 12) & 0x3ff;
 239                 imm11 = (x >> 1) & 0x7ff;
 240                 (*(uint16_t *)ptr) = (uint16_t) ((hi & 0xf800) |
 241                                      (s << 10) | imm10);
 242                 (*(uint16_t *)(ptr+2)) = (uint16_t) ((lo & 0xc000) |
 243                                 (j1 << 13) | blx_bit | (j2 << 11) |
 244                                 imm11);
 245             }
 246             return;
 247         case R_ARM_MOVT_ABS:
 248         case R_ARM_MOVW_ABS_NC:
 249             {
 250                 int x, imm4, imm12;
 251                 if (type == R_ARM_MOVT_ABS)
 252                     val >>= 16;
 253                 imm12 = val & 0xfff;
 254                 imm4 = (val >> 12) & 0xf;
 255                 x = (imm4 << 16) | imm12;
 256                 if (type == R_ARM_THM_MOVT_ABS)
 257                     *(int *)ptr |= x;
 258                 else
 259                     *(int *)ptr += x;
 260             }
 261             return;
 262         case R_ARM_THM_MOVT_ABS:
 263         case R_ARM_THM_MOVW_ABS_NC:
 264             {
 265                 int x, i, imm4, imm3, imm8;
 266                 if (type == R_ARM_THM_MOVT_ABS)
 267                     val >>= 16;
 268                 imm8 = val & 0xff;
 269                 imm3 = (val >> 8) & 0x7;
 270                 i = (val >> 11) & 1;
 271                 imm4 = (val >> 12) & 0xf;
 272                 x = (imm3 << 28) | (imm8 << 16) | (i << 10) | imm4;
 273                 if (type == R_ARM_THM_MOVT_ABS)
 274                     *(int *)ptr |= x;
 275                 else
 276                     *(int *)ptr += x;
 277             }
 278             return;
 279         case R_ARM_PREL31:
 280             {
 281                 int x;
 282                 x = (*(int *)ptr) & 0x7fffffff;
 283                 (*(int *)ptr) &= 0x80000000;
 284                 x = (x * 2) / 2;
 285                 x += val - addr;
 286                 if((x^(x>>1))&0x40000000)
 287                     tcc_error("can't relocate value at %x,%d",addr, type);
 288                 (*(int *)ptr) |= x & 0x7fffffff;
 289             }
 290         case R_ARM_ABS32:
 291             *(int *)ptr += val;
 292             return;
 293         case R_ARM_REL32:
 294             *(int *)ptr += val - addr;
 295             return;
 296         case R_ARM_GOTPC:
 297             *(int *)ptr += s1->got->sh_addr - addr;
 298             return;
 299         case R_ARM_GOTOFF:
 300             *(int *)ptr += val - s1->got->sh_addr;
 301             return;
 302         case R_ARM_GOT32:
 303             /* we load the got offset */
 304             *(int *)ptr += s1->sym_attrs[sym_index].got_offset;
 305             return;
 306         case R_ARM_COPY:
 307             return;
 308         case R_ARM_V4BX:
 309             /* trade Thumb support for ARMv4 support */
 310             if ((0x0ffffff0 & *(int*)ptr) == 0x012FFF10)
 311                 *(int*)ptr ^= 0xE12FFF10 ^ 0xE1A0F000; /* BX Rm -> MOV PC, Rm */
 312             return;
 313         case R_ARM_GLOB_DAT:
 314         case R_ARM_JUMP_SLOT:
 315             *(addr_t *)ptr = val;
 316             return;
 317         case R_ARM_NONE:
 318             /* Nothing to do.  Normally used to indicate a dependency
 319                on a certain symbol (like for exception handling under EABI).  */
 320             return;
 321         default:
 322             fprintf(stderr,"FIXME: handle reloc type %x at %x [%p] to %x\n",
 323                 type, (unsigned)addr, ptr, (unsigned)val);
 324             return;
 325     }
 326 }
 327
 328 #endif /* !TARGET_DEFS_ONLY */