i386-link.c

   1 #ifdef TARGET_DEFS_ONLY
   2
   3 #define EM_TCC_TARGET EM_386
   4
   5 /* relocation type for 32 bit data relocation */
   6 #define R_DATA_32   R_386_32
   7 #define R_DATA_PTR  R_386_32
   8 #define R_JMP_SLOT  R_386_JMP_SLOT
   9 #define R_GLOB_DAT  R_386_GLOB_DAT
  10 #define R_COPY      R_386_COPY
  11
  12 #define R_NUM       R_386_NUM
  13
  14 #define ELF_START_ADDR 0x08048000
  15 #define ELF_PAGE_SIZE  0x1000
  16
  17 #define PCRELATIVE_DLLPLT 0
  18 #define RELOCATE_DLLPLT 0
  19
  20 #else /* !TARGET_DEFS_ONLY */
  21
  22 #include "tcc.h"
  23
  24 /* Returns 1 for a code relocation, 0 for a data relocation. For unknown
  25    relocations, returns -1. */
  26 int code_reloc (int reloc_type)
  27 {
  28     switch (reloc_type) {
  29         case R_386_RELATIVE:
  30         case R_386_16:
  31         case R_386_32:
  32         case R_386_GOTPC:
  33         case R_386_GOTOFF:
  34         case R_386_GOT32:
  35         case R_386_GOT32X:
  36         case R_386_GLOB_DAT:
  37         case R_386_COPY:
  38             return 0;
  39
  40         case R_386_PC16:
  41         case R_386_PC32:
  42         case R_386_PLT32:
  43         case R_386_JMP_SLOT:
  44             return 1;
  45     }
  46
  47     tcc_error ("Unknown relocation type: %d", reloc_type);
  48     return -1;
  49 }
  50
  51 /* Returns an enumerator to describe wether and when the relocation needs a
  52    GOT and/or PLT entry to be created. See tcc.h for a description of the
  53    different values. */
  54 int gotplt_entry_type (int reloc_type)
  55 {
  56     switch (reloc_type) {
  57         case R_386_RELATIVE:
  58         case R_386_16:
  59         case R_386_GLOB_DAT:
  60         case R_386_JMP_SLOT:
  61         case R_386_COPY:
  62             return NO_GOTPLT_ENTRY;
  63
  64         case R_386_32:
  65             /* This relocations shouldn't normally need GOT or PLT
  66                slots if it weren't for simplicity in the code generator.
  67                See our caller for comments.  */
  68             return AUTO_GOTPLT_ENTRY;
  69
  70         case R_386_PC16:
  71         case R_386_PC32:
  72             return AUTO_GOTPLT_ENTRY;
  73
  74         case R_386_GOTPC:
  75         case R_386_GOTOFF:
  76             return BUILD_GOT_ONLY;
  77
  78         case R_386_GOT32:
  79         case R_386_GOT32X:
  80         case R_386_PLT32:
  81             return ALWAYS_GOTPLT_ENTRY;
  82     }
  83
  84     tcc_error ("Unknown relocation type: %d", reloc_type);
  85     return -1;
  86 }
  87
  88 ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
  89 {
  90     Section *plt = s1->plt;
  91     uint8_t *p;
  92     int modrm;
  93     unsigned plt_offset, relofs;
  94
  95     /* on i386 if we build a DLL, we add a %ebx offset */
  96     if (s1->output_type == TCC_OUTPUT_DLL)
  97         modrm = 0xa3;
  98     else
  99         modrm = 0x25;
 100
 101     /* empty PLT: create PLT0 entry that pushes the library indentifier
 102        (GOT + PTR_SIZE) and jumps to ld.so resolution routine
 103        (GOT + 2 * PTR_SIZE) */
 104     if (plt->data_offset == 0) {
 105         p = section_ptr_add(plt, 16);
 106         p[0] = 0xff; /* pushl got + PTR_SIZE */
 107         p[1] = modrm + 0x10;
 108         write32le(p + 2, PTR_SIZE);
 109         p[6] = 0xff; /* jmp *(got + PTR_SIZE * 2) */
 110         p[7] = modrm;
 111         write32le(p + 8, PTR_SIZE * 2);
 112     }
 113     plt_offset = plt->data_offset;
 114
 115     /* The PLT slot refers to the relocation entry it needs via offset.
 116        The reloc entry is created below, so its offset is the current
 117        data_offset */
 118     relofs = s1->got->reloc ? s1->got->reloc->data_offset : 0;
 119
 120     /* Jump to GOT entry where ld.so initially put the address of ip + 4 */
 121     p = section_ptr_add(plt, 16);
 122     p[0] = 0xff; /* jmp *(got + x) */
 123     p[1] = modrm;
 124     write32le(p + 2, got_offset);
 125     p[6] = 0x68; /* push $xxx */
 126     write32le(p + 7, relofs);
 127     p[11] = 0xe9; /* jmp plt_start */
 128     write32le(p + 12, -(plt->data_offset));
 129     return plt_offset;
 130 }
 131
 132 /* relocate the PLT: compute addresses and offsets in the PLT now that final
 133    address for PLT and GOT are known (see fill_program_header) */
 134 ST_FUNC void relocate_plt(TCCState *s1)
 135 {
 136     uint8_t *p, *p_end;
 137
 138     if (!s1->plt)
 139       return;
 140
 141     p = s1->plt->data;
 142     p_end = p + s1->plt->data_offset;
 143
 144     if (p < p_end) {
 145         add32le(p + 2, s1->got->sh_addr);
 146         add32le(p + 8, s1->got->sh_addr);
 147         p += 16;
 148         while (p < p_end) {
 149             add32le(p + 2, s1->got->sh_addr);
 150             p += 16;
 151         }
 152     }
 153 }
 154
 155 static ElfW_Rel *qrel; /* ptr to next reloc entry reused */
 156
 157 void relocate_init(Section *sr)
 158 {
 159     qrel = (ElfW_Rel *) sr->data;
 160 }
 161
 162 void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t addr, addr_t val)
 163 {
 164     int sym_index, esym_index;
 165
 166     sym_index = ELFW(R_SYM)(rel->r_info);
 167
 168     switch (type) {
 169         case R_386_32:
 170             if (s1->output_type == TCC_OUTPUT_DLL) {
 171                 esym_index = s1->sym_attrs[sym_index].dyn_index;
 172                 qrel->r_offset = rel->r_offset;
 173                 if (esym_index) {
 174                     qrel->r_info = ELFW(R_INFO)(esym_index, R_386_32);
 175                     qrel++;
 176                     return;
 177                 } else {
 178                     qrel->r_info = ELFW(R_INFO)(0, R_386_RELATIVE);
 179                     qrel++;
 180                 }
 181             }
 182             add32le(ptr, val);
 183             return;
 184         case R_386_PC32:
 185             if (s1->output_type == TCC_OUTPUT_DLL) {
 186                 /* DLL relocation */
 187                 esym_index = s1->sym_attrs[sym_index].dyn_index;
 188                 if (esym_index) {
 189                     qrel->r_offset = rel->r_offset;
 190                     qrel->r_info = ELFW(R_INFO)(esym_index, R_386_PC32);
 191                     qrel++;
 192                     return;
 193                 }
 194             }
 195             add32le(ptr, val - addr);
 196             return;
 197         case R_386_PLT32:
 198             add32le(ptr, val - addr);
 199             return;
 200         case R_386_GLOB_DAT:
 201         case R_386_JMP_SLOT:
 202             write32le(ptr, val);
 203             return;
 204         case R_386_GOTPC:
 205             add32le(ptr, s1->got->sh_addr - addr);
 206             return;
 207         case R_386_GOTOFF:
 208             add32le(ptr, val - s1->got->sh_addr);
 209             return;
 210         case R_386_GOT32:
 211         case R_386_GOT32X:
 212             /* we load the got offset */
 213             add32le(ptr, s1->sym_attrs[sym_index].got_offset);
 214             return;
 215         case R_386_16:
 216             if (s1->output_format != TCC_OUTPUT_FORMAT_BINARY) {
 217             output_file:
 218                 tcc_error("can only produce 16-bit binary files");
 219             }
 220             write16le(ptr, read16le(ptr) + val);
 221             return;
 222         case R_386_PC16:
 223             if (s1->output_format != TCC_OUTPUT_FORMAT_BINARY)
 224                 goto output_file;
 225             write16le(ptr, read16le(ptr) + val - addr);
 226             return;
 227         case R_386_RELATIVE:
 228             /* do nothing */
 229             return;
 230         case R_386_COPY:
 231             /* This reloction must copy initialized data from the library
 232             to the program .bss segment. Currently made like for ARM
 233             (to remove noise of defaukt case). Is this true?
 234             */
 235             return;
 236         default:
 237             fprintf(stderr,"FIXME: handle reloc type %d at %x [%p] to %x\n",
 238                 type, (unsigned)addr, ptr, (unsigned)val);
 239             return;
 240     }
 241 }
 242
 243 #endif /* !TARGET_DEFS_ONLY */