sysdeps/arm/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  ARM version.
   2    Copyright (C) 1995, 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #ifndef dl_machine_h
  21 #define dl_machine_h
  22
  23 #define ELF_MACHINE_NAME "ARM"
  24
  25 #include <sys/param.h>
  26
  27 #define VALID_ELF_ABIVERSION(ver)       (ver == 0)
  28 #define VALID_ELF_OSABI(osabi) \
  29   (osabi == ELFOSABI_SYSV || osabi == ELFOSABI_ARM)
  30 #define VALID_ELF_HEADER(hdr,exp,size) \
  31   memcmp (hdr,exp,size-2) == 0 \
  32   && VALID_ELF_OSABI (hdr[EI_OSABI]) \
  33   && VALID_ELF_ABIVERSION (hdr[EI_ABIVERSION])
  34
  35 #define CLEAR_CACHE(BEG,END)                                            \
  36 {                                                                       \
  37   register unsigned long _beg __asm ("a1") = (unsigned long)(BEG);      \
  38   register unsigned long _end __asm ("a2") = (unsigned long)(END);      \
  39   register unsigned long _flg __asm ("a3") = 0;                         \
  40   __asm __volatile ("swi 0x9f0002");                                    \
  41 }
  42
  43 /* Return nonzero iff E_MACHINE is compatible with the running host.  */
  44 static inline int __attribute__ ((unused))
  45 elf_machine_matches_host (Elf32_Half e_machine)
  46 {
  47   switch (e_machine)
  48     {
  49     case EM_ARM:
  50       return 1;
  51     default:
  52       return 0;
  53     }
  54 }
  55
  56
  57 /* Return the link-time address of _DYNAMIC.  Conveniently, this is the
  58    first element of the GOT.  This must be inlined in a function which
  59    uses global data.  */
  60 static inline Elf32_Addr __attribute__ ((unused))
  61 elf_machine_dynamic (void)
  62 {
  63   register Elf32_Addr *got asm ("r10");
  64   return *got;
  65 }
  66
  67
  68 /* Return the run-time load address of the shared object.  */
  69 static inline Elf32_Addr __attribute__ ((unused))
  70 elf_machine_load_address (void)
  71 {
  72   extern void __dl_start asm ("_dl_start");
  73   Elf32_Addr got_addr = (Elf32_Addr) &__dl_start;
  74   Elf32_Addr pcrel_addr;
  75   asm ("adr %0, _dl_start" : "=r" (pcrel_addr));
  76   return pcrel_addr - got_addr;
  77 }
  78
  79
  80 /* Set up the loaded object described by L so its unrelocated PLT
  81    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  82
  83 static inline int __attribute__ ((unused))
  84 elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
  85 {
  86   Elf32_Addr *got;
  87   extern void _dl_runtime_resolve (Elf32_Word);
  88   extern void _dl_runtime_profile (Elf32_Word);
  89
  90   if (l->l_info[DT_JMPREL] && lazy)
  91     {
  92       /* patb: this is different than i386 */
  93       /* The GOT entries for functions in the PLT have not yet been filled
  94          in.  Their initial contents will arrange when called to push an
  95          index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
  96          and then jump to _GLOBAL_OFFSET_TABLE[2].  */
  97       got = (Elf32_Addr *) l->l_info[DT_PLTGOT]->d_un.d_ptr;
  98       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
  99
 100       /* The got[2] entry contains the address of a function which gets
 101          called to get the address of a so far unresolved function and
 102          jump to it.  The profiling extension of the dynamic linker allows
 103          to intercept the calls to collect information.  In this case we
 104          don't store the address in the GOT so that all future calls also
 105          end in this function.  */
 106       if (profile)
 107         {
 108           got[2] = (Elf32_Addr) &_dl_runtime_profile;
 109           /* Say that we really want profiling and the timers are started.  */
 110           _dl_profile_map = l;
 111         }
 112       else
 113         /* This function will get called to fix up the GOT entry indicated by
 114            the offset on the stack, and then jump to the resolved address.  */
 115         got[2] = (Elf32_Addr) &_dl_runtime_resolve;
 116     }
 117   return lazy;
 118 }
 119
 120 /* This code is used in dl-runtime.c to call the `fixup' function
 121    and then redirect to the address it returns.  */
 122    // macro for handling PIC situation....
 123 #ifdef PIC
 124 #define CALL_ROUTINE(x) " ldr sl,0f
 125         add     sl, pc, sl
 126 1:      ldr     r2, 2f
 127         mov     lr, pc
 128         add     pc, sl, r2
 129         b       3f
 130 0:      .word   _GLOBAL_OFFSET_TABLE_ - 1b - 4
 131 2:      .word " #x "(GOTOFF)
 132 3:      "
 133 #else
 134 #define CALL_ROUTINE(x) " bl " #x
 135 #endif
 136
 137 #ifndef PROF
 138 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 139         .text
 140         .globl _dl_runtime_resolve
 141         .type _dl_runtime_resolve, #function
 142         .align 2
 143 _dl_runtime_resolve:
 144         @ we get called with
 145         @       stack[0] contains the return address from this call
 146         @       ip contains &GOT[n+3] (pointer to function)
 147         @       lr points to &GOT[2]
 148
 149         @ save almost everything; lr is already on the stack
 150         stmdb   sp!,{r0-r3,sl,fp}
 151
 152         @ prepare to call fixup()
 153         @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
 154         sub     r1, ip, lr
 155         sub     r1, r1, #4
 156         add     r1, r1, r1
 157
 158         @ get pointer to linker struct
 159         ldr     r0, [lr, #-4]
 160
 161         @ call fixup routine
 162         " CALL_ROUTINE(fixup) "
 163
 164         @ save the return
 165         mov     ip, r0
 166
 167         @ restore the stack
 168         ldmia   sp!,{r0-r3,sl,fp,lr}
 169
 170         @ jump to the newly found address
 171         mov     pc, ip
 172
 173         .size _dl_runtime_resolve, .-_dl_runtime_resolve
 174
 175         .globl _dl_runtime_profile
 176         .type _dl_runtime_profile, #function
 177         .align 2
 178 _dl_runtime_profile:
 179         @ save almost everything; lr is already on the stack
 180         stmdb   sp!,{r0-r3,sl,fp}
 181
 182         @ prepare to call fixup()
 183         @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
 184         sub     r1, ip, lr
 185         sub     r1, r1, #4
 186         add     r1, r1, r1
 187
 188         @ get pointer to linker struct
 189         ldr     r0, [lr, #-4]
 190
 191         @ call profiling fixup routine
 192         " CALL_ROUTINE(profile_fixup) "
 193
 194         @ save the return
 195         mov     ip, r0
 196
 197         @ restore the stack
 198         ldmia   sp!,{r0-r3,sl,fp,lr}
 199
 200         @ jump to the newly found address
 201         mov     pc, ip
 202
 203         .size _dl_runtime_resolve, .-_dl_runtime_resolve
 204         .previous
 205 ");
 206 #else // PROF
 207 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 208         .text
 209         .globl _dl_runtime_resolve
 210         .globl _dl_runtime_profile
 211         .type _dl_runtime_resolve, #function
 212         .type _dl_runtime_profile, #function
 213         .align 2
 214 _dl_runtime_resolve:
 215 _dl_runtime_profile:
 216         @ we get called with
 217         @       stack[0] contains the return address from this call
 218         @       ip contains &GOT[n+3] (pointer to function)
 219         @       lr points to &GOT[2]
 220
 221         @ save almost everything; return add is already on the stack
 222         stmdb   sp!,{r0-r3,sl,fp}
 223
 224         @ prepare to call fixup()
 225         @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
 226         sub     r1, ip, lr
 227         sub     r1, r1, #4
 228         add     r1, r1, r1
 229
 230         @ get pointer to linker struct
 231         ldr     r0, [lr, #-4]
 232
 233         @ call profiling fixup routine
 234         " CALL_ROUTINE(fixup) "
 235
 236         @ save the return
 237         mov     ip, r0
 238
 239         @ restore the stack
 240         ldmia   sp!,{r0-r3,sl,fp,lr}
 241
 242         @ jump to the newly found address
 243         mov     pc, ip
 244
 245         .size _dl_runtime_profile, .-_dl_runtime_profile
 246         .previous
 247 ");
 248 #endif //PROF
 249
 250 /* Mask identifying addresses reserved for the user program,
 251    where the dynamic linker should not map anything.  */
 252 #define ELF_MACHINE_USER_ADDRESS_MASK   0xf8000000UL
 253
 254 /* Initial entry point code for the dynamic linker.
 255    The C function `_dl_start' is the real entry point;
 256    its return value is the user program's entry point.  */
 257
 258 #define RTLD_START asm ("\
 259 .text
 260 .globl _start
 261 .globl _dl_start_user
 262 _start:
 263         @ at start time, all the args are on the stack
 264         mov     r0, sp
 265         bl      _dl_start
 266         @ returns user entry point in r0
 267 _dl_start_user:
 268         mov     r6, r0
 269         @ we are PIC code, so get global offset table
 270         ldr     sl, .L_GET_GOT
 271         add     sl, pc, sl
 272 .L_GOT_GOT:
 273         @ Store the highest stack address
 274         ldr     r1, .L_STACK_END
 275         ldr     r1, [sl, r1]
 276         str     sp, [r1]
 277         @ See if we were run as a command with the executable file
 278         @ name as an extra leading argument.
 279         ldr     r1, .L_SKIP_ARGS
 280         ldr     r1, [sl, r1]
 281         @ get the original arg count
 282         ldr     r0, [sp]
 283         @ subtract _dl_skip_args from it
 284         sub     r0, r0, r1
 285         @ adjust the stack pointer to skip them
 286         add     sp, sp, r1, lsl #2
 287         @ store the new argc in the new stack location
 288         str     r0, [sp]
 289
 290         @ now we enter a _dl_init_next loop
 291         ldr     r4, .L_MAIN_SEARCHLIST
 292         ldr     r4, [sl, r4]
 293         ldr     r4, [r4]
 294         @ call _dl_init_next to get the address of an initalizer
 295 0:      mov     r0, r4
 296         bl      _dl_init_next(PLT)
 297         cmp     r0, #0
 298         beq     1f
 299         @ call the shared-object initializer
 300         @ during this call, the stack may get moved around
 301         mov     lr, pc
 302         mov     pc, r0
 303         @ go back and look for another initializer
 304         b       0b
 305 1:      @ clear the startup flag
 306         ldr     r2, .L_STARTUP_FLAG
 307         ldr     r1, [sl, r2]
 308         @ we know r0==0 at this point
 309         str     r0, [r1]
 310         @ load the finalizer function
 311         ldr     r0, .L_FINI_PROC
 312         ldr     r0, [sl, r0]
 313         @ jump to the user_s entry point
 314         mov     pc, r6
 315 .L_GET_GOT:
 316         .word   _GLOBAL_OFFSET_TABLE_ - .L_GOT_GOT - 4  \n\
 317 .L_SKIP_ARGS:                                   \n\
 318         .word   _dl_skip_args(GOTOFF)           \n\
 319 .L_STARTUP_FLAG:
 320         .word   _dl_starting_up(GOT)
 321 .L_FINI_PROC:
 322         .word   _dl_fini(GOT)
 323 .L_STACK_END:
 324         .word   __libc_stack_end(GOT)
 325 .L_MAIN_SEARCHLIST:
 326         .word   _dl_main_searchlist(GOT)
 327 .previous\n\
 328 ");
 329
 330 /* Nonzero iff TYPE should not be allowed to resolve to one of
 331    the main executable's symbols, as for a COPY reloc.  */
 332 #define elf_machine_lookup_noexec_p(type) ((type) == R_ARM_COPY)
 333
 334 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 335    PLT entries should not be allowed to define the value.  */
 336 #define elf_machine_lookup_noplt_p(type) ((type) == R_ARM_JUMP_SLOT)
 337
 338 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 339 #define ELF_MACHINE_JMP_SLOT    R_ARM_JUMP_SLOT
 340
 341 /* The ARM never uses Elf32_Rela relocations.  */
 342 #define ELF_MACHINE_NO_RELA 1
 343
 344 /* We define an initialization functions.  This is called very early in
 345    _dl_sysdep_start.  */
 346 #define DL_PLATFORM_INIT dl_platform_init ()
 347
 348 extern const char *_dl_platform;
 349
 350 static inline void __attribute__ ((unused))
 351 dl_platform_init (void)
 352 {
 353   if (_dl_platform == NULL)
 354     /* We default to ARM
 355     This is where processors could be distinguished arm2, arm6, sa110, etc */
 356     _dl_platform = "ARM";
 357 }
 358
 359 static inline void
 360 elf_machine_fixup_plt (struct link_map *map, const Elf32_Rel *reloc,
 361                        Elf32_Addr *reloc_addr, Elf32_Addr value)
 362 {
 363   *reloc_addr = value;
 364 }
 365
 366 /* Return the final value of a plt relocation.  */
 367 static inline Elf32_Addr
 368 elf_machine_plt_value (struct link_map *map, const Elf32_Rel *reloc,
 369                        Elf32_Addr value)
 370 {
 371   return value;
 372 }
 373
 374 #endif /* !dl_machine_h */
 375
 376 #ifdef RESOLVE
 377
 378 extern char **_dl_argv;
 379
 380 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 381    MAP is the object containing the reloc.  */
 382
 383 static inline void
 384 elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
 385                  const Elf32_Sym *sym, const struct r_found_version *version,
 386                  Elf32_Addr *const reloc_addr)
 387 {
 388   if (ELF32_R_TYPE (reloc->r_info) == R_ARM_RELATIVE)
 389     {
 390 #ifndef RTLD_BOOTSTRAP
 391       if (map != &_dl_rtld_map) /* Already done in rtld itself.  */
 392 #endif
 393         *reloc_addr += map->l_addr;
 394     }
 395   else if (ELF32_R_TYPE (reloc->r_info) != R_ARM_NONE)
 396     {
 397       const Elf32_Sym *const refsym = sym;
 398       Elf32_Addr value = RESOLVE (&sym, version, ELF32_R_TYPE (reloc->r_info));
 399       if (sym)
 400         value += sym->st_value;
 401
 402       switch (ELF32_R_TYPE (reloc->r_info))
 403         {
 404         case R_ARM_COPY:
 405           if (sym == NULL)
 406             /* This can happen in trace mode if an object could not be
 407                found.  */
 408             break;
 409           if (sym->st_size > refsym->st_size
 410               || (_dl_verbose && sym->st_size < refsym->st_size))
 411             {
 412               const char *strtab;
 413
 414               strtab = (const void *) map->l_info[DT_STRTAB]->d_un.d_ptr;
 415               _dl_sysdep_error (_dl_argv[0] ?: "<program name unknown>",
 416                                 ": Symbol `", strtab + refsym->st_name,
 417                                 "' has different size in shared object, "
 418                                 "consider re-linking\n", NULL);
 419             }
 420           memcpy (reloc_addr, (void *) value, MIN (sym->st_size,
 421                                                    refsym->st_size));
 422           break;
 423         case R_ARM_GLOB_DAT:
 424         case R_ARM_JUMP_SLOT:
 425 #ifdef RTLD_BOOTSTRAP
 426           /* Fix weak undefined references.  */
 427           if (sym != NULL && sym->st_value == 0)
 428             *reloc_addr = 0;
 429           else
 430 #endif
 431             *reloc_addr = value;
 432           break;
 433         case R_ARM_ABS32:
 434           {
 435 #ifndef RTLD_BOOTSTRAP
 436            /* This is defined in rtld.c, but nowhere in the static
 437               libc.a; make the reference weak so static programs can
 438               still link.  This declaration cannot be done when
 439               compiling rtld.c (i.e.  #ifdef RTLD_BOOTSTRAP) because
 440               rtld.c contains the common defn for _dl_rtld_map, which
 441               is incompatible with a weak decl in the same file.  */
 442             weak_extern (_dl_rtld_map);
 443             if (map == &_dl_rtld_map)
 444               /* Undo the relocation done here during bootstrapping.
 445                  Now we will relocate it anew, possibly using a
 446                  binding found in the user program or a loaded library
 447                  rather than the dynamic linker's built-in definitions
 448                  used while loading those libraries.  */
 449               value -= map->l_addr + refsym->st_value;
 450 #endif
 451             *reloc_addr += value;
 452             break;
 453           }
 454         case R_ARM_PC24:
 455           {
 456              signed int addend;
 457
 458              addend = *reloc_addr & 0x00ffffff;
 459              if (addend & 0x00800000) addend |= 0xff000000;
 460
 461              value = value - (unsigned int)reloc_addr + (addend << 2);
 462              if (value & 0xfc000003)
 463                _dl_signal_error (0, map->l_name,
 464                           "R_ARM_PC24 relocation out of range");
 465
 466              value = value >> 2;
 467              value = (*reloc_addr & 0xff000000) | (value & 0x00ffffff);
 468              *reloc_addr = value;
 469           }
 470         break;
 471         default:
 472           _dl_reloc_bad_type (map, ELF32_R_TYPE (reloc->r_info), 0);
 473           break;
 474         }
 475     }
 476 }
 477
 478 static inline void
 479 elf_machine_lazy_rel (struct link_map *map,
 480                       Elf32_Addr l_addr, const Elf32_Rel *reloc)
 481 {
 482   Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
 483   /* Check for unexpected PLT reloc type.  */
 484   if (ELF32_R_TYPE (reloc->r_info) == R_ARM_JUMP_SLOT)
 485     *reloc_addr += l_addr;
 486   else
 487     _dl_reloc_bad_type (map, ELF32_R_TYPE (reloc->r_info), 1);
 488 }
 489
 490 #endif /* RESOLVE */