sysdeps/arm/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  ARM version.
   2    Copyright (C) 1995, 1996, 1997, 1998 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 #include <assert.h>
  28
  29 /* Return nonzero iff E_MACHINE is compatible with the running host.  */
  30 static inline int __attribute__ ((unused))
  31 elf_machine_matches_host (Elf32_Half e_machine)
  32 {
  33   switch (e_machine)
  34     {
  35     case EM_ARM:
  36       return 1;
  37     default:
  38       return 0;
  39     }
  40 }
  41
  42
  43 /* Return the link-time address of _DYNAMIC.  Conveniently, this is the
  44    first element of the GOT.  This must be inlined in a function which
  45    uses global data.  */
  46 static inline Elf32_Addr __attribute__ ((unused))
  47 elf_machine_dynamic (void)
  48 {
  49   register Elf32_Addr *got asm ("r10");
  50   return *got;
  51 }
  52
  53
  54 /* Return the run-time load address of the shared object.  */
  55 // patb
  56 static inline Elf32_Addr __attribute__ ((unused))
  57 elf_machine_load_address (void)
  58 {
  59   Elf32_Addr addr;
  60   asm (" ldr ip,.L1
  61         ldr r3,.L3
  62         add r3, r3, sl
  63         ldr ip,[sl, ip]
  64         sub ip, r3, ip
  65         b .L2
  66         .L1: .word _dl_start(GOT)
  67         .L3: .word _dl_start(GOTOFF)
  68         .L2: mov %0, ip"
  69        : "=r" (addr) : : "ip", "r3");
  70   return addr;
  71 }
  72
  73
  74 /* Set up the loaded object described by L so its unrelocated PLT
  75    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  76
  77 static inline int __attribute__ ((unused))
  78 elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
  79 {
  80   Elf32_Addr *got;
  81   extern void _dl_runtime_resolve (Elf32_Word);
  82   extern void _dl_runtime_profile (Elf32_Word);
  83
  84   if (l->l_info[DT_JMPREL] && lazy)
  85     {
  86       /* patb: this is different than i386 */
  87       /* The GOT entries for functions in the PLT have not yet been filled
  88          in.  Their initial contents will arrange when called to push an
  89          index into the .got section, load ip with &_GLOBAL_OFFSET_TABLE_[3],
  90          and then jump to _GLOBAL_OFFSET_TABLE[2].  */
  91       got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
  92       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
  93
  94       /* The got[2] entry contains the address of a function which gets
  95          called to get the address of a so far unresolved function and
  96          jump to it.  The profiling extension of the dynamic linker allows
  97          to intercept the calls to collect information.  In this case we
  98          don't store the address in the GOT so that all future calls also
  99          end in this function.  */
 100       if (profile)
 101         {
 102           got[2] = (Elf32_Addr) &_dl_runtime_profile;
 103           /* Say that we really want profiling and the timers are started.  */
 104           _dl_profile_map = l;
 105         }
 106       else
 107         /* This function will get called to fix up the GOT entry indicated by
 108            the offset on the stack, and then jump to the resolved address.  */
 109         got[2] = (Elf32_Addr) &_dl_runtime_resolve;
 110     }
 111   return lazy;
 112 }
 113
 114 /* This code is used in dl-runtime.c to call the `fixup' function
 115    and then redirect to the address it returns.  */
 116    // macro for handling PIC situation....
 117 #ifdef PIC
 118 #define CALL_ROUTINE(x) " ldr sl,0f
 119         add     sl, pc, sl
 120 1:      ldr     r2, 2f
 121         mov     lr, pc
 122         add     pc, sl, r2
 123         b       3f
 124 0:      .word   _GLOBAL_OFFSET_TABLE_ - 1b - 4
 125 2:      .word " #x "(GOTOFF)
 126 3:      "
 127 #else
 128 #define CALL_ROUTINE(x) " bl " #x
 129 #endif
 130
 131 #ifndef PROF
 132 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 133         .text
 134         .globl _dl_runtime_resolve
 135         .type _dl_runtime_resolve, #function
 136         .align 2
 137 _dl_runtime_resolve:
 138         @ we get called with
 139         @       stack[0] contains the return address from this call
 140         @       ip contains &GOT[n+3] (pointer to function)
 141         @       lr points to &GOT[2]
 142
 143         @ save almost everything; lr is already on the stack
 144         stmdb   sp!,{r0-r3,sl,fp}
 145
 146         @ prepare to call fixup()
 147         @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
 148         sub     r1, ip, lr
 149         sub     r1, r1, #4
 150         add     r1, r1, r1
 151
 152         @ get pointer to linker struct
 153         ldr     r0, [lr, #-4]
 154
 155         @ call fixup routine
 156         " CALL_ROUTINE(fixup) "
 157
 158         @ save the return
 159         mov     ip, r0
 160
 161         @ restore the stack
 162         ldmia   sp!,{r0-r3,sl,fp,lr}
 163
 164         @ jump to the newly found address
 165         mov     pc, ip
 166
 167         .size _dl_runtime_resolve, .-_dl_runtime_resolve
 168
 169         .globl _dl_runtime_profile
 170         .type _dl_runtime_profile, #function
 171         .align 2
 172 _dl_runtime_profile:
 173         @ save almost everything; lr is already on the stack
 174         stmdb   sp!,{r0-r3,sl,fp}
 175
 176         @ prepare to call fixup()
 177         @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
 178         sub     r1, ip, lr
 179         sub     r1, r1, #4
 180         add     r1, r1, r1
 181
 182         @ get pointer to linker struct
 183         ldr     r0, [lr, #-4]
 184
 185         @ call profiling fixup routine
 186         " CALL_ROUTINE(profile_fixup) "
 187
 188         @ save the return
 189         mov     ip, r0
 190
 191         @ restore the stack
 192         ldmia   sp!,{r0-r3,sl,fp,lr}
 193
 194         @ jump to the newly found address
 195         mov     pc, ip
 196
 197         .size _dl_runtime_resolve, .-_dl_runtime_resolve
 198         .previous
 199 ");
 200 #else // PROF
 201 # define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 202         .text
 203         .globl _dl_runtime_resolve
 204         .globl _dl_runtime_profile
 205         .type _dl_runtime_resolve, #function
 206         .type _dl_runtime_profile, #function
 207         .align 2
 208 _dl_runtime_resolve:
 209 _dl_runtime_profile:
 210         @ we get called with
 211         @       stack[0] contains the return address from this call
 212         @       ip contains &GOT[n+3] (pointer to function)
 213         @       lr points to &GOT[2]
 214
 215         @ save almost everything; return add is already on the stack
 216         stmdb   sp!,{r0-r3,sl,fp}
 217
 218         @ prepare to call fixup()
 219         @ change &GOT[n+3] into 8*n        NOTE: reloc are 8 bytes each
 220         sub     r1, ip, lr
 221         sub     r1, r1, #4
 222         add     r1, r1, r1
 223
 224         @ get pointer to linker struct
 225         ldr     r0, [lr, #-4]
 226
 227         @ call profiling fixup routine
 228         " CALL_ROUTINE(fixup) "
 229
 230         @ save the return
 231         mov     ip, r0
 232
 233         @ restore the stack
 234         ldmia   sp!,{r0-r3,sl,fp,lr}
 235
 236         @ jump to the newly found address
 237         mov     pc, ip
 238
 239         .size _dl_runtime_profile, .-_dl_runtime_profile
 240         .previous
 241 ");
 242 #endif //PROF
 243
 244 /* Mask identifying addresses reserved for the user program,
 245    where the dynamic linker should not map anything.  */
 246 #define ELF_MACHINE_USER_ADDRESS_MASK   0xf8000000UL
 247
 248 /* Initial entry point code for the dynamic linker.
 249    The C function `_dl_start' is the real entry point;
 250    its return value is the user program's entry point.  */
 251
 252 #define RTLD_START asm ("\
 253 .text
 254 .globl _start
 255 .globl _dl_start_user
 256 _start:
 257         @ at start time, all the args are on the stack
 258         mov     r0, sp
 259         bl      _dl_start
 260         @ returns user entry point in r0
 261 _dl_start_user:
 262         mov     r6, r0
 263         @ we are PIC code, so get global offset table
 264         ldr     sl, .L_GET_GOT
 265         add     sl, pc, sl
 266 .L_GOT_GOT:
 267         @ Store the highest stack address
 268         ldr     r1, .L_STACK_END
 269         ldr     r1, [sl, r1]
 270         str     sp, [r1]
 271         @ See if we were run as a command with the executable file
 272         @ name as an extra leading argument.
 273         ldr     r1, .L_SKIP_ARGS
 274         ldr     r1, [sl, r1]
 275         @ get the original arg count
 276         ldr     r0, [sp]
 277         @ subtract _dl_skip_args from it
 278         sub     r0, r0, r1
 279         @ adjust the stack pointer to skip them
 280         add     sp, sp, r1, lsl #2
 281         @ store the new argc in the new stack location
 282         str     r0, [sp]
 283
 284         @ now we enter a _dl_init_next loop
 285         ldr     r4, .L_MAIN_SEARCHLIST
 286         ldr     r4, [sl, r4]
 287         @ call _dl_init_next to get the address of an initalizer
 288 0:      mov     r0, r4
 289         bl      _dl_init_next(PLT)
 290         cmp     r0, #0
 291         beq     1f
 292         @ call the shared-object initializer
 293         @ during this call, the stack may get moved around
 294         mov     lr, pc
 295         mov     pc, r0
 296         @ go back and look for another initializer
 297         b       0b
 298 1:      @ clear the startup flag
 299         ldr     r2, .L_STARTUP_FLAG
 300         ldr     r1, [sl, r2]
 301         @ we know r0==0 at this point
 302         str     r0, [r1]
 303         @ load the finalizer function
 304         ldr     r0, .L_FINI_PROC
 305         ldr     r0, [sl, r0]
 306         @ jump to the user_s entry point
 307         mov     pc, r6
 308 .L_GET_GOT:
 309         .word   _GLOBAL_OFFSET_TABLE_ - .L_GOT_GOT - 4  \n\
 310 .L_SKIP_ARGS:                                   \n\
 311         .word   _dl_skip_args(GOTOFF)           \n\
 312 .L_STARTUP_FLAG:
 313         .word   _dl_starting_up(GOT)
 314 .L_FINI_PROC:
 315         .word   _dl_fini(GOT)
 316 .L_STACK_END:
 317         .word   __libc_stack_end(GOT)
 318 .L_MAIN_SEARCHLIST:
 319         .word   _dl_main_searchlist(GOT)
 320 .previous\n\
 321 ");
 322
 323 /* Nonzero iff TYPE should not be allowed to resolve to one of
 324    the main executable's symbols, as for a COPY reloc.  */
 325 #define elf_machine_lookup_noexec_p(type) ((type) == R_ARM_COPY)
 326
 327 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 328    PLT entries should not be allowed to define the value.  */
 329 #define elf_machine_lookup_noplt_p(type) ((type) == R_ARM_JUMP_SLOT)
 330
 331 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 332 #define ELF_MACHINE_JMP_SLOT    R_ARM_JUMP_SLOT
 333
 334 /* The ARM never uses Elf32_Rela relocations.  */
 335 #define ELF_MACHINE_NO_RELA 1
 336
 337 /* We define an initialization functions.  This is called very early in
 338    _dl_sysdep_start.  */
 339 #define DL_PLATFORM_INIT dl_platform_init ()
 340
 341 extern const char *_dl_platform;
 342
 343 static inline void __attribute__ ((unused))
 344 dl_platform_init (void)
 345 {
 346   if (_dl_platform == NULL)
 347     /* We default to ARM
 348     This is where processors could be distinguished arm2, arm6, sa110, etc */
 349     _dl_platform = "ARM";
 350 }
 351
 352 static inline void
 353 elf_machine_fixup_plt (struct link_map *map, const Elf32_Rel *reloc,
 354                        Elf32_Addr *reloc_addr, Elf32_Addr value)
 355 {
 356   *reloc_addr = value;
 357 }
 358
 359 /* Return the final value of a plt relocation.  */
 360 static inline Elf32_Addr
 361 elf_machine_plt_value (struct link_map *map, const Elf32_Rel *reloc,
 362                        Elf32_Addr value)
 363 {
 364   return value;
 365 }
 366
 367 #endif /* !dl_machine_h */
 368
 369 #ifdef RESOLVE
 370
 371 extern char **_dl_argv;
 372
 373 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 374    MAP is the object containing the reloc.  */
 375
 376 static inline void
 377 elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
 378                  const Elf32_Sym *sym, const struct r_found_version *version,
 379                  Elf32_Addr *const reloc_addr)
 380 {
 381   if (ELF32_R_TYPE (reloc->r_info) == R_ARM_RELATIVE)
 382     {
 383 #ifndef RTLD_BOOTSTRAP
 384       if (map != &_dl_rtld_map) /* Already done in rtld itself.  */
 385 #endif
 386         *reloc_addr += map->l_addr;
 387     }
 388   else if (ELF32_R_TYPE (reloc->r_info) != R_ARM_NONE)
 389     {
 390       const Elf32_Sym *const refsym = sym;
 391       Elf32_Addr value = RESOLVE (&sym, version, ELF32_R_TYPE (reloc->r_info));
 392       if (sym)
 393         value += sym->st_value;
 394
 395       switch (ELF32_R_TYPE (reloc->r_info))
 396         {
 397         case R_ARM_COPY:
 398           if (sym == NULL)
 399             /* This can happen in trace mode if an object could not be
 400                found.  */
 401             break;
 402           if (sym->st_size > refsym->st_size
 403               || (_dl_verbose && sym->st_size < refsym->st_size))
 404             {
 405               const char *strtab;
 406
 407               strtab = ((const char *) map->l_addr
 408                         + map->l_info[DT_STRTAB]->d_un.d_ptr);
 409               _dl_sysdep_error (_dl_argv[0] ?: "<program name unknown>",
 410                                 ": Symbol `", strtab + refsym->st_name,
 411                                 "' has different size in shared object, "
 412                                 "consider re-linking\n", NULL);
 413             }
 414           memcpy (reloc_addr, (void *) value, MIN (sym->st_size,
 415                                                    refsym->st_size));
 416           break;
 417         case R_ARM_GLOB_DAT:
 418         case R_ARM_JUMP_SLOT:
 419 #ifdef RTLD_BOOTSTRAP
 420           /* Fix weak undefined references.  */
 421           if (sym != NULL && sym->st_value == 0)
 422             *reloc_addr = 0;
 423           else
 424 #endif
 425             *reloc_addr = value;
 426           break;
 427         case R_ARM_ABS32:
 428           {
 429 #ifndef RTLD_BOOTSTRAP
 430            /* This is defined in rtld.c, but nowhere in the static
 431               libc.a; make the reference weak so static programs can
 432               still link.  This declaration cannot be done when
 433               compiling rtld.c (i.e.  #ifdef RTLD_BOOTSTRAP) because
 434               rtld.c contains the common defn for _dl_rtld_map, which
 435               is incompatible with a weak decl in the same file.  */
 436             weak_extern (_dl_rtld_map);
 437             if (map == &_dl_rtld_map)
 438               /* Undo the relocation done here during bootstrapping.
 439                  Now we will relocate it anew, possibly using a
 440                  binding found in the user program or a loaded library
 441                  rather than the dynamic linker's built-in definitions
 442                  used while loading those libraries.  */
 443               value -= map->l_addr + refsym->st_value;
 444 #endif
 445             *reloc_addr += value;
 446             break;
 447           }
 448         default:
 449           assert (! "unexpected dynamic reloc type");
 450           break;
 451         }
 452     }
 453 }
 454
 455 static inline void
 456 elf_machine_lazy_rel (Elf32_Addr l_addr, const Elf32_Rel *reloc)
 457 {
 458   Elf32_Addr *const reloc_addr = (void *) (l_addr + reloc->r_offset);
 459   /* Check for unexpected PLT reloc type.  */
 460   assert (ELF32_R_TYPE (reloc->r_info) == R_ARM_JUMP_SLOT);
 461   *reloc_addr += l_addr;
 462 }
 463
 464 #endif /* RESOLVE */