aboutsummaryrefslogtreecommitdiff
path: root/sysdeps/powerpc/dl-machine.h
blob: 526887da18c566937332e8680f1f6f52d373937e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
/* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#define ELF_MACHINE_NAME "powerpc"

#include <assert.h>
#include <string.h>
#include <link.h>

/* stuff for the PLT */
#define PLT_INITIAL_ENTRY_WORDS 18
#define PLT_LONGBRANCH_ENTRY_WORDS 10
#define PLT_DOUBLE_SIZE (1<<13)
#define PLT_ENTRY_START_WORDS(entry_number) \
  (PLT_INITIAL_ENTRY_WORDS + (entry_number)*2 + \
   ((entry_number) > PLT_DOUBLE_SIZE ? \
    ((entry_number) - PLT_DOUBLE_SIZE)*2 : \
    0))
#define PLT_DATA_START_WORDS(num_entries) PLT_ENTRY_START_WORDS(num_entries)

#define OPCODE_ADDI(rd,ra,simm) \
  (0x38000000 | (rd) << 21 | (ra) << 16 | (simm) & 0xffff)
#define OPCODE_ADDIS(rd,ra,simm) \
  (0x3c000000 | (rd) << 21 | (ra) << 16 | (simm) & 0xffff)
#define OPCODE_ADD(rd,ra,rb) \
  (0x7c000214 | (rd) << 21 | (ra) << 16 | (rb) << 11)
#define OPCODE_B(target) (0x48000000 | (target) & 0x03fffffc)
#define OPCODE_BA(target) (0x48000002 | (target) & 0x03fffffc)
#define OPCODE_BCTR() 0x4e800420
#define OPCODE_LWZ(rd,d,ra) \
  (0x80000000 | (rd) << 21 | (ra) << 16 | (d) & 0xffff)
#define OPCODE_MTCTR(rd) (0x7C0903A6 | (rd) << 21)
#define OPCODE_RLWINM(ra,rs,sh,mb,me) \
  (0x54000000 | (rs) << 21 | (ra) << 16 | (sh) << 11 | (mb) << 6 | (me) << 1)

#define OPCODE_LI(rd,simm)    OPCODE_ADDI(rd,0,simm)
#define OPCODE_SLWI(ra,rs,sh) OPCODE_RLWINM(ra,rs,sh,0,31-sh)

#define PPC_DCBST(where) asm __volatile__ ("dcbst 0,%0" : : "r"(where))
#define PPC_SYNC asm __volatile__ ("sync")
#define PPC_ISYNC asm __volatile__ ("sync; isync")
#define PPC_ICBI(where) asm __volatile__ ("icbi 0,%0" : : "r"(where))

/* Use this when you've modified some code, but it won't be in the
   instruction fetch queue (or when it doesn't matter if it is). */
#define MODIFIED_CODE_NOQUEUE(where) \
     do { PPC_DCBST(where); PPC_SYNC; PPC_ICBI(where); } while (0)
/* Use this when it might be in the instruction queue. */
#define MODIFIED_CODE(where) \
     do { PPC_DCBST(where); PPC_SYNC; PPC_ICBI(where); PPC_ISYNC; } while (0)


/* Return nonzero iff E_MACHINE is compatible with the running host.  */
static inline int
elf_machine_matches_host (Elf32_Half e_machine)
{
  return e_machine == EM_PPC;
}


/* Return the link-time address of _DYNAMIC, stored as
   the first value in the GOT. */
static inline Elf32_Addr
elf_machine_dynamic (void)
{
  Elf32_Addr *got;
  asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
       : "=l"(got));
  return *got;
}

/* Return the run-time load address of the shared object.  */
static inline Elf32_Addr
elf_machine_load_address (void)
{
  unsigned *got;
  unsigned *branchaddr;

  /* This is much harder than you'd expect.  Possibly I'm missing something.
     The 'obvious' way:

       Apparently, "bcl 20,31,$+4" is what should be used to load LR
       with the address of the next instruction.
       I think this is so that machines that do bl/blr pairing don't
       get confused.

     asm ("bcl 20,31,0f ;"
	  "0: mflr 0 ;"
	  "lis %0,0b@ha;"
	  "addi %0,%0,0b@l;"
	  "subf %0,%0,0"
	  : "=b" (addr) : : "r0", "lr");

     doesn't work, because the linker doesn't have to (and in fact doesn't)
     update the @ha and @l references; the loader (which runs after this
     code) will do that.

     Instead, we use the following trick:

     The linker puts the _link-time_ address of _DYNAMIC at the first
     word in the GOT. We could branch to that address, if we wanted,
     by using an @local reloc; the linker works this out, so it's safe
     to use now. We can't, of course, actually branch there, because
     we'd cause an illegal instruction exception; so we need to compute
     the address ourselves. That gives us the following code: */

  /* Get address of the 'b _DYNAMIC@local'...  */
  asm ("bl 0f ;"
       "b _DYNAMIC@local;"
       "0:"
       : "=l"(branchaddr));

  /* ... and the address of the GOT.  */
  asm (" bl _GLOBAL_OFFSET_TABLE_-4@local"
       : "=l"(got));

  /* So now work out the difference between where the branch actually points,
     and the offset of that location in memory from the start of the file.  */
  return (Elf32_Addr)branchaddr - *got +
    (*branchaddr & 0x3fffffc |
     (int)(*branchaddr << 6 & 0x80000000) >> 6);
}

#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */

/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
   LOADADDR is the load address of the object; INFO is an array indexed
   by DT_* of the .dynamic section info.  */

#ifdef RESOLVE

static inline void
elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
		  const Elf32_Sym *sym, const struct r_found_version *version)
{
  Elf32_Addr *const reloc_addr = (Elf32_Addr *)(map->l_addr + reloc->r_offset);
  Elf32_Word loadbase, finaladdr;
  const int rinfo = ELF32_R_TYPE (reloc->r_info);

  if (rinfo == R_PPC_NONE)
    return;

  assert (sym != NULL);
  if (ELF32_ST_TYPE (sym->st_info) == STT_SECTION ||
      rinfo == R_PPC_RELATIVE)
    {
      /* Has already been relocated.  */
      loadbase = map->l_addr;
      finaladdr = loadbase + reloc->r_addend;
    }
  else
    {
      int flags;

      /* We never want to use a PLT entry as the destination of a
	 reloc, when what is being relocated is a branch. This is
	 partly for efficiency, but mostly so we avoid loops.  */
      if (rinfo == R_PPC_REL24 ||
	  rinfo == R_PPC_ADDR24 ||
	  rinfo == R_PPC_JMP_SLOT)
	flags = DL_LOOKUP_NOPLT;
      else if (rinfo == R_PPC_COPY)
	flags = DL_LOOKUP_NOEXEC;
      else
	flags = 0;

      loadbase = (Elf32_Word) (char *) (RESOLVE (&sym, version, flags));
      if (sym == NULL)
	{
	  /* Weak symbol that wasn't actually defined anywhere.  */
	  assert(loadbase == 0);
	  finaladdr = reloc->r_addend;
	}
      else
	finaladdr = (loadbase + (Elf32_Word) (char *) sym->st_value +
		     reloc->r_addend);
    }

  /* This is an if/else if chain because GCC 2.7.2.[012] turns case
     statements into non-PIC table lookups.  When a later version
     comes out that fixes this, this should be changed.  */
  if (rinfo == R_PPC_ADDR16_LO)
    {
      *(Elf32_Half*) reloc_addr = finaladdr;
    }
  else if (rinfo == R_PPC_ADDR16_HI)
    {
      *(Elf32_Half*) reloc_addr = finaladdr >> 16;
    }
  else if (rinfo == R_PPC_ADDR16_HA)
    {
      *(Elf32_Half*) reloc_addr = finaladdr + 0x8000 >> 16;
    }
  else if (rinfo == R_PPC_REL24)
    {
      Elf32_Sword delta = finaladdr - (Elf32_Word) (char *) reloc_addr;
      assert (delta << 6 >> 6 == delta);
      *reloc_addr = *reloc_addr & 0xfc000003 | delta & 0x3fffffc;
    }
  else if (rinfo == R_PPC_UADDR32 ||
      rinfo == R_PPC_GLOB_DAT ||
      rinfo == R_PPC_ADDR32 ||
      rinfo == R_PPC_RELATIVE)
    {
      *reloc_addr = finaladdr;
    }
  else if (rinfo == R_PPC_ADDR24)
    {
      assert (finaladdr << 6 >> 6 == finaladdr);
      *reloc_addr = *reloc_addr & 0xfc000003 | finaladdr & 0x3fffffc;
    }
  else if (rinfo == R_PPC_COPY)
    {
      /* Memcpy is safe to use here, because ld.so doesn't have any
	 COPY relocs (it's self-contained).  */
      memcpy (reloc_addr, (char *) finaladdr, sym->st_size);
    }
  else if (rinfo == R_PPC_REL32)
    {
      *reloc_addr = finaladdr - (Elf32_Word) (char *) reloc_addr;
    }
  else if (rinfo == R_PPC_JMP_SLOT)
    {
      Elf32_Sword delta = finaladdr - (Elf32_Word) (char *) reloc_addr;
      if (delta << 6 >> 6 == delta)
	*reloc_addr = OPCODE_B(delta);
      else if (finaladdr <= 0x01fffffc || finaladdr >= 0xfe000000)
	*reloc_addr = OPCODE_BA(finaladdr);
      else
	{
	  Elf32_Word *plt = (Elf32_Word *)((char *)map->l_addr +
					   map->l_info[DT_PLTGOT]->d_un.d_val);
	  Elf32_Word index = (reloc_addr - plt - PLT_INITIAL_ENTRY_WORDS)/2;
	  Elf32_Word offset = index * 2 + PLT_INITIAL_ENTRY_WORDS;

	  if (index >= PLT_DOUBLE_SIZE)
	    {
	     /* Slots greater than or equal to 2^13 have 4 words
		available instead of two.  */
	      plt[offset  ] = OPCODE_LI (11,finaladdr);
	      plt[offset+1] = OPCODE_ADDIS (11,11,finaladdr + 0x8000 >> 16);
	      plt[offset+2] = OPCODE_MTCTR (11);
	      plt[offset+3] = OPCODE_BCTR ();
	    }
	  else
	    {
	      Elf32_Word num_plt_entries;
	      Elf32_Word rel_offset_words;

	      num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
				 / sizeof(Elf32_Rela));
	      rel_offset_words = PLT_DATA_START_WORDS (num_plt_entries);

	      plt[offset  ] = OPCODE_LI (11,index * 4);
	      plt[offset+1] = OPCODE_B (-(4 * (offset + 1
					       - PLT_LONGBRANCH_ENTRY_WORDS)));
	      plt[index + rel_offset_words] = finaladdr;
	    }
	}
      MODIFIED_CODE(reloc_addr);
    }
  else
    assert (! "unexpected dynamic reloc type");

  if (rinfo == R_PPC_ADDR16_LO ||
      rinfo == R_PPC_ADDR16_HI ||
      rinfo == R_PPC_ADDR16_HA ||
      rinfo == R_PPC_REL24 ||
      rinfo == R_PPC_ADDR24)
    MODIFIED_CODE_NOQUEUE (reloc_addr);
}

#define ELF_MACHINE_NO_REL 1

#endif

/* Nonzero iff TYPE describes relocation of a PLT entry, so
   PLT entries should not be allowed to define the value.  */
#define elf_machine_pltrel_p(type) ((type) == R_PPC_JMP_SLOT)

/* Set up the loaded object described by L so its unrelocated PLT
   entries will jump to the on-demand fixup code in dl-runtime.c.  */
static inline void
elf_machine_runtime_setup (struct link_map *map, int lazy)
{
  if (map->l_info[DT_JMPREL])
    {
      int i;
      /* Fill in the PLT. Its initial contents are directed to a
	 function earlier in the PLT which arranges for the dynamic
	 linker to be called back.  */
      Elf32_Word *plt = (Elf32_Word *) ((char *) map->l_addr
					+ map->l_info[DT_PLTGOT]->d_un.d_val);
      Elf32_Word num_plt_entries = (map->l_info[DT_PLTRELSZ]->d_un.d_val
				    / sizeof (Elf32_Rela));
      Elf32_Word rel_offset_words = PLT_DATA_START_WORDS (num_plt_entries);
      extern void _dl_runtime_resolve (void);
      Elf32_Word size_modified;

      if (lazy)
	for (i = 0; i < num_plt_entries; i++)
	{
	  Elf32_Word offset = PLT_ENTRY_START_WORDS(i);

	  if (i >= PLT_DOUBLE_SIZE)
	    {
	      plt[offset	] = OPCODE_LI (11, i * 4);
	      plt[offset+1] = OPCODE_ADDIS (11, 11, i * 4 + 0x8000 >> 16);
	      plt[offset+2] = OPCODE_B (-(4 * (offset + 2)));
	    }
	  else
	    {
	      plt[offset	] = OPCODE_LI (11, i * 4);
	      plt[offset+1] = OPCODE_B(-(4 * (offset + 1)));
	    }

	  /* Multiply index of entry, by 0xC.  */
	  plt[0] = OPCODE_SLWI (12, 11, 1);
	  plt[1] = OPCODE_ADD (11, 12, 11);
	  if ((Elf32_Word) (char *) _dl_runtime_resolve <= 0x01fffffc
	      || (Elf32_Word) (char *) _dl_runtime_resolve >= 0xfe000000)
	    {
	      plt[2] = OPCODE_LI (12, (Elf32_Word) (char *) map);
	      plt[3] = OPCODE_ADDIS (12, 12,
				     (Elf32_Word) (char *) map + 0x8000 >> 16);
	      plt[4] = OPCODE_BA ((Elf32_Word) (char *) _dl_runtime_resolve);
	    }
	}
      else
	{
	  plt[2] = OPCODE_LI (12, (Elf32_Word) (char *) _dl_runtime_resolve);
	  plt[3] = OPCODE_ADDIS(12, 12, 0x8000 +
				((Elf32_Word) (char *) _dl_runtime_resolve
				 >> 16));
	  plt[4] = OPCODE_MTCTR (12);
	  plt[5] = OPCODE_LI (12, (Elf32_Word) (char *) map);
	  plt[6] = OPCODE_ADDIS (12, 12, ((Elf32_Word) (char *) map
					  + 0x8000 >> 16));
	  plt[7] = OPCODE_BCTR ();
	}
      plt[PLT_LONGBRANCH_ENTRY_WORDS] =
	OPCODE_ADDIS (11, 11, (Elf32_Word) (char*) (plt + rel_offset_words)
		      + 0x8000 >> 16);
      plt[PLT_LONGBRANCH_ENTRY_WORDS+1] =
	OPCODE_LWZ(11,(Elf32_Word)(char*)(plt+rel_offset_words),11);
      plt[PLT_LONGBRANCH_ENTRY_WORDS+2] = OPCODE_MTCTR (11);
      plt[PLT_LONGBRANCH_ENTRY_WORDS+3] = OPCODE_BCTR ();

      size_modified = lazy ? rel_offset_words : PLT_INITIAL_ENTRY_WORDS;
      /* Now we need to keep the caches in sync.  */
      for (i = 0; i < size_modified; i+=8)
	PPC_DCBST (plt + i);
      PPC_SYNC;
      for (i = 0; i < size_modified; i+=8)
	PPC_ICBI (plt + i);
      PPC_ISYNC;
    }
}

static inline void
elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
{
  assert (ELF32_R_TYPE (reloc->r_info) == R_PPC_JMP_SLOT);
  /* elf_machine_runtime_setup handles this. */
}

/* The PLT uses Elf32_Rela relocs.  */
#define elf_machine_relplt elf_machine_rela

  /* This code is used in dl-runtime.c to call the `fixup' function
     and then redirect to the address it returns. It is called
     from code built in the PLT by elf_machine_runtime_setup. */
#define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
	.section \".text\"
	.align 2
	.globl _dl_runtime_resolve
	.type _dl_runtime_resolve,@function
_dl_runtime_resolve:
 # We need to save the registers used to pass parameters.
 # We build a stack frame to put them in.
	stwu 1,-48(1)
	mflr 0
	stw 3,16(1)
	stw 4,20(1)
	stw 0,52(1)
	stw 5,24(1)
 # We also need to save some of the condition register fields.
	mfcr 0
	stw 6,28(1)
	stw 7,32(1)
	stw 8,36(1)
	stw 9,40(1)
	stw 10,44(1)
	stw 0,12(1)
 # The code that calls this has put parameters for `fixup' in r12 and r11.
	mr 3,12
	mr 4,11
	bl fixup
 # 'fixup' returns the address we want to branch to.
	mtctr 3
 # Put the registers back...
	lwz 0,52(1)
	lwz 10,44(1)
	lwz 9,40(1)
	mtlr 0
	lwz 0,12(1)
	lwz 8,36(1)
	lwz 7,32(1)
	lwz 6,28(1)
	mtcrf 0xFF,0
	lwz 5,24(1)
	lwz 4,20(1)
	lwz 3,16(1)
 # ...unwind the stack frame, and jump to the PLT entry we updated.
	addi 1,1,48
	bctr
0:
	.size	 _dl_runtime_resolve,0b-_dl_runtime_resolve
 # undo '.section text'.
	.previous
");

/* Initial entry point code for the dynamic linker.
   The C function `_dl_start' is the real entry point;
   its return value is the user program's entry point.	*/
#define RTLD_START \
asm ("\
	.text
	.align 2
	.globl _start
	.type _start,@function
_start:
 # We start with the following on the stack, from top:
 # argc (4 bytes)
 # arguments for program (terminated by NULL)
 # environment variables (terminated by NULL)
 # arguments for the program loader
 # FIXME: perhaps this should do the same trick as elf/start.c?

 # Call _dl_start with one parameter pointing at argc
	mr 3,1
 #  (we have to frob the stack pointer a bit to allow room for
 #   _dl_start to save the link register)
	li 4,0
	addi 1,1,-16
	stw 4,0(1)
	bl _dl_start@local

 # Now, we do our main work of calling initialisation procedures.
 # The ELF ABI doesn't say anything about parameters for these,
 # so we just pass argc, argv, and the environment.
 # Changing these is strongly discouraged (not least because argc is
 # passed by value!).

 #  put our GOT pointer in r31
	bl _GLOBAL_OFFSET_TABLE_-4@local
	mflr 31
 #  the address of _start in r30
	mr 30,3
 #  &_dl_argc in 29, &_dl_argv in 27, and _dl_default_scope in 28
	lwz 28,_dl_default_scope@got(31)
	lwz 29,_dl_argc@got(31)
	lwz 27,_dl_argv@got(31)
0:
 #  call initfunc = _dl_init_next(_dl_default_scope[2])
	lwz 3,8(28)
	bl _dl_init_next@plt
 # if initfunc is NULL, we exit the loop
	mr. 0,3
	beq 1f
 # call initfunc(_dl_argc, _dl_argv, _dl_argv+_dl_argc+1)
	mtlr 0
	lwz 3,0(29)
	lwz 4,0(27)
	slwi 5,3,2
	add 5,4,5
	addi 5,5,4
	blrl
 # and loop.
	b 0b
1:
 # Now, to conform to the ELF ABI, we have to:
 # pass argv (actually _dl_argv) in r4
	lwz 4,0(27)
 # pass argc (actually _dl_argc) in r3
	lwz 3,0(29)
 # pass envp (actually _dl_argv+_dl_argc+1) in r5
	slwi 5,3,2
	add 5,4,5
	addi 5,5,4
 # pass the auxilary vector in r6. This is passed just after _envp.
	addi 6,5,-4
2:	lwzu 0,4(6)
	cmpwi 1,0,0
	bne 2b
	addi 6,6,4
 # pass a termination function pointer (in this case _dl_fini) in r7
	lwz 7,_dl_fini@got(31)
 # now, call the start function in r30...
	mtctr 30
 # pass the stack pointer in r1 (so far so good), pointing to a NULL value
 # (this lets our startup code distinguish between a program linked statically,
 # which linux will call with argc on top of the stack which will hopefully
 # never be zero, and a dynamically linked program which will always have
 # a NULL on the top of the stack).
 # Take the opportunity to clear LR, so anyone who accidentally returns
 # from _start gets SEGV.
	li 0,0
	stw 0,0(1)
	mtlr 0
 # and also clear _dl_starting_up
	lwz 26,_dl_starting_up@got(31)
	stw 0,0(26)
 # go do it!
	bctr
0:
	.size	 _start,0b-_start
 # undo '.section text'.
	.previous
");

#define ELF_PREFERRED_ADDRESS_DATA					      \
static ElfW(Addr) _dl_preferred_address = 0;

#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref)		      \
( {									      \
   ElfW(Addr) prefd;							      \
   if (mapstartpref != 0 && _dl_preferred_address == 0)			      \
     _dl_preferred_address = mapstartpref;				      \
   if (mapstartpref != 0)						      \
     prefd = mapstartpref;						      \
   else if (_dl_preferred_address < maplength + 0x50000)		      \
     prefd = 0;								      \
   else									      \
     prefd = _dl_preferred_address =					      \
       ((_dl_preferred_address - maplength - 0x10000)			      \
	& ~(_dl_pagesize - 1));						      \
   prefd;								      \
} )

#define ELF_FIXED_ADDRESS(loader, mapstart)				      \
( {									      \
   if (mapstart != 0 && _dl_preferred_address < mapstart)		      \
     _dl_preferred_address = mapstart;					      \
} )

#define ELF_FIXUP_RETURNS_ADDRESS 1