about summary refs log tree commit diff
path: root/sysdeps/alpha/dl-machine.h
blob: cd4f86a69ca91fce1b3c9ec2c73421d5c228dfa1 (plain) (blame)
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
/* Machine-dependent ELF dynamic relocation inline functions.  Alpha version.
   Copyright (C) 1996, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Richard Henderson <rth@tamu.edu>.

   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.  */

/* This was written in the absence of an ABI -- don't expect
   it to remain unchanged.  */

#ifndef dl_machine_h
#define dl_machine_h 1

#define ELF_MACHINE_NAME "alpha"

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


/* Return nonzero iff E_MACHINE is compatible with the running host.  */
static inline int
elf_machine_matches_host (Elf64_Word e_machine)
{
  return e_machine == EM_ALPHA;
}

/* Return the link-time address of _DYNAMIC.  The multiple-got-capable
   linker no longer allocates the first .got entry for this.  But not to
   worry, no special tricks are needed.  */
static inline Elf64_Addr
elf_machine_dynamic (void)
{
#ifndef NO_AXP_MULTI_GOT_LD
  return (Elf64_Addr) &_DYNAMIC;
#else
  register Elf64_Addr *gp __asm__ ("$29");
  return gp[-4096];
#endif
}

/* Return the run-time load address of the shared object.  */
static inline Elf64_Addr
elf_machine_load_address (void)
{
  /* NOTE: While it is generally unfriendly to put data in the text
     segment, it is only slightly less so when the "data" is an
     instruction.  While we don't have to worry about GLD just yet, an
     optimizing linker might decide that our "data" is an unreachable
     instruction and throw it away -- with the right switches, DEC's
     linker will do this.  What ought to happen is we should add
     something to GAS to allow us access to the new GPREL_HI32/LO32
     relocation types stolen from OSF/1 3.0.  */
  /* This code relies on the fact that BRADDR relocations do not
     appear in dynamic relocation tables.  Not that that would be very
     useful anyway -- br/bsr has a 4MB range and the shared libraries
     are usually many many terabytes away.  */

  Elf64_Addr dot;
  long zero_disp;

  asm("br %0, 1f\n\t"
      ".weak __load_address_undefined\n\t"
      "br $0, __load_address_undefined\n"
      "1:"
      : "=r"(dot));

  zero_disp = *(int *)dot;
  zero_disp = (zero_disp << 43) >> 41;

  return dot + 4 + zero_disp;
}

/* 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 int
elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
{
  Elf64_Addr plt;
  extern void _dl_runtime_resolve (void);
  extern void _dl_runtime_profile (void);

  if (l->l_info[DT_JMPREL] && lazy)
    {
      /* The GOT entries for the functions in the PLT have not been
	 filled in yet.  Their initial contents are directed to the
	 PLT which arranges for the dynamic linker to be called.  */
      plt = l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr;

      /* This function will be called to perform the relocation.  */
      if (!profile)
        *(Elf64_Addr *)(plt + 16) = (Elf64_Addr) &_dl_runtime_resolve;
      else
	{
	  *(Elf64_Addr *)(plt + 16) = (Elf64_Addr) &_dl_runtime_profile;
	  /* Say that we really want profiling and the timers are started.  */
	  _dl_profile_map = l;
	}

      /* Identify this shared object */
      *(Elf64_Addr *)(plt + 24) = (Elf64_Addr) l;

      /* If the first instruction of the plt entry is not
	 "br $28, plt0", we cannot do lazy relocation.  */
      lazy = (*(unsigned *)(plt + 32) == 0xc39ffff7);
    }

  return lazy;
}

/* This code is used in dl-runtime.c to call the `fixup' function
   and then redirect to the address it returns.  */
#define TRAMPOLINE_TEMPLATE(tramp_name, fixup_name, IMB) asm ( "\
	.globl " #tramp_name "
	.ent " #tramp_name "
" #tramp_name ":
	lda	$sp, -168($sp)
	.frame	$sp, 168, $26
	/* Preserve all registers that C normally doesn't.  */
	stq	$26, 0($sp)
	stq	$0, 8($sp)
	stq	$1, 16($sp)
	stq	$2, 24($sp)
	stq	$3, 32($sp)
	stq	$4, 40($sp)
	stq	$5, 48($sp)
	stq	$6, 56($sp)
	stq	$7, 64($sp)
	stq	$8, 72($sp)
	stq	$16, 80($sp)
	stq	$17, 88($sp)
	stq	$18, 96($sp)
	stq	$19, 104($sp)
	stq	$20, 112($sp)
	stq	$21, 120($sp)
	stq	$22, 128($sp)
	stq	$23, 136($sp)
	stq	$24, 144($sp)
	stq	$25, 152($sp)
	stq	$29, 160($sp)
	.mask	0x27ff01ff, -168
	/* Set up our $gp */
	br	$gp, .+4
	ldgp	$gp, 0($gp)
	.prologue 1
	/* Set up the arguments for fixup: */
	/* $16 = link_map out of plt0 */
	/* $17 = offset of reloc entry = ($28 - $27 - 20) /12 * 24 */
	/* $18 = return address */
	subq	$28, $27, $17
	ldq	$16, 8($27)
	subq	$17, 20, $17
	mov	$26, $18
	addq	$17, $17, $17
	/* Do the fixup */
	bsr	$26, " ASM_ALPHA_NG_SYMBOL_PREFIX #fixup_name "..ng
	/* Move the destination address into position.  */
	mov	$0, $27
	/* Restore program registers.  */
	ldq	$26, 0($sp)
	ldq	$0, 8($sp)
	ldq	$1, 16($sp)
	ldq	$2, 24($sp)
	ldq	$3, 32($sp)
	ldq	$4, 40($sp)
	ldq	$5, 48($sp)
	ldq	$6, 56($sp)
	ldq	$7, 64($sp)
	ldq	$8, 72($sp)
	ldq	$16, 80($sp)
	ldq	$17, 88($sp)
	ldq	$18, 96($sp)
	ldq	$19, 104($sp)
	ldq	$20, 112($sp)
	ldq	$21, 120($sp)
	ldq	$22, 128($sp)
	ldq	$23, 136($sp)
	ldq	$24, 144($sp)
	ldq	$25, 152($sp)
	ldq	$29, 160($sp)
	/* Flush the Icache after having modified the .plt code.  */
	" #IMB "
	/* Clean up and turn control to the destination */
	lda	$sp, 168($sp)
	jmp	$31, ($27)
	.end " #tramp_name)

#ifndef PROF
#define ELF_MACHINE_RUNTIME_TRAMPOLINE 				\
  TRAMPOLINE_TEMPLATE (_dl_runtime_resolve, fixup, imb);	\
  TRAMPOLINE_TEMPLATE (_dl_runtime_profile, profile_fixup, #nop);
#else
#define ELF_MACHINE_RUNTIME_TRAMPOLINE				\
  TRAMPOLINE_TEMPLATE (_dl_runtime_resolve, fixup, imb);	\
  strong_alias (_dl_runtime_resolve, _dl_runtime_profile, #nop);
#endif

/* 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
	.globl _start
	.ent _start
_start:
	br	$gp, 0f
0:	ldgp	$gp, 0($gp)
	/* Pass pointer to argument block to _dl_start.  */
	mov	$sp, $16
	bsr	$26, "ASM_ALPHA_NG_SYMBOL_PREFIX"_dl_start..ng
	.end _start
	/* FALLTHRU */
	.globl _dl_start_user
	.ent _dl_start_user
_dl_start_user:
	/* Save the user entry point address in s0.  */
	mov	$0, $9
	/* See if we were run as a command with the executable file
	   name as an extra leading argument.  If so, adjust the stack
	   pointer to skip _dl_skip_args words.  */
	ldl	$1, _dl_skip_args
	beq	$1, 0f
	ldq	$2, 0($sp)
	subq	$2, $1, $2
	s8addq	$1, $sp, $sp
	stq	$2, 0($sp)
	/* Load _dl_default_scope[2] into s1 to pass to _dl_init_next.  */
0:	ldq	$10, _dl_default_scope+16
	/* Call _dl_init_next to return the address of an initializer
	   function to run.  */
1:	mov	$10, $16
	jsr	$26, _dl_init_next
	ldgp	$gp, 0($26)
	beq	$0, 2f
	mov	$0, $27
	jsr	$26, ($0)
	ldgp	$gp, 0($26)
	br	1b
2:	/* Clear the startup flag.  */
	.set at
	stl	$31, _dl_starting_up
	.set noat
	/* Pass our finalizer function to the user in $0. */
	lda	$0, _dl_fini
	/* Jump to the user's entry point.  */
	mov	$9, $27
	jmp	($9)
	.end _dl_start_user
.previous");

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

/* Nonzero iff TYPE should not be allowed to resolve to one of
   the main executable's symbols, as for a COPY reloc, which we don't use.  */
#define elf_machine_lookup_noexec_p(type)  (0)

/* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
#define ELF_MACHINE_JMP_SLOT	 R_ALPHA_JMP_SLOT

/* The alpha never uses Elf64_Rel relocations.  */
#define ELF_MACHINE_NO_REL 1

/* Fix up the instructions of a PLT entry to invoke the function
   rather than the dynamic linker.  */
static inline void
elf_machine_fixup_plt(struct link_map *l, const Elf64_Rela *reloc,
		      Elf64_Addr *got_addr, Elf64_Addr value)
{
  const Elf64_Rela *rela_plt;
  Elf64_Word *plte;
  long edisp;

  /* Store the value we are going to load.  */
  *got_addr = value;

  /* Recover the PLT entry address by calculating reloc's index into the
     .rela.plt, and finding that entry in the .plt.  */
  rela_plt = (void *)(l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr);
  plte = (void *)(l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr + 32);
  plte += 3 * (reloc - rela_plt);

  /* Find the displacement from the plt entry to the function.  */
  edisp = (long)(value - (Elf64_Addr)&plte[3]) / 4;

  if (edisp >= -0x100000 && edisp < 0x100000)
    {
      /* If we are in range, use br to perfect branch prediction and
	 elide the dependency on the address load.  This case happens,
	 e.g., when a shared library call is resolved to the same library.  */

      int hi, lo;
      hi = value - (Elf64_Addr)&plte[0];
      lo = (short)hi;
      hi = (hi - lo) >> 16;

      /* Emit "lda $27,lo($27)" */
      plte[1] = 0x237b0000 | (lo & 0xffff);

      /* Emit "br $31,function" */
      plte[2] = 0xc3e00000 | (edisp & 0x1fffff);

      /* Think about thread-safety -- the previous instructions must be
	 committed to memory before the first is overwritten.  */
      __asm__ __volatile__("wmb" : : : "memory");

      /* Emit "ldah $27,hi($27)" */
      plte[0] = 0x277b0000 | (hi & 0xffff);
    }
  else
    {
      /* Don't bother with the hint since we already know the hint is
	 wrong.  Eliding it prevents the wrong page from getting pulled
	 into the cache.  */

      int hi, lo;
      hi = (Elf64_Addr)got_addr - (Elf64_Addr)&plte[0];
      lo = (short)hi;
      hi = (hi - lo) >> 16;

      /* Emit "ldq $27,lo($27)" */
      plte[1] = 0xa77b0000 | (lo & 0xffff);

      /* Emit "jmp $31,($27)" */
      plte[2] = 0x6bfb0000;

      /* Think about thread-safety -- the previous instructions must be
	 committed to memory before the first is overwritten.  */
      __asm__ __volatile__("wmb" : : : "memory");

      /* Emit "ldah $27,hi($27)" */
      plte[0] = 0x277b0000 | (hi & 0xffff);
    }

  /* At this point, if we've been doing runtime resolution, Icache is dirty.
     This will be taken care of in _dl_runtime_resolve.  If instead we are
     doing this as part of non-lazy startup relocation, that bit of code
     hasn't made it into Icache yet, so there's nothing to clean up.  */
}

/* Return the final value of a plt relocation.  */
static inline Elf64_Addr
elf_machine_plt_value (struct link_map *map, const Elf64_Rela *reloc,
		       Elf64_Addr value)
{
  return value + reloc->r_addend;
}

#endif /* !dl_machine_h */

#ifdef RESOLVE

/* Perform the relocation specified by RELOC and SYM (which is fully resolved).
   MAP is the object containing the reloc.  */
static inline void
elf_machine_rela (struct link_map *map,
		  const Elf64_Rela *reloc,
		  const Elf64_Sym *sym,
		  const struct r_found_version *version,
		  Elf64_Addr *const reloc_addr)
{
  unsigned long const r_type = ELF64_R_TYPE (reloc->r_info);

#ifndef RTLD_BOOTSTRAP
  /* This is defined in rtld.c, but nowhere in the static libc.a; make the
     reference weak so static programs can still link.  This declaration
     cannot be done when compiling rtld.c (i.e.  #ifdef RTLD_BOOTSTRAP)
     because rtld.c contains the common defn for _dl_rtld_map, which is
     incompatible with a weak decl in the same file.  */
  weak_extern (_dl_rtld_map);
#endif

  /* We cannot use a switch here because we cannot locate the switch
     jump table until we've self-relocated.  */

  if (r_type == R_ALPHA_RELATIVE)
    {
#ifndef RTLD_BOOTSTRAP
      /* Already done in dynamic linker.  */
      if (map != &_dl_rtld_map)
#endif
	*reloc_addr += map->l_addr;
    }
  else if (r_type == R_ALPHA_NONE)
    return;
  else
    {
      Elf64_Addr loadbase, sym_value;

      loadbase = RESOLVE (&sym, version, r_type);
      sym_value = sym ? loadbase + sym->st_value : 0;
      sym_value += reloc->r_addend;

      if (r_type == R_ALPHA_GLOB_DAT)
	*reloc_addr = sym_value;
      else if (r_type == R_ALPHA_JMP_SLOT)
	elf_machine_fixup_plt (map, reloc, reloc_addr, sym_value);
      else if (r_type == R_ALPHA_REFQUAD)
	{
	  sym_value += *reloc_addr;
#ifndef RTLD_BOOTSTRAP
	  if (map == &_dl_rtld_map)
	    {
	      /* Undo the relocation done here during bootstrapping.
		 Now we will relocate anew, possibly using a binding
		 found in the user program or a loaded library rather
		 than the dynamic linker's built-in definitions used
		 while loading those libraries.  */
	      const Elf64_Sym *const dlsymtab
		= (void *)(map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr);
	      sym_value -= map->l_addr;
	      sym_value -= dlsymtab[ELF64_R_SYM(reloc->r_info)].st_value;
	      sym_value -= reloc->r_addend;
	    }
#endif
	  *reloc_addr = sym_value;
	}
      else
	assert (! "unexpected dynamic reloc type");
    }
}

static inline void
elf_machine_lazy_rel (struct link_map *map, const Elf64_Rela *reloc)
{
  Elf64_Addr * const reloc_addr = (void *)(map->l_addr + reloc->r_offset);
  unsigned long const r_type = ELF64_R_TYPE (reloc->r_info);

  if (r_type == R_ALPHA_JMP_SLOT)
    {
      /* Perform a RELATIVE reloc on the .got entry that transfers
	 to the .plt.  */
      *reloc_addr += map->l_addr;
    }
  else if (r_type == R_ALPHA_NONE)
    return;
  else
    assert (! "unexpected PLT reloc type");
}

#endif /* RESOLVE */