about summary refs log tree commit diff
path: root/sysdeps/powerpc/dl-machine.h
blob: 0307a2924a2f9011493ec6dcebd2da43714d8fab (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
/* Machine-dependent ELF dynamic relocation inline functions.  PowerPC version.
   Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000 
   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.  */

#ifndef dl_machine_h
#define dl_machine_h

#define ELF_MACHINE_NAME "powerpc"

#include <assert.h>

/* 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 int *got;
  unsigned int *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
	  + ((int)(*branchaddr << 6 & 0xffffff00) >> 6));
}

#define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) /* nothing */

/* 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, and register 0,
 # which is used by _mcount; the registers are saved in a stack frame.
	stwu 1,-64(1)
	stw 0,12(1)
	stw 3,16(1)
	stw 4,20(1)
 # The code that calls this has put parameters for `fixup' in r12 and r11.
	mr 3,12
	stw 5,24(1)
	mr 4,11
	stw 6,28(1)
	mflr 0
 # We also need to save some of the condition register fields.
	stw 7,32(1)
	stw 0,48(1)
	stw 8,36(1)
	mfcr 0
	stw 9,40(1)
	stw 10,44(1)
	stw 0,8(1)
	bl fixup@local
 # 'fixup' returns the address we want to branch to.
	mtctr 3
 # Put the registers back...
	lwz 0,48(1)
	lwz 10,44(1)
	lwz 9,40(1)
	mtlr 0
	lwz 8,36(1)
	lwz 0,8(1)
	lwz 7,32(1)
	lwz 6,28(1)
	mtcrf 0xFF,0
	lwz 5,24(1)
	lwz 4,20(1)
	lwz 3,16(1)
	lwz 0,12(1)
 # ...unwind the stack frame, and jump to the PLT entry we updated.
	addi 1,1,64
	bctr
	.size	 _dl_runtime_resolve,.-_dl_runtime_resolve

	.align 2
	.globl _dl_prof_resolve
	.type _dl_prof_resolve,@function
_dl_prof_resolve:
 # We need to save the registers used to pass parameters, and register 0,
 # which is used by _mcount; the registers are saved in a stack frame.
	stwu 1,-64(1)
        stw 0,12(1)
	stw 3,16(1)
	stw 4,20(1)
 # The code that calls this has put parameters for `fixup' in r12 and r11.
	mr 3,12
	stw 5,24(1)
	mr 4,11
	stw 6,28(1)
	mflr 5
 # We also need to save some of the condition register fields.
	stw 7,32(1)
	stw 5,48(1)
	stw 8,36(1)
	mfcr 0
	stw 9,40(1)
	stw 10,44(1)
	stw 0,8(1)
	bl profile_fixup@local
 # 'fixup' returns the address we want to branch to.
	mtctr 3
 # Put the registers back...
	lwz 0,48(1)
	lwz 10,44(1)
	lwz 9,40(1)
	mtlr 0
	lwz 8,36(1)
	lwz 0,8(1)
	lwz 7,32(1)
	lwz 6,28(1)
	mtcrf 0xFF,0
	lwz 5,24(1)
	lwz 4,20(1)
	lwz 3,16(1)
        lwz 0,12(1)
 # ...unwind the stack frame, and jump to the PLT entry we updated.
	addi 1,1,64
	bctr
	.size	 _dl_prof_resolve,.-_dl_prof_resolve
 # Undo '.section text'.
	.previous
");

/* The actual _start code is in dl-start.S.  Use a really
   ugly bit of assembler to let dl-start.o see _dl_start.  */
#define RTLD_START asm (".globl _dl_start");

/* Decide where a relocatable object should be loaded.  */
extern ElfW(Addr)
__elf_preferred_address(struct link_map *loader, size_t maplength,
			ElfW(Addr) mapstartpref);
#define ELF_PREFERRED_ADDRESS(loader, maplength, mapstartpref) \
  __elf_preferred_address (loader, maplength, mapstartpref)

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

/* Nonzero iff TYPE describes relocation of a PLT entry, so
   PLT entries should not be allowed to define the value.  */
/* 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.  */
#define elf_machine_lookup_noplt_p(type) ((type) == R_PPC_REL24 ||            \
					  (type) == R_PPC_ADDR24 ||           \
					  (type) == R_PPC_JMP_SLOT)

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

/* 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.
   Also install a small trampoline to be used by entries that have
   been relocated to an address too far away for a single branch.  */
extern int __elf_machine_runtime_setup (struct link_map *map,
					int lazy, int profile);
#define elf_machine_runtime_setup __elf_machine_runtime_setup

static inline void
elf_machine_lazy_rel (struct link_map *map,
		      Elf32_Addr l_addr, const Elf32_Rela *reloc)
{
  /* elf_machine_runtime_setup handles this. */
}

/* Change the PLT entry whose reloc is 'reloc' to call the actual routine.  */
extern Elf32_Addr __elf_machine_fixup_plt (struct link_map *map,
					   const Elf32_Rela *reloc,
					   Elf32_Addr *reloc_addr,
					   Elf32_Addr finaladdr);

static inline Elf32_Addr
elf_machine_fixup_plt (struct link_map *map, lookup_t t,
		       const Elf32_Rela *reloc,
		       Elf32_Addr *reloc_addr, Elf64_Addr finaladdr)
{
  return __elf_machine_fixup_plt (map, reloc, reloc_addr, finaladdr);
}

/* Return the final value of a plt relocation.  */
static inline Elf32_Addr
elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
		       Elf32_Addr value)
{
  return value + reloc->r_addend;
}

#endif /* dl_machine_h */

#ifdef RESOLVE

/* Do the actual processing of a reloc, once its target address
   has been determined.  */
extern void __process_machine_rela (struct link_map *map,
				    const Elf32_Rela *reloc,
				    const Elf32_Sym *sym,
				    const Elf32_Sym *refsym,
				    Elf32_Addr *const reloc_addr,
				    Elf32_Addr finaladdr,
				    int rinfo);

/* 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.  */

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)
{
  const Elf32_Sym *const refsym = sym;
  Elf32_Word loadbase, finaladdr;
  const int rinfo = ELF32_R_TYPE (reloc->r_info);

  if (rinfo == R_PPC_NONE)
    return;

  /* The condition on the next two lines is a hack around a bug in Solaris
     tools on Sparc.  It's not clear whether it should really be here at all,
     but if not the binutils need to be changed.  */
  if (rinfo == R_PPC_RELATIVE
      || (sym->st_shndx != SHN_UNDEF
	  && ELF32_ST_BIND (sym->st_info) == STB_LOCAL))
    {
      /* Has already been relocated.  */
      loadbase = map->l_addr;
      finaladdr = loadbase + reloc->r_addend;
    }
  else
    {
      loadbase = (Elf32_Word) (char *) (RESOLVE (&sym, version,
						 ELF32_R_TYPE(reloc->r_info)));
      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);
    }

  /* A small amount of code is duplicated here for speed.  In libc,
     more than 90% of the relocs are R_PPC_RELATIVE; in the X11 shared
     libraries, 60% are R_PPC_RELATIVE, 24% are R_PPC_GLOB_DAT or
     R_PPC_ADDR32, and 16% are R_PPC_JMP_SLOT (which this routine
     wouldn't usually handle).  As an bonus, doing this here allows
     the switch statement in __process_machine_rela to work.  */
  if (rinfo == R_PPC_RELATIVE
      || rinfo == R_PPC_GLOB_DAT
      || rinfo == R_PPC_ADDR32)
    {
      *reloc_addr = finaladdr;
    }
  else
    __process_machine_rela (map, reloc, sym, refsym,
			    reloc_addr, finaladdr, rinfo);
}

#define ELF_MACHINE_NO_REL 1

/* The SVR4 ABI specifies that the JMPREL relocs must be inside the
   DT_RELA table.  */
#define ELF_MACHINE_PLTREL_OVERLAP 1

#endif /* RESOLVE */