1 /* BFD support for handling relocation entries.
2 Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
3 Written by Cygnus Support.
5 This file is part of BFD, the Binary File Descriptor library.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
25 BFD maintains relocations in much the same way it maintains
26 symbols: they are left alone until required, then read in
27 en-mass and translated into an internal form. A common
28 routine <<bfd_perform_relocation>> acts upon the
29 canonical form to do the fixup.
31 Relocations are maintained on a per section basis,
32 while symbols are maintained on a per BFD basis.
34 All that a back end has to do to fit the BFD interface is to create
35 a <<struct reloc_cache_entry>> for each relocation
36 in a particular section, and fill in the right bits of the structures.
51 typedef arelent, howto manager, Relocations, Relocations
56 This is the structure of a relocation entry:
60 .typedef enum bfd_reloc_status
62 . {* No errors detected *}
65 . {* The relocation was performed, but there was an overflow. *}
68 . {* The address to relocate was not within the section supplied. *}
69 . bfd_reloc_outofrange,
71 . {* Used by special functions *}
74 . {* Unsupported relocation size requested. *}
75 . bfd_reloc_notsupported,
80 . {* The symbol to relocate against was undefined. *}
81 . bfd_reloc_undefined,
83 . {* The relocation was performed, but may not be ok - presently
84 . generated only when linking i960 coff files with i960 b.out
85 . symbols. If this type is returned, the error_message argument
86 . to bfd_perform_relocation will be set. *}
89 . bfd_reloc_status_type;
92 .typedef struct reloc_cache_entry
94 . {* A pointer into the canonical table of pointers *}
95 . struct symbol_cache_entry **sym_ptr_ptr;
97 . {* offset in section *}
98 . bfd_size_type address;
100 . {* addend for relocation value *}
103 . {* Pointer to how to perform the required relocation *}
104 . const struct reloc_howto_struct *howto;
113 Here is a description of each of the fields within an <<arelent>>:
117 The symbol table pointer points to a pointer to the symbol
118 associated with the relocation request. It is
119 the pointer into the table returned by the back end's
120 <<get_symtab>> action. @xref{Symbols}. The symbol is referenced
121 through a pointer to a pointer so that tools like the linker
122 can fix up all the symbols of the same name by modifying only
123 one pointer. The relocation routine looks in the symbol and
124 uses the base of the section the symbol is attached to and the
125 value of the symbol as the initial relocation offset. If the
126 symbol pointer is zero, then the section provided is looked up.
130 The <<address>> field gives the offset in bytes from the base of
131 the section data which owns the relocation record to the first
132 byte of relocatable information. The actual data relocated
133 will be relative to this point; for example, a relocation
134 type which modifies the bottom two bytes of a four byte word
135 would not touch the first byte pointed to in a big endian
140 The <<addend>> is a value provided by the back end to be added (!)
141 to the relocation offset. Its interpretation is dependent upon
142 the howto. For example, on the 68k the code:
148 | return foo[0x12345678];
151 Could be compiled into:
154 | moveb @@#12345678,d0
160 This could create a reloc pointing to <<foo>>, but leave the
161 offset in the data, something like:
164 |RELOCATION RECORDS FOR [.text]:
168 |00000000 4e56 fffc ; linkw fp,#-4
169 |00000004 1039 1234 5678 ; moveb @@#12345678,d0
170 |0000000a 49c0 ; extbl d0
171 |0000000c 4e5e ; unlk fp
175 Using coff and an 88k, some instructions don't have enough
176 space in them to represent the full address range, and
177 pointers have to be loaded in two parts. So you'd get something like:
180 | or.u r13,r0,hi16(_foo+0x12345678)
181 | ld.b r2,r13,lo16(_foo+0x12345678)
185 This should create two relocs, both pointing to <<_foo>>, and with
186 0x12340000 in their addend field. The data would consist of:
189 |RELOCATION RECORDS FOR [.text]:
191 |00000002 HVRT16 _foo+0x12340000
192 |00000006 LVRT16 _foo+0x12340000
194 |00000000 5da05678 ; or.u r13,r0,0x5678
195 |00000004 1c4d5678 ; ld.b r2,r13,0x5678
196 |00000008 f400c001 ; jmp r1
199 The relocation routine digs out the value from the data, adds
200 it to the addend to get the original offset, and then adds the
201 value of <<_foo>>. Note that all 32 bits have to be kept around
202 somewhere, to cope with carry from bit 15 to bit 16.
204 One further example is the sparc and the a.out format. The
205 sparc has a similar problem to the 88k, in that some
206 instructions don't have room for an entire offset, but on the
207 sparc the parts are created in odd sized lumps. The designers of
208 the a.out format chose to not use the data within the section
209 for storing part of the offset; all the offset is kept within
210 the reloc. Anything in the data should be ignored.
213 | sethi %hi(_foo+0x12345678),%g2
214 | ldsb [%g2+%lo(_foo+0x12345678)],%i0
218 Both relocs contain a pointer to <<foo>>, and the offsets
222 |RELOCATION RECORDS FOR [.text]:
224 |00000004 HI22 _foo+0x12345678
225 |00000008 LO10 _foo+0x12345678
227 |00000000 9de3bf90 ; save %sp,-112,%sp
228 |00000004 05000000 ; sethi %hi(_foo+0),%g2
229 |00000008 f048a000 ; ldsb [%g2+%lo(_foo+0)],%i0
230 |0000000c 81c7e008 ; ret
231 |00000010 81e80000 ; restore
236 The <<howto>> field can be imagined as a
237 relocation instruction. It is a pointer to a structure which
238 contains information on what to do with all of the other
239 information in the reloc record and data section. A back end
240 would normally have a relocation instruction set and turn
241 relocations into pointers to the correct structure on input -
242 but it would be possible to create each howto field on demand.
248 <<enum complain_overflow>>
250 Indicates what sort of overflow checking should be done when
251 performing a relocation.
255 .enum complain_overflow
257 . {* Do not complain on overflow. *}
258 . complain_overflow_dont,
260 . {* Complain if the bitfield overflows, whether it is considered
261 . as signed or unsigned. *}
262 . complain_overflow_bitfield,
264 . {* Complain if the value overflows when considered as signed
266 . complain_overflow_signed,
268 . {* Complain if the value overflows when considered as an
269 . unsigned number. *}
270 . complain_overflow_unsigned
279 The <<reloc_howto_type>> is a structure which contains all the
280 information that libbfd needs to know to tie up a back end's data.
283 .struct symbol_cache_entry; {* Forward declaration *}
285 .typedef struct reloc_howto_struct
287 . {* The type field has mainly a documetary use - the back end can
288 . do what it wants with it, though normally the back end's
289 . external idea of what a reloc number is stored
290 . in this field. For example, a PC relative word relocation
291 . in a coff environment has the type 023 - because that's
292 . what the outside world calls a R_PCRWORD reloc. *}
295 . {* The value the final relocation is shifted right by. This drops
296 . unwanted data from the relocation. *}
297 . unsigned int rightshift;
299 . {* The size of the item to be relocated. This is *not* a
300 . power-of-two measure. To get the number of bytes operated
301 . on by a type of relocation, use bfd_get_reloc_size. *}
304 . {* The number of bits in the item to be relocated. This is used
305 . when doing overflow checking. *}
306 . unsigned int bitsize;
308 . {* Notes that the relocation is relative to the location in the
309 . data section of the addend. The relocation function will
310 . subtract from the relocation value the address of the location
311 . being relocated. *}
312 . boolean pc_relative;
314 . {* The bit position of the reloc value in the destination.
315 . The relocated value is left shifted by this amount. *}
316 . unsigned int bitpos;
318 . {* What type of overflow error should be checked for when
320 . enum complain_overflow complain_on_overflow;
322 . {* If this field is non null, then the supplied function is
323 . called rather than the normal function. This allows really
324 . strange relocation methods to be accomodated (e.g., i960 callj
326 . bfd_reloc_status_type (*special_function)
327 . PARAMS ((bfd *abfd,
328 . arelent *reloc_entry,
329 . struct symbol_cache_entry *symbol,
331 . asection *input_section,
333 . char **error_message));
335 . {* The textual name of the relocation type. *}
338 . {* When performing a partial link, some formats must modify the
339 . relocations rather than the data - this flag signals this.*}
340 . boolean partial_inplace;
342 . {* The src_mask selects which parts of the read in data
343 . are to be used in the relocation sum. E.g., if this was an 8 bit
344 . bit of data which we read and relocated, this would be
345 . 0x000000ff. When we have relocs which have an addend, such as
346 . sun4 extended relocs, the value in the offset part of a
347 . relocating field is garbage so we never use it. In this case
348 . the mask would be 0x00000000. *}
351 . {* The dst_mask selects which parts of the instruction are replaced
352 . into the instruction. In most cases src_mask == dst_mask,
353 . except in the above special case, where dst_mask would be
354 . 0x000000ff, and src_mask would be 0x00000000. *}
357 . {* When some formats create PC relative instructions, they leave
358 . the value of the pc of the place being relocated in the offset
359 . slot of the instruction, so that a PC relative relocation can
360 . be made just by adding in an ordinary offset (e.g., sun3 a.out).
361 . Some formats leave the displacement part of an instruction
362 . empty (e.g., m88k bcs); this flag signals the fact.*}
363 . boolean pcrel_offset;
374 The HOWTO define is horrible and will go away.
377 .#define HOWTO(C, R,S,B, P, BI, O, SF, NAME, INPLACE, MASKSRC, MASKDST, PC) \
378 . {(unsigned)C,R,S,B, P, BI, O,SF,NAME,INPLACE,MASKSRC,MASKDST,PC}
381 And will be replaced with the totally magic way. But for the
382 moment, we are compatible, so do it this way.
385 .#define NEWHOWTO( FUNCTION, NAME,SIZE,REL,IN) HOWTO(0,0,SIZE,0,REL,0,complain_overflow_dont,FUNCTION, NAME,false,0,0,IN)
388 Helper routine to turn a symbol into a relocation value.
390 .#define HOWTO_PREPARE(relocation, symbol) \
392 . if (symbol != (asymbol *)NULL) { \
393 . if (bfd_is_com_section (symbol->section)) { \
397 . relocation = symbol->value; \
409 int bfd_get_reloc_size (const reloc_howto_type *);
412 For a reloc_howto_type that operates on a fixed number of bytes,
413 this returns the number of bytes operated on.
417 bfd_get_reloc_size (howto)
418 const reloc_howto_type *howto;
438 How relocs are tied together in an <<asection>>:
440 .typedef unsigned char bfd_byte;
442 .typedef struct relent_chain {
444 . struct relent_chain *next;
453 bfd_perform_relocation
456 bfd_reloc_status_type
457 bfd_perform_relocation
459 arelent *reloc_entry,
461 asection *input_section,
463 char **error_message);
466 If @var{output_bfd} is supplied to this function, the
467 generated image will be relocatable; the relocations are
468 copied to the output file after they have been changed to
469 reflect the new state of the world. There are two ways of
470 reflecting the results of partial linkage in an output file:
471 by modifying the output data in place, and by modifying the
472 relocation record. Some native formats (e.g., basic a.out and
473 basic coff) have no way of specifying an addend in the
474 relocation type, so the addend has to go in the output data.
475 This is no big deal since in these formats the output data
476 slot will always be big enough for the addend. Complex reloc
477 types with addends were invented to solve just this problem.
478 The @var{error_message} argument is set to an error message if
479 this return @code{bfd_reloc_dangerous}.
484 bfd_reloc_status_type
485 bfd_perform_relocation (abfd, reloc_entry, data, input_section, output_bfd,
488 arelent *reloc_entry;
490 asection *input_section;
492 char **error_message;
495 bfd_reloc_status_type flag = bfd_reloc_ok;
496 bfd_size_type addr = reloc_entry->address;
497 bfd_vma output_base = 0;
498 const reloc_howto_type *howto = reloc_entry->howto;
499 asection *reloc_target_output_section;
502 symbol = *(reloc_entry->sym_ptr_ptr);
503 if ((symbol->section == &bfd_abs_section)
504 && output_bfd != (bfd *) NULL)
506 reloc_entry->address += input_section->output_offset;
510 /* If we are not producing relocateable output, return an error if
511 the symbol is not defined. An undefined weak symbol is
512 considered to have a value of zero (SVR4 ABI, p. 4-27). */
513 if (symbol->section == &bfd_und_section
514 && (symbol->flags & BSF_WEAK) == 0
515 && output_bfd == (bfd *) NULL)
516 flag = bfd_reloc_undefined;
518 /* If there is a function supplied to handle this relocation type,
519 call it. It'll return `bfd_reloc_continue' if further processing
521 if (howto->special_function)
523 bfd_reloc_status_type cont;
524 cont = howto->special_function (abfd, reloc_entry, symbol, data,
525 input_section, output_bfd,
527 if (cont != bfd_reloc_continue)
531 /* Is the address of the relocation really within the section? */
532 if (reloc_entry->address > input_section->_cooked_size)
533 return bfd_reloc_outofrange;
535 /* Work out which section the relocation is targetted at and the
536 initial relocation command value. */
538 /* Get symbol value. (Common symbols are special.) */
539 if (bfd_is_com_section (symbol->section))
542 relocation = symbol->value;
545 reloc_target_output_section = symbol->section->output_section;
547 /* Convert input-section-relative symbol value to absolute. */
548 if (output_bfd && howto->partial_inplace == false)
551 output_base = reloc_target_output_section->vma;
553 relocation += output_base + symbol->section->output_offset;
555 /* Add in supplied addend. */
556 relocation += reloc_entry->addend;
558 /* Here the variable relocation holds the final address of the
559 symbol we are relocating against, plus any addend. */
561 if (howto->pc_relative == true)
563 /* This is a PC relative relocation. We want to set RELOCATION
564 to the distance between the address of the symbol and the
565 location. RELOCATION is already the address of the symbol.
567 We start by subtracting the address of the section containing
570 If pcrel_offset is set, we must further subtract the position
571 of the location within the section. Some targets arrange for
572 the addend to be the negative of the position of the location
573 within the section; for example, i386-aout does this. For
574 i386-aout, pcrel_offset is false. Some other targets do not
575 include the position of the location; for example, m88kbcs,
576 or ELF. For those targets, pcrel_offset is true.
578 If we are producing relocateable output, then we must ensure
579 that this reloc will be correctly computed when the final
580 relocation is done. If pcrel_offset is false we want to wind
581 up with the negative of the location within the section,
582 which means we must adjust the existing addend by the change
583 in the location within the section. If pcrel_offset is true
584 we do not want to adjust the existing addend at all.
586 FIXME: This seems logical to me, but for the case of
587 producing relocateable output it is not what the code
588 actually does. I don't want to change it, because it seems
589 far too likely that something will break. */
592 input_section->output_section->vma + input_section->output_offset;
594 if (howto->pcrel_offset == true)
595 relocation -= reloc_entry->address;
598 if (output_bfd != (bfd *) NULL)
600 if (howto->partial_inplace == false)
602 /* This is a partial relocation, and we want to apply the relocation
603 to the reloc entry rather than the raw data. Modify the reloc
604 inplace to reflect what we now know. */
605 reloc_entry->addend = relocation;
606 reloc_entry->address += input_section->output_offset;
611 /* This is a partial relocation, but inplace, so modify the
614 If we've relocated with a symbol with a section, change
615 into a ref to the section belonging to the symbol. */
617 reloc_entry->address += input_section->output_offset;
620 if (abfd->xvec->flavour == bfd_target_coff_flavour
621 && strcmp (abfd->xvec->name, "aixcoff-rs6000") != 0)
624 /* For m68k-coff, the addend was being subtracted twice during
625 relocation with -r. Removing the line below this comment
626 fixes that problem; see PR 2953.
628 However, Ian wrote the following, regarding removing the line below,
629 which explains why it is still enabled: --djm
631 If you put a patch like that into BFD you need to check all the COFF
632 linkers. I am fairly certain that patch will break coff-i386 (e.g.,
633 SCO); see coff_i386_reloc in coff-i386.c where I worked around the
634 problem in a different way. There may very well be a reason that the
635 code works as it does.
637 Hmmm. The first obvious point is that bfd_perform_relocation should
638 not have any tests that depend upon the flavour. It's seem like
639 entirely the wrong place for such a thing. The second obvious point
640 is that the current code ignores the reloc addend when producing
641 relocateable output for COFF. That's peculiar. In fact, I really
642 have no idea what the point of the line you want to remove is.
644 A typical COFF reloc subtracts the old value of the symbol and adds in
645 the new value to the location in the object file (if it's a pc
646 relative reloc it adds the difference between the symbol value and the
647 location). When relocating we need to preserve that property.
649 BFD handles this by setting the addend to the negative of the old
650 value of the symbol. Unfortunately it handles common symbols in a
651 non-standard way (it doesn't subtract the old value) but that's a
652 different story (we can't change it without losing backward
653 compatibility with old object files) (coff-i386 does subtract the old
654 value, to be compatible with existing coff-i386 targets, like SCO).
656 So everything works fine when not producing relocateable output. When
657 we are producing relocateable output, logically we should do exactly
658 what we do when not producing relocateable output. Therefore, your
659 patch is correct. In fact, it should probably always just set
660 reloc_entry->addend to 0 for all cases, since it is, in fact, going to
661 add the value into the object file. This won't hurt the COFF code,
662 which doesn't use the addend; I'm not sure what it will do to other
663 formats (the thing to check for would be whether any formats both use
664 the addend and set partial_inplace).
666 When I wanted to make coff-i386 produce relocateable output, I ran
667 into the problem that you are running into: I wanted to remove that
668 line. Rather than risk it, I made the coff-i386 relocs use a special
669 function; it's coff_i386_reloc in coff-i386.c. The function
670 specifically adds the addend field into the object file, knowing that
671 bfd_perform_relocation is not going to. If you remove that line, then
672 coff-i386.c will wind up adding the addend field in twice. It's
673 trivial to fix; it just needs to be done.
675 The problem with removing the line is just that it may break some
676 working code. With BFD it's hard to be sure of anything. The right
677 way to deal with this is simply to build and test at least all the
678 supported COFF targets. It should be straightforward if time and disk
679 space consuming. For each target:
681 2) generate some executable, and link it using -r (I would
682 probably use paranoia.o and link against newlib/libc.a, which
683 for all the supported targets would be available in
684 /usr/cygnus/progressive/H-host/target/lib/libc.a).
685 3) make the change to reloc.c
686 4) rebuild the linker
688 6) if the resulting object files are the same, you have at least
690 7) if they are different you have to figure out which version is
693 relocation -= reloc_entry->addend;
695 reloc_entry->addend = 0;
699 reloc_entry->addend = relocation;
705 reloc_entry->addend = 0;
708 /* FIXME: This overflow checking is incomplete, because the value
709 might have overflowed before we get here. For a correct check we
710 need to compute the value in a size larger than bitsize, but we
711 can't reasonably do that for a reloc the same size as a host
713 FIXME: We should also do overflow checking on the result after
714 adding in the value contained in the object file. */
715 if (howto->complain_on_overflow != complain_overflow_dont)
719 /* Get the value that will be used for the relocation, but
720 starting at bit position zero. */
721 if (howto->rightshift > howto->bitpos)
722 check = relocation >> (howto->rightshift - howto->bitpos);
724 check = relocation << (howto->bitpos - howto->rightshift);
725 switch (howto->complain_on_overflow)
727 case complain_overflow_signed:
729 /* Assumes two's complement. */
730 bfd_signed_vma reloc_signed_max = (1 << (howto->bitsize - 1)) - 1;
731 bfd_signed_vma reloc_signed_min = ~reloc_signed_max;
733 /* The above right shift is incorrect for a signed value.
734 Fix it up by forcing on the upper bits. */
735 if (howto->rightshift > howto->bitpos
736 && (bfd_signed_vma) relocation < 0)
737 check |= ((bfd_vma) - 1
739 >> (howto->rightshift - howto->bitpos)));
740 if ((bfd_signed_vma) check > reloc_signed_max
741 || (bfd_signed_vma) check < reloc_signed_min)
742 flag = bfd_reloc_overflow;
745 case complain_overflow_unsigned:
747 /* Assumes two's complement. This expression avoids
748 overflow if howto->bitsize is the number of bits in
750 bfd_vma reloc_unsigned_max =
751 (((1 << (howto->bitsize - 1)) - 1) << 1) | 1;
753 if ((bfd_vma) check > reloc_unsigned_max)
754 flag = bfd_reloc_overflow;
757 case complain_overflow_bitfield:
759 /* Assumes two's complement. This expression avoids
760 overflow if howto->bitsize is the number of bits in
762 bfd_vma reloc_bits = (((1 << (howto->bitsize - 1)) - 1) << 1) | 1;
764 if (((bfd_vma) check & ~reloc_bits) != 0
765 && ((bfd_vma) check & ~reloc_bits) != (-1 & ~reloc_bits))
767 /* The above right shift is incorrect for a signed
768 value. See if turning on the upper bits fixes the
770 if (howto->rightshift > howto->bitpos
771 && (bfd_signed_vma) relocation < 0)
773 check |= ((bfd_vma) - 1
775 >> (howto->rightshift - howto->bitpos)));
776 if (((bfd_vma) check & ~reloc_bits) != (-1 & ~reloc_bits))
777 flag = bfd_reloc_overflow;
780 flag = bfd_reloc_overflow;
790 Either we are relocating all the way, or we don't want to apply
791 the relocation to the reloc entry (probably because there isn't
792 any room in the output format to describe addends to relocs)
795 /* The cast to bfd_vma avoids a bug in the Alpha OSF/1 C compiler
796 (OSF version 1.3, compiler version 3.11). It miscompiles the
810 x <<= (unsigned long) s.i0;
814 printf ("succeeded (%lx)\n", x);
818 relocation >>= (bfd_vma) howto->rightshift;
820 /* Shift everything up to where it's going to be used */
822 relocation <<= (bfd_vma) howto->bitpos;
824 /* Wait for the day when all have the mask in them */
827 i instruction to be left alone
828 o offset within instruction
829 r relocation offset to apply
838 i i i i i o o o o o from bfd_get<size>
839 and S S S S S to get the size offset we want
840 + r r r r r r r r r r to get the final value to place
841 and D D D D D to chop to right size
842 -----------------------
845 ... i i i i i o o o o o from bfd_get<size>
846 and N N N N N get instruction
847 -----------------------
853 -----------------------
854 R R R R R R R R R R put into bfd_put<size>
858 x = ( (x & ~howto->dst_mask) | (((x & howto->src_mask) + relocation) & howto->dst_mask))
864 char x = bfd_get_8 (abfd, (char *) data + addr);
866 bfd_put_8 (abfd, x, (unsigned char *) data + addr);
873 short x = bfd_get_16 (abfd, (bfd_byte *) data + addr);
875 bfd_put_16 (abfd, x, (unsigned char *) data + addr);
881 long x = bfd_get_32 (abfd, (bfd_byte *) data + addr);
883 bfd_put_32 (abfd, x, (bfd_byte *) data + addr);
888 long x = bfd_get_32 (abfd, (bfd_byte *) data + addr);
889 relocation = -relocation;
891 bfd_put_32 (abfd, x, (bfd_byte *) data + addr);
903 bfd_vma x = bfd_get_64 (abfd, (bfd_byte *) data + addr);
905 bfd_put_64 (abfd, x, (bfd_byte *) data + addr);
912 return bfd_reloc_other;
918 /* This relocation routine is used by some of the backend linkers.
919 They do not construct asymbol or arelent structures, so there is no
920 reason for them to use bfd_perform_relocation. Also,
921 bfd_perform_relocation is so hacked up it is easier to write a new
922 function than to try to deal with it.
924 This routine does a final relocation. It should not be used when
925 generating relocateable output.
927 FIXME: This routine ignores any special_function in the HOWTO,
928 since the existing special_function values have been written for
929 bfd_perform_relocation.
931 HOWTO is the reloc howto information.
932 INPUT_BFD is the BFD which the reloc applies to.
933 INPUT_SECTION is the section which the reloc applies to.
934 CONTENTS is the contents of the section.
935 ADDRESS is the address of the reloc within INPUT_SECTION.
936 VALUE is the value of the symbol the reloc refers to.
937 ADDEND is the addend of the reloc. */
939 bfd_reloc_status_type
940 _bfd_final_link_relocate (howto, input_bfd, input_section, contents, address,
942 const reloc_howto_type *howto;
944 asection *input_section;
952 /* Sanity check the address. */
953 if (address > input_section->_cooked_size)
954 return bfd_reloc_outofrange;
956 /* This function assumes that we are dealing with a basic relocation
957 against a symbol. We want to compute the value of the symbol to
958 relocate to. This is just VALUE, the value of the symbol, plus
959 ADDEND, any addend associated with the reloc. */
960 relocation = value + addend;
962 /* If the relocation is PC relative, we want to set RELOCATION to
963 the distance between the symbol (currently in RELOCATION) and the
964 location we are relocating. Some targets (e.g., i386-aout)
965 arrange for the contents of the section to be the negative of the
966 offset of the location within the section; for such targets
967 pcrel_offset is false. Other targets (e.g., m88kbcs or ELF)
968 simply leave the contents of the section as zero; for such
969 targets pcrel_offset is true. If pcrel_offset is false we do not
970 need to subtract out the offset of the location within the
971 section (which is just ADDRESS). */
972 if (howto->pc_relative)
974 relocation -= (input_section->output_section->vma
975 + input_section->output_offset);
976 if (howto->pcrel_offset)
977 relocation -= address;
980 return _bfd_relocate_contents (howto, input_bfd, relocation,
984 /* Relocate a given location using a given value and howto. */
986 bfd_reloc_status_type
987 _bfd_relocate_contents (howto, input_bfd, relocation, location)
988 const reloc_howto_type *howto;
997 /* If the size is negative, negate RELOCATION. This isn't very
1000 relocation = -relocation;
1002 /* Get the value we are going to relocate. */
1003 size = bfd_get_reloc_size (howto);
1010 x = bfd_get_8 (input_bfd, location);
1013 x = bfd_get_16 (input_bfd, location);
1016 x = bfd_get_32 (input_bfd, location);
1020 x = bfd_get_64 (input_bfd, location);
1027 /* Check for overflow. FIXME: We may drop bits during the addition
1028 which we don't check for. We must either check at every single
1029 operation, which would be tedious, or we must do the computations
1030 in a type larger than bfd_vma, which would be inefficient. */
1032 if (howto->complain_on_overflow != complain_overflow_dont)
1035 bfd_signed_vma signed_check;
1037 bfd_signed_vma signed_add;
1039 if (howto->rightshift == 0)
1042 signed_check = (bfd_signed_vma) relocation;
1046 /* Drop unwanted bits from the value we are relocating to. */
1047 check = relocation >> howto->rightshift;
1049 /* If this is a signed value, the rightshift just dropped
1050 leading 1 bits (assuming twos complement). */
1051 if ((bfd_signed_vma) relocation >= 0)
1052 signed_check = check;
1054 signed_check = (check
1056 & ~((bfd_vma) - 1 >> howto->rightshift)));
1059 /* Get the value from the object file. */
1060 add = x & howto->src_mask;
1062 /* Get the value from the object file with an appropriate sign.
1063 The expression involving howto->src_mask isolates the upper
1064 bit of src_mask. If that bit is set in the value we are
1065 adding, it is negative, and we subtract out that number times
1066 two. If src_mask includes the highest possible bit, then we
1067 can not get the upper bit, but that does not matter since
1068 signed_add needs no adjustment to become negative in that
1071 if ((add & (((~howto->src_mask) >> 1) & howto->src_mask)) != 0)
1072 signed_add -= (((~howto->src_mask) >> 1) & howto->src_mask) << 1;
1074 /* Add the value from the object file, shifted so that it is a
1076 if (howto->bitpos == 0)
1079 signed_check += signed_add;
1083 check += add >> howto->bitpos;
1085 /* For the signed case we use ADD, rather than SIGNED_ADD,
1086 to avoid warnings from SVR4 cc. This is OK since we
1087 explictly handle the sign bits. */
1088 if (signed_add >= 0)
1089 signed_check += add >> howto->bitpos;
1091 signed_check += ((add >> howto->bitpos)
1093 & ~((bfd_vma) - 1 >> howto->bitpos)));
1096 switch (howto->complain_on_overflow)
1098 case complain_overflow_signed:
1100 /* Assumes two's complement. */
1101 bfd_signed_vma reloc_signed_max = (1 << (howto->bitsize - 1)) - 1;
1102 bfd_signed_vma reloc_signed_min = ~reloc_signed_max;
1104 if (signed_check > reloc_signed_max
1105 || signed_check < reloc_signed_min)
1109 case complain_overflow_unsigned:
1111 /* Assumes two's complement. This expression avoids
1112 overflow if howto->bitsize is the number of bits in
1114 bfd_vma reloc_unsigned_max =
1115 (((1 << (howto->bitsize - 1)) - 1) << 1) | 1;
1117 if (check > reloc_unsigned_max)
1121 case complain_overflow_bitfield:
1123 /* Assumes two's complement. This expression avoids
1124 overflow if howto->bitsize is the number of bits in
1126 bfd_vma reloc_bits = (((1 << (howto->bitsize - 1)) - 1) << 1) | 1;
1128 if ((check & ~reloc_bits) != 0
1129 && (((bfd_vma) signed_check & ~reloc_bits)
1130 != (-1 & ~reloc_bits)))
1139 /* Put RELOCATION in the right bits. */
1140 relocation >>= (bfd_vma) howto->rightshift;
1141 relocation <<= (bfd_vma) howto->bitpos;
1143 /* Add RELOCATION to the right bits of X. */
1144 x = ((x & ~howto->dst_mask)
1145 | (((x & howto->src_mask) + relocation) & howto->dst_mask));
1147 /* Put the relocated value back in the object file. */
1154 bfd_put_8 (input_bfd, x, location);
1157 bfd_put_16 (input_bfd, x, location);
1160 bfd_put_32 (input_bfd, x, location);
1164 bfd_put_64 (input_bfd, x, location);
1171 return overflow ? bfd_reloc_overflow : bfd_reloc_ok;
1177 howto manager, , typedef arelent, Relocations
1182 When an application wants to create a relocation, but doesn't
1183 know what the target machine might call it, it can find out by
1184 using this bit of code.
1193 The insides of a reloc code. The idea is that, eventually, there
1194 will be one enumerator for every type of relocation we ever do.
1195 Pass one of these values to <<bfd_reloc_type_lookup>>, and it'll
1196 return a howto pointer.
1198 This does mean that the application must determine the correct
1199 enumerator value; you can't get a howto pointer from a random set
1204 .typedef enum bfd_reloc_code_real
1206 . {* Basic absolute relocations *}
1214 . {* PC-relative relocations *}
1215 . BFD_RELOC_64_PCREL,
1216 . BFD_RELOC_32_PCREL,
1217 . BFD_RELOC_24_PCREL, {* used by i960 *}
1218 . BFD_RELOC_16_PCREL,
1219 . BFD_RELOC_8_PCREL,
1221 . {* Linkage-table relative *}
1222 . BFD_RELOC_32_BASEREL,
1223 . BFD_RELOC_16_BASEREL,
1224 . BFD_RELOC_8_BASEREL,
1226 . {* The type of reloc used to build a contructor table - at the moment
1227 . probably a 32 bit wide abs address, but the cpu can choose. *}
1230 . {* 8 bits wide, but used to form an address like 0xffnn *}
1233 . {* 32-bit pc-relative, shifted right 2 bits (i.e., 30-bit
1234 . word displacement, e.g. for SPARC) *}
1235 . BFD_RELOC_32_PCREL_S2,
1236 . {* signed 16-bit pc-relative, shifted right 2 bits (e.g. for MIPS) *}
1237 . BFD_RELOC_16_PCREL_S2,
1238 . {* this is used on the Alpha *}
1239 . BFD_RELOC_23_PCREL_S2,
1241 . {* High 22 bits of 32-bit value, placed into lower 22 bits of
1242 . target word; simple reloc. *}
1244 . {* Low 10 bits. *}
1247 . {* For systems that allocate a Global Pointer register, these are
1248 . displacements off that register. These relocation types are
1249 . handled specially, because the value the register will have is
1250 . decided relatively late. *}
1251 . BFD_RELOC_GPREL16,
1252 . BFD_RELOC_GPREL32,
1254 . {* Reloc types used for i960/b.out. *}
1255 . BFD_RELOC_I960_CALLJ,
1257 . {* now for the sparc/elf codes *}
1258 . BFD_RELOC_NONE, {* actually used *}
1259 . BFD_RELOC_SPARC_WDISP22,
1260 . BFD_RELOC_SPARC22,
1261 . BFD_RELOC_SPARC13,
1262 . BFD_RELOC_SPARC_GOT10,
1263 . BFD_RELOC_SPARC_GOT13,
1264 . BFD_RELOC_SPARC_GOT22,
1265 . BFD_RELOC_SPARC_PC10,
1266 . BFD_RELOC_SPARC_PC22,
1267 . BFD_RELOC_SPARC_WPLT30,
1268 . BFD_RELOC_SPARC_COPY,
1269 . BFD_RELOC_SPARC_GLOB_DAT,
1270 . BFD_RELOC_SPARC_JMP_SLOT,
1271 . BFD_RELOC_SPARC_RELATIVE,
1272 . BFD_RELOC_SPARC_UA32,
1274 . {* these are a.out specific? *}
1275 . BFD_RELOC_SPARC_BASE13,
1276 . BFD_RELOC_SPARC_BASE22,
1278 . {* some relocations we're using for sparc v9
1279 . -- subject to change *}
1280 . BFD_RELOC_SPARC_10,
1281 . BFD_RELOC_SPARC_11,
1282 .#define BFD_RELOC_SPARC_64 BFD_RELOC_64
1283 . BFD_RELOC_SPARC_OLO10,
1284 . BFD_RELOC_SPARC_HH22,
1285 . BFD_RELOC_SPARC_HM10,
1286 . BFD_RELOC_SPARC_LM22,
1287 . BFD_RELOC_SPARC_PC_HH22,
1288 . BFD_RELOC_SPARC_PC_HM10,
1289 . BFD_RELOC_SPARC_PC_LM22,
1290 . BFD_RELOC_SPARC_WDISP16,
1291 . BFD_RELOC_SPARC_WDISP19,
1292 . BFD_RELOC_SPARC_GLOB_JMP,
1293 . BFD_RELOC_SPARC_LO7,
1295 . {* Alpha ECOFF relocations. Some of these treat the symbol or "addend"
1296 . in some special way. *}
1297 . {* For GPDISP_HI16 ("gpdisp") relocations, the symbol is ignored when
1298 . writing; when reading, it will be the absolute section symbol. The
1299 . addend is the displacement in bytes of the "lda" instruction from
1300 . the "ldah" instruction (which is at the address of this reloc). *}
1301 . BFD_RELOC_ALPHA_GPDISP_HI16,
1302 . {* For GPDISP_LO16 ("ignore") relocations, the symbol is handled as
1303 . with GPDISP_HI16 relocs. The addend is ignored when writing the
1304 . relocations out, and is filled in with the file's GP value on
1305 . reading, for convenience. *}
1306 . BFD_RELOC_ALPHA_GPDISP_LO16,
1308 . {* The Alpha LITERAL/LITUSE relocs are produced by a symbol reference;
1309 . the assembler turns it into a LDQ instruction to load the address of
1310 . the symbol, and then fills in a register in the real instruction.
1312 . The LITERAL reloc, at the LDQ instruction, refers to the .lita
1313 . section symbol. The addend is ignored when writing, but is filled
1314 . in with the file's GP value on reading, for convenience, as with the
1315 . GPDISP_LO16 reloc.
1317 . The LITUSE reloc, on the instruction using the loaded address, gives
1318 . information to the linker that it might be able to use to optimize
1319 . away some literal section references. The symbol is ignored (read
1320 . as the absolute section symbol), and the "addend" indicates the type
1321 . of instruction using the register:
1322 . 1 - "memory" fmt insn
1323 . 2 - byte-manipulation (byte offset reg)
1324 . 3 - jsr (target of branch)
1326 . The GNU linker currently doesn't do any of this optimizing. *}
1327 . BFD_RELOC_ALPHA_LITERAL,
1328 . BFD_RELOC_ALPHA_LITUSE,
1330 . {* The HINT relocation indicates a value that should be filled into the
1331 . "hint" field of a jmp/jsr/ret instruction, for possible branch-
1332 . prediction logic which may be provided on some processors. *}
1333 . BFD_RELOC_ALPHA_HINT,
1335 . {* Bits 27..2 of the relocation address shifted right 2 bits;
1336 . simple reloc otherwise. *}
1337 . BFD_RELOC_MIPS_JMP,
1339 . {* High 16 bits of 32-bit value; simple reloc. *}
1341 . {* High 16 bits of 32-bit value but the low 16 bits will be sign
1342 . extended and added to form the final result. If the low 16
1343 . bits form a negative number, we need to add one to the high value
1344 . to compensate for the borrow when the low bits are added. *}
1346 . {* Low 16 bits. *}
1348 . {* Like BFD_RELOC_HI16_S, but PC relative. *}
1349 . BFD_RELOC_PCREL_HI16_S,
1350 . {* Like BFD_RELOC_LO16, but PC relative. *}
1351 . BFD_RELOC_PCREL_LO16,
1353 . {* relocation relative to the global pointer. *}
1354 .#define BFD_RELOC_MIPS_GPREL BFD_RELOC_GPREL16
1356 . {* Relocation against a MIPS literal section. *}
1357 . BFD_RELOC_MIPS_LITERAL,
1359 . {* MIPS ELF relocations. *}
1360 . BFD_RELOC_MIPS_GOT16,
1361 . BFD_RELOC_MIPS_CALL16,
1362 .#define BFD_RELOC_MIPS_GPREL32 BFD_RELOC_GPREL32
1364 . {* i386/elf relocations *}
1365 . BFD_RELOC_386_GOT32,
1366 . BFD_RELOC_386_PLT32,
1367 . BFD_RELOC_386_COPY,
1368 . BFD_RELOC_386_GLOB_DAT,
1369 . BFD_RELOC_386_JUMP_SLOT,
1370 . BFD_RELOC_386_RELATIVE,
1371 . BFD_RELOC_386_GOTOFF,
1372 . BFD_RELOC_386_GOTPC,
1374 . {* PowerPC/POWER (RS/6000) relocs. *}
1375 . {* 26 bit relative branch. Low two bits must be zero. High 24
1376 . bits installed in bits 6 through 29 of instruction. *}
1377 . BFD_RELOC_PPC_B26,
1378 . {* 26 bit absolute branch, like BFD_RELOC_PPC_B26 but absolute. *}
1379 . BFD_RELOC_PPC_BA26,
1380 . {* 16 bit TOC relative reference. *}
1381 . BFD_RELOC_PPC_TOC16,
1383 . {* this must be the highest numeric value *}
1385 . } bfd_reloc_code_real_type;
1391 bfd_reloc_type_lookup
1394 const struct reloc_howto_struct *
1395 bfd_reloc_type_lookup (bfd *abfd, bfd_reloc_code_real_type code);
1398 Return a pointer to a howto structure which, when
1399 invoked, will perform the relocation @var{code} on data from the
1405 const struct reloc_howto_struct *
1406 bfd_reloc_type_lookup (abfd, code)
1408 bfd_reloc_code_real_type code;
1410 return BFD_SEND (abfd, reloc_type_lookup, (abfd, code));
1413 static reloc_howto_type bfd_howto_32 =
1414 HOWTO (0, 00, 2, 32, false, 0, complain_overflow_bitfield, 0, "VRT32", false, 0xffffffff, 0xffffffff, true);
1419 bfd_default_reloc_type_lookup
1422 const struct reloc_howto_struct *bfd_default_reloc_type_lookup
1423 (bfd *abfd, bfd_reloc_code_real_type code);
1426 Provides a default relocation lookup routine for any architecture.
1431 const struct reloc_howto_struct *
1432 bfd_default_reloc_type_lookup (abfd, code)
1434 bfd_reloc_code_real_type code;
1438 case BFD_RELOC_CTOR:
1439 /* The type of reloc used in a ctor, which will be as wide as the
1440 address - so either a 64, 32, or 16 bitter. */
1441 switch (bfd_get_arch_info (abfd)->bits_per_address)
1446 return &bfd_howto_32;
1455 return (const struct reloc_howto_struct *) NULL;
1461 bfd_generic_relax_section
1464 boolean bfd_generic_relax_section
1467 struct bfd_link_info *,
1471 Provides default handling for relaxing for back ends which
1472 don't do relaxing -- i.e., does nothing.
1477 bfd_generic_relax_section (abfd, section, link_info, again)
1480 struct bfd_link_info *link_info;
1489 bfd_generic_get_relocated_section_contents
1493 bfd_generic_get_relocated_section_contents (bfd *abfd,
1494 struct bfd_link_info *link_info,
1495 struct bfd_link_order *link_order,
1497 boolean relocateable,
1501 Provides default handling of relocation effort for back ends
1502 which can't be bothered to do it efficiently.
1507 bfd_generic_get_relocated_section_contents (abfd, link_info, link_order, data,
1508 relocateable, symbols)
1510 struct bfd_link_info *link_info;
1511 struct bfd_link_order *link_order;
1513 boolean relocateable;
1516 /* Get enough memory to hold the stuff */
1517 bfd *input_bfd = link_order->u.indirect.section->owner;
1518 asection *input_section = link_order->u.indirect.section;
1520 long reloc_size = bfd_get_reloc_upper_bound (input_bfd, input_section);
1521 arelent **reloc_vector = NULL;
1527 reloc_vector = (arelent **) malloc (reloc_size);
1528 if (reloc_vector == NULL && reloc_size != 0)
1530 bfd_set_error (bfd_error_no_memory);
1534 /* read in the section */
1535 if (!bfd_get_section_contents (input_bfd,
1539 input_section->_raw_size))
1542 /* We're not relaxing the section, so just copy the size info */
1543 input_section->_cooked_size = input_section->_raw_size;
1544 input_section->reloc_done = true;
1546 reloc_count = bfd_canonicalize_reloc (input_bfd,
1550 if (reloc_count < 0)
1553 if (reloc_count > 0)
1556 for (parent = reloc_vector; *parent != (arelent *) NULL;
1559 char *error_message = (char *) NULL;
1560 bfd_reloc_status_type r =
1561 bfd_perform_relocation (input_bfd,
1565 relocateable ? abfd : (bfd *) NULL,
1570 asection *os = input_section->output_section;
1572 /* A partial link, so keep the relocs */
1573 os->orelocation[os->reloc_count] = *parent;
1577 if (r != bfd_reloc_ok)
1581 case bfd_reloc_undefined:
1582 if (!((*link_info->callbacks->undefined_symbol)
1583 (link_info, bfd_asymbol_name (*(*parent)->sym_ptr_ptr),
1584 input_bfd, input_section, (*parent)->address)))
1587 case bfd_reloc_dangerous:
1588 BFD_ASSERT (error_message != (char *) NULL);
1589 if (!((*link_info->callbacks->reloc_dangerous)
1590 (link_info, error_message, input_bfd, input_section,
1591 (*parent)->address)))
1594 case bfd_reloc_overflow:
1595 if (!((*link_info->callbacks->reloc_overflow)
1596 (link_info, bfd_asymbol_name (*(*parent)->sym_ptr_ptr),
1597 (*parent)->howto->name, (*parent)->addend,
1598 input_bfd, input_section, (*parent)->address)))
1601 case bfd_reloc_outofrange:
1610 if (reloc_vector != NULL)
1611 free (reloc_vector);
1615 if (reloc_vector != NULL)
1616 free (reloc_vector);