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- /* BFD support for handling relocation entries.
- Copyright (C) 1990-1991 Free Software Foundation, Inc.
- Written by Cygnus Support.
-
- This file is part of BFD, the Binary File Descriptor library.
-
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2 of the License, or
- (at your option) any later version.
-
- This program 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 General Public License for more details.
-
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
-
- /*
- SECTION
- Relocations
-
- BFD maintains relocations in much the same was as it maintains
- symbols; they are left alone until required, then read in
- en-mass and traslated into an internal form. There is a common
- routine <<bfd_perform_relocation>> which acts upon the
- canonical form to to the actual fixup.
-
- Note that relocations are maintained on a per section basis,
- whilst symbols are maintained on a per BFD basis.
-
- All a back end has to do to fit the BFD interface is to create
- as many <<struct reloc_cache_entry>> as there are relocations
- in a particuar section, and fill in the right bits:
-
- @menu
- @* typedef arelent::
- @* howto manager::
- @end menu
-
- */
- #include "bfd.h"
- #include "sysdep.h"
- #include "libbfd.h"
- #include "seclet.h"
- /*doc*
- INODE
- typedef arelent, howto manager, Relocations, Relocations
-
- SUBSECTION
- typedef arelent
-
- This is the structure of a relocation entry:
-
- CODE_FRAGMENT
- .
- .typedef enum bfd_reloc_status
- .{
- . {* No errors detected *}
- . bfd_reloc_ok,
- .
- . {* The relocation was performed, but there was an overflow. *}
- . bfd_reloc_overflow,
- .
- . {* The address to relocate was not within the section supplied*}
- . bfd_reloc_outofrange,
- .
- . {* Used by special functions *}
- . bfd_reloc_continue,
- .
- . {* Unused *}
- . bfd_reloc_notsupported,
- .
- . {* Unsupported relocation size requested. *}
- . bfd_reloc_other,
- .
- . {* The symbol to relocate against was undefined.*}
- . bfd_reloc_undefined,
- .
- . {* The relocation was performed, but may not be ok - presently
- . generated only when linking i960 coff files with i960 b.out
- . symbols. *}
- . bfd_reloc_dangerous
- . }
- . bfd_reloc_status_type;
- .
- .
- .typedef struct reloc_cache_entry
- .{
- . {* A pointer into the canonical table of pointers *}
- . struct symbol_cache_entry **sym_ptr_ptr;
- .
- . {* offset in section *}
- . rawdata_offset address;
- .
- . {* addend for relocation value *}
- . bfd_vma addend;
- .
- . {* Pointer to how to perform the required relocation *}
- . CONST struct reloc_howto_struct *howto;
- .
- .} arelent;
-
- */
-
- /*
- DESCRIPTION
-
- Here is a description of each of the fields within a relent:
-
- o sym_ptr_ptr
-
- The symbol table pointer points to a pointer to the symbol
- associated with the relocation request. This would naturally
- be the pointer into the table returned by the back end's
- get_symtab action. @xref{Symbols}. The symbol is referenced
- through a pointer to a pointer so that tools like the linker
- can fix up all the symbols of the same name by modifying only
- one pointer. The relocation routine looks in the symbol and
- uses the base of the section the symbol is attached to and the
- value of the symbol as the initial relocation offset. If the
- symbol pointer is zero, then the section provided is looked up.
-
- o address
-
- The address field gives the offset in bytes from the base of
- the section data which owns the relocation record to the first
- byte of relocatable information. The actual data relocated
- will be relative to this point - for example, a relocation
- type which modifies the bottom two bytes of a four byte word
- would not touch the first byte pointed to in a big endian
- world. @item addend The addend is a value provided by the back
- end to be added (!) to the relocation offset. Its
- interpretation is dependent upon the howto. For example, on
- the 68k the code:
-
-
- | char foo[];
- | main()
- | {
- | return foo[0x12345678];
- | }
-
- Could be compiled into:
-
- | linkw fp,#-4
- | moveb @@#12345678,d0
- | extbl d0
- | unlk fp
- | rts
-
-
- This could create a reloc pointing to foo, but leave the
- offset in the data (something like)
-
-
- |RELOCATION RECORDS FOR [.text]:
- |offset type value
- |00000006 32 _foo
- |
- |00000000 4e56 fffc ; linkw fp,#-4
- |00000004 1039 1234 5678 ; moveb @@#12345678,d0
- |0000000a 49c0 ; extbl d0
- |0000000c 4e5e ; unlk fp
- |0000000e 4e75 ; rts
-
-
- Using coff and an 88k, some instructions don't have enough
- space in them to represent the full address range, and
- pointers have to be loaded in two parts. So you'd get something like:
-
-
- | or.u r13,r0,hi16(_foo+0x12345678)
- | ld.b r2,r13,lo16(_foo+0x12345678)
- | jmp r1
-
-
- This whould create two relocs, both pointing to _foo, and with
- 0x12340000 in their addend field. The data would consist of:
-
-
- |RELOCATION RECORDS FOR [.text]:
- |offset type value
- |00000002 HVRT16 _foo+0x12340000
- |00000006 LVRT16 _foo+0x12340000
-
- |00000000 5da05678 ; or.u r13,r0,0x5678
- |00000004 1c4d5678 ; ld.b r2,r13,0x5678
- |00000008 f400c001 ; jmp r1
-
-
- The relocation routine digs out the value from the data, adds
- it to the addend to get the original offset and then adds the
- value of _foo. Note that all 32 bits have to be kept around
- somewhere, to cope with carry from bit 15 to bit 16.
-
- On further example is the sparc and the a.out format. The
- sparc has a similar problem to the 88k, in that some
- instructions don't have room for an entire offset, but on the
- sparc the parts are created odd sized lumps. The designers of
- the a.out format chose not to use the data within the section
- for storing part of the offset; all the offset is kept within
- the reloc. Any thing in the data should be ignored.
-
- | save %sp,-112,%sp
- | sethi %hi(_foo+0x12345678),%g2
- | ldsb [%g2+%lo(_foo+0x12345678)],%i0
- | ret
- | restore
-
- Both relocs contains a pointer to foo, and the offsets would
- contain junk.
-
-
- |RELOCATION RECORDS FOR [.text]:
- |offset type value
- |00000004 HI22 _foo+0x12345678
- |00000008 LO10 _foo+0x12345678
-
- |00000000 9de3bf90 ; save %sp,-112,%sp
- |00000004 05000000 ; sethi %hi(_foo+0),%g2
- |00000008 f048a000 ; ldsb [%g2+%lo(_foo+0)],%i0
- |0000000c 81c7e008 ; ret
- |00000010 81e80000 ; restore
-
-
- o howto
-
- The howto field can be imagined as a
- relocation instruction. It is a pointer to a struct which
- contains information on what to do with all the other
- information in the reloc record and data section. A back end
- would normally have a relocation instruction set and turn
- relocations into pointers to the correct structure on input -
- but it would be possible to create each howto field on demand.
-
- */
-
-
- /*
- SUBSUBSECTION
- <<reloc_howto_type>>
-
- The <<reloc_howto_type>> is a structure which contains all the
- information that BFD needs to know to tie up a back end's data.
-
- CODE_FRAGMENT
- .struct symbol_cache_entry; {* Forward declaration *}
- .
- .typedef CONST struct reloc_howto_struct
- .{
- . {* The type field has mainly a documetary use - the back end can
- . to what it wants with it, though the normally the back end's
- . external idea of what a reloc number would be would be stored
- . in this field. For example, the a PC relative word relocation
- . in a coff environment would have the type 023 - because that's
- . what the outside world calls a R_PCRWORD reloc. *}
- . unsigned int type;
- .
- . {* The value the final relocation is shifted right by. This drops
- . unwanted data from the relocation. *}
- . unsigned int rightshift;
- .
- . {* The size of the item to be relocated - 0, is one byte, 1 is 2
- . bytes, 3 is four bytes. *}
- . unsigned int size;
- .
- . {* Now obsolete *}
- . unsigned int bitsize;
- .
- . {* Notes that the relocation is relative to the location in the
- . data section of the addend. The relocation function will
- . subtract from the relocation value the address of the location
- . being relocated. *}
- . boolean pc_relative;
- .
- . {* Now obsolete *}
- . unsigned int bitpos;
- .
- . {* Now obsolete *}
- . boolean absolute;
- .
- . {* Causes the relocation routine to return an error if overflow
- . is detected when relocating. *}
- . boolean complain_on_overflow;
- .
- . {* If this field is non null, then the supplied function is
- . called rather than the normal function. This allows really
- . strange relocation methods to be accomodated (eg, i960 callj
- . instructions). *}
- . bfd_reloc_status_type EXFUN ((*special_function),
- . (bfd *abfd,
- . arelent *reloc_entry,
- . struct symbol_cache_entry *symbol,
- . PTR data,
- . asection *input_section));
- .
- . {* The textual name of the relocation type. *}
- . char *name;
- .
- . {* When performing a partial link, some formats must modify the
- . relocations rather than the data - this flag signals this.*}
- . boolean partial_inplace;
- .
- . {* The src_mask is used to select what parts of the read in data
- . are to be used in the relocation sum. Eg, if this was an 8 bit
- . bit of data which we read and relocated, this would be
- . 0x000000ff. When we have relocs which have an addend, such as
- . sun4 extended relocs, the value in the offset part of a
- . relocating field is garbage so we never use it. In this case
- . the mask would be 0x00000000. *}
- . bfd_word src_mask;
- .
- . {* The dst_mask is what parts of the instruction are replaced
- . into the instruction. In most cases src_mask == dst_mask,
- . except in the above special case, where dst_mask would be
- . 0x000000ff, and src_mask would be 0x00000000. *}
- . bfd_word dst_mask;
- .
- . {* When some formats create PC relative instructions, they leave
- . the value of the pc of the place being relocated in the offset
- . slot of the instruction, so that a PC relative relocation can
- . be made just by adding in an ordinary offset (eg sun3 a.out).
- . Some formats leave the displacement part of an instruction
- . empty (eg m88k bcs), this flag signals the fact.*}
- . boolean pcrel_offset;
- .
- .} reloc_howto_type;
-
- */
-
- /*
- FUNCTION
- the HOWTO macro
-
- DESCRIPTION
- The HOWTO define is horrible and will go away.
-
-
- .#define HOWTO(C, R,S,B, P, BI, ABS, O, SF, NAME, INPLACE, MASKSRC, MASKDST, PC) \
- . {(unsigned)C,R,S,B, P, BI, ABS,O,SF,NAME,INPLACE,MASKSRC,MASKDST,PC}
-
- DESCRIPTION
- And will be replaced with the totally magic way. But for the
- moment, we are compatible, so do it this way..
-
-
- .#define NEWHOWTO( FUNCTION, NAME,SIZE,REL,IN) HOWTO(0,0,SIZE,0,REL,0,false,false,FUNCTION, NAME,false,0,0,IN)
- .
- DESCRIPTION
- Helper routine to turn a symbol into a relocation value.
-
- .#define HOWTO_PREPARE(relocation, symbol) \
- . { \
- . if (symbol != (asymbol *)NULL) { \
- . if (symbol->section == &bfd_com_section) { \
- . relocation = 0; \
- . } \
- . else { \
- . relocation = symbol->value; \
- . } \
- . } \
- .}
-
- */
-
- /*
- TYPEDEF
- reloc_chain
-
- DESCRIPTION
-
- How relocs are tied together
-
- .typedef unsigned char bfd_byte;
- .
- .typedef struct relent_chain {
- . arelent relent;
- . struct relent_chain *next;
- .} arelent_chain;
-
- */
-
-
-
- /*
- FUNCTION
- bfd_perform_relocation
-
- SYNOPSIS
- bfd_reloc_status_type
- bfd_perform_relocation
- (bfd * abfd,
- arelent *reloc_entry,
- PTR data,
- asection *input_section,
- bfd *output_bfd);
-
- DESCRIPTION
- If an output_bfd is supplied to this function the generated
- image will be relocatable, the relocations are copied to the
- output file after they have been changed to reflect the new
- state of the world. There are two ways of reflecting the
- results of partial linkage in an output file; by modifying the
- output data in place, and by modifying the relocation record.
- Some native formats (eg basic a.out and basic coff) have no
- way of specifying an addend in the relocation type, so the
- addend has to go in the output data. This is no big deal
- since in these formats the output data slot will always be big
- enough for the addend. Complex reloc types with addends were
- invented to solve just this problem.
-
- */
-
-
- bfd_reloc_status_type
- DEFUN(bfd_perform_relocation,(abfd,
- reloc_entry,
- data,
- input_section,
- output_bfd),
- bfd *abfd AND
- arelent *reloc_entry AND
- PTR data AND
- asection *input_section AND
- bfd *output_bfd)
- {
- bfd_vma relocation;
- bfd_reloc_status_type flag = bfd_reloc_ok;
- bfd_vma addr = reloc_entry->address ;
- bfd_vma output_base = 0;
- reloc_howto_type *howto = reloc_entry->howto;
- asection *reloc_target_output_section ;
-
- asymbol *symbol;
-
- symbol = *( reloc_entry->sym_ptr_ptr);
- if ((symbol->section == &bfd_und_section) && output_bfd == (bfd *)NULL) {
- flag = bfd_reloc_undefined;
- }
-
- if (howto->special_function){
- bfd_reloc_status_type cont;
- cont = howto->special_function(abfd,
- reloc_entry,
- symbol,
- data,
- input_section);
- if (cont != bfd_reloc_continue) return cont;
- }
-
- /*
- Work out which section the relocation is targetted at and the
- initial relocation command value.
- */
-
-
- if (symbol->section == &bfd_com_section) {
- relocation = 0;
- }
- else {
- relocation = symbol->value;
- }
-
-
- reloc_target_output_section = symbol->section->output_section;
-
- if (output_bfd && howto->partial_inplace==false) {
- output_base = 0;
- }
- else {
- output_base = reloc_target_output_section->vma;
-
- }
-
- relocation += output_base + symbol->section->output_offset;
-
-
- relocation += reloc_entry->addend ;
-
-
- if(reloc_entry->address > input_section->_cooked_size)
- {
- return bfd_reloc_outofrange;
- }
-
-
- if (howto->pc_relative == true)
- {
- /*
- Anything which started out as pc relative should end up that
- way too.
-
- There are two ways we can see a pcrel instruction. Sometimes
- the pcrel displacement has been partially calculated, it
- includes the distance from the start of the section to the
- instruction in it (eg sun3), and sometimes the field is
- totally blank - eg m88kbcs.
- */
-
-
- relocation -=
- input_section->output_section->vma + input_section->output_offset;
-
- if (howto->pcrel_offset == true) {
- relocation -= reloc_entry->address;
- }
-
- }
-
- if (output_bfd!= (bfd *)NULL) {
- if ( howto->partial_inplace == false) {
- /*
- This is a partial relocation, and we want to apply the relocation
- to the reloc entry rather than the raw data. Modify the reloc
- inplace to reflect what we now know.
- */
- reloc_entry->addend = relocation ;
- reloc_entry->address += input_section->output_offset;
- return flag;
- }
- else
- {
- /* This is a partial relocation, but inplace, so modify the
- reloc record a bit.
-
- If we've relocated with a symbol with a section, change
- into a ref to the section belonging to the symbol
- */
- reloc_entry->addend = relocation ;
- reloc_entry->address += input_section->output_offset;
-
-
- }
- }
- else
- {
-
- reloc_entry->addend = 0;
- }
-
-
-
- /*
- Either we are relocating all the way, or we don't want to apply
- the relocation to the reloc entry (probably because there isn't
- any room in the output format to describe addends to relocs)
- */
- relocation >>= howto->rightshift;
-
- /* Shift everything up to where it's going to be used */
-
- relocation <<= howto->bitpos;
-
- /* Wait for the day when all have the mask in them */
-
- /* What we do:
- i instruction to be left alone
- o offset within instruction
- r relocation offset to apply
- S src mask
- D dst mask
- N ~dst mask
- A part 1
- B part 2
- R result
-
- Do this:
- i i i i i o o o o o from bfd_get<size>
- and S S S S S to get the size offset we want
- + r r r r r r r r r r to get the final value to place
- and D D D D D to chop to right size
- -----------------------
- A A A A A
- And this:
- ... i i i i i o o o o o from bfd_get<size>
- and N N N N N get instruction
- -----------------------
- ... B B B B B
-
- And then:
- B B B B B
- or A A A A A
- -----------------------
- R R R R R R R R R R put into bfd_put<size>
- */
-
- #define DOIT(x) \
- x = ( (x & ~howto->dst_mask) | (((x & howto->src_mask) + relocation) & howto->dst_mask))
-
- switch (howto->size)
- {
- case 0:
- {
- char x = bfd_get_8(abfd, (char *)data + addr);
- DOIT(x);
- bfd_put_8(abfd,x, (unsigned char *) data + addr);
- }
- break;
-
- case 1:
- {
- short x = bfd_get_16(abfd, (bfd_byte *)data + addr);
- DOIT(x);
- bfd_put_16(abfd, x, (unsigned char *)data + addr);
- }
- break;
- case 2:
- {
- long x = bfd_get_32(abfd, (bfd_byte *) data + addr);
- DOIT(x);
- bfd_put_32(abfd,x, (bfd_byte *)data + addr);
- }
- break;
- case 3:
-
- /* Do nothing */
- break;
- default:
- return bfd_reloc_other;
- }
-
- return flag;
- }
-
-
-
- /*
- INODE
- howto manager, , typedef arelent, Relocations
-
- SECTION
- The howto manager
-
- When an application wants to create a relocation, but doesn't
- know what the target machine might call it, it can find out by
- using this bit of code.
-
- */
-
- /*
- TYPEDEF
- bfd_reloc_code_type
-
- DESCRIPTION
- The insides of a reloc code
-
- CODE_FRAGMENT
- .
- .typedef enum bfd_reloc_code_real
- .{
- . {* 16 bits wide, simple reloc *}
- . BFD_RELOC_16,
- .
- . {* 8 bits wide, but used to form an address like 0xffnn *}
- . BFD_RELOC_8_FFnn,
- .
- . {* 8 bits wide, simple *}
- . BFD_RELOC_8,
- .
- . {* 8 bits wide, pc relative *}
- . BFD_RELOC_8_PCREL,
- .
- . {* The type of reloc used to build a contructor table - at the
- . moment probably a 32 bit wide abs address, but the cpu can
- . choose. *}
- .
- . BFD_RELOC_CTOR
- . } bfd_reloc_code_real_type;
- */
-
-
-
- /*
- SECTION
- bfd_reloc_type_lookup
-
- SYNOPSIS
- CONST struct reloc_howto_struct *
- bfd_reloc_type_lookup
- (CONST bfd_arch_info_type *arch, bfd_reloc_code_type code);
-
- DESCRIPTION
- This routine returns a pointer to a howto struct which when
- invoked, will perform the supplied relocation on data from the
- architecture noted.
-
- */
-
-
- CONST struct reloc_howto_struct *
- DEFUN(bfd_reloc_type_lookup,(arch, code),
- CONST bfd_arch_info_type *arch AND
- bfd_reloc_code_type code)
- {
- return arch->reloc_type_lookup(arch, code);
- }
-
- static reloc_howto_type bfd_howto_32 =
- HOWTO(0, 00,2,32,false,0,false,true,0,"VRT32", false,0xffffffff,0xffffffff,true);
-
-
- /*
- INTERNAL_FUNCTION
- bfd_default_reloc_type_lookup
-
- SYNOPSIS
- CONST struct reloc_howto_struct *bfd_default_reloc_type_lookup
- (CONST struct bfd_arch_info *,
- bfd_reloc_code_type code);
-
- DESCRIPTION
- Provides a default relocation lookuperer for any architectue
-
-
- */
- CONST struct reloc_howto_struct *
- DEFUN(bfd_default_reloc_type_lookup,(arch, code),
- CONST struct bfd_arch_info *arch AND
- bfd_reloc_code_type code)
- {
- switch (code)
- {
- case BFD_RELOC_CTOR:
- /* The type of reloc used in a ctor, which will be as wide as the
- address - so either a 64, 32, or 16 bitter.. */
- switch (arch->bits_per_address) {
- case 64:
- BFD_FAIL();
- case 32:
- return &bfd_howto_32;
- case 16:
- BFD_FAIL();
- default:
- BFD_FAIL();
- }
- default:
- BFD_FAIL();
- }
- return (struct reloc_howto_struct *)NULL;
- }
-
-
- /*
- INTERNAL_FUNCTION
- bfd_generic_relax_section
-
- SYNOPSIS
- boolean bfd_generic_relax_section
- (bfd *abfd,
- asection *section,
- asymbol **symbols);
-
- DESCRIPTION
- Provides default handling for relaxing for back ends which
- don't do relaxing - ie does nothing
- */
-
- boolean
- DEFUN(bfd_generic_relax_section,(abfd, section, symbols),
- bfd *abfd AND
- asection *section AND
- asymbol **symbols)
- {
-
- return false;
-
- }
-
-
- /*
- INTERNAL_FUNCTION
- bfd_generic_get_relocated_section_contents
-
- SYNOPSIS
- bfd_byte *
- bfd_generic_get_relocated_section_contents(bfd *abfd,
- struct bfd_seclet_struct *seclet)
-
- DESCRIPTION
- Provides default handling of relocation effort for back ends
- which can't be bothered to do it efficiently.
-
- */
-
- bfd_byte *
- DEFUN(bfd_generic_get_relocated_section_contents,(abfd, seclet),
- bfd *abfd AND
- struct bfd_seclet_struct *seclet)
- {
- extern bfd_error_vector_type bfd_error_vector;
-
- /* Get enough memory to hold the stuff */
- bfd *input_bfd = seclet->u.indirect.section->owner;
- asection *input_section = seclet->u.indirect.section;
-
- bfd_byte *data = (bfd_byte *) bfd_xmalloc(input_section->_raw_size);
-
- bfd_size_type reloc_size = bfd_get_reloc_upper_bound(input_bfd,
- input_section);
- arelent **reloc_vector = (arelent **) bfd_xmalloc(reloc_size);
-
- /* read in the section */
- bfd_get_section_contents(input_bfd,
- input_section,
- data,
- 0,
- input_section->_raw_size);
-
- /* We're not relaxing the section, so just copy the size info */
- input_section->_cooked_size = input_section->_raw_size;
- input_section->reloc_done = true;
-
-
- if (bfd_canonicalize_reloc(input_bfd,
- input_section,
- reloc_vector,
- seclet->u.indirect.symbols) )
- {
- arelent **parent;
- for (parent = reloc_vector; * parent != (arelent *)NULL;
- parent++)
- {
- bfd_reloc_status_type r=
- bfd_perform_relocation(input_bfd,
- *parent,
- data,
- input_section, 0);
-
-
- if (r != bfd_reloc_ok)
- {
- switch (r)
- {
- case bfd_reloc_undefined:
- bfd_error_vector.undefined_symbol(*parent, seclet);
- break;
- case bfd_reloc_dangerous:
- bfd_error_vector.reloc_dangerous(*parent, seclet);
- break;
- case bfd_reloc_outofrange:
- case bfd_reloc_overflow:
- bfd_error_vector.reloc_value_truncated(*parent, seclet);
- break;
- default:
- abort();
- break;
- }
-
- }
- }
- }
-
- free((char *)reloc_vector);
- return data;
-
-
- }
-
-