606 lines
23 KiB
Plaintext
606 lines
23 KiB
Plaintext
@section coff backends
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BFD supports a number of different flavours of coff format.
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The major differences between formats are the sizes and
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alignments of fields in structures on disk, and the occasional
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extra field.
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Coff in all its varieties is implemented with a few common
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files and a number of implementation specific files. For
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example, The 88k bcs coff format is implemented in the file
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@file{coff-m88k.c}. This file @code{#include}s
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@file{coff/m88k.h} which defines the external structure of the
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coff format for the 88k, and @file{coff/internal.h} which
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defines the internal structure. @file{coff-m88k.c} also
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defines the relocations used by the 88k format
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@xref{Relocations}.
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The Intel i960 processor version of coff is implemented in
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@file{coff-i960.c}. This file has the same structure as
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@file{coff-m88k.c}, except that it includes @file{coff/i960.h}
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rather than @file{coff-m88k.h}.
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@subsection Porting to a new version of coff
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The recommended method is to select from the existing
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implementations the version of coff which is most like the one
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you want to use. For example, we'll say that i386 coff is
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the one you select, and that your coff flavour is called foo.
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Copy @file{i386coff.c} to @file{foocoff.c}, copy
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@file{../include/coff/i386.h} to @file{../include/coff/foo.h},
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and add the lines to @file{targets.c} and @file{Makefile.in}
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so that your new back end is used. Alter the shapes of the
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structures in @file{../include/coff/foo.h} so that they match
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what you need. You will probably also have to add
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@code{#ifdef}s to the code in @file{coff/internal.h} and
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@file{coffcode.h} if your version of coff is too wild.
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You can verify that your new BFD backend works quite simply by
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building @file{objdump} from the @file{binutils} directory,
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and making sure that its version of what's going on and your
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host system's idea (assuming it has the pretty standard coff
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dump utility, usually called @code{att-dump} or just
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@code{dump}) are the same. Then clean up your code, and send
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what you've done to Cygnus. Then your stuff will be in the
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next release, and you won't have to keep integrating it.
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@subsection How the coff backend works
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@subsubsection File layout
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The Coff backend is split into generic routines that are
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applicable to any Coff target and routines that are specific
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to a particular target. The target-specific routines are
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further split into ones which are basically the same for all
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Coff targets except that they use the external symbol format
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or use different values for certain constants.
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The generic routines are in @file{coffgen.c}. These routines
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work for any Coff target. They use some hooks into the target
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specific code; the hooks are in a @code{bfd_coff_backend_data}
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structure, one of which exists for each target.
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The essentially similar target-specific routines are in
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@file{coffcode.h}. This header file includes executable C code.
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The various Coff targets first include the appropriate Coff
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header file, make any special defines that are needed, and
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then include @file{coffcode.h}.
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Some of the Coff targets then also have additional routines in
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the target source file itself.
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For example, @file{coff-i960.c} includes
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@file{coff/internal.h} and @file{coff/i960.h}. It then
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defines a few constants, such as @code{I960}, and includes
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@file{coffcode.h}. Since the i960 has complex relocation
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types, @file{coff-i960.c} also includes some code to
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manipulate the i960 relocs. This code is not in
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@file{coffcode.h} because it would not be used by any other
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target.
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@subsubsection Bit twiddling
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Each flavour of coff supported in BFD has its own header file
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describing the external layout of the structures. There is also
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an internal description of the coff layout, in
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@file{coff/internal.h}. A major function of the
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coff backend is swapping the bytes and twiddling the bits to
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translate the external form of the structures into the normal
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internal form. This is all performed in the
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@code{bfd_swap}_@i{thing}_@i{direction} routines. Some
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elements are different sizes between different versions of
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coff; it is the duty of the coff version specific include file
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to override the definitions of various packing routines in
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@file{coffcode.h}. E.g., the size of line number entry in coff is
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sometimes 16 bits, and sometimes 32 bits. @code{#define}ing
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@code{PUT_LNSZ_LNNO} and @code{GET_LNSZ_LNNO} will select the
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correct one. No doubt, some day someone will find a version of
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coff which has a varying field size not catered to at the
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moment. To port BFD, that person will have to add more @code{#defines}.
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Three of the bit twiddling routines are exported to
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@code{gdb}; @code{coff_swap_aux_in}, @code{coff_swap_sym_in}
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and @code{coff_swap_lineno_in}. @code{GDB} reads the symbol
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table on its own, but uses BFD to fix things up. More of the
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bit twiddlers are exported for @code{gas};
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@code{coff_swap_aux_out}, @code{coff_swap_sym_out},
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@code{coff_swap_lineno_out}, @code{coff_swap_reloc_out},
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@code{coff_swap_filehdr_out}, @code{coff_swap_aouthdr_out},
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@code{coff_swap_scnhdr_out}. @code{Gas} currently keeps track
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of all the symbol table and reloc drudgery itself, thereby
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saving the internal BFD overhead, but uses BFD to swap things
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on the way out, making cross ports much safer. Doing so also
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allows BFD (and thus the linker) to use the same header files
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as @code{gas}, which makes one avenue to disaster disappear.
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@subsubsection Symbol reading
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The simple canonical form for symbols used by BFD is not rich
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enough to keep all the information available in a coff symbol
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table. The back end gets around this problem by keeping the original
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symbol table around, "behind the scenes".
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When a symbol table is requested (through a call to
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@code{bfd_canonicalize_symtab}), a request gets through to
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@code{coff_get_normalized_symtab}. This reads the symbol table from
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the coff file and swaps all the structures inside into the
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internal form. It also fixes up all the pointers in the table
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(represented in the file by offsets from the first symbol in
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the table) into physical pointers to elements in the new
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internal table. This involves some work since the meanings of
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fields change depending upon context: a field that is a
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pointer to another structure in the symbol table at one moment
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may be the size in bytes of a structure at the next. Another
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pass is made over the table. All symbols which mark file names
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(@code{C_FILE} symbols) are modified so that the internal
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string points to the value in the auxent (the real filename)
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rather than the normal text associated with the symbol
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(@code{".file"}).
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At this time the symbol names are moved around. Coff stores
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all symbols less than nine characters long physically
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within the symbol table; longer strings are kept at the end of
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the file in the string table. This pass moves all strings
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into memory and replaces them with pointers to the strings.
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The symbol table is massaged once again, this time to create
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the canonical table used by the BFD application. Each symbol
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is inspected in turn, and a decision made (using the
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@code{sclass} field) about the various flags to set in the
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@code{asymbol}. @xref{Symbols}. The generated canonical table
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shares strings with the hidden internal symbol table.
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Any linenumbers are read from the coff file too, and attached
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to the symbols which own the functions the linenumbers belong to.
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@subsubsection Symbol writing
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Writing a symbol to a coff file which didn't come from a coff
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file will lose any debugging information. The @code{asymbol}
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structure remembers the BFD from which the symbol was taken, and on
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output the back end makes sure that the same destination target as
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source target is present.
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When the symbols have come from a coff file then all the
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debugging information is preserved.
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Symbol tables are provided for writing to the back end in a
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vector of pointers to pointers. This allows applications like
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the linker to accumulate and output large symbol tables
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without having to do too much byte copying.
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This function runs through the provided symbol table and
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patches each symbol marked as a file place holder
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(@code{C_FILE}) to point to the next file place holder in the
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list. It also marks each @code{offset} field in the list with
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the offset from the first symbol of the current symbol.
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Another function of this procedure is to turn the canonical
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value form of BFD into the form used by coff. Internally, BFD
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expects symbol values to be offsets from a section base; so a
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symbol physically at 0x120, but in a section starting at
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0x100, would have the value 0x20. Coff expects symbols to
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contain their final value, so symbols have their values
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changed at this point to reflect their sum with their owning
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section. This transformation uses the
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@code{output_section} field of the @code{asymbol}'s
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@code{asection} @xref{Sections}.
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@itemize @bullet
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@item
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@code{coff_mangle_symbols}
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@end itemize
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This routine runs though the provided symbol table and uses
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the offsets generated by the previous pass and the pointers
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generated when the symbol table was read in to create the
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structured hierachy required by coff. It changes each pointer
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to a symbol into the index into the symbol table of the asymbol.
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@itemize @bullet
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@item
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@code{coff_write_symbols}
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@end itemize
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This routine runs through the symbol table and patches up the
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symbols from their internal form into the coff way, calls the
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bit twiddlers, and writes out the table to the file.
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@findex coff_symbol_type
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@subsubsection @code{coff_symbol_type}
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@strong{Description}@*
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The hidden information for an @code{asymbol} is described in a
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@code{combined_entry_type}:
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@example
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typedef struct coff_ptr_struct
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@{
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/* Remembers the offset from the first symbol in the file for
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this symbol. Generated by coff_renumber_symbols. */
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unsigned int offset;
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/* Should the value of this symbol be renumbered. Used for
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XCOFF C_BSTAT symbols. Set by coff_slurp_symbol_table. */
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unsigned int fix_value : 1;
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/* Should the tag field of this symbol be renumbered.
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Created by coff_pointerize_aux. */
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unsigned int fix_tag : 1;
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/* Should the endidx field of this symbol be renumbered.
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Created by coff_pointerize_aux. */
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unsigned int fix_end : 1;
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/* Should the x_csect.x_scnlen field be renumbered.
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Created by coff_pointerize_aux. */
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unsigned int fix_scnlen : 1;
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/* Fix up an XCOFF C_BINCL/C_EINCL symbol. The value is the
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index into the line number entries. Set by coff_slurp_symbol_table. */
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unsigned int fix_line : 1;
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/* The container for the symbol structure as read and translated
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from the file. */
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union
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@{
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union internal_auxent auxent;
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struct internal_syment syment;
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@} u;
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@} combined_entry_type;
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/* Each canonical asymbol really looks like this: */
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typedef struct coff_symbol_struct
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@{
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/* The actual symbol which the rest of BFD works with */
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asymbol symbol;
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/* A pointer to the hidden information for this symbol */
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combined_entry_type *native;
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/* A pointer to the linenumber information for this symbol */
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struct lineno_cache_entry *lineno;
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/* Have the line numbers been relocated yet ? */
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boolean done_lineno;
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@} coff_symbol_type;
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@end example
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@findex bfd_coff_backend_data
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@subsubsection @code{bfd_coff_backend_data}
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@example
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/* COFF symbol classifications. */
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enum coff_symbol_classification
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@{
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/* Global symbol. */
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COFF_SYMBOL_GLOBAL,
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/* Common symbol. */
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COFF_SYMBOL_COMMON,
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/* Undefined symbol. */
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COFF_SYMBOL_UNDEFINED,
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/* Local symbol. */
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COFF_SYMBOL_LOCAL,
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/* PE section symbol. */
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COFF_SYMBOL_PE_SECTION
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@};
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@end example
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Special entry points for gdb to swap in coff symbol table parts:
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@example
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typedef struct
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@{
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void (*_bfd_coff_swap_aux_in)
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PARAMS ((bfd *, PTR, int, int, int, int, PTR));
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void (*_bfd_coff_swap_sym_in)
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PARAMS ((bfd *, PTR, PTR));
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void (*_bfd_coff_swap_lineno_in)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int (*_bfd_coff_swap_aux_out)
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PARAMS ((bfd *, PTR, int, int, int, int, PTR));
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unsigned int (*_bfd_coff_swap_sym_out)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int (*_bfd_coff_swap_lineno_out)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int (*_bfd_coff_swap_reloc_out)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int (*_bfd_coff_swap_filehdr_out)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int (*_bfd_coff_swap_aouthdr_out)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int (*_bfd_coff_swap_scnhdr_out)
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PARAMS ((bfd *, PTR, PTR));
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unsigned int _bfd_filhsz;
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unsigned int _bfd_aoutsz;
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unsigned int _bfd_scnhsz;
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unsigned int _bfd_symesz;
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unsigned int _bfd_auxesz;
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unsigned int _bfd_relsz;
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unsigned int _bfd_linesz;
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unsigned int _bfd_filnmlen;
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boolean _bfd_coff_long_filenames;
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boolean _bfd_coff_long_section_names;
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unsigned int _bfd_coff_default_section_alignment_power;
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boolean _bfd_coff_force_symnames_in_strings;
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unsigned int _bfd_coff_debug_string_prefix_length;
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void (*_bfd_coff_swap_filehdr_in)
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PARAMS ((bfd *, PTR, PTR));
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void (*_bfd_coff_swap_aouthdr_in)
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PARAMS ((bfd *, PTR, PTR));
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void (*_bfd_coff_swap_scnhdr_in)
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PARAMS ((bfd *, PTR, PTR));
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void (*_bfd_coff_swap_reloc_in)
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PARAMS ((bfd *abfd, PTR, PTR));
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boolean (*_bfd_coff_bad_format_hook)
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PARAMS ((bfd *, PTR));
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boolean (*_bfd_coff_set_arch_mach_hook)
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PARAMS ((bfd *, PTR));
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PTR (*_bfd_coff_mkobject_hook)
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PARAMS ((bfd *, PTR, PTR));
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boolean (*_bfd_styp_to_sec_flags_hook)
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PARAMS ((bfd *, PTR, const char *, asection *, flagword *));
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void (*_bfd_set_alignment_hook)
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PARAMS ((bfd *, asection *, PTR));
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boolean (*_bfd_coff_slurp_symbol_table)
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PARAMS ((bfd *));
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boolean (*_bfd_coff_symname_in_debug)
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PARAMS ((bfd *, struct internal_syment *));
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boolean (*_bfd_coff_pointerize_aux_hook)
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PARAMS ((bfd *, combined_entry_type *, combined_entry_type *,
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unsigned int, combined_entry_type *));
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boolean (*_bfd_coff_print_aux)
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PARAMS ((bfd *, FILE *, combined_entry_type *, combined_entry_type *,
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combined_entry_type *, unsigned int));
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void (*_bfd_coff_reloc16_extra_cases)
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PARAMS ((bfd *, struct bfd_link_info *, struct bfd_link_order *, arelent *,
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bfd_byte *, unsigned int *, unsigned int *));
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int (*_bfd_coff_reloc16_estimate)
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PARAMS ((bfd *, asection *, arelent *, unsigned int,
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struct bfd_link_info *));
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enum coff_symbol_classification (*_bfd_coff_classify_symbol)
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PARAMS ((bfd *, struct internal_syment *));
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boolean (*_bfd_coff_compute_section_file_positions)
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PARAMS ((bfd *));
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boolean (*_bfd_coff_start_final_link)
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PARAMS ((bfd *, struct bfd_link_info *));
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boolean (*_bfd_coff_relocate_section)
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PARAMS ((bfd *, struct bfd_link_info *, bfd *, asection *, bfd_byte *,
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struct internal_reloc *, struct internal_syment *, asection **));
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reloc_howto_type *(*_bfd_coff_rtype_to_howto)
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PARAMS ((bfd *, asection *, struct internal_reloc *,
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struct coff_link_hash_entry *, struct internal_syment *,
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bfd_vma *));
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boolean (*_bfd_coff_adjust_symndx)\
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PARAMS ((bfd *, struct bfd_link_info *, bfd *, asection *,
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struct internal_reloc *, boolean *));
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boolean (*_bfd_coff_link_add_one_symbol)
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PARAMS ((struct bfd_link_info *, bfd *, const char *, flagword,
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asection *, bfd_vma, const char *, boolean, boolean,
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struct bfd_link_hash_entry **));
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boolean (*_bfd_coff_link_output_has_begun)
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PARAMS ((bfd *, struct coff_final_link_info *));
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boolean (*_bfd_coff_final_link_postscript)
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PARAMS ((bfd *, struct coff_final_link_info *));
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@} bfd_coff_backend_data;
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#define coff_backend_info(abfd) \
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((bfd_coff_backend_data *) (abfd)->xvec->backend_data)
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#define bfd_coff_swap_aux_in(a,e,t,c,ind,num,i) \
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((coff_backend_info (a)->_bfd_coff_swap_aux_in) (a,e,t,c,ind,num,i))
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#define bfd_coff_swap_sym_in(a,e,i) \
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((coff_backend_info (a)->_bfd_coff_swap_sym_in) (a,e,i))
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#define bfd_coff_swap_lineno_in(a,e,i) \
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((coff_backend_info ( a)->_bfd_coff_swap_lineno_in) (a,e,i))
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#define bfd_coff_swap_reloc_out(abfd, i, o) \
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((coff_backend_info (abfd)->_bfd_coff_swap_reloc_out) (abfd, i, o))
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#define bfd_coff_swap_lineno_out(abfd, i, o) \
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((coff_backend_info (abfd)->_bfd_coff_swap_lineno_out) (abfd, i, o))
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#define bfd_coff_swap_aux_out(a,i,t,c,ind,num,o) \
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((coff_backend_info (a)->_bfd_coff_swap_aux_out) (a,i,t,c,ind,num,o))
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#define bfd_coff_swap_sym_out(abfd, i,o) \
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((coff_backend_info (abfd)->_bfd_coff_swap_sym_out) (abfd, i, o))
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#define bfd_coff_swap_scnhdr_out(abfd, i,o) \
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((coff_backend_info (abfd)->_bfd_coff_swap_scnhdr_out) (abfd, i, o))
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#define bfd_coff_swap_filehdr_out(abfd, i,o) \
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((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_out) (abfd, i, o))
|
|
|
|
#define bfd_coff_swap_aouthdr_out(abfd, i,o) \
|
|
((coff_backend_info (abfd)->_bfd_coff_swap_aouthdr_out) (abfd, i, o))
|
|
|
|
#define bfd_coff_filhsz(abfd) (coff_backend_info (abfd)->_bfd_filhsz)
|
|
#define bfd_coff_aoutsz(abfd) (coff_backend_info (abfd)->_bfd_aoutsz)
|
|
#define bfd_coff_scnhsz(abfd) (coff_backend_info (abfd)->_bfd_scnhsz)
|
|
#define bfd_coff_symesz(abfd) (coff_backend_info (abfd)->_bfd_symesz)
|
|
#define bfd_coff_auxesz(abfd) (coff_backend_info (abfd)->_bfd_auxesz)
|
|
#define bfd_coff_relsz(abfd) (coff_backend_info (abfd)->_bfd_relsz)
|
|
#define bfd_coff_linesz(abfd) (coff_backend_info (abfd)->_bfd_linesz)
|
|
#define bfd_coff_filnmlen(abfd) (coff_backend_info (abfd)->_bfd_filnmlen)
|
|
#define bfd_coff_long_filenames(abfd) \
|
|
(coff_backend_info (abfd)->_bfd_coff_long_filenames)
|
|
#define bfd_coff_long_section_names(abfd) \
|
|
(coff_backend_info (abfd)->_bfd_coff_long_section_names)
|
|
#define bfd_coff_default_section_alignment_power(abfd) \
|
|
(coff_backend_info (abfd)->_bfd_coff_default_section_alignment_power)
|
|
#define bfd_coff_swap_filehdr_in(abfd, i,o) \
|
|
((coff_backend_info (abfd)->_bfd_coff_swap_filehdr_in) (abfd, i, o))
|
|
|
|
#define bfd_coff_swap_aouthdr_in(abfd, i,o) \
|
|
((coff_backend_info (abfd)->_bfd_coff_swap_aouthdr_in) (abfd, i, o))
|
|
|
|
#define bfd_coff_swap_scnhdr_in(abfd, i,o) \
|
|
((coff_backend_info (abfd)->_bfd_coff_swap_scnhdr_in) (abfd, i, o))
|
|
|
|
#define bfd_coff_swap_reloc_in(abfd, i, o) \
|
|
((coff_backend_info (abfd)->_bfd_coff_swap_reloc_in) (abfd, i, o))
|
|
|
|
#define bfd_coff_bad_format_hook(abfd, filehdr) \
|
|
((coff_backend_info (abfd)->_bfd_coff_bad_format_hook) (abfd, filehdr))
|
|
|
|
#define bfd_coff_set_arch_mach_hook(abfd, filehdr)\
|
|
((coff_backend_info (abfd)->_bfd_coff_set_arch_mach_hook) (abfd, filehdr))
|
|
#define bfd_coff_mkobject_hook(abfd, filehdr, aouthdr)\
|
|
((coff_backend_info (abfd)->_bfd_coff_mkobject_hook) (abfd, filehdr, aouthdr))
|
|
|
|
#define bfd_coff_styp_to_sec_flags_hook(abfd, scnhdr, name, section, flags_ptr)\
|
|
((coff_backend_info (abfd)->_bfd_styp_to_sec_flags_hook)\
|
|
(abfd, scnhdr, name, section, flags_ptr))
|
|
|
|
#define bfd_coff_set_alignment_hook(abfd, sec, scnhdr)\
|
|
((coff_backend_info (abfd)->_bfd_set_alignment_hook) (abfd, sec, scnhdr))
|
|
|
|
#define bfd_coff_slurp_symbol_table(abfd)\
|
|
((coff_backend_info (abfd)->_bfd_coff_slurp_symbol_table) (abfd))
|
|
|
|
#define bfd_coff_symname_in_debug(abfd, sym)\
|
|
((coff_backend_info (abfd)->_bfd_coff_symname_in_debug) (abfd, sym))
|
|
|
|
#define bfd_coff_force_symnames_in_strings(abfd)\
|
|
(coff_backend_info (abfd)->_bfd_coff_force_symnames_in_strings)
|
|
|
|
#define bfd_coff_debug_string_prefix_length(abfd)\
|
|
(coff_backend_info (abfd)->_bfd_coff_debug_string_prefix_length)
|
|
|
|
#define bfd_coff_print_aux(abfd, file, base, symbol, aux, indaux)\
|
|
((coff_backend_info (abfd)->_bfd_coff_print_aux)\
|
|
(abfd, file, base, symbol, aux, indaux))
|
|
|
|
#define bfd_coff_reloc16_extra_cases(abfd, link_info, link_order, reloc, data, src_ptr, dst_ptr)\
|
|
((coff_backend_info (abfd)->_bfd_coff_reloc16_extra_cases)\
|
|
(abfd, link_info, link_order, reloc, data, src_ptr, dst_ptr))
|
|
|
|
#define bfd_coff_reloc16_estimate(abfd, section, reloc, shrink, link_info)\
|
|
((coff_backend_info (abfd)->_bfd_coff_reloc16_estimate)\
|
|
(abfd, section, reloc, shrink, link_info))
|
|
|
|
#define bfd_coff_classify_symbol(abfd, sym)\
|
|
((coff_backend_info (abfd)->_bfd_coff_classify_symbol)\
|
|
(abfd, sym))
|
|
|
|
#define bfd_coff_compute_section_file_positions(abfd)\
|
|
((coff_backend_info (abfd)->_bfd_coff_compute_section_file_positions)\
|
|
(abfd))
|
|
|
|
#define bfd_coff_start_final_link(obfd, info)\
|
|
((coff_backend_info (obfd)->_bfd_coff_start_final_link)\
|
|
(obfd, info))
|
|
#define bfd_coff_relocate_section(obfd,info,ibfd,o,con,rel,isyms,secs)\
|
|
((coff_backend_info (ibfd)->_bfd_coff_relocate_section)\
|
|
(obfd, info, ibfd, o, con, rel, isyms, secs))
|
|
#define bfd_coff_rtype_to_howto(abfd, sec, rel, h, sym, addendp)\
|
|
((coff_backend_info (abfd)->_bfd_coff_rtype_to_howto)\
|
|
(abfd, sec, rel, h, sym, addendp))
|
|
#define bfd_coff_adjust_symndx(obfd, info, ibfd, sec, rel, adjustedp)\
|
|
((coff_backend_info (abfd)->_bfd_coff_adjust_symndx)\
|
|
(obfd, info, ibfd, sec, rel, adjustedp))
|
|
#define bfd_coff_link_add_one_symbol(info,abfd,name,flags,section,value,string,cp,coll,hashp)\
|
|
((coff_backend_info (abfd)->_bfd_coff_link_add_one_symbol)\
|
|
(info, abfd, name, flags, section, value, string, cp, coll, hashp))
|
|
|
|
#define bfd_coff_link_output_has_begun(a,p) \
|
|
((coff_backend_info (a)->_bfd_coff_link_output_has_begun) (a,p))
|
|
#define bfd_coff_final_link_postscript(a,p) \
|
|
((coff_backend_info (a)->_bfd_coff_final_link_postscript) (a,p))
|
|
|
|
@end example
|
|
@subsubsection Writing relocations
|
|
To write relocations, the back end steps though the
|
|
canonical relocation table and create an
|
|
@code{internal_reloc}. The symbol index to use is removed from
|
|
the @code{offset} field in the symbol table supplied. The
|
|
address comes directly from the sum of the section base
|
|
address and the relocation offset; the type is dug directly
|
|
from the howto field. Then the @code{internal_reloc} is
|
|
swapped into the shape of an @code{external_reloc} and written
|
|
out to disk.
|
|
|
|
@subsubsection Reading linenumbers
|
|
Creating the linenumber table is done by reading in the entire
|
|
coff linenumber table, and creating another table for internal use.
|
|
|
|
A coff linenumber table is structured so that each function
|
|
is marked as having a line number of 0. Each line within the
|
|
function is an offset from the first line in the function. The
|
|
base of the line number information for the table is stored in
|
|
the symbol associated with the function.
|
|
|
|
Note: The PE format uses line number 0 for a flag indicating a
|
|
new source file.
|
|
|
|
The information is copied from the external to the internal
|
|
table, and each symbol which marks a function is marked by
|
|
pointing its...
|
|
|
|
How does this work ?
|
|
|
|
@subsubsection Reading relocations
|
|
Coff relocations are easily transformed into the internal BFD form
|
|
(@code{arelent}).
|
|
|
|
Reading a coff relocation table is done in the following stages:
|
|
|
|
@itemize @bullet
|
|
|
|
@item
|
|
Read the entire coff relocation table into memory.
|
|
|
|
@item
|
|
Process each relocation in turn; first swap it from the
|
|
external to the internal form.
|
|
|
|
@item
|
|
Turn the symbol referenced in the relocation's symbol index
|
|
into a pointer into the canonical symbol table.
|
|
This table is the same as the one returned by a call to
|
|
@code{bfd_canonicalize_symtab}. The back end will call that
|
|
routine and save the result if a canonicalization hasn't been done.
|
|
|
|
@item
|
|
The reloc index is turned into a pointer to a howto
|
|
structure, in a back end specific way. For instance, the 386
|
|
and 960 use the @code{r_type} to directly produce an index
|
|
into a howto table vector; the 88k subtracts a number from the
|
|
@code{r_type} field and creates an addend field.
|
|
@end itemize
|
|
|