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6724ff46c8
* aoutx.h, archive.c, archures.c, bfd.c, bfd.texinfo, cache.c, coffcode.h, core.c, format.c, libbfd.c, libbfd.h, libcoff.h, opncls.c, reloc.c, section.c, syms.c, targets.c (documentation segments): used BFD (caps) more consistently as a name in discourse, fixed a few other minor typos and uses of fonts
584 lines
15 KiB
C
584 lines
15 KiB
C
/* Object file "section" support for the BFD library.
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Copyright (C) 1990-1991 Free Software Foundation, Inc.
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Written by Cygnus Support.
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This file is part of BFD, the Binary File Descriptor library.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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/*doc*
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@section Sections
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Sections are supported in BFD in @code{section.c}.
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The raw data contained within a BFD is maintained through the section
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abstraction. A single BFD may have any number of sections, and keeps
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hold of them by pointing to the first, each one points to the next in
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the list.
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@menu
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* Section Input::
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* Section Output::
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* typedef asection::
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* section prototypes::
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@end menu
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@node Section Input, Section Output,,Sections
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@comment node-name, next, previous, up
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@subsection Section Input
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When a BFD is opened for reading, the section structures are created
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and attatched to the BFD.
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Each section has a name which describes the section in the outside
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world - for example, @code{a.out} would contain at least three
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sections, called @code{.text}, @code{.data} and @code{.bss}.
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Sometimes a BFD will contain more than the 'natural' number of
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sections. A back end may attatch other sections containing constructor
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data, or an application may add a section (using bfd_make_section) to
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the sections attatched to an already open BFD. For example, the linker
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creates a supernumary section @code{COMMON} for each input file's BFD
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to hold information about common storage.
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The raw data is not necessarily read in at the same time as the
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section descriptor is created. Some targets may leave the data in
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place until a @code{bfd_get_section_contents} call is made. Other back
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ends may read in all the data at once - For example; an S-record file
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has to be read once to determine the size of the data. An IEEE-695
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file doesn't contain raw data in sections, but data and relocation
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expressions intermixed, so the data area has to be parsed to get out
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the data and relocations.
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@node Section Output,typedef asection,Section Input,Sections
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@subsection Section Output
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To write a new object style BFD, the various sections to be written
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have to be created. They are attatched to the BFD in the same way as
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input sections, data is written to the sections using
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@code{bfd_set_section_contents}.
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The linker uses the fields @code{output_section} and
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@code{output_offset} to create an output file.
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The data to be written comes from input sections attatched to the
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output sections. The output section structure can be considered a
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filter for the input section, the output section determines the vma of
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the output data and the name, but the input section determines the
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offset into the output section of the data to be written.
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Eg to create a section "O", starting at 0x100, 0x123 long, containing two
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subsections, "A" at offset 0x0 (ie at vma 0x100) and "B" at offset
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0x20 (ie at vma 0x120) the structures would look like:
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*+
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section name "A"
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output_offset 0x00
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size 0x20
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output_section -----------> section name "O"
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| vma 0x100
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section name "B" | size 0x123
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output_offset 0x20 |
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size 0x103 |
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output_section --------|
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*-
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*/
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#include "sysdep.h"
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#include "bfd.h"
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#include "libbfd.h"
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/*doc*
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@node typedef asection,section prototypes,Section Output,Sections
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@subsection typedef asection
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*/
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/*proto*
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The shape of a section struct:
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*+++
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$typedef struct sec {
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The name of the section, the name isn't a copy, the pointer is
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the same as that passed to bfd_make_section.
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$ CONST char *name;
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The next section in the list belonging to the BFD, or NULL.
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$ struct sec *next;
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The field flags contains attributes of the section. Some of these
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flags are read in from the object file, and some are synthesized from
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other information.
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$flagword flags;
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$#define SEC_NO_FLAGS 0x000
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Tells the OS to allocate space for this section when loaded.
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This would clear for a section containing debug information only.
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$#define SEC_ALLOC 0x001
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Tells the OS to load the section from the file when loading.
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This would be clear for a .bss section
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$#define SEC_LOAD 0x002
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The section contains data still to be relocated, so there will be some
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relocation information too.
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$#define SEC_RELOC 0x004
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Obsolete ?
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$#define SEC_BALIGN 0x008
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A signal to the OS that the section contains read only data.
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$#define SEC_READONLY 0x010
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The section contains code only.
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$#define SEC_CODE 0x020
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The section contains data only.
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$#define SEC_DATA 0x040
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The section will reside in ROM.
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$#define SEC_ROM 0x080
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The section contains constructor information. This section type is
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used by the linker to create lists of constructors and destructors
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used by @code{g++}. When a back end sees a symbol which should be used
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in a constructor list, it creates a new section for the type of name
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(eg @code{__CTOR_LIST__}), attatches the symbol to it and builds a
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relocation. To build the lists of constructors, all the linker has to
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to is catenate all the sections called @code{__CTOR_LIST__} and
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relocte the data contained within - exactly the operations it would
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peform on standard data.
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$#define SEC_CONSTRUCTOR 0x100
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The section is a constuctor, and should be placed at the end of the ..
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$#define SEC_CONSTRUCTOR_TEXT 0x1100
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$#define SEC_CONSTRUCTOR_DATA 0x2100
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$#define SEC_CONSTRUCTOR_BSS 0x3100
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The section has contents - a bss section could be
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@code{SEC_ALLOC} | @code{SEC_HAS_CONTENTS}, a debug section could be
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@code{SEC_HAS_CONTENTS}
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$#define SEC_HAS_CONTENTS 0x200
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An instruction to the linker not to output sections containing
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this flag even if they have information which would normally be written.
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$#define SEC_NEVER_LOAD 0x400
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The base address of the section in the address space of the target.
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$ bfd_vma vma;
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The size of the section in bytes of the loaded section. This contains
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a value even if the section has no contents (eg, the size of @code{.bss}).
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$ bfd_size_type size;
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If this section is going to be output, then this value is the
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offset into the output section of the first byte in the input
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section. Eg, if this was going to start at the 100th byte in the
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output section, this value would be 100.
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$ bfd_vma output_offset;
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The output section through which to map on output.
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$ struct sec *output_section;
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The alignment requirement of the section, as an exponent - eg 3
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aligns to 2^3 (or 8)
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$ unsigned int alignment_power;
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If an input section, a pointer to a vector of relocation records for
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the data in this section.
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$ struct reloc_cache_entry *relocation;
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If an output section, a pointer to a vector of pointers to
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relocation records for the data in this section.
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$ struct reloc_cache_entry **orelocation;
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The number of relocation records in one of the above
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$ unsigned reloc_count;
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Which section is it 0..nth
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$ int index;
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Information below is back end specific - and not always used or
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updated
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File position of section data
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$ file_ptr filepos;
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File position of relocation info
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$ file_ptr rel_filepos;
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File position of line data
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$ file_ptr line_filepos;
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Pointer to data for applications
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$ PTR userdata;
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$ struct lang_output_section *otheruserdata;
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Attached line number information
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$ alent *lineno;
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Number of line number records
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$ unsigned int lineno_count;
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When a section is being output, this value changes as more
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linenumbers are written out
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$ file_ptr moving_line_filepos;
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what the section number is in the target world
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$ unsigned int target_index;
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$ PTR used_by_bfd;
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If this is a constructor section then here is a list of the
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relocations created to relocate items within it.
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$ struct relent_chain *constructor_chain;
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The BFD which owns the section.
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$ bfd *owner;
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$} asection ;
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*---
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*/
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/*doc*
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@node section prototypes,Section,typedef section,Sections
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@subsection section prototypes
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*/
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/*proto* bfd_get_section_by_name
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Runs through the provided @var{abfd} and returns the @code{asection}
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who's name matches that provided, otherwise NULL. @xref{Sections}, for more information.
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*; PROTO(asection *, bfd_get_section_by_name,
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(bfd *abfd, CONST char *name));
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*/
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asection *
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DEFUN(bfd_get_section_by_name,(abfd, name),
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bfd *abfd AND
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CONST char *name)
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{
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asection *sect;
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for (sect = abfd->sections; sect != NULL; sect = sect->next)
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if (!strcmp (sect->name, name)) return sect;
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return NULL;
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}
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/*proto* bfd_make_section
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This function creates a new empty section called @var{name} and attatches it
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to the end of the chain of sections for the BFD supplied. An attempt to
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create a section with a name which is already in use, returns the old
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section by that name instead.
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Possible errors are:
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@table @code
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@item invalid_operation
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If output has already started for this BFD.
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@item no_memory
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If obstack alloc fails.
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@end table
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*; PROTO(asection *, bfd_make_section, (bfd *, CONST char *name));
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*/
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sec_ptr
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DEFUN(bfd_make_section,(abfd, name),
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bfd *abfd AND
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CONST char * name)
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{
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asection *newsect;
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asection ** prev = &abfd->sections;
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asection * sect = abfd->sections;
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if (abfd->output_has_begun) {
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bfd_error = invalid_operation;
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return NULL;
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}
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while (sect) {
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if (!strcmp(sect->name, name)) return sect;
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prev = §->next;
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sect = sect->next;
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}
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newsect = (asection *) bfd_zalloc(abfd, sizeof (asection));
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if (newsect == NULL) {
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bfd_error = no_memory;
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return NULL;
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}
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newsect->name = name;
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newsect->index = abfd->section_count++;
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newsect->flags = SEC_NO_FLAGS;
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newsect->userdata = 0;
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newsect->next = (asection *)NULL;
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newsect->relocation = (arelent *)NULL;
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newsect->reloc_count = 0;
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newsect->line_filepos =0;
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newsect->owner = abfd;
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if (BFD_SEND (abfd, _new_section_hook, (abfd, newsect)) != true) {
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free (newsect);
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return NULL;
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}
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*prev = newsect;
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return newsect;
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}
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/*proto* bfd_set_section_flags
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Attempts to set the attributes of the section named in the BFD
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supplied to the value. Returns true on success, false on error.
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Possible error returns are:
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@table @code
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@item invalid operation
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The section cannot have one or more of the attributes requested. For
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example, a .bss section in @code{a.out} may not have the
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@code{SEC_HAS_CONTENTS} field set.
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@end table
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*; PROTO(boolean, bfd_set_section_flags,
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(bfd *, asection *, flagword));
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*/
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boolean
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DEFUN(bfd_set_section_flags,(abfd, section, flags),
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bfd *abfd AND
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sec_ptr section AND
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flagword flags)
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{
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if ((flags & bfd_applicable_section_flags (abfd)) != flags) {
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bfd_error = invalid_operation;
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return false;
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}
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section->flags = flags;
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return true;
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}
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/*proto* bfd_map_over_sections
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Calls the provided function @var{func} for each section attatched to
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the BFD @var{abfd}, passing @var{obj} as an argument. The function
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will be called as if by
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@example
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func(abfd, the_section, obj);
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@end example
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*; PROTO(void, bfd_map_over_sections,
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(bfd *abfd, void (*func)(), PTR obj));
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This is the prefered method for iterating over sections, an
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alternative would be to use a loop:
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@example
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section *p;
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for (p = abfd->sections; p != NULL; p = p->next)
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func(abfd, p, ...)
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@end example
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*/
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/*VARARGS2*/
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void
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DEFUN(bfd_map_over_sections,(abfd, operation, user_storage),
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bfd *abfd AND
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void (*operation)() AND
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PTR user_storage)
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{
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asection *sect;
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int i = 0;
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for (sect = abfd->sections; sect != NULL; i++, sect = sect->next)
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(*operation) (abfd, sect, user_storage);
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if (i != abfd->section_count) /* Debugging */
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abort();
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}
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/*proto* bfd_set_section_size
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Sets @var{section} to the size @var{val}. If the operation is ok, then
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@code{true} is returned, else @code{false}.
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Possible error returns:
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@table @code
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@item invalid_operation
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Writing has started to the BFD, so setting the size is invalid
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@end table
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*; PROTO(boolean, bfd_set_section_size,
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(bfd *, asection *, bfd_size_type val));
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*/
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boolean
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DEFUN(bfd_set_section_size,(abfd, ptr, val),
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bfd *abfd AND
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sec_ptr ptr AND
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bfd_size_type val)
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{
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/* Once you've started writing to any section you cannot create or change
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the size of any others. */
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if (abfd->output_has_begun) {
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bfd_error = invalid_operation;
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return false;
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}
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ptr->size = val;
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return true;
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}
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/*proto* bfd_set_section_contents
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Sets the contents of the section @var{section} in BFD @var{abfd} to
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the data starting in memory at @var{data}. The data is written to the
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output section starting at offset @var{offset} for @var{count} bytes.
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Normally @code{true} is returned, else @code{false}. Possible error
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returns are:
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@table @code
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@item no_contents
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The output section does not have the @code{SEC_HAS_CONTENTS}
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attribute, so nothing can be written to it.
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@item and some more too
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@end table
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This routine is front end to the back end function @code{_bfd_set_section_contents}.
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*; PROTO(boolean, bfd_set_section_contents,
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(bfd *abfd,
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asection *section,
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PTR data,
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file_ptr offset,
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bfd_size_type count));
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*/
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boolean
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DEFUN(bfd_set_section_contents,(abfd, section, location, offset, count),
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bfd *abfd AND
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sec_ptr section AND
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PTR location AND
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file_ptr offset AND
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bfd_size_type count)
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{
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if (!(bfd_get_section_flags(abfd, section) & SEC_HAS_CONTENTS))
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{
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bfd_error = no_contents;
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return(false);
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}
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if (BFD_SEND (abfd, _bfd_set_section_contents,
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(abfd, section, location, offset, count)))
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{
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abfd->output_has_begun = true;
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return true;
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}
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return false;
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}
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/*proto* bfd_get_section_contents
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This function reads data from @var{section} in BFD @var{abfd} into
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memory starting at @var{location}. The data is read at an offset of
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@var{offset} from the start of the input section, and is read for
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@var{count} bytes.
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If the contents of a constuctor with the @code{SEC_CONSTUCTOR} flag
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set are requested, then the @var{location} is filled with zeroes.
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If no errors occur, @code{true} is returned, else @code{false}.
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Possible errors are:
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@table @code
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@item unknown yet
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@end table
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*; PROTO(boolean, bfd_get_section_contents,
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(bfd *abfd, asection *section, PTR location,
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file_ptr offset, bfd_size_type count));
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*/
|
|
boolean
|
|
DEFUN(bfd_get_section_contents,(abfd, section, location, offset, count),
|
|
bfd *abfd AND
|
|
sec_ptr section AND
|
|
PTR location AND
|
|
file_ptr offset AND
|
|
bfd_size_type count)
|
|
{
|
|
if (section->flags & SEC_CONSTRUCTOR)
|
|
{
|
|
memset(location, 0, (unsigned)count);
|
|
return true;
|
|
}
|
|
else
|
|
{
|
|
return (BFD_SEND (abfd, _bfd_get_section_contents,
|
|
(abfd, section, location, offset, count)));
|
|
}
|
|
}
|
|
|