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