Here is the section structure:
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;
/* Which section is it; 0..nth. */
int index;
/* The next section in the list belonging to the BFD, or NULL. */
struct sec *next;
/* The field flags contains attributes of the section. Some
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 loading.
This is 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 is clear for a .bss section. */
#define SEC_LOAD 0x002
/* The section contains data still to be relocated, so there is
some relocation information too. */
#define SEC_RELOC 0x004
#if 0 /* Obsolete ? */
#define SEC_BALIGN 0x008
#endif
/* 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 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 (e.g., __CTOR_LIST__), attaches
the symbol to it, and builds a relocation. To build the lists
of constructors, all the linker has to do is catenate all the
sections called __CTOR_LIST__ and relocate the data
contained within - exactly the operations it would peform on
standard data. */
#define SEC_CONSTRUCTOR 0x100
/* The section is a constuctor, and should be placed at the
end of the text, data, or bss section(?). */
#define SEC_CONSTRUCTOR_TEXT 0x1100
#define SEC_CONSTRUCTOR_DATA 0x2100
#define SEC_CONSTRUCTOR_BSS 0x3100
/* The section has contents - a data section could be
SEC_ALLOC | SEC_HAS_CONTENTS; a debug section could be
SEC_HAS_CONTENTS */
#define SEC_HAS_CONTENTS 0x200
/* An instruction to the linker to not output the section
even if it has information which would normally be written. */
#define SEC_NEVER_LOAD 0x400
/* The section is a COFF shared library section. This flag is
only for the linker. If this type of section appears in
the input file, the linker must copy it to the output file
without changing the vma or size. FIXME: Although this
was originally intended to be general, it really is COFF
specific (and the flag was renamed to indicate this). It
might be cleaner to have some more general mechanism to
allow the back end to control what the linker does with
sections. */
#define SEC_COFF_SHARED_LIBRARY 0x800
/* The section contains common symbols (symbols may be defined
multiple times, the value of a symbol is the amount of
space it requires, and the largest symbol value is the one
used). Most targets have exactly one of these (which we
translate to bfd_com_section_ptr), but ECOFF has two. */
#define SEC_IS_COMMON 0x8000
/* The section contains only debugging information. For
example, this is set for ELF .debug and .stab sections.
strip tests this flag to see if a section can be
discarded. */
#define SEC_DEBUGGING 0x10000
/* The contents of this section are held in memory pointed to
by the contents field. This is checked by
bfd_get_section_contents, and the data is retrieved from
memory if appropriate. */
#define SEC_IN_MEMORY 0x20000
/* The contents of this section are to be excluded by the
linker for executable and shared objects unless those
objects are to be further relocated. */
#define SEC_EXCLUDE 0x40000
/* The contents of this section are to be sorted by the
based on the address specified in the associated symbol
table. */
#define SEC_SORT_ENTRIES 0x80000
/* When linking, duplicate sections of the same name should be
discarded, rather than being combined into a single section as
is usually done. This is similar to how common symbols are
handled. See SEC_LINK_DUPLICATES below. */
#define SEC_LINK_ONCE 0x100000
/* If SEC_LINK_ONCE is set, this bitfield describes how the linker
should handle duplicate sections. */
#define SEC_LINK_DUPLICATES 0x600000
/* This value for SEC_LINK_DUPLICATES means that duplicate
sections with the same name should simply be discarded. */
#define SEC_LINK_DUPLICATES_DISCARD 0x0
/* This value for SEC_LINK_DUPLICATES means that the linker
should warn if there are any duplicate sections, although
it should still only link one copy. */
#define SEC_LINK_DUPLICATES_ONE_ONLY 0x200000
/* This value for SEC_LINK_DUPLICATES means that the linker
should warn if any duplicate sections are a different size. */
#define SEC_LINK_DUPLICATES_SAME_SIZE 0x400000
/* This value for SEC_LINK_DUPLICATES means that the linker
should warn if any duplicate sections contain different
contents. */
#define SEC_LINK_DUPLICATES_SAME_CONTENTS 0x600000
/* This section was created by the linker as part of dynamic
relocation or other arcane processing. It is skipped when
going through the first-pass output, trusting that someone
else up the line will take care of it later. */
#define SEC_LINKER_CREATED 0x800000
/* End of section flags. */
/* Some internal packed boolean fields. */
/* See the vma field. */
unsigned int user_set_vma : 1;
/* Whether relocations have been processed. */
unsigned int reloc_done : 1;
/* A mark flag used by some of the linker backends. */
unsigned int linker_mark : 1;
/* End of internal packed boolean fields. */
/* The virtual memory address of the section - where it will be
at run time. The symbols are relocated against this. The
user_set_vma flag is maintained by bfd; if it's not set, the
backend can assign addresses (for example, in a.out, where
the default address for .data is dependent on the specific
target and various flags). */
bfd_vma vma;
/* The load address of the section - where it would be in a
rom image; really only used for writing section header
information. */
bfd_vma lma;
/* The size of the section in bytes, as it will be output.
contains a value even if the section has no contents (e.g., the
size of .bss). This will be filled in after relocation */
bfd_size_type _cooked_size;
/* The original size on disk of the section, in bytes. Normally this
value is the same as the size, but if some relaxing has
been done, then this value will be bigger. */
bfd_size_type _raw_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. E.g., 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 of 2 -
e.g., 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;
/* 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;
/* If the SEC_IN_MEMORY flag is set, this points to the actual
contents. */
unsigned char *contents;
/* 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 */
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;
/* A symbol which points at this section only */
struct symbol_cache_entry *symbol;
struct symbol_cache_entry **symbol_ptr_ptr;
struct bfd_link_order *link_order_head;
struct bfd_link_order *link_order_tail;
} asection ;
/* These sections are global, and are managed by BFD. The application
and target back end are not permitted to change the values in
these sections. New code should use the section_ptr macros rather
than referring directly to the const sections. The const sections
may eventually vanish. */
#define BFD_ABS_SECTION_NAME "*ABS*"
#define BFD_UND_SECTION_NAME "*UND*"
#define BFD_COM_SECTION_NAME "*COM*"
#define BFD_IND_SECTION_NAME "*IND*"
/* the absolute section */
extern const asection bfd_abs_section;
#define bfd_abs_section_ptr ((asection *) &bfd_abs_section)
#define bfd_is_abs_section(sec) ((sec) == bfd_abs_section_ptr)
/* Pointer to the undefined section */
extern const asection bfd_und_section;
#define bfd_und_section_ptr ((asection *) &bfd_und_section)
#define bfd_is_und_section(sec) ((sec) == bfd_und_section_ptr)
/* Pointer to the common section */
extern const asection bfd_com_section;
#define bfd_com_section_ptr ((asection *) &bfd_com_section)
/* Pointer to the indirect section */
extern const asection bfd_ind_section;
#define bfd_ind_section_ptr ((asection *) &bfd_ind_section)
#define bfd_is_ind_section(sec) ((sec) == bfd_ind_section_ptr)
extern const struct symbol_cache_entry * const bfd_abs_symbol;
extern const struct symbol_cache_entry * const bfd_com_symbol;
extern const struct symbol_cache_entry * const bfd_und_symbol;
extern const struct symbol_cache_entry * const bfd_ind_symbol;
#define bfd_get_section_size_before_reloc(section) \
(section->reloc_done ? (abort(),1): (section)->_raw_size)
#define bfd_get_section_size_after_reloc(section) \
((section->reloc_done) ? (section)->_cooked_size: (abort(),1))
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