bfdt.texi

这个是LINUX下的GDB调度工具的源码

@section @code{typedef bfd}
A BFD has type @code{bfd}; objects of this type are the
cornerstone of any application using BFD. Using BFD
consists of making references though the BFD and to data in the BFD.

Here is the structure that defines the type @code{bfd}.  It
contains the major data about the file and pointers
to the rest of the data.


@example

struct bfd
@{
  /* A unique identifier of the BFD  */
  unsigned int id;

  /* The filename the application opened the BFD with.  */
  const char *filename;

  /* A pointer to the target jump table.  */
  const struct bfd_target *xvec;

  /* The IOSTREAM, and corresponding IO vector that provide access
     to the file backing the BFD.  */
  void *iostream;
  const struct bfd_iovec *iovec;

  /* Is the file descriptor being cached?  That is, can it be closed as
     needed, and re-opened when accessed later?  */
  bfd_boolean cacheable;

  /* Marks whether there was a default target specified when the
     BFD was opened. This is used to select which matching algorithm
     to use to choose the back end.  */
  bfd_boolean target_defaulted;

  /* The caching routines use these to maintain a
     least-recently-used list of BFDs.  */
  struct bfd *lru_prev, *lru_next;

  /* When a file is closed by the caching routines, BFD retains
     state information on the file here...  */
  ufile_ptr where;

  /* ... and here: (``once'' means at least once).  */
  bfd_boolean opened_once;

  /* Set if we have a locally maintained mtime value, rather than
     getting it from the file each time.  */
  bfd_boolean mtime_set;

  /* File modified time, if mtime_set is TRUE.  */
  long mtime;

  /* Reserved for an unimplemented file locking extension.  */
  int ifd;

  /* The format which belongs to the BFD. (object, core, etc.)  */
  bfd_format format;

  /* The direction with which the BFD was opened.  */
  enum bfd_direction
    @{
      no_direction = 0,
      read_direction = 1,
      write_direction = 2,
      both_direction = 3
    @}
  direction;

  /* Format_specific flags.  */
  flagword flags;

  /* Currently my_archive is tested before adding origin to
     anything. I believe that this can become always an add of
     origin, with origin set to 0 for non archive files.  */
  ufile_ptr origin;

  /* Remember when output has begun, to stop strange things
     from happening.  */
  bfd_boolean output_has_begun;

  /* A hash table for section names.  */
  struct bfd_hash_table section_htab;

  /* Pointer to linked list of sections.  */
  struct bfd_section *sections;

  /* The place where we add to the section list.  */
  struct bfd_section **section_tail;

  /* The number of sections.  */
  unsigned int section_count;

  /* Stuff only useful for object files:
     The start address.  */
  bfd_vma start_address;

  /* Used for input and output.  */
  unsigned int symcount;

  /* Symbol table for output BFD (with symcount entries).  */
  struct bfd_symbol  **outsymbols;

  /* Used for slurped dynamic symbol tables.  */
  unsigned int dynsymcount;

  /* Pointer to structure which contains architecture information.  */
  const struct bfd_arch_info *arch_info;

  /* Flag set if symbols from this BFD should not be exported.  */
  bfd_boolean no_export;

  /* Stuff only useful for archives.  */
  void *arelt_data;
  struct bfd *my_archive;      /* The containing archive BFD.  */
  struct bfd *next;            /* The next BFD in the archive.  */
  struct bfd *archive_head;    /* The first BFD in the archive.  */
  bfd_boolean has_armap;

  /* A chain of BFD structures involved in a link.  */
  struct bfd *link_next;

  /* A field used by _bfd_generic_link_add_archive_symbols.  This will
     be used only for archive elements.  */
  int archive_pass;

  /* Used by the back end to hold private data.  */
  union
    @{
      struct aout_data_struct *aout_data;
      struct artdata *aout_ar_data;
      struct _oasys_data *oasys_obj_data;
      struct _oasys_ar_data *oasys_ar_data;
      struct coff_tdata *coff_obj_data;
      struct pe_tdata *pe_obj_data;
      struct xcoff_tdata *xcoff_obj_data;
      struct ecoff_tdata *ecoff_obj_data;
      struct ieee_data_struct *ieee_data;
      struct ieee_ar_data_struct *ieee_ar_data;
      struct srec_data_struct *srec_data;
      struct ihex_data_struct *ihex_data;
      struct tekhex_data_struct *tekhex_data;
      struct elf_obj_tdata *elf_obj_data;
      struct nlm_obj_tdata *nlm_obj_data;
      struct bout_data_struct *bout_data;
      struct mmo_data_struct *mmo_data;
      struct sun_core_struct *sun_core_data;
      struct sco5_core_struct *sco5_core_data;
      struct trad_core_struct *trad_core_data;
      struct som_data_struct *som_data;
      struct hpux_core_struct *hpux_core_data;
      struct hppabsd_core_struct *hppabsd_core_data;
      struct sgi_core_struct *sgi_core_data;
      struct lynx_core_struct *lynx_core_data;
      struct osf_core_struct *osf_core_data;
      struct cisco_core_struct *cisco_core_data;
      struct versados_data_struct *versados_data;
      struct netbsd_core_struct *netbsd_core_data;
      struct mach_o_data_struct *mach_o_data;
      struct mach_o_fat_data_struct *mach_o_fat_data;
      struct bfd_pef_data_struct *pef_data;
      struct bfd_pef_xlib_data_struct *pef_xlib_data;
      struct bfd_sym_data_struct *sym_data;
      void *any;
    @}
  tdata;

  /* Used by the application to hold private data.  */
  void *usrdata;

  /* Where all the allocated stuff under this BFD goes.  This is a
     struct objalloc *, but we use void * to avoid requiring the inclusion
     of objalloc.h.  */
  void *memory;
@};

@end example
@section Error reporting
Most BFD functions return nonzero on success (check their
individual documentation for precise semantics).  On an error,
they call @code{bfd_set_error} to set an error condition that callers
can check by calling @code{bfd_get_error}.
If that returns @code{bfd_error_system_call}, then check
@code{errno}.

The easiest way to report a BFD error to the user is to
use @code{bfd_perror}.

@subsection Type @code{bfd_error_type}
The values returned by @code{bfd_get_error} are defined by the
enumerated type @code{bfd_error_type}.


@example

typedef enum bfd_error
@{
  bfd_error_no_error = 0,
  bfd_error_system_call,
  bfd_error_invalid_target,
  bfd_error_wrong_format,
  bfd_error_wrong_object_format,
  bfd_error_invalid_operation,
  bfd_error_no_memory,
  bfd_error_no_symbols,
  bfd_error_no_armap,
  bfd_error_no_more_archived_files,
  bfd_error_malformed_archive,
  bfd_error_file_not_recognized,
  bfd_error_file_ambiguously_recognized,
  bfd_error_no_contents,
  bfd_error_nonrepresentable_section,
  bfd_error_no_debug_section,
  bfd_error_bad_value,
  bfd_error_file_truncated,
  bfd_error_file_too_big,
  bfd_error_invalid_error_code
@}
bfd_error_type;

@end example
@findex bfd_get_error
@subsubsection @code{bfd_get_error}
@strong{Synopsis}
@example
bfd_error_type bfd_get_error (void);
@end example
@strong{Description}@*
Return the current BFD error condition.

@findex bfd_set_error
@subsubsection @code{bfd_set_error}
@strong{Synopsis}
@example
void bfd_set_error (bfd_error_type error_tag);
@end example
@strong{Description}@*
Set the BFD error condition to be @var{error_tag}.

@findex bfd_errmsg
@subsubsection @code{bfd_errmsg}
@strong{Synopsis}
@example
const char *bfd_errmsg (bfd_error_type error_tag);
@end example
@strong{Description}@*
Return a string describing the error @var{error_tag}, or
the system error if @var{error_tag} is @code{bfd_error_system_call}.

@findex bfd_perror
@subsubsection @code{bfd_perror}
@strong{Synopsis}
@example
void bfd_perror (const char *message);
@end example
@strong{Description}@*
Print to the standard error stream a string describing the
last BFD error that occurred, or the last system error if
the last BFD error was a system call failure.  If @var{message}
is non-NULL and non-empty, the error string printed is preceded
by @var{message}, a colon, and a space.  It is followed by a newline.

@subsection BFD error handler
Some BFD functions want to print messages describing the
problem.  They call a BFD error handler function.  This
function may be overridden by the program.

The BFD error handler acts like printf.


@example

typedef void (*bfd_error_handler_type) (const char *, ...);

@end example
@findex bfd_set_error_handler
@subsubsection @code{bfd_set_error_handler}
@strong{Synopsis}
@example
bfd_error_handler_type bfd_set_error_handler (bfd_error_handler_type);
@end example
@strong{Description}@*
Set the BFD error handler function.  Returns the previous
function.

@findex bfd_set_error_program_name
@subsubsection @code{bfd_set_error_program_name}
@strong{Synopsis}
@example
void bfd_set_error_program_name (const char *);
@end example
@strong{Description}@*
Set the program name to use when printing a BFD error.  This
is printed before the error message followed by a colon and
space.  The string must not be changed after it is passed to
this function.

@findex bfd_get_error_handler
@subsubsection @code{bfd_get_error_handler}
@strong{Synopsis}
@example
bfd_error_handler_type bfd_get_error_handler (void);
@end example
@strong{Description}@*
Return the BFD error handler function.

@section Symbols


@findex bfd_get_reloc_upper_bound
@subsubsection @code{bfd_get_reloc_upper_bound}
@strong{Synopsis}
@example
long bfd_get_reloc_upper_bound (bfd *abfd, asection *sect);
@end example
@strong{Description}@*
Return the number of bytes required to store the
relocation information associated with section @var{sect}
attached to bfd @var{abfd}.  If an error occurs, return -1.

@findex bfd_canonicalize_reloc
@subsubsection @code{bfd_canonicalize_reloc}
@strong{Synopsis}
@example
long bfd_canonicalize_reloc
   (bfd *abfd, asection *sec, arelent **loc, asymbol **syms);
@end example
@strong{Description}@*
Call the back end associated with the open BFD
@var{abfd} and translate the external form of the relocation
information attached to @var{sec} into the internal canonical
form.  Place the table into memory at @var{loc}, which has
been preallocated, usually by a call to
@code{bfd_get_reloc_upper_bound}.  Returns the number of relocs, or
-1 on error.

The @var{syms} table is also needed for horrible internal magic
reasons.

@findex bfd_set_reloc
@subsubsection @code{bfd_set_reloc}
@strong{Synopsis}
@example
void bfd_set_reloc
   (bfd *abfd, asection *sec, arelent **rel, unsigned int count);
@end example
@strong{Description}@*
Set the relocation pointer and count within
section @var{sec} to the values @var{rel} and @var{count}.
The argument @var{abfd} is ignored.

@findex bfd_set_file_flags
@subsubsection @code{bfd_set_file_flags}
@strong{Synopsis}