int to boolean; update all callers. Pass MAP_SHARED if not
writable--it's required on Solaris. Cast fprintf argument to
avoid warning.
* bfd-in.h (bfd_get_file_window): Update declaration.
* bfd-in2.h: Rebuild.
* aoutx.h: Update calls to bfd_get_file_window.
Cast realloc and malloc return values. If malloc or realloc fail,
set bfd_error_no_memory.
* bfd-in.h (bfd_get_file_window): Change type to boolean.
* bfd-in2.h: Rebuild.
Added some new interfaces, and a new entry in the target vector. Under the new
interfaces, mmap will be used if available, otherwise malloc/seek/read, as
before. Old interfaces all still intact.
Most configurations (including all used by "--enable-targets=all") simply
changed to call the default routine for that entry in the target vector. I
might've missed some targets only included in special configurations.
Support for a.out symbol and string table reading now goes through new
interfaces, and will use mmap when available.
Linker hooks (e.g., avoiding reallocation under malloc) not ready yet.
constructors and a few other special cases.
* coff-rs6000.c (rs6000coff_vec): Set symbol_leading_char back to
zero, reverting yesterday's change.
* bfd-in.h (bfd_xcoff_link_record_set): Declare.
(bfd_xcoff_link_count_reloc): Declare.
(bfd_xcoff_record_link_assignment): Declare.
* bfd-in2.h: Rebuild.
HOST_64BIT_LONG. Check that various header files exist. Check
that fcntl exists. Call BFD_BINARY_FOPEN. Check whether malloc
and/or free need to be declared. Don't make a link to sysdep.h.
Define TRAD_HEADER for various hosts.
* configure: Rebuild.
* configure.host: Don't set my_host. Add definitions taken from
host header files for various entries. Remove entries which now
do nothing.
* acconfig.h: New file.
* config.h.in: New file, built by autoheader.
* sysdep.h: New file.
* Makefile.in (do_distclean): Don't remove sysdep.h.
(RECONFIG): Remove.
(LOCAL_H_DEPS): New variable.
($(BFD_LIBS)): Use $(LOCAL_H_DEPS) rather than libbfd.h and
$(RECONFIG).
($(BFD_MACHINES), $(BFD_BACKENDS)): Likewise.
($(OPTIONAL_BACKENDS)): Likewise.
(stmp-bfd.h): Just substitute for BFD_HOST_64BIT_LONG, rather than
looking through sysdep.h.
* bfd-in.h (BFD_HOST_64BIT_LONG): Define; set by Makefile.
(BFD_HOST_64_BIT): Define based on BFD_HOST_64BIT_LONG.
(fprintf_vma, sprintf_vma): Likewise.
(int64_type, uint64_type): Don't define.
* bfd-in2.h: Rebuild.
* archures.c, bfd.c, srec.c: Include <ctype.h>.
* elfcore.h: Check HAVE_SYS_PROCFS_H rather than HAVE_PROCFS.
* lynx-core.c: Include stuff from old hosts/lynx.h.
* opncls.c (bfd_fdopenr): Check HAVE_FNCTL and defined (F_GETFL),
rather than NO_FCNTL.
* targets.c (bfd_target_list): Check HOST_HPPAHPUX and ! __STDC__
rather than NATIVE_HPPAHPUX_COMPILER.
* trad-core.c: Don't include <errno.h>. Include TRAD_HEADER if it
is defined.
* hosts/*.h: Remove all header files which merely include,
declare, and define things. Leave header files which define
information needed by trad-core.c.
saw_needed field.
* elfcode.h (elf_link_add_object_symbols): If elf_dt_needed_name
is an empty string, don't make a DT_NEEDED entry in the output
file. Record all DT_NEEDED entries found in input dynamic
objects.
(elf_link_output_extsym): Don't check saw_needed when issuing
warnings.
* elf.c (_bfd_elf_link_hash_table_init): Initialize needed, not
saw_needed.
(bfd_elf_get_needed_list): New function.
* bfd-in.h (struct bfd_elf_link_needed_list): Define.
(bfd_elf_get_needed_list): Define.
* bfd-in2.h: Rebuild.
PR 7083.
to bfd_tttrue, bfd_fffalse so as not to conflict with functions.
* coffswap.h (coff_swap_scnhdr_out): Remove version that was
hacked for MPW C.
* mpw-config.in: Set shell vars instead of pasting to makefile
for each configuration, edit coffswap.h to make MPW C not choke.
(i386-unknown-coff, sh-hitachi-hms): Recognize.
* mpw-make.in (BFD_LIBS): Add versados.c.o.
* versados.c (versados_scan): Properly cast results from bfd_alloc.
to the target vector.
* libbfd-in.h (_bfd_generic_bfd_copy_private_symbol_data): Define.
(_bfd_nolink_bfd_link_split_section): Likewise.
(bfd_generic_link_split_section): Declare.
* syms.c (bfd_copy_private_symbol_data): Define.
* linker.c (bf_link_split_section): Likewise.
* som.c (som_bfd_copy_private_symbol_data): New function
(som_bfd_link_split_section): Likewise.
* All other targets updated with default versions of new routines.
* Take out my braindamaged bfd_true/bfd_false changes from earlier
today. Replace with just:
* bfd-in.h: (TRUE_FALSE_ALREADY_DEFINED): Define this if
compiling with g++-2.6 or later.
* bfd-in2.h: Rebuilt.
compiling with g++-2.6 or later.
(bfd_set_section_vma): Use bfd_true and bfd_false rather than
true and false.
(bfd_set_section_alignment): Likewise.
(bfd_set_section_userdata): Likewise.
(bfd_set_cacheable): Likewise.
* bfd-in2.h: Rebuilt.
(elf_dt_needed_name): New accessor macro.
* elfcode.h (elf_link_add_object_symbols): If elf_dt_needed_name
is set, use that instead of the filename for the DT_NEEDED dynamic
entry.
* elf.c (bfd_elf_set_dt_needed_name): New function.
* bfd-in.h (bfd_elf_set_dt_needed_name): Declare.
* bfd-in2.h: Rebuilt.
argument, and set it to the .interp section.
* bfd-in.h (bfd_elf32_size_dynamic_sections): Update prototype.
(bfd_elf64_size_dynamic_sections): Likewise.
* bfd-in2.h: Rebuilt.
Eric Youngdale <ericy@cais.com>.
* libelf.h (struct elf_backend_data): Add new fields for dynamic
linking: elf_backend_create_dynamic_sections,
elf_backend_adjust_dynamic_symbol,
elf_backend_size_dynamic_sections,
elf_backend_finish_dynamic_symbol,
elf_backend_finish_dynamic_sections.
(struct elf_link_hash_entry): Change type of align field to
bfd_size_type. Add fields dynindx, dynstr_index, weakdef,
elf_link_hash_flags.
(struct elf_link_hash_table): Add fields dynobj, dynsymcount,
dynstr, bucketcount.
(bfd_elf32_swap_reloc_in, bfd_elf32_swap_reloc_out): Declare.
(bfd_elf32_swap_reloca_in, bfd_elf32_swap_reloca_out): Declare.
(bfd_elf32_swap_dyn_in, bfd_elf32_swap_dyn_out): Declare.
(bfd_elf32_add_dynamic_entry): Declare.
(bfd_elf64_swap_reloc_in, bfd_elf64_swap_reloc_out): Declare.
(bfd_elf64_swap_reloca_in, bfd_elf64_swap_reloca_out): Declare.
(bfd_elf64_swap_dyn_in, bfd_elf64_swap_dyn_out): Declare.
(bfd_elf64_add_dynamic_entry): Declare.
* elfcode.h (Elf_External_Dyn): Define.
(elf_swap_reloc_in): Define as macro using NAME. Make externally
visible.
(elf_swap_reloc_out): Likewise.
(elf_swap_reloca_in, elf_swap_reloca_out): Likewise.
(elf_swap_dyn_in, elf_swap_dyn_out): Define as macro using NAME
and as new externally visible function.
(elf_fake_sections): Set section type of dynamic sections based on
section names.
(elf_write_phdrs): Remove.
(assign_file_position_for_section): Add new align argument.
Change all callers.
(get_program_header_size): New static function.
(struct seg_info): Remove.
(map_program_segments): Completely rewrite.
(assign_file_positions_except_relocs): Completely rewrite.
(assign_file_positions_for_relocs): Don't set a file position for
sections which already have one. Don't bother to align the file
position here.
(section_from_elf_index): Handle SHT_HASH and SHT_DYNAMIC
section types.
(elf_section_from_bfd_section): Likewise.
(elf_slurp_symbol_table): If section_from_elf_index fails, just
use bfd_abs_section rather than returning an error.
(elf_sizeof_headers): Make useful.
(elf_link_record_dynamic_symbol): New static function.
(elf_link_add_object_symbols): Handle dynamic objects.
(elf_link_create_dynamic_sections): New static function.
(elf_add_dynamic_entry): Define as macro using NAME and as new
externally visible function.
(NAME(bfd_elf,record_link_assignment)): New function.
(elf_buckets): New static variable.
(NAME(bfd_elf,size_dynamic_sections)): New function.
(struct elf_final_link_info): Add dynsym_sec and hash_sec fields.
(elf_bfd_final_link): Handle dynamic linking. Create a section
symbol for all ELF sections, not all BFD sections. Store section
symbol index in target_index field, not index field. Traverse
over global symbols even if stripping.
(elf_link_output_extsym): Output dynamic symbols. Mark symbols
defined by dynamic objects as undefined.
(elf_link_input_bfd): Ignore dynamic objects. Use target_index
field for section relocs, and make sure it is set.
(elf_reloc_link_order): Use target_index field for section relocs,
and make sure it is set.
* elf.c (elf_link_hash_newfunc): Initialize dynindx, dynstr_index,
weakdef and elf_link_hash_flags fields.
(_bfd_elf_link_hash_table_create): Initialize dynobj, dynsymcount,
dynstr and bucketcount fields.
* elf32-target.h: Initialize new dynamic linking fields.
* elf64-target.h: Likewise.
* elf32-i386.c: New functions for dynamic linking support.
* elf32-sparc.c: Likewise.
* bfd-in.h (bfd_elf32_record_link_assignment): Declare.
(bfd_elf64_record_link_assignment): Declare.
(bfd_elf32_size_dynamic_sections): Declare.
(bfd_elf64_size_dynamic_sections): Declare.
* bfd-in2.h: Rebuilt.
Removed _bfd_debug_info_start, _bfd_debug_info_end and
_bfd_debug_info_accumulate, which were never used.
(BFD_JUMP_TABLE_GENERIC, BFD_JUMP_TABLE_COPY): Defined.
(BFD_JUMP_TABLE_CORE, BFD_JUMP_TABLE_ARCHIVE): Defined.
(BFD_JUMP_TABLE_SYMBOLS, BFD_JUMP_TABLE_RELOCS): Defined.
(BFD_JUMP_TABLE_WRITE, BFD_JUMP_TABLE_LINK): Defined.
* All backends: Changed to use the new BFD_JUMP_TABLE_* macros
rather than the single JUMP_TABLE macro. Removed many of the
weird macro definitions needed to support the monolithic
JUMP_TABLE.
* bfd-in.h (JUMP_TABLE): Removed.
* libbfd-in.h: Define a bunch of macros, and declare a few
functions, for use with the new BFD_JUMP_TABLE_* macros.
* libbfd.c (_bfd_dummy_new_section_hook): Removed.
(bfd_false): Set bfd_error_invalid_operation.
(bfd_nullvoidptr): Likewise.
(bfd_n1): New function.
(_bfd_nocore_core_file_matches_executable_p): Renamed from
_bfd_dummy_core_file_matches_executable_p.
(_bfd_nocore_core_file_failing_command): Similar rename. Set
bfd_error_invalid_operation.
(_bfd_nocore_core_file_failing_signal): Likewise.
(_bfd_generic_get_section_contents): Renamed from
bfd_generic_get_section_contents. Changed all callers.
(_bfd_generic_set_section_contents): Similar rename.
* ieee.c: #if 0 out ieee_bfd_debug_info_start,
ieee_bfd_debug_info_end, ieee_bfd_debug_info_accumulate. They
were never called.
* bfd-in2.h: Rebuilt.
* libbfd.h: Rebuilt.
Remove decl of type symclass; wasn't used.
* bfd.c: Document error handling, including code fragments
containing the error decls that were in bfd-in.h.
Remove DEFUNs.
* bfd-in2.h: Regenerated.
oasys.c (oasys_write_sections): Rename
bfd_error_nonrepresentable_section to nonrepresentable_section.
None of the other bfd error names start with "bfd_error".
Remove errors symbol_not_found and no_relocation_info, which seem
to be unused.
* bfd-in2.h: Regenerated.
* bfd-in.h: (bfd_boolean): Add workaround for systems that also
define true and false as enums.
(ALMOST_STDC): Add as alternative to __STDC__.
* bfd-in2.h: Rebuilt.
* syms.c (bfd_print_symbol_vandf): Convert a PTR to FILE*.
ECOFF--added a bunch of functions. Also:
(ecoff_sec_to_styp_flags): Set flags for .pdata and .xdata.
(ecoff_slurp_symbolic_header): New function.
(ecoff_slurp_symbolic_info): Call ecoff_slurp_symbolic_header.
(ecoff_compute_reloc_file_positions): New function.
(ecoff_set_section_contents): Get out quickly if count is zero.
Check errors better.
(ecoff_write_object_contents): Put .xdata section in data segment.
Call ecoff_compute_reloc_file_positions. Don't output relocs or
external symbols if outsymbols is NULL.
(ecoff_bfd_final_link): Completely rewritten.
* libecoff.h: Include bfdlink.h.
(struct ecoff_backend_data): Add relocate_section field.
(ecoff_data_type): Add sym_hashes and symndx_to_section fields.
(struct ecoff_link_hash_entry): Define.
(struct ecoff_link_hash_table): Define.
(ecoff_bfd_link_add_symbols): Declare as function, not macro.
(ecoff_bfd_link_hash_table_create): Likewise.
* ecofflink.c (bfd_ecoff_debug_one_external): New function.
(bfd_ecoff_debug_externals): Call bfd_ecoff_debug_one_external.
* bfd-in.h (bfd_ecoff_debug_one_external): Declare.
* bfd-in2.h: Rebuilt.
* coff-alpha.c (alpha_howto_table): Mark BRADDR as
partial_inplace, and set the src_mask to 0x1fffff.
(alpha_ecoff_get_relocated_section_contents): Remove unused
variable gp_warned.
(alpha_convert_external_reloc): New static function.
(alpha_relocate_section): New static function.
(alpha_ecoff_backend_data): Initialize relocate_section field.
* coff-mips.c (mips_relocate_refhi): New static function.
(mips_relocate_section): New static function.
(mips_ecoff_backend_data): Initialize relocate_section field.
more efficient backend code can be written for specific object
files. Only existing efficient backend is a.out.
* seclet.c, seclet.h: Removed.
* hash.c, linker.c, genlink.h: New files.
* bfd-in.h: Removed bfd_error_vector. Declared hash table
structures and functions.
(JUMP_TABLE): Removed bfd_seclet_link, added
bfd_link_hash_table_create, bfd_link_add_symbols and
bfd_final_link.
* All backends: Changed accordingly.
* bfd-in2.h: Rebuilt.
* bfd.c (struct _bfd): Added link_next and archive_pass fields.
Removed ld_symbols field.
(bfd_nonrepresentable_section, bfd_undefined_symbol,
bfd_reloc_value_truncated, bfd_reloc_is_dangerous,
bfd_error_vector): Removed.
(bfd_default_error_trap, bfd_error_trap,
bfd_error_nonrepresentabltrap): Removed.
(bfd_get_relocated_section_contents): Pass link_info. Pass
link_order instead of seclet. Pass symbols.
(bfd_relax_section): Pass link_info.
(bfd_seclet_link): Removed.
(bfd_link_hash_table_create, bfd_link_add_symbols,
bfd_final_link): New macros.
* libbfd-in.h: If __GNUC__ is defined and alloca is not, define
alloca as __builtin_alloca. Declare internal linking functions.
* libbfd.h: Rebuilt.
* libbfd.c (bfd_seek): Comment out fseek assertion. It's worked
for months.
* reloc.c (reloc_howto_type): Added error_message argument to
special_function field. Changed all callers and all definitions.
(bfd_get_reloc_size): Make argument a const pointer.
(bfd_perform_relocation): Add error_message argument to hold
string set if return value if bfd_reloc_dangerous. Changed all
callers.
(_bfd_final_link_relocate, _bfd_relocate_contents): New functions.
* section.c (asection): Renamed seclets_head and seclets_tail to
link_order_head and link_order_tail.
* targets.c (bfd_target): Replaced seclet argument with link_info
and link_order and symbols arguments in
bfd_get_relocated_section_contents. Added symbols argument to
bfd_relax_section. Removed bfd_seclet_link. Added
bfd_link_hash_table_create, bfd_link_add_symbols and
bfd_final_link.
* libaout.h (struct aoutdata): Added external_syms,
external_sym_count, external_strings, sym_hashes fields.
(obj_aout_external_syms, obj_aout_external_sym_count,
obj_aout_external_strings, obj_aout_sym_hashes): New accessor
macros.
(WRITE_HEADERS): Only output symbols if outsymbols is not NULL.
* aoutx.h: Wrote new back end linker routines.
(translate_to_native_sym_flags): Return boolean value. Don't use
bfd_error_vector.
(NAME(aout,write_syms)): Return boolean value. Check return value
of translate_to_native_sym_flags and bfd_write.
* aout-target.h (final_link_callback): New function.
(MY_bfd_final_link): New function.
* aout-adobe.c (aout_adobe_write_object_contents): Check return
value of aout_32_write_syms.
* hp300hpux.c (MY(write_object_contents)): Likewise.
* i386lynx.c (WRITE_HEADERS): Likewise.
* libaout.h (WRITE_HEADERS): Likewise.
* bout.c: Changed functions to use link_info->callbacks rather
than bfd_error_vector, and link_orders rather than seclets.
* coff-alpha.c: Likewise.
* coff-h8300.c: Likewise.
* coff-h8500.c: Likewise.
* coff-sh.c: Likewise.
* coff-z8k.c: Likewise.
* elf32-hppa.c: Likewise.
* reloc16.c: Likewise.
* coff-alpha.c (alpha_ecoff_get_relocated_section_contents): Look
up _gp in the hash table rather than in outsymbols.
* coff-a29k.c (a29k_reloc): Pass errors back in new error_message
argument rather than printing them.
* coffcode.h (bfd_coff_reloc16_extra_cases): Take link_info and
link_order arguments rather than seclet. Changed all uses and
definitions.
(bfd_coff_reloc16_estimate): Pass link_info arguments. Changed
all uses and definitions.
* libcoff.h: Rebuilt.
* ecoff.c (ecoff_get_extr): If symbol is defined by linker, but
not by ECOFF, make it scAbs.
(ecoff_bfd_final_link): Renamed from ecoff_bfd_seclet_link and
rewritten.
* elf32-mips.c (mips_elf_final_link): Renamed from
mips_elf_seclet_link and rewritten.
* elf32-hppa.c (elf32_hppa_stub_description): Added link_info
field.
(new_stub, add_stub_by_name, hppa_elf_build_arg_reloc_stub,
hppa_elf_build_long_branch_stub, hppa_look_for_stubs_in_section):
Added link_info arguments. Changed all callers.
* elfcode.h (elf_slurp_symbol_table): Don't quit if outsymbols is
not NULL.
* oasys.c (oasys_write_sections): Return boolean value rather than
using bfd_error_vector.
(oasys_write_object_contents): Check return value of
oasys_write_sections.
* hosts/std-host.h: Don't declare qsort or strtol.
* Makefile.in: Rebuild dependencies.
(BFD_LIBS): Removed seclet.o. Added hash.o and linker.o.
(CFILES): Removed seclet.c. Added hash.c and linker.c.
(HFILES): Removed seclet.h. Added genlink.h.
routines.
* ecoff.c (ecoff_clear_output_flags, ecoff_rel, ecoff_dump_seclet,
ecoff_add_string, ecoff_get_debug): Removed. Functionality now in
ecofflink.c.
(ecoff_get_extr, ecoff_set_index): New functions.
(ecoff_slurp_symbolic_info): Don't save raw_size.
(ecoff_bfd_seclet_link): Rewrote to use ecofflink.c functions.
(ecoff_compute_section_file_positions): Don't set EXEC_P just
because there is a start address.
(ecoff_write_object_contents): Handle external symbols here. Use
ecofflink.c functions to write out debugging information.
* elf32-mips.c (mips_elf_read_ecoff_info, mips_elf_get_extr,
mips_elf_set_index): New functions.
(mips_elf_seclet_link): Discard empty sections, the .options
section and .gptab sections. Handle linking .mdebug section.
* libecoff.h (ecoff_data_type): Removed raw_size and ifdbase.
* libelf.h (elf_symbol_type): Added mips_extr to tc_data union.
* bfd-in.h: Added prototypes for routines in ecofflink.c (some are
called by gas, so they are public).
* bfd-in2.h: Rebuilt.
* Makefile.in (BFD_LIBS): Added ecofflink.o.
(CFILES): Added ecofflink.c.
(ecofflink.o): New target. Rebuilt dependencies.
the wrong place to edit this file.
* Makefile.in (install): Install ansidecl.h and obstack.h in the
same places where we install bfd.h.
* libieee.h: Add FIXME about removing limit on number of sections.
Thu Oct 8 08:52:48 1992 Steve Chamberlain (sac@thepub.cygnus.com)
Now a bfd knows whether underscores are normally prepended
to symbols in its file format. Helps with error messages.
* aout-adobe.c, aout-target.h, bout.c, coff-a29k.c, coff-h8300.c,
coff-z8k.c: targets set so they have leading underscore
* coff-i386.c, coff-i960.c, coff-m68k.c, coff-mips.c, coff-m88k.c,
coff-rs6000.c, coff-we32k.c, elf.c, ieee.c, srec.c: targets set
without leading underscore flag
* targets.c: add symbol leading char to xvec description
* bfd-in.h (bfd_get_symbol_leading_char): new macro.
Major change; changed calling convention for
bfd_get_relocated_section_contents so that caller allocates
memory for section data.
* coffcode.h (bfd_coff_get_relocated_section_contents), reloc.c,
seclet.c, targets.c, bfd.c: reflect new convention.
* coffcode.h (styp_to_sec_flags): if styp_flags is not a special
case, then use reasonable default values for SEC_* flags.
Mon Sep 30 15:13:46 1991 Steve Chamberlain (steve at cygnus.com)
* cpu-a29k.c, cpu-i386.c, cpu-m68k.c, cpu-mips.c, cpu-vax.c,
cpu-h8300.c, cpu-i960.c, cpu-m88k.c, cpu-sparc.c: added. These
files will eventually contain processor specific bits for bfd,
like strange relocation information and dis/assembly. So far only
the H8 has been even partially done. This work also ties in with
the change in handling architectures.
* amdcoff.c: (a29k_reloc) fix error message.
* aout-f1.h: (choose_reloc_size) now calls bfd_get_arch to
discover the architecture of the bfd. (sunos4_callback) calls the
function bfd_set_arch_mach rather than stuffing stuff directly
into the bfd. (sunos4_write_object_contents), changed names of
accessor functions.
* aoutx.h: (set_arch_mach) now calls bfd_default_set_arch_mach to
setup the environment.
* archive.c: (bfd_slurp_coff_armap) coff archives always have the
headers in big endian format, regardless of the endianess of the
host or target.
* archures.c: totally changed. Now an architecture is represented
with a pointer to an info structure rather than an enumerated type
and a long. The old info is available as two elements in the
structure. Future enhancements to architecure support will
involve pointers to methods being placed into the info structure.
* bfd.c: changed the definition of the bfd structure for the new
architecture stuff.
* bout.c: (b_out_set_arch_mach) changed to use the new
architecture mechanism.
* coffcode.h: (coff_set_arch_mach, coff_set_flags) changed to use
the new architecture mechanism.
* configure.in: added h8 stuff.
* ieee.c: too many changes to note. Now ieee files written with
bfd gas and ld can be read by gld and ieee only linkers and
simulators.
* libbfd.c, libbfd.h: changed prototype of bfd_write.
* newsos3.c: (newos3_callback) now calls bfd_set_arch_mach rather
than fixing the structure directly.
* oasys.c: (oasys_object_p) now calls bfd_default_set_arch_mach rather
than fixing the structure directly.
* opncls.c: (new_bfd) makes sure that bfd_init has been called
before opening a bfd.
* srec.c: (srec_set_arch_mach) now calls bfd_default_set_arch_mach
rather than fixing the structure directly.
* targets.c: (target_vector) now by defining SELECT_VECS (perhaps
in the t/hmake file) a user can select which backends they want
linked with bfd without changing the source.
* init.c: new, looks after initializing modules.
* howto.c: for future use, will allow an application to work out
what cookie to use as a handle on a relcoatio howto.
