[PING][PATCH v3] gdb, configure: Add disable-formats option for configure

[Guinevere Larsen <guinevere@redhat.com>]

Ping :)

-- 
Cheers,
Guinevere Larsen
She/Her/Hers


On 3/7/25 8:58 AM, Guinevere Larsen wrote:
> GDB has support for many binary file formats, some which might be very
> unlikely to be found in some situations (such as the COFF format in
> linux). This commit introduces the option for a user to choose which
> formats GDB will support at build configuration time.
>
> This is especially useful to avoid possible security concerns with
> readers that aren't expected to be used at all, as they are one of
> the simplest vectors for an attacker to try and hit GDB with.  This
> change can also reduce the size of the final binary, if that is a
> concern.
>
> This commit adds a switch to the configure script allowing a user to
> only enable selected file formats, called --enable-binary-file-formats.
> The default behavior when the switch is omitted is to compile all file
> formats, keeping the original behavior of the script. At the time of
> this commit, the valid options for this option are: dbx, coff (which
> includes coff-pe), xcoff, mips, elf, macho and all. All is treated
> especially, activating all supported readers.
>
> A few targets may require specific binary file format support, as they
> directly call functions defined by the file reader. Specifically,
> windows targets require coff support, and rs6000 aix and lynx178 targets
> require xcoff support. Considering that those formats are the main - or
> only - one available in those targets, I believe it makes sense to
> re-enable those readers. If that happens, the script will emit the
> following warning:
>
>    FOO is required to support one or more requested targets. Adding it
>
> Users aren't able to force the disabling of those formats, since GDB
> will not compile without those readers. Ideally we'd like to be able
> to disable even those formats, in case a user wants to build GDB only
> to examine remote files for example, but the current infrastructure
> for the file format readers doesn't allow us to do it.
>
> Mach-O and elf support are also dependent on BFD support being compiled
> in.  In case one of those was requested and BFD does not support them,
> the following error is emitted:
>
>      FOO was requested, but BFD does not support it.
>
> Finally, this configure switch is also printed by the "show
> configuration" command in GDB.
> ---
>   gdb/Makefile.in      | 13 +++----
>   gdb/NEWS             | 11 ++++++
>   gdb/README           | 24 +++++++++++++
>   gdb/config.in        |  3 ++
>   gdb/configure        | 81 +++++++++++++++++++++++++++++++++++++++++---
>   gdb/configure.ac     | 65 +++++++++++++++++++++++++++++++++--
>   gdb/configure.format | 51 ++++++++++++++++++++++++++++
>   gdb/configure.tgt    | 20 +++++++++--
>   gdb/doc/gdb.texinfo  |  8 +++++
>   gdb/top.c            |  5 +++
>   10 files changed, 264 insertions(+), 17 deletions(-)
>   create mode 100644 gdb/configure.format
>
> diff --git a/gdb/Makefile.in b/gdb/Makefile.in
> index a24c86fcff8..778ed54090f 100644
> --- a/gdb/Makefile.in
> +++ b/gdb/Makefile.in
> @@ -904,13 +904,15 @@ ALL_TARGET_OBS = \
>   	vax-tdep.o \
>   	windows-tdep.o \
>   	x86-tdep.o \
> -	xcoffread.o \
>   	xstormy16-tdep.o \
>   	xtensa-config.o \
>   	xtensa-linux-tdep.o \
>   	xtensa-tdep.o \
>   	z80-tdep.o
>   
> +# Object files for reading specific types of debug information.
> +FORMAT_OBS = @FORMAT_OBS@
> +
>   # The following native-target dependent variables are defined on
>   # configure.nat.
>   NAT_FILE = @NAT_FILE@
> @@ -1067,8 +1069,6 @@ COMMON_SFILES = \
>   	c-varobj.c \
>   	charset.c \
>   	cli-out.c \
> -	coff-pe-read.c \
> -	coffread.c \
>   	complaints.c \
>   	completer.c \
>   	copying.c \
> @@ -1082,7 +1082,6 @@ COMMON_SFILES = \
>   	d-lang.c \
>   	d-namespace.c \
>   	d-valprint.c \
> -	dbxread.c \
>   	dcache.c \
>   	debug.c \
>   	debuginfod-support.c \
> @@ -1174,7 +1173,6 @@ COMMON_SFILES = \
>   	memtag.c \
>   	minidebug.c \
>   	minsyms.c \
> -	mipsread.c \
>   	namespace.c \
>   	objc-lang.c \
>   	objfiles.c \
> @@ -1267,7 +1265,6 @@ SFILES = \
>   	d-exp.y \
>   	dtrace-probe.c \
>   	elf-none-tdep.c \
> -	elfread.c \
>   	f-exp.y \
>   	gcore-elf.c \
>   	gdb.c \
> @@ -1887,7 +1884,6 @@ ALLDEPFILES = \
>   	x86-gnu-nat.c \
>   	x86-nat.c \
>   	x86-tdep.c \
> -	xcoffread.c \
>   	xstormy16-tdep.c \
>   	xtensa-config.c \
>   	xtensa-linux-nat.c \
> @@ -1909,7 +1905,8 @@ COMMON_OBS = $(DEPFILES) $(CONFIG_OBS) $(YYOBJ) \
>   	$(SUBDIR_CLI_OBS) \
>   	$(SUBDIR_MI_OBS) \
>   	$(SUBDIR_TARGET_OBS) \
> -	$(SUBDIR_GCC_COMPILE_OBS)
> +	$(SUBDIR_GCC_COMPILE_OBS) \
> +	$(FORMAT_OBS)
>   
>   SUBDIRS = doc @subdirs@ data-directory
>   CLEANDIRS = $(SUBDIRS)
> diff --git a/gdb/NEWS b/gdb/NEWS
> index f5dbf5c3350..2a916d356ef 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -85,6 +85,17 @@ qXfer:threads:read
>   * Support for stabs debugging format and the a.out/dbx object format is
>     deprecated, and will be removed in GDB 18.
>   
> +* Configure changes
> +
> +enable-binary-file-formats=[FORMAT,...]
> +enable-binary-file-formats=all
> +  A user can now decide to only compile support for certain file formats.
> +  The available formats at this point are: dbx, coff, xcoff, elf, mach-o
> +  and mips.  Some targets require specific file formats to be available,
> +  and in such cases, the configure script will warn the user and add
> +  support anyway.  By default, all formats will be compiled in, to
> +  continue the behavior from before adding the switch.
> +
>   *** Changes in GDB 16
>   
>   * Support for Nios II targets has been removed as this architecture
> diff --git a/gdb/README b/gdb/README
> index b6eb3f12c56..0168afe7cd1 100644
> --- a/gdb/README
> +++ b/gdb/README
> @@ -417,6 +417,30 @@ more obscure GDB `configure' options are not listed here.
>        There is no convenient way to generate a list of all available
>        targets.
>   
> +`--enable-binary-file-formats=FORMAT,FORMAT,...'
> +`--enable-binary-file-formats=all'
> +    Configure GDB to only be be able to read selected file formats.
> +    The special value "all" causes all file formats to be compiled
> +    in, and is the the default behavior of the option.  This option
> +    is meant for advanced users who are sure of what they expect,
> +    if you are unsure which options you will need on your debugging
> +    sessions, we recommend that you not use this feature.  The
> +    accepted options are:
> +      * coff: Main format on windows systems. This is required to
> +        compile with windows target support;
> +      * dbx (also known as a.out): is a legacy file format, this
> +        is recommended if you know you will be dealing with this
> +        file format;
> +      * elf: Main format of linux systems. This is heavily
> +        recommended when compiling with linux support;
> +      * macho: Main format on MacOS systems, this is heavily
> +        recommended when compiling for those targets;
> +      * mips (also known as ecoff): this is the main file format
> +        for targets running on MIPS CPUs. It is heavily recommended
> +        when supporting those targets.
> +      * xcoff: Main format of AIX systems, this is required to
> +        compile for AIX targets and rs6000 CPUs.
> +
>   `--with-gdb-datadir=PATH'
>        Set the GDB-specific data directory.  GDB will look here for
>        certain supporting files or scripts.  This defaults to the `gdb'
> diff --git a/gdb/config.in b/gdb/config.in
> index db63aeaec75..248ebaa68af 100644
> --- a/gdb/config.in
> +++ b/gdb/config.in
> @@ -733,6 +733,9 @@
>   /* Define to 1 if you have the ANSI C header files. */
>   #undef STDC_HEADERS
>   
> +/* Which file formats were requested at configure time. */
> +#undef SUPPORTED_FORMATS
> +
>   /* automatically load a system-wide gdbinit file */
>   #undef SYSTEM_GDBINIT
>   
> diff --git a/gdb/configure b/gdb/configure
> index bdc405e01b3..8229ccaa588 100755
> --- a/gdb/configure
> +++ b/gdb/configure
> @@ -706,6 +706,7 @@ LIBGUI
>   LTLIBLZMA
>   LIBLZMA
>   HAVE_LIBLZMA
> +FORMAT_OBS
>   SER_HARDWIRE
>   WERROR_CFLAGS
>   WARN_CFLAGS
> @@ -934,6 +935,7 @@ with_relocated_sources
>   with_auto_load_dir
>   with_auto_load_safe_path
>   enable_targets
> +enable_binary_file_formats
>   enable_64_bit_bfd
>   with_amd_dbgapi
>   enable_tui
> @@ -1645,6 +1647,9 @@ Optional Features:
>     --disable-nls           do not use Native Language Support
>     --enable-targets=TARGETS
>                             alternative target configurations
> +  --enable-binary-file-formats=FILE_FORMATS
> +                          enable support for selected file formats (default
> +                          'all')
>     --enable-64-bit-bfd     64-bit support (on hosts with narrower word sizes)
>     --enable-tui            enable full-screen terminal user interface (TUI)
>     --enable-gdbtk          enable gdbtk graphical user interface (GUI)
> @@ -11500,7 +11505,7 @@ else
>     lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
>     lt_status=$lt_dlunknown
>     cat > conftest.$ac_ext <<_LT_EOF
> -#line 11503 "configure"
> +#line 11508 "configure"
>   #include "confdefs.h"
>   
>   #if HAVE_DLFCN_H
> @@ -11606,7 +11611,7 @@ else
>     lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
>     lt_status=$lt_dlunknown
>     cat > conftest.$ac_ext <<_LT_EOF
> -#line 11609 "configure"
> +#line 11614 "configure"
>   #include "confdefs.h"
>   
>   #if HAVE_DLFCN_H
> @@ -24875,6 +24880,18 @@ esac
>   fi
>   
>   
> +# Check whether --enable-binary_file_formats was given.
> +if test "${enable_binary_file_formats+set}" = set; then :
> +  enableval=$enable_binary_file_formats; case "${enableval}" in
> + yes | "") as_fn_error $? "enable-formats option must specify file formats or 'all'" "$LINENO" 5
> +            ;;
> +  no)       enable_binary_file_formats= ;;
> +  *)        enable_binary_file_formats=$enableval ;;
> +esac
> +else
> +  enable_binary_file_formats=all
> +fi
> +
>   
>   # Check whether --enable-64-bit-bfd was given.
>   if test "${enable_64_bit_bfd+set}" = set; then :
> @@ -24958,11 +24975,20 @@ fi
>   TARGET_OBS=
>   all_targets=
>   HAVE_NATIVE_GCORE_TARGET=
> +# File formats that will be enabled based on the selected
> +# target(s).  These are chosen because they are required to
> +# compile one or more of the selected targets.
> +target_formats=
> +# If all targets were requested, this is all formats that should
> +# accompany them.  These are just the ones required for compilation
> +# to succeed, not the formats suggested based on targets.
> +all_target_formats="coff xcoff"
>   
>   for targ_alias in `echo $target_alias $enable_targets | sed 's/,/ /g'`
>   do
>     if test "$targ_alias" = "all"; then
>       all_targets=true
> +    target_formats=$all_target_formats
>     else
>       # Canonicalize the secondary target names.
>       result=`$ac_config_sub $targ_alias 2>/dev/null`
> @@ -31553,6 +31579,10 @@ fi
>   # Note that WIN32APILIBS is set by GDB_AC_COMMON.
>   WIN32LIBS="$WIN32LIBS $WIN32APILIBS"
>   
> +# Object files to be used when building with support for all file formats.
> +all_binary_format_obs="dbxread.o mipsread.o coffread.o coff-pe-read.o xcoffread.o"
> +
> +support_elf=no
>   # Add ELF support to GDB, but only if BFD includes ELF support.
>   
>     OLD_CFLAGS=$CFLAGS
> @@ -31605,7 +31635,7 @@ $as_echo "$gdb_cv_var_elf" >&6; }
>     LDFLAGS=$OLD_LDFLAGS
>     LIBS=$OLD_LIBS
>   if test "$gdb_cv_var_elf" = yes; then
> -  CONFIG_OBS="$CONFIG_OBS elfread.o stap-probe.o dtrace-probe.o \
> +  CONFIG_OBS="$CONFIG_OBS stap-probe.o dtrace-probe.o \
>   		gcore-elf.o elf-none-tdep.o"
>   
>   $as_echo "#define HAVE_ELF 1" >>confdefs.h
> @@ -31669,9 +31699,12 @@ if test "$ac_res" != no; then :
>   fi
>   
>     fi
> +  support_elf=yes
> +  all_binary_format_obs="$all_binary_format_obs elfread.o"
>   fi
>   
>   # Add macho support to GDB, but only if BFD includes it.
> +support_macho=no
>   
>     OLD_CFLAGS=$CFLAGS
>     OLD_LDFLAGS=$LDFLAGS
> @@ -31723,9 +31756,49 @@ $as_echo "$gdb_cv_var_macho" >&6; }
>     LDFLAGS=$OLD_LDFLAGS
>     LIBS=$OLD_LIBS
>   if test "$gdb_cv_var_macho" = yes; then
> -  CONFIG_OBS="$CONFIG_OBS machoread.o"
> +  support_macho=yes
> +  all_binary_format_obs="$all_binary_format_obs machoread.o"
> +fi
> +
> +FORMAT_OBS=
> +
> +if test "$enable_binary_file_formats" != "all"; then
> +    # Formats that are required by some requested target(s).
> +    # Warn users that they are added, so no one is surprised.
> +    for req in $target_formats; do
> +	if ! echo "$enable_binary_file_formats" | grep -wq "$req"; then
> +	    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: \"$req is required to support one or more requested targets.  Adding it\"" >&5
> +$as_echo "$as_me: WARNING: \"$req is required to support one or more requested targets.  Adding it\"" >&2;}
> +	    enable_binary_file_formats="${enable_binary_file_formats},$req"
> +	fi
> +    done
> +
> +
> +cat >>confdefs.h <<_ACEOF
> +#define SUPPORTED_FORMATS "$enable_binary_file_formats"
> +_ACEOF
> +
>   fi
>   
> +enable_binary_file_formats=$(echo $enable_binary_file_formats | sed 's/,/ /g')
> +
> +for format in $enable_binary_file_formats
> +do
> +    if test "$format" = "elf"; then
> +	if test "$support_elf" != "yes"; then
> +	    as_fn_error but BFD does not support it." "\"elf support was requested" "$LINENO" 5;
> +	fi
> +    elif test "$format" = "macho"; then
> +	if test "$support_macho" != "yes"; then
> +	    as_fn_error but BFD does not support it." "\"Mach-O support was requested" "$LINENO" 5;
> +	fi
> +    fi
> +
> +    . ${srcdir}/configure.format
> +done
> +
> +
> +
>   # Add any host-specific objects to GDB.
>   CONFIG_OBS="${CONFIG_OBS} ${gdb_host_obs}"
>   
> diff --git a/gdb/configure.ac b/gdb/configure.ac
> index fb77e79e73b..c5e774962ce 100644
> --- a/gdb/configure.ac
> +++ b/gdb/configure.ac
> @@ -191,6 +191,15 @@ AS_HELP_STRING([--enable-targets=TARGETS], [alternative target configurations]),
>   	;;
>   esac])
>   
> +AC_ARG_ENABLE(binary_file_formats,
> +	      AS_HELP_STRING([--enable-binary-file-formats=FILE_FORMATS],
> +			     [enable support for selected file formats (default 'all')]),
> +[case "${enableval}" in
> + yes | "") AC_MSG_ERROR(enable-formats option must specify file formats or 'all')
> +            ;;
> +  no)       enable_binary_file_formats= ;;
> +  *)        enable_binary_file_formats=$enableval ;;
> +esac], [enable_binary_file_formats=all])
>   
>   BFD_64_BIT
>   
> @@ -211,11 +220,20 @@ fi
>   TARGET_OBS=
>   all_targets=
>   HAVE_NATIVE_GCORE_TARGET=
> +# File formats that will be enabled based on the selected
> +# target(s).  These are chosen because they are required to
> +# compile one or more of the selected targets.
> +target_formats=
> +# If all targets were requested, this is all formats that should
> +# accompany them.  These are just the ones required for compilation
> +# to succeed, not the formats suggested based on targets.
> +all_target_formats="coff xcoff"
>   
>   for targ_alias in `echo $target_alias $enable_targets | sed 's/,/ /g'`
>   do
>     if test "$targ_alias" = "all"; then
>       all_targets=true
> +    target_formats=$all_target_formats
>     else
>       # Canonicalize the secondary target names.
>       result=`$ac_config_sub $targ_alias 2>/dev/null`
> @@ -1903,11 +1921,15 @@ fi
>   # Note that WIN32APILIBS is set by GDB_AC_COMMON.
>   WIN32LIBS="$WIN32LIBS $WIN32APILIBS"
>   
> +# Object files to be used when building with support for all file formats.
> +all_binary_format_obs="dbxread.o mipsread.o coffread.o coff-pe-read.o xcoffread.o"
> +
> +support_elf=no
>   # Add ELF support to GDB, but only if BFD includes ELF support.
>   GDB_AC_CHECK_BFD([for ELF support in BFD], gdb_cv_var_elf,
>                    [bfd_get_elf_phdr_upper_bound (NULL)], elf-bfd.h)
>   if test "$gdb_cv_var_elf" = yes; then
> -  CONFIG_OBS="$CONFIG_OBS elfread.o stap-probe.o dtrace-probe.o \
> +  CONFIG_OBS="$CONFIG_OBS stap-probe.o dtrace-probe.o \
>   		gcore-elf.o elf-none-tdep.o"
>     AC_DEFINE(HAVE_ELF, 1,
>   	    [Define if ELF support should be included.])
> @@ -1915,15 +1937,54 @@ if test "$gdb_cv_var_elf" = yes; then
>     if test "$plugins" = "yes"; then
>       AC_SEARCH_LIBS(dlopen, dl)
>     fi
> +  support_elf=yes
> +  all_binary_format_obs="$all_binary_format_obs elfread.o"
>   fi
>   
>   # Add macho support to GDB, but only if BFD includes it.
> +support_macho=no
>   GDB_AC_CHECK_BFD([for Mach-O support in BFD], gdb_cv_var_macho,
>                    [bfd_mach_o_lookup_command (NULL, 0, NULL)], mach-o.h)
>   if test "$gdb_cv_var_macho" = yes; then
> -  CONFIG_OBS="$CONFIG_OBS machoread.o"
> +  support_macho=yes
> +  all_binary_format_obs="$all_binary_format_obs machoread.o"
> +fi
> +
> +FORMAT_OBS=
> +
> +if test "$enable_binary_file_formats" != "all"; then
> +    # Formats that are required by some requested target(s).
> +    # Warn users that they are added, so no one is surprised.
> +    for req in $target_formats; do
> +	if ! echo "$enable_binary_file_formats" | grep -wq "$req"; then
> +	    AC_MSG_WARN("$req is required to support one or more requested targets.  Adding it")
> +	    enable_binary_file_formats="${enable_binary_file_formats},$req"
> +	fi
> +    done
> +
> +    AC_DEFINE_UNQUOTED(SUPPORTED_FORMATS, "$enable_binary_file_formats",
> +		       Which file formats were requested at configure time. )
>   fi
>   
> +enable_binary_file_formats=$(echo $enable_binary_file_formats | sed 's/,/ /g')
> +
> +for format in $enable_binary_file_formats
> +do
> +    if test "$format" = "elf"; then
> +	if test "$support_elf" != "yes"; then
> +	    AC_MSG_ERROR("elf support was requested, but BFD does not support it.");
> +	fi
> +    elif test "$format" = "macho"; then
> +	if test "$support_macho" != "yes"; then
> +	    AC_MSG_ERROR("Mach-O support was requested, but BFD does not support it.");
> +	fi
> +    fi
> +
> +    . ${srcdir}/configure.format
> +done
> +
> +AC_SUBST(FORMAT_OBS)
> +
>   # Add any host-specific objects to GDB.
>   CONFIG_OBS="${CONFIG_OBS} ${gdb_host_obs}"
>   
> diff --git a/gdb/configure.format b/gdb/configure.format
> new file mode 100644
> index 00000000000..5ac86359037
> --- /dev/null
> +++ b/gdb/configure.format
> @@ -0,0 +1,51 @@
> +# Copyright (C) 2024-2025 Free Software Foundation, Inc.
> +#
> +# This file is part of GDB.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# This file is used to decide which files need to be compiled to support
> +# the requested file formats
> +
> +case $format in
> +    xcoff)
> +	FORMAT_OBS="$FORMAT_OBS xcoffread.o"
> +	;;
> +
> +    # Despite the naming convention implying coff-pe to be a separate
> +    # reader, it is in fact just a helper for coffread;
> +    coff)
> +	FORMAT_OBS="$FORMAT_OBS coffread.o coff-pe-read.o"
> +	;;
> +
> +    dbx)
> +	FORMAT_OBS="$FORMAT_OBS dbxread.o"
> +	;;
> +
> +    elf)
> +	FORMAT_OBS="$FORMAT_OBS elfread.o"
> +	;;
> +
> +    macho)
> +	FORMAT_OBS="$FORMAT_OBS machoread.o"
> +	;;
> +
> +    mips)
> +	FORMAT_OBS="$FORMAT_OBS mipsread.o"
> +	;;
> +
> +    all)
> +	FORMAT_OBS="$all_binary_format_obs"
> +	;;
> +esac
> diff --git a/gdb/configure.tgt b/gdb/configure.tgt
> index 18a15c032c3..064deddc97b 100644
> --- a/gdb/configure.tgt
> +++ b/gdb/configure.tgt
> @@ -496,7 +496,7 @@ powerpc-*-openbsd*)
>   	;;
>   powerpc-*-aix* | rs6000-*-* | powerpc64-*-aix*)
>   	# Target: PowerPC running AIX
> -	gdb_target_obs="rs6000-tdep.o rs6000-aix-tdep.o xcoffread.o \
> +	gdb_target_obs="rs6000-tdep.o rs6000-aix-tdep.o \
>   			ppc-sysv-tdep.o solib-aix.o \
>   			ravenscar-thread.o ppc-ravenscar-thread.o"
>   	;;
> @@ -512,8 +512,8 @@ powerpc*-*-linux*)
>   powerpc-*-lynx*178)
>   	# Target: PowerPC running Lynx178.
>   	gdb_target_obs="rs6000-tdep.o rs6000-lynx178-tdep.o \
> -			xcoffread.o ppc-sysv-tdep.o \
> -			ravenscar-thread.o ppc-ravenscar-thread.o"
> +			ppc-sysv-tdep.o ravenscar-thread.o \
> +			ppc-ravenscar-thread.o"
>   	;;
>   powerpc*-*-*)
>   	# Target: PowerPC running eabi
> @@ -817,3 +817,17 @@ for t in x ${gdb_target_obs}; do
>       gdb_have_gcore=true
>     fi
>   done
> +
> +# Decide which file formats are absolutely required based on
> +# the requested targets.  Warn later that they are added, in
> +# case the user didn't manually request them, or all readers.
> +# It's fine to add the same format multiple times since the
> +# loop that reads the options to FORMAT_OBS will ensure that
> +# they are only added once.
> +for i in $gdb_target_obs; do
> +    case "${i}" in
> +    *"windows-tdep.o" ) target_formats="${target_formats} coff";;
> +    "rs6000-aix-tdep.o" ) target_formats="${target_formats} xcoff";;
> +    "rs6000-lynx178-tdep.o" ) target_formats="${target_formats} xcoff";;
> +    esac
> +done
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 95a881e9dff..26434183769 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -41258,6 +41258,14 @@ Configure @value{GDBN} for cross-debugging programs running on the
>   specified list of targets.  The special value @samp{all} configures
>   @value{GDBN} for debugging programs running on any target it supports.
>   
> +@item --enable-binary-file-formats=@r{[}@var{format}@r{]}@dots{}
> +@itemx --enable-binary-file-formats=all
> +Configure @value{GDBN} to support certain binary file formats.  If a
> +format is the main (or only) file format for a given target, the
> +configure script may add support to it anyway, and warn the user.
> +If not given, all file formats that @value{GDBN} supports are compiled
> +in.
> +
>   @item --with-gdb-datadir=@var{path}
>   Set the @value{GDBN}-specific data directory.  @value{GDBN} will look
>   here for certain supporting files or scripts.  This defaults to the
> diff --git a/gdb/top.c b/gdb/top.c
> index b2575bc2b58..9342085b3a9 100644
> --- a/gdb/top.c
> +++ b/gdb/top.c
> @@ -1595,6 +1595,11 @@ This GDB was configured as follows:\n\
>   	     --with-system-gdbinit-dir=%s%s\n\
>   "), SYSTEM_GDBINIT_DIR, SYSTEM_GDBINIT_DIR_RELOCATABLE ? " (relocatable)" : "");
>   
> +#ifdef SUPPORTED_FORMATS
> +  gdb_printf (stream, _("\
> +	     --enable-binary-file-formats=%s\n"), SUPPORTED_FORMATS);
> +#endif
> +
>     /* We assume "relocatable" will be printed at least once, thus we always
>        print this text.  It's a reasonably safe assumption for now.  */
>     gdb_printf (stream, _("\n\