[PATCH v4] gdb, configure: Add disable-formats option for configure

Guinevere Larsen
2025-04-08T13:49:42Z

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.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
---

Changes for v4:
* Removed configure.format
* Moved .c files back to the Makefile

---
gdb/Makefile.in | 20 ++++++----
gdb/NEWS | 11 ++++++
gdb/README | 24 ++++++++++++
gdb/config.in | 3 ++
gdb/configure | 89 +++++++++++++++++++++++++++++++++++++++++++--
gdb/configure.ac | 73 ++++++++++++++++++++++++++++++++++++-
gdb/configure.tgt | 20 ++++++++--
gdb/doc/gdb.texinfo | 8 ++++
gdb/top.c | 5 +++
9 files changed, 236 insertions(+), 17 deletions(-)

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 0c4102d2565..eee9f243755 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -904,13 +904,22 @@ 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.
+coff_SRCS = coffread.c coff-pe-read.c
+dbx_ARCS = dbxread.c
+elf_SRCS = elfread.c
+macho_SRCS = machoread.c
+mips_SRCS = mipsread.c
+xcoff_SRCS = xcoffread.c
+FORMAT_SRCS = @FORMAT_SRCS@
+FORMAT_OBS = $(patsubst %.c,%.o,$(FORMAT_SRCS))
+
# The following native-target dependent variables are defined on
# configure.nat.
NAT_FILE = @NAT_FILE@
@@ -1067,8 +1076,6 @@ COMMON_SFILES = \
c-varobj.c \
charset.c \
cli-out.c \
- coff-pe-read.c \
- coffread.c \
complaints.c \
completer.c \
copying.c \
@@ -1082,7 +1089,6 @@ COMMON_SFILES = \
d-lang.c \
d-namespace.c \
d-valprint.c \
- dbxread.c \
dcache.c \
debug.c \
debuginfod-support.c \
@@ -1178,7 +1184,6 @@ COMMON_SFILES = \
memtag.c \
minidebug.c \
minsyms.c \
- mipsread.c \
namespace.c \
objc-lang.c \
objfiles.c \
@@ -1271,7 +1276,6 @@ SFILES = \
d-exp.y \
dtrace-probe.c \
elf-none-tdep.c \
- elfread.c \
f-exp.y \
gcore-elf.c \
gdb.c \
@@ -1895,7 +1899,6 @@ ALLDEPFILES = \
x86-gnu-nat.c \
x86-nat.c \
x86-tdep.c \
- xcoffread.c \
xstormy16-tdep.c \
xtensa-config.c \
xtensa-linux-nat.c \
@@ -1916,7 +1919,8 @@ COMMON_OBS = $(DEPFILES) $(CONFIG_OBS) $(YYOBJ) \
$(patsubst %.c,%.o,$(COMMON_SFILES)) \
$(SUBDIR_CLI_OBS) \
$(SUBDIR_MI_OBS) \
- $(SUBDIR_TARGET_OBS)
+ $(SUBDIR_TARGET_OBS) \
+ $(FORMAT_OBS)

SUBDIRS = doc @subdirs@ data-directory
CLEANDIRS = $(SUBDIRS)
diff --git a/gdb/NEWS b/gdb/NEWS
index 99ec392d4c4..df9f1653d64 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -117,6 +117,17 @@ 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.
+
* A new configure option was added, allowing support for the compile
subsystem to be disabled at configure time, in the form of
--disable-gdb-compile.
diff --git a/gdb/README b/gdb/README
index 8836120d7ca..e104cf93fad 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 86ff67d2898..68afb89201f 100644
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -736,6 +736,9 @@
/* 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 e8a649f2ef0..434afa25c9a 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -706,6 +706,7 @@ LIBGUI
LTLIBLZMA
LIBLZMA
HAVE_LIBLZMA
+FORMAT_SRCS
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
@@ -1646,6 +1648,9 @@ 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)
@@ -11503,7 +11508,7 @@ else
lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
lt_status=$lt_dlunknown
cat > conftest.$ac_ext <<_LT_EOF
-#line 11506 "configure"
+#line 11511 "configure"
#include "confdefs.h"

#if HAVE_DLFCN_H
@@ -11609,7 +11614,7 @@ else
lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
lt_status=$lt_dlunknown
cat > conftest.$ac_ext <<_LT_EOF
-#line 11612 "configure"
+#line 11617 "configure"
#include "confdefs.h"

#if HAVE_DLFCN_H
@@ -24878,6 +24883,18 @@ 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 :
@@ -24961,11 +24978,20 @@ 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 $targ_alias 2>/dev/null`
@@ -31602,6 +31628,10 @@ fi
# Note that WIN32APILIBS is set by GDB_AC_COMMON.
WIN32LIBS="$WIN32LIBS $WIN32APILIBS"

+# Object files to be used when building with support for all file formats.
+all_binary_format_obs="\$(dbx_SRCS) \$(mips_SRCS) \$(coff_SRCS) \$(xcoff_SRCS)"
+
+support_elf=no
# Add ELF support to GDB, but only if BFD includes ELF support.

OLD_CFLAGS=$CFLAGS
@@ -31654,7 +31684,7 @@ $as_echo "$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"

$as_echo "#define HAVE_ELF 1" >>confdefs.h
@@ -31718,9 +31748,12 @@ if test "$ac_res" != no; then :
fi

fi
+ support_elf=yes
+ all_binary_format_obs="$all_binary_format_obs \$(elf_SRCS)"
fi

# Add macho support to GDB, but only if BFD includes it.
+support_macho=no

OLD_CFLAGS=$CFLAGS
OLD_LDFLAGS=$LDFLAGS
@@ -31772,9 +31805,57 @@ $as_echo "$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="$all_binary_format_obs \$(macho_SRCS)"
+fi
+
+FORMAT_SRCS=
+
+if test "$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" "$LINENO" 5;
+ fi
+ fi
+
+ if test "$format" = "all"; then
+ FORMAT_SRCS="$all_binary_format_obs"
+ # We don't break here in case the user requested Mach-O or ELF, but
+ # BFD is not configured to support it. If we were to break, we would
+ # silently drop the requested support instead of erroring out.
+ else
+ fmt=$(echo "$format _SRCS" | sed 's/ //')
+ FORMAT_SRCS="$FORMAT_SRCS \$($fmt)"
+ fi
+done
+
+
+
# Add any host-specific objects to GDB.
CONFIG_OBS="${CONFIG_OBS} ${gdb_host_obs}"

diff --git a/gdb/configure.ac b/gdb/configure.ac
index 2411b10ca40..ca4f50f2644 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 $targ_alias 2>/dev/null`
@@ -1923,11 +1941,15 @@ fi
# Note that WIN32APILIBS is set by GDB_AC_COMMON.
WIN32LIBS="$WIN32LIBS $WIN32APILIBS"

+# Object files to be used when building with support for all file formats.
+all_binary_format_obs="\$(dbx_SRCS) \$(mips_SRCS) \$(coff_SRCS) \$(xcoff_SRCS)"
+
+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="$CONFIG_OBS stap-probe.o dtrace-probe.o \
gcore-elf.o elf-none-tdep.o"
AC_DEFINE(HAVE_ELF, 1,
[Define if ELF support should be included.])
@@ -1935,15 +1957,62 @@ if test "$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 \$(elf_SRCS)"
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="$all_binary_format_obs \$(macho_SRCS)"
+fi
+
+FORMAT_SRCS=
+
+if test "$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 "$support_macho" != "yes"; then
+ AC_MSG_ERROR("Mach-O support was requested, but BFD does not support it.");
+ fi
+ fi
+
+ if test "$format" = "all"; then
+ FORMAT_SRCS="$all_binary_format_obs"
+ # We don't break here in case the user requested Mach-O or ELF, but
+ # BFD is not configured to support it. If we were to break, we would
+ # silently drop the requested support instead of erroring out.
+ else
+ fmt=$(echo "$format _SRCS" | sed 's/ //')
+ FORMAT_SRCS="$FORMAT_SRCS \$($fmt)"
+ fi
+done
+
+AC_SUBST(FORMAT_SRCS)
+
# Add any host-specific objects to GDB.
CONFIG_OBS="${CONFIG_OBS} ${gdb_host_obs}"

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 4e4509a4649..ce26b26fe96 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -41269,6 +41269,14 @@ 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 80d0ec5e679..a14781df973 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\

base-commit: d8c3e4901650e35ddf5083f693b8a21b9d24fcc6
--
2.49.0