The attached patch enables the EH Frame Registry to be explicitly disabled
with a configure option "-disable-eh-frame-registry", thereby removing code to
support it in crtstuff.c
Default behaviour is unchanged since USE_EH_FRAME_REGISTRY was previously
referenced only internally in crtstuff.c, and now is only defined to 0
when it would previously have not been defined at all.
>From 31fdea3564fd0a9a25547df0d5052133d7bdc8a6 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <joze...@mittosystems.com>
Date: Tue, 29 Oct 2019 12:55:11 +0000
Subject: [PATCH 1/3] libgcc: Add --disable-eh-frame-registry configure option
gcc/ChangeLog:
2019-11-06 Jozef Lawrynowicz <joze...@mittosystems.com>
* doc/install.texi: Document --disable-eh-frame-registry.
libgcc/ChangeLog:
2019-11-06 Jozef Lawrynowicz <joze...@mittosystems.com>
* Makefile.in: Add USE_EH_FRAME_REGISTRY variable.
Use USE_EH_FRAME_REGISTRY variable in CRTSTUFF_CFLAGS.
* configure: Regenerate.
* configure.ac: Support --disable-eh-frame-registry.
* crtstuff.c [!USE_EH_FRAME_REGISTRY]: Define USE_EH_FRAME_REGISTRY.
s/#ifdef USE_EH_FRAME_REGISTRY/#if USE_EH_FRAME_REGISTRY/.
s/#if defined(USE_EH_FRAME_REGISTRY)/#if USE_EH_FRAME_REGISTRY/.
---
gcc/doc/install.texi | 11 +++++++++++
libgcc/Makefile.in | 4 +++-
libgcc/configure | 22 ++++++++++++++++++++++
libgcc/configure.ac | 17 +++++++++++++++++
libgcc/crtstuff.c | 22 +++++++++++++---------
5 files changed, 66 insertions(+), 10 deletions(-)
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 563de705881..af61a34a477 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1314,6 +1314,17 @@ Disable TM clone registry in libgcc. It is enabled in libgcc by default.
This option helps to reduce code size for embedded targets which do
not use transactional memory.
+@item --disable-eh-frame-registry
+Disable the EH frame registry in libgcc. It is enabled in libgcc by default
+for most ELF targets.
+
+This should not be used unless exceptions have been disabled for the target
+configuration.
+
+This option reduces code size by removing functionality to register the
+exception handling frame information that would normally run before
+@samp{main()}.
+
@item --with-cpu=@var{cpu}
@itemx --with-cpu-32=@var{cpu}
@itemx --with-cpu-64=@var{cpu}
diff --git a/libgcc/Makefile.in b/libgcc/Makefile.in
index 5608352a900..59f7f3cc381 100644
--- a/libgcc/Makefile.in
+++ b/libgcc/Makefile.in
@@ -261,6 +261,8 @@ CET_FLAGS = @CET_FLAGS@
USE_TM_CLONE_REGISTRY = @use_tm_clone_registry@
+USE_EH_FRAME_REGISTRY = @use_eh_frame_registry@
+
# Defined in libgcc2.c, included only in the static library.
LIB2FUNCS_ST = _eprintf __gcc_bcmp
@@ -301,7 +303,7 @@ CRTSTUFF_CFLAGS = -O2 $(GCC_CFLAGS) $(INCLUDES) $(MULTILIB_CFLAGS) -g0 \
$(NO_PIE_CFLAGS) -finhibit-size-directive -fno-inline -fno-exceptions \
-fno-zero-initialized-in-bss -fno-toplevel-reorder -fno-tree-vectorize \
-fbuilding-libgcc -fno-stack-protector $(FORCE_EXPLICIT_EH_REGISTRY) \
- $(INHIBIT_LIBC_CFLAGS) $(USE_TM_CLONE_REGISTRY)
+ $(INHIBIT_LIBC_CFLAGS) $(USE_TM_CLONE_REGISTRY) $(USE_EH_FRAME_REGSITRY)
# Extra flags to use when compiling crt{begin,end}.o.
CRTSTUFF_T_CFLAGS =
diff --git a/libgcc/configure b/libgcc/configure
index 117e9c97e57..341c609252e 100755
--- a/libgcc/configure
+++ b/libgcc/configure
@@ -605,6 +605,7 @@ solaris_ld_v2_maps
real_host_noncanonical
accel_dir_suffix
use_tm_clone_registry
+use_eh_frame_registry
force_explicit_eh_registry
CET_FLAGS
fixed_point
@@ -713,6 +714,7 @@ enable_decimal_float
with_system_libunwind
enable_cet
enable_explicit_exception_frame_registration
+enable_eh_frame_registry
enable_tm_clone_registry
with_glibc_version
enable_tls
@@ -1357,6 +1359,7 @@ Optional Features:
register exception tables explicitly at module
start, for use e.g. for compatibility with
installations without PT_GNU_EH_FRAME support
+ --disable-eh-frame-registry disable EH frame registry
--disable-tm-clone-registry disable TM clone registry
--enable-tls Use thread-local storage [default=yes]
@@ -4956,6 +4959,25 @@ fi
+# EH Frame Registry is implicitly enabled by default (although it is not
+# "forced"), and libgcc/crtstuff.c will setup the support for it if it is
+# supported by the target. So we don't handle --enable-eh-frame-registry.
+# Check whether --enable-eh-frame-registry was given.
+if test "${enable_eh_frame_registry+set}" = set; then :
+ enableval=$enable_eh_frame_registry;
+use_eh_frame_registry=
+if test "$enable_eh_frame_registry" = no; then
+ if test "$enable_explicit_exception_frame_registration" = yes; then
+ as_fn_error $? "Can't --disable-eh-frame-registry with
+ with --enable-explicit-exception-frame-registration" "$LINENO" 5
+ fi
+ use_eh_frame_registry=-DUSE_EH_FRAME_REGISTRY=0
+fi
+
+fi
+
+
+
# Check whether --enable-tm-clone-registry was given.
if test "${enable_tm_clone_registry+set}" = set; then :
enableval=$enable_tm_clone_registry;
diff --git a/libgcc/configure.ac b/libgcc/configure.ac
index f63c5e736e5..cf2eb9c984a 100644
--- a/libgcc/configure.ac
+++ b/libgcc/configure.ac
@@ -261,6 +261,23 @@ fi
])
AC_SUBST([force_explicit_eh_registry])
+# EH Frame Registry is implicitly enabled by default (although it is not
+# "forced"), and libgcc/crtstuff.c will setup the support for it if it is
+# supported by the target. So we don't handle --enable-eh-frame-registry.
+AC_ARG_ENABLE([eh-frame-registry],
+[ --disable-eh-frame-registry disable EH frame registry],
+[
+use_eh_frame_registry=
+if test "$enable_eh_frame_registry" = no; then
+ if test "$enable_explicit_exception_frame_registration" = yes; then
+ AC_MSG_ERROR([Can't --disable-eh-frame-registry with
+ with --enable-explicit-exception-frame-registration])
+ fi
+ use_eh_frame_registry=-DUSE_EH_FRAME_REGISTRY=0
+fi
+])
+AC_SUBST([use_eh_frame_registry])
+
AC_ARG_ENABLE([tm-clone-registry],
[ --disable-tm-clone-registry disable TM clone registry],
[
diff --git a/libgcc/crtstuff.c b/libgcc/crtstuff.c
index ae6328d317d..9a3247b7848 100644
--- a/libgcc/crtstuff.c
+++ b/libgcc/crtstuff.c
@@ -136,9 +136,13 @@ call_ ## FUNC (void) \
# error "Can't use explicit exception-frame-registration without __LIBGCC_EH_FRAME_SECTION_NAME__"
# endif
#endif
+#ifndef USE_EH_FRAME_REGISTRY
#if defined(__LIBGCC_EH_FRAME_SECTION_NAME__) && (!defined(USE_PT_GNU_EH_FRAME) || defined(USE_EH_FRAME_REGISTRY_ALWAYS))
-# define USE_EH_FRAME_REGISTRY
+# define USE_EH_FRAME_REGISTRY 1
+#else
+# define USE_EH_FRAME_REGISTRY 0
#endif
+#endif /* USE_EH_FRAME_REGISTRY */
#if defined(__LIBGCC_EH_FRAME_SECTION_NAME__) \
&& __LIBGCC_EH_TABLES_CAN_BE_READ_ONLY__
# define EH_FRAME_SECTION_CONST const
@@ -257,7 +261,7 @@ STATIC func_ptr __DTOR_LIST__[1]
#endif /* __DTOR_LIST__ alternatives */
#endif /* USE_INITFINI_ARRAY */
-#ifdef USE_EH_FRAME_REGISTRY
+#if USE_EH_FRAME_REGISTRY
/* Stick a label at the beginning of the frame unwind info so we can register
and deregister it with the exception handling library code. */
STATIC EH_FRAME_SECTION_CONST char __EH_FRAME_BEGIN__[]
@@ -412,7 +416,7 @@ __do_global_dtors_aux (void)
deregister_tm_clones ();
#endif /* USE_TM_CLONE_REGISTRY */
-#ifdef USE_EH_FRAME_REGISTRY
+#if USE_EH_FRAME_REGISTRY
#ifdef CRT_GET_RFIB_DATA
/* If we used the new __register_frame_info_bases interface,
make sure that we deregister from the same place. */
@@ -452,7 +456,7 @@ CRT_CALL_STATIC_FUNCTION (__LIBGCC_INIT_SECTION_ASM_OP__,
__do_global_dtors_aux_1)
#endif
-#if defined(USE_EH_FRAME_REGISTRY) || USE_TM_CLONE_REGISTRY
+#if USE_EH_FRAME_REGISTRY || USE_TM_CLONE_REGISTRY
/* Stick a call to __register_frame_info into the .init section. For some
reason calls with no arguments work more reliably in .init, so stick the
call in another function. */
@@ -460,7 +464,7 @@ CRT_CALL_STATIC_FUNCTION (__LIBGCC_INIT_SECTION_ASM_OP__,
static void __attribute__((used))
frame_dummy (void)
{
-#ifdef USE_EH_FRAME_REGISTRY
+#if USE_EH_FRAME_REGISTRY
static struct object object;
#ifdef CRT_GET_RFIB_DATA
void *tbase, *dbase;
@@ -555,13 +559,13 @@ __do_global_dtors (void)
deregister_tm_clones ();
#endif /* USE_TM_CLONE_REGISTRY */
-#ifdef USE_EH_FRAME_REGISTRY
+#if USE_EH_FRAME_REGISTRY
if (__deregister_frame_info)
__deregister_frame_info (__EH_FRAME_BEGIN__);
#endif
}
-#if defined(USE_EH_FRAME_REGISTRY) || USE_TM_CLONE_REGISTRY
+#if USE_EH_FRAME_REGISTRY || USE_TM_CLONE_REGISTRY
/* A helper function for __do_global_ctors, which is in crtend.o. Here
in crtbegin.o, we can reference a couple of symbols not visible there.
Plus, since we're before libgcc.a, we have no problems referencing
@@ -569,7 +573,7 @@ __do_global_dtors (void)
void
__do_global_ctors_1(void)
{
-#ifdef USE_EH_FRAME_REGISTRY
+#if USE_EH_FRAME_REGISTRY
static struct object object;
if (__register_frame_info)
__register_frame_info (__EH_FRAME_BEGIN__, &object);
@@ -733,7 +737,7 @@ void
__do_global_ctors (void)
{
func_ptr *p;
-#if defined(USE_EH_FRAME_REGISTRY) || USE_TM_CLONE_REGISTRY
+#if USE_EH_FRAME_REGISTRY || USE_TM_CLONE_REGISTRY
__do_global_ctors_1();
#endif
for (p = __CTOR_END__ - 1; *p != (func_ptr) -1; p--)
--
2.17.1
