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Re: initfini.c -> crt[in].S
On Tue, 7 Feb 2012, Roland McGrath wrote:
> > Source line information ought to work; I've removed those options. CFI is
> > riskier and I'm not sure it will work for these fragments in a useful way
> > given that they aren't complete functions (gas doesn't like .cfi_startproc
> > without matching .cfi_endproc).
>
> startproc/endproc don't really need to coincide with functions as such.
> They just drive the CFI resolution logic. Anyway, CFI can be left for
> later. (But it might be good to do it soonish, so its presence here
> sets the model for other arch code to follow.)
I'd think it would be more interesting (but hard) to have CFI that covers
whatever calls go in the middle of .init/.fini, than just to cover the
instructions in the prologue and epilogue by treating those as separate
functions.
> It's fine to use an abstract description like yours when the condition
> has hairy syntax like this one does. But the [] convention makes it
Indeeed, I tried the [] syntax, but with [ifneq (,$(wildcard
$(sysdirs:%=%/crti.S)))] the logs are even less readable.
> > +ifeq (,$(wildcard $(sysdirs:%=%/crti.S)))
>
> Please add a comment here about the reason for conditional kludgery, and
> its temporariness. It could include a link to a wiki page describing
> the transition and deadline.
Comments added, here and elsewhere as requested. ChangeLogs updated as
suggested. I think a wiki page is probably overkill (I was planning a
mailing list message explaining the change to both libc-alpha and
libc-ports), but if created it would better be added after the code is
actually in so it describes something actually in the code people can just
check out.
> > + .hidden PREINIT_FUNCTION
>
> What does .hidden even mean on an undefined symbol?
It sets STV_HIDDEN on the undefined symbol. See
<http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20218> for why GCC generates
it. Given that the symbol will always be defined, and have hidden
visibility on the definition, it's not strictly necessary (the visibility
from the definition will apply as the most restrictive visibility in any
object in the link) - but it seems cleaner to me to give the symbol the
same visibility on the use as on the definition, just as GCC does.
> I don't have a strong opinion about whether to tab-align operands or
> not, but please be consistent. If you're going to use tabs, choose a
> number of tabs that makes all the lines nearby line up exactly. (My
> tendency is mostly not to use tabs, roughly consistent with GNU style
> for C et al where we don't usually tab-align assignments and such.)
Spaces now used consistently for both instructions and directives.
2012-02-07 Joseph Myers <joseph@codesourcery.com>
Support crti.S and crtn.S provided directly by architectures.
* csu/Makefile (generated): Do not append for crti.S in sysdirs.
(omit-deps): Likewise.
(CFLAGS-initfini.s): Do not define variable for crti.S in sysdirs.
($(crtstuff:%=$(objpfx)%.o)): Disable rule for crti.S in sysdirs.
($(objpfx)initfini.s): Likewise.
($(objpfx)crti.S): Likewise.
($(objpfx)crtn.S): Likewise.
($(patsubst %,$(objpfx)crt%.o,i n)): Likewise.
($(objpfx)defs.h): Likewise.
(initfini.c): Remove vpath directive for crti.S in sysdirs.
* sysdeps/i386/crti.S, sysdeps/i386/crtn.S: New files, based on
compiler output for sysdeps/generic/initfini.c.
* sysdeps/i386/elf/Makefile: Remove file.
* sysdeps/i386/Makefile (CFLAGS-initfini.s): Remove variable.
nptl:
2012-02-07 Joseph Myers <joseph@codesourcery.com>
Support crti.S and crtn.S provided directly by architectures.
* Makefile (omit-deps): Do not append for crti.S in sysdirs.
(CFLAGS-pt-initfini.s): Do not define variable for crti.S in
sysdirs.
($(objpfx)pt-initfini.s): Disable rule for crti.S in sysdirs.
($(objpfx)crti.S): Likewise.
($(objpfx)crtn.S): Likewise.
($(objpfx)defs.h): Likewise.
($(objpfx)crti.o): Likewise.
($(objpfx)crtn.o): Likewise.
(pt-initfini.c): Remove vpath directive for crti.S in sysdirs.
($(objpfx)crti.o): New rule for crti.S in sysdirs.
* pt-crti.S: New file.
* sysdeps/unix/sysv/linux/i386/Makefile: Remove file.
diff --git a/csu/Makefile b/csu/Makefile
index 601264d..05bc0e4 100644
--- a/csu/Makefile
+++ b/csu/Makefile
@@ -84,6 +84,13 @@ crtstuff = crti crtn
install-lib += $(crtstuff:=.o)
extra-objs += $(crtstuff:=.o)
+
+# Conditionals on the existence of a sysdeps version of crti.S are
+# temporary until all targets either have such a file or have been
+# removed, after which the old approach of postprocessing compiler
+# output will be removed.
+ifeq (,$(wildcard $(sysdirs:%=%/crti.S)))
+
generated += $(crtstuff:=.S) initfini.s defs.h
omit-deps += $(crtstuff)
@@ -122,6 +129,8 @@ $(objpfx)defs.h: $(objpfx)initfini.s
endif
+endif
+
extra-objs += abi-note.o init.o
asm-CPPFLAGS += -I$(objpfx).
diff --git a/nptl/Makefile b/nptl/Makefile
index 0c317b0..81661b3 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -335,15 +335,23 @@ ifneq (,$(patsubst .,,$(multidir)))
generated-dirs := $(firstword $(subst /, , $(multidir)))
crti-objs += $(multidir)/crti.o
crtn-objs += $(multidir)/crtn.o
+# Conditionals on the existence of a sysdeps version of crti.S are
+# temporary until all targets either have such a file or have been
+# removed, after which the old approach of postprocessing compiler
+# output will be removed.
+ifeq (,$(wildcard $(sysdirs:%=%/crti.S)))
omit-deps += $(multidir)/crti $(multidir)/crtn
+endif
$(objpfx)$(multidir):
mkdir -p $@
endif
extra-objs += $(crti-objs) $(crtn-objs)
+ifeq (,$(wildcard $(sysdirs:%=%/crti.S)))
omit-deps += crti crtn
CFLAGS-pt-initfini.s = -g0 -fPIC -fno-inline-functions $(fno-unit-at-a-time)
endif
+endif
CFLAGS-flockfile.c = -D_IO_MTSAFE_IO
CFLAGS-ftrylockfile.c = -D_IO_MTSAFE_IO
@@ -542,15 +550,24 @@ $(addprefix $(objpfx),$(tests) $(test-srcs)): $(objpfx)libpthread.a
endif
ifeq ($(build-shared),yes)
+ifeq (,$(wildcard $(sysdirs:%=%/crti.S)))
vpath pt-initfini.c $(sysdirs)
$(objpfx)pt-initfini.s: pt-initfini.c
$(compile.c) -S $(CFLAGS-pt-initfini.s) -finhibit-size-directive \
$(patsubst -f%,-fno-%,$(exceptions)) -o $@
+endif
$(objpfx)tst-cleanup0.out: /dev/null $(objpfx)tst-cleanup0
$(make-test-out) 2>&1 | cmp - tst-cleanup0.expect > $@
+ifneq (,$(wildcard $(sysdirs:%=%/crti.S)))
+
+$(objpfx)crti.o: $(objpfx)pt-crti.o
+ ln -f $< $@
+
+else
+
# We only have one kind of startup code files. Static binaries and
# shared libraries are build using the PIC version.
$(objpfx)crti.S: $(objpfx)pt-initfini.s
@@ -572,6 +589,8 @@ $(objpfx)crti.o: $(objpfx)crti.S $(objpfx)defs.h
$(objpfx)crtn.o: $(objpfx)crtn.S $(objpfx)defs.h
$(compile.S) -g0 $(ASFLAGS-.os) -o $@
+endif
+
ifneq ($(multidir),.)
$(objpfx)$(multidir)/crti.o: $(objpfx)crti.o $(objpfx)$(multidir)/
ln -f $< $@
diff --git a/nptl/pt-crti.S b/nptl/pt-crti.S
new file mode 100644
index 0000000..3ea359d
--- /dev/null
+++ b/nptl/pt-crti.S
@@ -0,0 +1,44 @@
+/* Special .init and .fini section support for libpthread.
+ Copyright (C) 2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ In addition to the permissions in the GNU Lesser General Public
+ License, the Free Software Foundation gives you unlimited
+ permission to link the compiled version of this file with other
+ programs, and to distribute those programs without any restriction
+ coming from the use of this file. (The GNU Lesser General Public
+ License restrictions do apply in other respects; for example, they
+ cover modification of the file, and distribution when not linked
+ into another program.)
+
+ Note that people who make modified versions of this file are not
+ obligated to grant this special exception for their modified
+ versions; it is their choice whether to do so. The GNU Lesser
+ General Public License gives permission to release a modified
+ version without this exception; this exception also makes it
+ possible to release a modified version which carries forward this
+ exception.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+/* Arrange for __pthread_initialize_minimal_internal to be called at
+ libpthread startup, instead of conditionally calling
+ __gmon_start__. */
+
+#define PREINIT_FUNCTION __pthread_initialize_minimal_internal
+#define PREINIT_FUNCTION_WEAK 0
+
+#include <crti.S>
diff --git a/nptl/sysdeps/unix/sysv/linux/i386/Makefile b/nptl/sysdeps/unix/sysv/linux/i386/Makefile
deleted file mode 100644
index 48eef38..0000000
--- a/nptl/sysdeps/unix/sysv/linux/i386/Makefile
+++ /dev/null
@@ -1,3 +0,0 @@
-ifeq ($(subdir),nptl)
-CFLAGS-pt-initfini.s += -fno-asynchronous-unwind-tables
-endif
diff --git a/sysdeps/i386/Makefile b/sysdeps/i386/Makefile
index 661473e..e1deece 100644
--- a/sysdeps/i386/Makefile
+++ b/sysdeps/i386/Makefile
@@ -5,12 +5,6 @@ asm-CPPFLAGS += -DGAS_SYNTAX
# The i386 `long double' is a distinct type we support.
long-double-fcts = yes
-ifeq ($(subdir),csu)
-# On i686 we must avoid generating the trampoline functions generated
-# to get the GOT pointer.
-CFLAGS-initfini.s += -march=i386 -mtune=i386
-endif
-
ifeq ($(subdir),gmon)
sysdep_routines += i386-mcount
endif
diff --git a/sysdeps/i386/crti.S b/sysdeps/i386/crti.S
new file mode 100644
index 0000000..dfec2cb
--- /dev/null
+++ b/sysdeps/i386/crti.S
@@ -0,0 +1,85 @@
+/* Special .init and .fini section support for x86.
+ Copyright (C) 1995-2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ In addition to the permissions in the GNU Lesser General Public
+ License, the Free Software Foundation gives you unlimited
+ permission to link the compiled version of this file with other
+ programs, and to distribute those programs without any restriction
+ coming from the use of this file. (The GNU Lesser General Public
+ License restrictions do apply in other respects; for example, they
+ cover modification of the file, and distribution when not linked
+ into another program.)
+
+ Note that people who make modified versions of this file are not
+ obligated to grant this special exception for their modified
+ versions; it is their choice whether to do so. The GNU Lesser
+ General Public License gives permission to release a modified
+ version without this exception; this exception also makes it
+ possible to release a modified version which carries forward this
+ exception.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+/* crti.S puts a function prologue at the beginning of the .init and
+ .fini sections and defines global symbols for those addresses, so
+ they can be called as functions. The symbols _init and _fini are
+ magic and cause the linker to emit DT_INIT and DT_FINI. */
+
+#include <libc-symbols.h>
+#include <sysdep.h>
+
+#ifndef PREINIT_FUNCTION
+# define PREINIT_FUNCTION __gmon_start__
+#endif
+
+#ifndef PREINIT_FUNCTION_WEAK
+# define PREINIT_FUNCTION_WEAK 1
+#endif
+
+#if PREINIT_FUNCTION_WEAK
+ weak_extern (PREINIT_FUNCTION)
+#else
+ .hidden PREINIT_FUNCTION
+#endif
+
+ .section .init,"ax",@progbits
+ .p2align 2
+ .globl _init
+ .type _init, @function
+_init:
+ pushl %ebx
+ /* Maintain 16-byte stack alignment for called functions. */
+ subl $8, %esp
+ LOAD_PIC_REG (bx)
+#if PREINIT_FUNCTION_WEAK
+ movl PREINIT_FUNCTION@GOT(%ebx), %eax
+ testl %eax, %eax
+ je .Lno_weak_fn
+ call PREINIT_FUNCTION@PLT
+.Lno_weak_fn:
+#else
+ call PREINIT_FUNCTION
+#endif
+
+ .section .fini,"ax",@progbits
+ .p2align 2
+ .globl _fini
+ .type _fini, @function
+_fini:
+ pushl %ebx
+ subl $8, %esp
+ LOAD_PIC_REG (bx)
diff --git a/sysdeps/i386/crtn.S b/sysdeps/i386/crtn.S
new file mode 100644
index 0000000..2ea2a38
--- /dev/null
+++ b/sysdeps/i386/crtn.S
@@ -0,0 +1,48 @@
+/* Special .init and .fini section support for x86.
+ Copyright (C) 1995-2012 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ In addition to the permissions in the GNU Lesser General Public
+ License, the Free Software Foundation gives you unlimited
+ permission to link the compiled version of this file with other
+ programs, and to distribute those programs without any restriction
+ coming from the use of this file. (The GNU Lesser General Public
+ License restrictions do apply in other respects; for example, they
+ cover modification of the file, and distribution when not linked
+ into another program.)
+
+ Note that people who make modified versions of this file are not
+ obligated to grant this special exception for their modified
+ versions; it is their choice whether to do so. The GNU Lesser
+ General Public License gives permission to release a modified
+ version without this exception; this exception also makes it
+ possible to release a modified version which carries forward this
+ exception.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+/* crtn.S puts function epilogues in the .init and .fini sections
+ corresponding to the prologues in crti.S. */
+
+ .section .init,"ax",@progbits
+ addl $8, %esp
+ popl %ebx
+ ret
+
+ .section .fini,"ax",@progbits
+ addl $8, %esp
+ popl %ebx
+ ret
diff --git a/sysdeps/i386/elf/Makefile b/sysdeps/i386/elf/Makefile
deleted file mode 100644
index 61064d4..0000000
--- a/sysdeps/i386/elf/Makefile
+++ /dev/null
@@ -1,4 +0,0 @@
-ifeq ($(subdir),csu)
-# Turn off -fasynchronous-unwind-tables
-CFLAGS-initfini.s += -fno-asynchronous-unwind-tables
-endif
--
Joseph S. Myers
joseph@codesourcery.com