Re: __gmon_start__ symbol vs. dependencies between shared libraries

[Kaz Kojima <kkojima at rr dot iij4u dot or dot jp>]

Daniel Jacobowitz <drow@false.org> wrote:
> On Tue, Dec 01, 2009 at 10:31:07AM +0100, Thomas Schwinge wrote:
>> That is, __gmon_start__ is required for order2mod3.so, and is bound to
>> order2mod1.so's (weak) definition.  Correct would be that order2mod3.so
>> falls back to its *own* (weak) definition of it, unless the real
>> definition of this symbol is linked in through gcrt1.o.
>> 
>> The following tiny patch fixes this, and makes the following tests pass,
>> which failed previously: elf/reldep3.out, elf/neededtest.out,
>> elf/order2.out.
> 
> I'm not sure this patch has the effect you wanted.  If you have a
> weak, hidden definition, will the linker ever call a strong version
> if it's in a different DSO?  I don't think so; .hidden will suppress a
> dynamic relocation against the __gmon_start__ name.
> 
> SH seems to be the only architecture with a weak definition of
> __gmon_start__.  And it isn't doing anything, that I can see.
> Should it be replaced with a conditional function call?

I think so too.  The generic/initfini.c trick didn't work for SH
because of the constant pools and sh/elf/initfini.c was made by
hand with modifying the assembler output for generic/initfini.c
so that those constant pools are placed appropriately.  I've
attached an updated initfini.c with redoing that process which
is almost mechanical.  Thomas, does it work for you?

Regards,
	kaz

/* Special .init and .fini section support for SH.
   Copyright (C) 2000, 2002, 2009 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.  */

/* This file is compiled into assembly code which is then munged by a sed
   script into two files: crti.s and crtn.s.

   * 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.

   * crtn.s puts the corresponding function epilogues
   in the .init and .fini sections. */

__asm__ ("\
\n\
#include \"defs.h\"\n\
\n\
/*@HEADER_ENDS*/\n\
\n\
/*@TESTS_BEGIN*/\n\
	.align 5\n\
/*@TESTS_END*/\n\
\n\
/*@_init_PROLOG_BEGINS*/\n\
	.section	.init,\"ax\",@progbits\n\
	.align 5\n\
	.global	_init\n\
	.type	_init, @function\n\
_init:\n\
	mov.l	r12,@-r15\n\
	mov.l	r14,@-r15\n\
	sts.l	pr,@-r15\n\
#ifdef SHARED\n\
	mova	.L12,r0\n\
	mov.l	.L12,r12\n\
	add	r0,r12\n\
	mov.l	.L13,r0\n\
	mov.l	@(r0,r12),r1\n\
#else\n\
	mov.l	.L13,r1\n\
#endif\n\
	tst	r1,r1\n\
	bt/s	.L8\n\
	mov	r15,r14\n\
#ifdef SHARED\n\
	mov.l	.L14,r1\n\
	bsrf	r1\n\
.LPCS0:\n\
#else\n\
	jsr	@r1\n\
#endif\n\
	nop\n\
.L8:\n\
	bra	1f\n\
	nop\n\
	.align 2\n\
#ifdef SHARED\n\
.L12:\n\
	.long	_GLOBAL_OFFSET_TABLE_\n\
.L13:\n\
	.long	__gmon_start__@GOT\n\
.L14:\n\
	.long	__gmon_start__@PLT-(.LPCS0+2-(.))\n\
#else\n\
.L13:\n\
	.long	__gmon_start__\n\
#endif\n\
1:\n\
	ALIGN\n\
	END_INIT\n\
\n\
/*@_init_PROLOG_ENDS*/\n\
\n\
/*@_init_EPILOG_BEGINS*/\n\
	.section .init\n\
	mov	r14,r15\n\
	lds.l	@r15+,pr\n\
	mov.l	@r15+,r14\n\
	mov.l	@r15+,r12\n\
	rts	\n\
	nop\n\
	END_INIT\n\
\n\
/*@_init_EPILOG_ENDS*/\n\
\n\
/*@_fini_PROLOG_BEGINS*/\n\
	.section	.fini,\"ax\",@progbits\n\
	.align 5\n\
	.global	_fini\n\
	.type	_fini, @function\n\
_fini:\n\
	mov.l	r12,@-r15\n\
	mov.l	r14,@-r15\n\
	sts.l	pr,@-r15\n\
#ifdef SHARED\n\
	mova	.L19,r0\n\
	mov.l	.L19,r12\n\
	add	r0,r12\n\
#endif\n\
	mov	r15,r14\n\
	ALIGN\n\
	END_FINI\n\
\n\
/*@_fini_PROLOG_ENDS*/\n\
	mov.l	.L20,r1\n\
#ifdef SHARED\n\
	bsrf	r1\n\
.LPCS1:\n\
#else\n\
	jsr	@r1\n\
#endif\n\
	nop\n\
	bra	1f\n\
	nop\n\
	.align 2\n\
#ifdef SHARED\n\
.L19:\n\
	.long	_GLOBAL_OFFSET_TABLE_\n\
.L20:\n\
	.long	i_am_not_a_leaf@PLT-(.LPCS1+2-(.))\n\
#else\n\
.L20:\n\
	.long	i_am_not_a_leaf\n\
#endif\n\
1:\n\
/*@_fini_EPILOG_BEGINS*/\n\
	.section .fini\n\
	mov	r14,r15\n\
	lds.l	@r15+,pr\n\
	mov.l	@r15+,r14\n\
	mov.l	@r15+,r12\n\
	rts	\n\
	nop\n\
	END_FINI\n\
\n\
/*@_fini_EPILOG_ENDS*/\n\
\n\
/*@TRAILER_BEGINS*/\n\
	.weak	__gmon_start__\n\
");