glibc/ports/sysdeps/tile/crti.S
Chris Metcalf fedff58953 tile: support very large shared objects
With gcc 4.8 tilegx has support for -mcmodel=large, to tolerate very
large shared objects.  This option changes the compiler output to
not include direct jump instructions, which have a range of only
2^30, i.e +/- 512MB.  Instead the compiler marshalls the target PCs
into registers and then uses jump- or call-to-register instructions.

For glibc, the upshot is that we need to arrange for a few functions
to tolerate the possibility of a large range between the PC and
the target.  In particular, the crti.S and start.S code needs
to be able to reach from .init to the PLT, as does gmon-start.c.
The elf-init.c code has the reverse problem, needing to call from
libc_nonshared.a (linked at the end of shared objects) back to the
_init section at the beginning.

No other functions in *_nonshared.a need to be built this way, as
they only call the PLT (or potentially each other), but all of that
code is linked at the very end of the shared object.

We don't build the standard -static archives with this option as the
performance cost is high enough and the use case is rare enough that
it doesn't seem worthwhile.  Instead, we would encourage developers
who need the -static model with huge executables to build a private
copy of glibc and configure it with -mcmodel=large.

Note that libc.so et al don't need any changes; the only changes
are for code that is statically linked into user code built with
-mcmodel=large.

For the assembly code, I just rewrote it so that it unconditionally
uses the large model.  To be able to pass -mcmodel=large to
csu/elf-init.c and csu/gmon-start.c, I need to check to see if the
compiler supports that flag, since gcc 4.7 doesn't; I added the
support by creating a small Makefile fragment that just runs the
compiler to check.
2012-11-06 09:48:49 -05:00

125 lines
3.6 KiB
ArmAsm

/* Special .init and .fini section support for tile.
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, see
<http://www.gnu.org/licenses/>. */
/* 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
.align 8
.globl _init
.type _init, @function
_init:
{
move r29, sp
ADDI_PTR r28, sp, -REGSIZE
ST sp, lr
}
ADDI_PTR sp, sp, -(2 * REGSIZE)
ST r28, r29
#if PREINIT_FUNCTION_WEAK
lnk r2
0:
# ifdef __tilegx__
moveli r1, hw2_last(_GLOBAL_OFFSET_TABLE_ - 0b)
{
shl16insli r1, r1, hw1(_GLOBAL_OFFSET_TABLE_ - 0b)
moveli r0, hw1_last_got(PREINIT_FUNCTION)
}
{
shl16insli r1, r1, hw0(_GLOBAL_OFFSET_TABLE_ - 0b)
shl16insli r0, r0, hw0_got(PREINIT_FUNCTION)
}
# else
{
moveli r1, lo16(_GLOBAL_OFFSET_TABLE_ - 0b)
moveli r0, got_lo16(PREINIT_FUNCTION)
}
{
auli r1, r1, ha16(_GLOBAL_OFFSET_TABLE_ - 0b)
auli r0, r0, got_ha16(PREINIT_FUNCTION)
}
# endif
ADD_PTR r0, r0, r1
ADD_PTR r0, r0, r2
LD_PTR r0, r0
BEQZ r0, .Lno_weak_fn
jalr r0
#elif defined(__tilegx__)
/* Since we are calling from the start of the object to the PLT,
call by loading the full address into a register. */
lnk r2
0:
moveli r0, hw2_last_plt(PREINIT_FUNCTION - 0b)
shl16insli r0, r0, hw1_plt(PREINIT_FUNCTION - 0b)
shl16insli r0, r0, hw0_plt(PREINIT_FUNCTION - 0b)
add r0, r0, r2
jalr r0
#else
jal plt(PREINIT_FUNCTION)
#endif
.Lno_weak_fn:
.section .fini,"ax",@progbits
.align 8
.globl _fini
.type _fini, @function
_fini:
{
move r29, sp
ADDI_PTR r28, sp, -REGSIZE
ST sp, lr
}
ADDI_PTR sp, sp, -(2 * REGSIZE)
ST r28, r29