Hi Marek,
On Tue, Feb 21, 2012 at 12:24 PM, Marek Vasut <marek.va...@gmail.com> wrote:
>> Hi Albert,
>>
>> On Tue, Feb 21, 2012 at 5:11 AM, Albert ARIBAUD
>>
>> <albert.u.b...@aribaud.net> wrote:
>> > Hi Simon,
>> >
>> > Le 21/02/2012 07:17, Simon Glass a écrit :
>> >> Most ARM CPUs use a very similar link script. This adds a basic
>> >> script that can be used by most CPUs.
>> >>
>> >> Two new symbols are introduced which are intended to eventually be
>> >> defined on all architectures to make things easier for generic
>> >> relocation and reduce special-case code for each architecture:
>> >>
>> >> __text_start is the start of the text area (equivalent to the existing
>> >> _start on ARM). It marks the start of the region which must be copied
>> >> to a new location during relocation.
>> >
>> > Please name it _image_copy_start, not __text_start
>>
>> OK will do
>>
>> >> __image_copy_end is the end of the region which must be copied to a new
>> >> location during relocation. It is normally equal to the start of the BSS
>> >> region, but this can vary in some cases (SPL?). Making this an explicit
>> >> symbol on its own removes any ambiguity and permits common code to
>> >> always do the right thing.
>> >>
>> >> This new script makes use of CPUDIR, now defined by both Makefile and
>> >> spl/Makefile, to find the directory containing the start.o object file,
>> >> which is always placed first in the image.
>> >>
>> >> To permit MMU setup prior to relocation (as used by pxa) we add an area
>> >> to the link script which contains space for this. This is taken
>> >> from commit 7f4cfcf. CPUs can put the contents in there using their
>> >> start.S file. BTW, shouldn't that area be 16KB-aligned?
>> >>
>> >> Signed-off-by: Simon Glass<s...@chromium.org>
>> >> ---
>> >> Changes in v3:
>> >> - Add more comments in the commit message
>> >> - Add section for MMU area, as required by pxa
>> >>
>> >> arch/arm/cpu/u-boot.lds | 91
>> >> +++++++++++++++++++++++++++++++++++++++++++++++
>> >> 1 files changed, 91 insertions(+), 0 deletions(-)
>> >> create mode 100644 arch/arm/cpu/u-boot.lds
>> >>
>> >> diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
>> >> new file mode 100644
>> >> index 0000000..7a859fc
>> >> --- /dev/null
>> >> +++ b/arch/arm/cpu/u-boot.lds
>> >> @@ -0,0 +1,91 @@
>> >> +/*
>> >> + * Copyright (c) 2004-2008 Texas Instruments
>> >> + *
>> >> + * (C) Copyright 2002
>> >> + * Gary Jennejohn, DENX Software Engineering,<ga...@denx.de>
>> >> + *
>> >> + * See file CREDITS for list of people who contributed to this
>> >> + * project.
>> >> + *
>> >> + * This program is free software; you can redistribute it and/or
>> >> + * modify it under the terms of the GNU General Public License as
>> >> + * published by the Free Software Foundation; either version 2 of
>> >> + * the License, or (at your option) any later version.
>> >> + *
>> >> + * This program 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 General Public License for more details.
>> >> + *
>> >> + * You should have received a copy of the GNU General Public License
>> >> + * along with this program; if not, write to the Free Software
>> >> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
>> >> + * MA 02111-1307 USA
>> >> + */
>> >> +
>> >> +OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
>> >> +OUTPUT_ARCH(arm)
>> >> +ENTRY(_start)
>> >> +SECTIONS
>> >> +{
>> >> + . = 0x00000000;
>> >> +
>> >> + . = ALIGN(4);
>> >> + .text :
>> >> + {
>> >> + __text_start = .;
>> >> + CPUDIR/start.o (.text)
>> >> + *(.text)
>> >> + }
>> >> +
>> >> + . = ALIGN(4);
>> >> + .rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) }
>> >> +
>> >> + . = ALIGN(4);
>> >> + .data : {
>> >> + *(.data)
>> >> + }
>> >> +
>> >> + . = ALIGN(4);
>> >> +
>> >> + . = .;
>> >> + __u_boot_cmd_start = .;
>> >> + .u_boot_cmd : { *(.u_boot_cmd) }
>> >> + __u_boot_cmd_end = .;
>> >> +
>> >> + . = ALIGN(4);
>> >
>> > This "ALIGN(4)" is what upsets my edminiv2 build and makes it not
>> > binary-identical. It is not in the current arm926ejs liner script. I will
>> > check if adding it to the current arm926ejs script produces a working and
>> > binary-identical u-boot.
>>
>> OK, but realistically we copy a word at a time (at least) and the
>> .rel.dyn region is going to be word-aligned I think. All we are doing
>> here is making sure that the image ends on a word boundary, which
>> seems reasonable to me.
>>
>> In other words, I would like the __image_copy_start and
>> __image_copy_end symbols to be word-aligned.
>>
>> >> + __image_copy_end = .;
>> >> +
>> >> + .rel.dyn : {
>> >> + __rel_dyn_start = .;
>> >> + *(.rel*)
>> >> + __rel_dyn_end = .;
>> >> + }
>> >> +
>> >> + .dynsym : {
>> >> + __dynsym_start = .;
>> >> + *(.dynsym)
>> >> + }
>> >> +
>> >> + _end = .;
>> >
>> > Below is what I assume to be the reservation for MMU.
>> >
>> >> + . = ALIGN(4096);
>> >> +
>> >> + .mmutable : {
>> >> + *(.mmutable)
>> >> + }
>> >
>> > ... and I don't like it at all, more so if it is going to be actually 16
>> > KB, because it seems to me we're wasting memory and creating a hole in
>> > the middle of our in-RAM binary, and I'm not sure we need to do it here
>> > in the first place. Do we need to have that MMU region mapped over DDR?
>> > And if so, do we need to have it mapped in the middle of u-boot? Plus
>> > you're placing it after .dynsym and .rel.dyn, but possibly overlaid with
>> > .bss. Normally this area should have gone by the time we get to use BSS,
>> > but assumption is the mother of all screw-ups.
>>
>> Yes it will be 16KB, although of course only if it exists. At present
>> it is only used for pxa so including it here allows pxa boards to
>> build.
>>
>> The hole is not in the middle of the binary, but at the end. The BSS
>> may overlay it if large enough, but that doesn't take affect until
>> after relocation.
>>
>> I'm not thrilled with it either, but it does allow us to have an
>> option to set up the MMU table at compile time for those that need it.
>> Having thought about it a bit more I feel that we should be able to
>> set this up at run-time instead, but still, it is needed at present
>> for pxa, so...
>>
>> I have question also, for Marek. Should this be 16KB aligned, since
>> ARM needs this I think. The alignment is currently provided by pxa's
>> start.S but we might as well be explicit here I think.
>
> Yes, but I believe it should be only 4k aligned. This part is special in more
> ways actually.
>
> This is only used on PXA250, since that has no SRAM and therefore no place for
> stack at boottime. But to allow locking cachelines (to create space for stack)
> we need the MMU table ready. Therefore I created the MMU table with 1:1
> mapping
> in the ROM at compile time and in the init code I point the MMU to this table.
>
> That's about it
OK thank you. Since this isn't needed for other CPUs and given
Albert's concerns I will mark this section as deprecated in my v4
patch, just to make sure others don't start using it.
>
> M
Regards,
Simon
>
>>
>> >> + .bss __rel_dyn_start (OVERLAY) : {
>> >> + __bss_start = .;
>> >> + *(.bss)
>> >> + . = ALIGN(4);
>> >> + __bss_end__ = .;
>> >> + }
>> >> +
>> >> + /DISCARD/ : { *(.dynstr*) }
>> >> + /DISCARD/ : { *(.dynamic*) }
>> >> + /DISCARD/ : { *(.plt*) }
>> >> + /DISCARD/ : { *(.interp*) }
>> >> + /DISCARD/ : { *(.gnu*) }
>> >> +}
>> >
>> > Amicalement,
>> > --
>> > Albert.
>>
>> Regards,
>> Simon
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