[U-Boot] [PATCH] ARM: Fix __bss_start and __bss_end in linker scripts
Benoît Thébaudeau
benoit.thebaudeau at advansee.com
Fri Apr 5 15:56:46 CEST 2013
Hi Albert,
On Friday, April 5, 2013 8:00:43 AM, Albert ARIBAUD wrote:
> Hi Benoît,
>
> CC:ing Stephen Warren who wrote commit 2b7818d4 which git blame tells
> me added the ASSERT() to arch/arm/cpu/u-boot.lds, and Tom Rini to help
> decide what to do.
>
> On Fri, 5 Apr 2013 05:44:55 +0200 (CEST), Benoît Thébaudeau
> <benoit.thebaudeau at advansee.com> wrote:
>
> > Hi Albert,
> >
> > On Friday, April 5, 2013 1:54:38 AM, Albert ARIBAUD wrote:
> > > Hi Benoît,
> > >
> > > On Fri, 5 Apr 2013 01:13:51 +0200 (CEST), Benoît Thébaudeau
> > > <benoit.thebaudeau at advansee.com> wrote:
> > >
> > > > On Friday, April 5, 2013 1:05:53 AM, Benoît Thébaudeau wrote:
> > > > > Hi Albert,
> > > > >
> > > > > On Friday, April 5, 2013 12:13:53 AM, Albert ARIBAUD wrote:
> > > > > > Subject: [PATCH] ARM: Fix __bss_start and __bss_end in linker
> > > > > > scripts
> > > > > >
> > > > > > Commit 3ebd1cbc introduced compiler-generated __bss_start
> > > > > > and __bss_end__ and commit c23561e7 rewrote all __bss_end__
> > > > > > as __bss_end. Their merge caused silent and harmless but
> > > > > > potentially bug-inducing clashes between compiler- and linker-
> > > > > > enerated __bss_end symbols.
> > > > > >
> > > > > > Make __bss_end and __bss_start compiler-only, and create
> > > > > > __bss_base and __bss_limit for linker-only use.
> > > > > >
> > > > > > Reported-by: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
> > > > > > Signed-off-by: Albert ARIBAUD <albert.u.boot at aribaud.net>
> > > > > > ---
> > > > > > arch/arm/cpu/ixp/u-boot.lds | 14 ++++++++++----
> > > > > > arch/arm/cpu/u-boot.lds | 14 ++++++++++----
> > > > > > board/actux1/u-boot.lds | 14 ++++++++++----
> > > > > > board/actux2/u-boot.lds | 14 ++++++++++----
> > > > > > board/actux3/u-boot.lds | 14 ++++++++++----
> > > > > > board/dvlhost/u-boot.lds | 14 ++++++++++----
> > > > > > board/freescale/mx31ads/u-boot.lds | 14 ++++++++++----
> > > > > > 7 files changed, 70 insertions(+), 28 deletions(-)
> > > > > >
> > > > > > diff --git a/arch/arm/cpu/ixp/u-boot.lds
> > > > > > b/arch/arm/cpu/ixp/u-boot.lds
> > > > > > index 8345b55..c999829 100644
> > > > > > --- a/arch/arm/cpu/ixp/u-boot.lds
> > > > > > +++ b/arch/arm/cpu/ixp/u-boot.lds
> > > > > > @@ -67,17 +67,23 @@ SECTIONS
> > > > > >
> > > > > > _end = .;
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.dynstr*) }
> > > > > > diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
> > > > > > index 3a1083d..0543b06 100644
> > > > > > --- a/arch/arm/cpu/u-boot.lds
> > > > > > +++ b/arch/arm/cpu/u-boot.lds
> > > > > > @@ -81,18 +81,24 @@ SECTIONS
> > > > > > *(.mmutable)
> > > > > > }
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > >
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.dynstr*) }
> > > > > > diff --git a/board/actux1/u-boot.lds b/board/actux1/u-boot.lds
> > > > > > index c76728a..7e5c4d8 100644
> > > > > > --- a/board/actux1/u-boot.lds
> > > > > > +++ b/board/actux1/u-boot.lds
> > > > > > @@ -74,17 +74,23 @@ SECTIONS
> > > > > >
> > > > > > _end = .;
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.dynstr*) }
> > > > > > diff --git a/board/actux2/u-boot.lds b/board/actux2/u-boot.lds
> > > > > > index 984f70e..ce1b7c9 100644
> > > > > > --- a/board/actux2/u-boot.lds
> > > > > > +++ b/board/actux2/u-boot.lds
> > > > > > @@ -74,17 +74,23 @@ SECTIONS
> > > > > >
> > > > > > _end = .;
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.dynstr*) }
> > > > > > diff --git a/board/actux3/u-boot.lds b/board/actux3/u-boot.lds
> > > > > > index fc48cf0..3e091dd 100644
> > > > > > --- a/board/actux3/u-boot.lds
> > > > > > +++ b/board/actux3/u-boot.lds
> > > > > > @@ -74,17 +74,23 @@ SECTIONS
> > > > > >
> > > > > > _end = .;
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.dynstr*) }
> > > > > > diff --git a/board/dvlhost/u-boot.lds b/board/dvlhost/u-boot.lds
> > > > > > index b13d3e1..fe3c21b 100644
> > > > > > --- a/board/dvlhost/u-boot.lds
> > > > > > +++ b/board/dvlhost/u-boot.lds
> > > > > > @@ -74,17 +74,23 @@ SECTIONS
> > > > > >
> > > > > > _end = .;
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.dynstr*) }
> > > > > > diff --git a/board/freescale/mx31ads/u-boot.lds
> > > > > > b/board/freescale/mx31ads/u-boot.lds
> > > > > > index 264c4e8..e6885a5 100644
> > > > > > --- a/board/freescale/mx31ads/u-boot.lds
> > > > > > +++ b/board/freescale/mx31ads/u-boot.lds
> > > > > > @@ -80,17 +80,23 @@ SECTIONS
> > > > > >
> > > > > > _end = .;
> > > > > >
> > > > > > +/*
> > > > > > + * Compiler-generated __bss_start and __bss_end, see
> > > > > > arch/arm/lib/bss.c
> > > > > > + * __bss_base and __bss_limit are for linker only (overlay
> > > > > > ordering)
> > > > > > + */
> > > > > > +
> > > > > > .bss_start __rel_dyn_start (OVERLAY) : {
> > > > > > KEEP(*(.__bss_start));
> > > > > > + HIDDEN(__bss_base = .);
> > > > > > }
> > > > > >
> > > > > > - .bss __bss_start (OVERLAY) : {
> > > > > > + .bss __bss_base (OVERLAY) : {
> > > > > > *(.bss*)
> > > > > > . = ALIGN(4);
> > > > > > - __bss_end = .;
> > > > > > + HIDDEN(__bss_limit = .);
> > > > > > }
> > > > > > - .bss_end __bss_end (OVERLAY) : {
> > > > > > - KEEP(*(__bss_end));
> > > > > > + .bss_end __bss_limit (OVERLAY) : {
> > > > > > + KEEP(*(.__bss_end));
> > > > > > }
> > > > > >
> > > > > > /DISCARD/ : { *(.bss*) }
> > > > > > --
> > > > > > 1.7.10.4
> > > > > >
> > > > > >
> > > > >
> > > > > Looks good, but what about the __bss_end in
> > > > > ASSERT(__bss_end < (CONFIG_SPL_TEXT_BASE + CONFIG_SPL_MAX_SIZE), "SPL
> > > > > image
> > > > > too big");
> > > > > ?
> > > > >
> > > > > Shouldn't it be replaced with __bss_limit, or even better, with
> > > > > __image_copy_end
> > > > > (why should BSS be taken into account for SPL image size?)?
> > > >
> > > > I meant __bss_base, not __image_copy_end.
> > >
> > > Part of SPL can use BSS, once board_init_f() has handed things over to
> > > board_init_r(),
> >
> > I agree with that.
> >
> > > and this test is meant to ensure that .text+.data+.bss
> > > fits in the RAM available to SPL. This ASSERT() compares the upper
> > > limit of this RAM to the upper limit of the SPL needs, i.e. __bss_end.
> > >
> > > IOW, this ASSERT is about how much memory SPL will use when it runs,
> >
> > This is where there might be an issue with the definition / usage of
> > CONFIG_SPL_MAX_SIZE.
> >
> > I had understood that this is the purpose of this assert, but this usage of
> > CONFIG_SPL_MAX_SIZE, while frequent on arm, conflicts with its definition
> > in
> > README, as well as with some arm and other usages, e.g. in
> > include/configs/am335x_evm.h or include/configs/p1_p2_rdb_pc.h.
It's not even that frequent on ARM. I've looked at a few other ARM linker
scripts (arm1136, omap), and they don't count bss in CONFIG_SPL_MAX_SIZE.
> > The README's definition is also how I understood this config when
> > discussing it
> > with Scott about my 16/30, which led to the #error test that was added at
> > some
> > point to this patch.
>
> Sorry, I'd missed that. Adding Stephen for any comment regarding the
> ASSERT() and CONFIG_SPL_MAX_SIZE semantics.
>
> > According to README, CONFIG_SPL_MAX_SIZE is for text + data + rodata (i.e.
> > for
> > the size of the binary image file to be programmed on the target device),
> > while
> > CONFIG_SPL_BSS_MAX_SIZE is dedicated to the BSS. Hence, in order to comply
> > with
> > this definition, that assert should either use __bss_base/__bss_start, or
> > compare against CONFIG_SPL_MAX_SIZE + CONFIG_SPL_BSS_MAX_SIZE, depending on
> > whether it's supposed to test the binary image size or the memory
> > footprint.
> > There could even be asserts testing both. This would anyway be a new patch
> > separate from this one.
>
> It would indeed be a different patch.
>
> IIUC, this future patch would increase the limit for SPL run-time size,
> as the constant against which the ASS tests __bss_end for would
> necessarily be greater than it is now. Correct? If so, this future
> patch should not break any target, as it would loosen the constraint,
> not tighten it.
Yes, it would either be the same or relaxed a bit, depending on the chosen
option:
- Define CONFIG_SPL_BSS_MAX_SIZE and test against CONFIG_SPL_MAX_SIZE +
CONFIG_SPL_BSS_MAX_SIZE, the sum remaining the same as or being larger than
currently, depending on the new values for CONFIG_SPL_MAX_SIZE and
CONFIG_SPL_BSS_MAX_SIZE.
- Define a new config meaning text + data + rodata + bss (e.g.
CONFIG_SPL_MAX_RAM_SIZE or CONFIG_SPL_MAX_MEM_FOOTPRINT), and just replace
CONFIG_SPL_MAX_SIZE with it for the users of arch/arm/cpu/u-boot*.lds, taking
care that this was the only meaning those users were giving to
CONFIG_SPL_MAX_SIZE.
The first option would probably be preferable, using the same value for
CONFIG_SPL_MAX_SIZE, and a non-zero value for CONFIG_SPL_BSS_MAX_SIZE.
> Tom, would such a patch, if posted today, be acceptable for 2013.04?
>
> > If you decided not to change that, CONFIG_SPL_MAX_SIZE would have different
> > meanings depending on the board, and CONFIG_SPL_PAD_TO could be smaller
> > than it
> > in some cases, so the #error test in my 16/30 could be removed, but no such
> > case
> > exists so far, making this 16/30 change not strictly necessary for now.
>
> IF a patch is posted, it should be done above your series, and take
> care of fixing 16/30 as necessary.
If this assert is fixed according to the README definition, nothing needs to be
changed in 16/30.
> Now, pending Tom's approval, the question is: who does this future
> patch?
>
> Benoît, You obviously have most of the necessary inputs, but I might
> be more available to prepare a patch now. Your pick -- and in any case,
> you earn a second Reported-By: badge. :)
I let you handle this, and approved for my RB badge. :)
Best regards,
Benoît
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