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.thebaud...@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.thebaud...@advansee.com>
> > > > Signed-off-by: Albert ARIBAUD <albert.u.b...@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.
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.
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.
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.
> while OTOH, image_copy_end is about how much code from SPL need to
> becopied from e.g. NAND to RAM to make it run.
Right.
> As for bss_limit, as indicated, it is only for linker convenience, so
> that overlaid sections are mapped properly; it should not be used to
> signify something about the image itself)
OK, I'm fine with that. They have the same value, so it's only a matter of
taste. I spotted that just because you said __bss_limit is for linker stuff, and
it is an assert for the linker, but __bss_end is just fine too, all the more the
resulting assert is then identical to the one in arch/arm/cpu/u-boot-spl.lds.
Best regards,
Benoît
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