[U-Boot] [PATCH] ARM: Fix __bss_start and __bss_end in linker scripts
Albert ARIBAUD
albert.u.boot at aribaud.net
Fri Apr 5 21:28:21 CEST 2013
On Fri, 5 Apr 2013 21:17:40 +0200, Albert ARIBAUD
<albert.u.boot at aribaud.net> wrote:
> Hi Tom,
>
> On Fri, 5 Apr 2013 13:55:21 -0400, Tom Rini <trini at ti.com> wrote:
>
> > On Fri, Apr 05, 2013 at 07:32:54PM +0200, Beno??t Th??baudeau wrote:
> > > Hi Tom,
> > >
> > > On Friday, April 5, 2013 6:00:30 PM, Tom Rini wrote:
> > > > On Fri, Apr 05, 2013 at 03:56:46PM +0200, Beno??t Th??baudeau wrote:
> > > > > Hi Albert,
> > > > >
> > > > > On Friday, April 5, 2013 8:00:43 AM, Albert ARIBAUD wrote:
> > > > > > Hi Beno??t,
> > > > [snip]
> > > > > > 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.
> > > >
> > > > I think the problem is that Tegra really needs the second case as their
> > > > constraint is "must fit below next part of payload". We can assume the
> > > > users of that linker script today care about footprint and update their
> > > > define I believe. da850evm and the rest of the davinci platforms would
> > > > also be a case to convert to this, but the omap*/am3* platforms would
> > > > not.
> > >
> > > Yes, then let's have an assert in arch/arm/cpu/u-boot*.lds with a
> > > different config name (as in option 2 above) just for Tegra, and
> > > another assert for CONFIG_SPL_MAX_SIZE against __bss_start.
> > >
> > > And all users of CONFIG_SPL_MAX_SIZE should be checked to make sure
> > > that there is not another special case somewhere.
> >
> > I didn't audit the PowerPC targets, but on ARM we have, roughly:
> > - Tegra (covered in Stephen's email, and in short, must include BSS in
> > size check) which uses SPL_MAX_SIZE to include BSS
> > - OMAP*/AM3* which does not constrain BSS to SPL_MAX_SIZE
> > - DaVinci which must also constrain BSS to the initial RAM, but for
> > different reasons.
> > - iMX which also uses SPL_BSS_MAX to cover the BSS separate from the
> > rest of the program.
>
> How about this?
>
> 1. In the u-boot*.lds files, doing separate asserts for SPL and SPL BSS
> max size, with the SPL assert being further divided in two cases
> depending on BSS max size being defined or not:
>
> #if defined(CONFIG_SPL_MAX_SIZE)
> #if defined(CONFIG_SPL_BSS_MAX_SIZE)
> ASSERT( __bss_end - __image_copy_start < (CONFIG_SPL_TEXT_BASE + \
> CONFIG_SPL_MAX_SIZE), "SPL image code+BSS too big");
> #else
> ASSERT( __bss_end - __image_copy_start < CONFIG_SPL_TEXT_BASE, \
> CONFIG_SPL_MAX_SIZE), "SPL image code too big");
> #endif
#endif
(sorry)
> #if defined(CONFIG_SPL_BSS_MAX_SIZE)
> ASSERT( __bss_end - __bss_start < CONFIG_SPL_TEXT_BASE, \
> CONFIG_SPL_BSS_MAX_SIZE), "SPL image BSS too big");
> #endif
>
> 2. Defining CONFIG_SPL_BSS_MAX_SIZE only for Tegra, Davinci, IMX (where
> CONFIG_SPL_BSS_MAX_SIZE is actually the gap size)
>
> 3. *Not* defining CONFIG_SPL_MAX_SIZE or CONFIG_SPL_BSS_MAX_SIZE for
> OMAP*/AM3*
>
> 4. Adjusting README descriptions of CONFIG_SPL_[BSS_]MAX_SIZE and
> ensuring Makefile uses the right size for --pad-to, as well as
> the few other files which use CONFIG_SPL_MAX_SIZE.
>
> Amicalement,
Amicalement,
--
Albert.
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