[U-Boot] [PATCH 0/5] Optimize ARM relocation

[Albert ARIBAUD]

Hi Benoît,

On Wed, 15 May 2013 01:58:23 +0200 (CEST), Benoît Thébaudeau
<benoit.thebaudeau at advansee.com> wrote:

> Hi Albert,
> 
> On Tuesday, May 14, 2013 10:16:01 PM, Albert ARIBAUD wrote:
> > On Tue, 14 May 2013 22:02:55 +0200, Albert ARIBAUD
> > <albert.u.boot at aribaud.net> wrote:
> > 
> > > *** NOTE: this series applies over the 'Factorize
> > > ARM relocate_code instances' series.
> > > 
> > > This series optimizes relocation by ensuring ARM
> > > binaries only use one type of relocation record,
> > > R_ARM_RELATIVE., then optimizing relocation code
> > > accordingly.
> > > 
> > > The only known case where relocation records other
> > > than R_ARM_RELATIVE are generated is when a reference
> > > is made to a symbol defined in the linker script, e.g.
> > > __image_copy_start, __image_copy_end, __rel_dyn_start,
> > > __rel_dyn_end, and __dynsym_start.
> > > 
> > > Moving the definition of these symbols from the linker
> > > scripts into a C module causes their references' types
> > > to become R_ARM_RELATIVE.
> > > 
> > > First, arch/arm/lib/bss.c is replaced by a more generic
> > > arch/arm/lib/sections.c where all section symbols will
> > > be defined.
> > > 
> > > Second, __image_copy_start and __image_copy_end symbols
> > > are moved from linker scripts to arch/arm/lib/sections.c
> > > 
> > > Third, __rel_dyn_start, __rel_dyn_end and __synsym_start
> > > are moved from linker scripts into arch/arm/lib/sections.c
> > > 
> > > Fourth, a check is added to the build system to ensure
> > > that ELF U-Boot binaries only use R_ARM_RELATIVE records.
> > > 
> > > Last, relocate_code is optimized
> > 
> > Hmm, it seems I need to see my work posted on the list to discover how
> > I could have done it better... I just noticed that if ARM binaries only
> > have R_ARM_RELATIVE record types, then all the .dynsym sections can
> > actually be dropped from the binaries. So, if I reorder the series and
> > put patch 5/5 first, then I can eliminate patch 3/5, or more to the
> > point, replace it with one which eliminates all dynsym stuff from linker
> > scripts, further reducing code size. That'll go in V2...
> 
> Indeed.

Correction: if I out patch 4/5, not 5/5 -- 4/5 is the patch that
ensures only relative relocations are present, and 5/5 depends on
previous patches in the series (at least 1/5 and 2/5).

So the new order will be 4/5, 1/5, 2/5, amended 3/5, 5/5.

> Best regards,
> Benoît

Amicalement,
-- 
Albert.