From: Tom Rini <trini@ti.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH v2 2/2] arm: work around assembler bug
Date: Tue, 10 Jul 2012 10:50:34 -0700 [thread overview]
Message-ID: <20120710175034.GH5053@oliver-linux> (raw)
In-Reply-To: <20120710174433.GA6010@nvidia.com>
On Tue, Jul 10, 2012 at 10:44:33AM -0700, Allen Martin wrote:
> On Tue, Jul 10, 2012 at 10:25:05AM -0700, Tom Rini wrote:
> > * PGP Signed by an unknown key
> >
> > On Tue, Jul 10, 2012 at 10:00:17AM -0700, Allen Martin wrote:
> > > Disable sibling call optimization based on binutils version. This is
> > > to work around a bug in the assember in binutils versions < 2.22.
> > > Branches to weak symbols can be incorrectly optimized in thumb mode to
> > > a short branch (b.n instruction) that won't reach when the symbol gets
> > > preempted.
> > >
> > > http://sourceware.org/bugzilla/show_bug.cgi?id=12532
> > >
> > > Signed-off-by: Allen Martin <amartin@nvidia.com>
> > > ---
> > > changes for v2:
> > > -changed GAS_BUG_12532 from yes/no to y/n to be consistent
> > > -added additional warning about code size increase
> > > ---
> > > arch/arm/config.mk | 21 +++++++++++++++++++++
> > > 1 file changed, 21 insertions(+)
> > >
> > > diff --git a/arch/arm/config.mk b/arch/arm/config.mk
> > > index 3f4453a..bcabf17 100644
> > > --- a/arch/arm/config.mk
> > > +++ b/arch/arm/config.mk
> > > @@ -87,3 +87,24 @@ endif
> > > ifndef CONFIG_NAND_SPL
> > > LDFLAGS_u-boot += -pie
> > > endif
> > > +
> > > +#
> > > +# binutils versions < 2.22 have a bug in the assembler where branches
> > > +# to weak symbols can be incorrectly optimized in thumb mode to a
> > > +# short branch (b.n instruction) that won't reach when the symbol
> > > +# gets preempted
> > > +#
> > > +# http://sourceware.org/bugzilla/show_bug.cgi?id=12532
> > > +#
> > > +ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
> > > +ifeq ($(GAS_BUG_12532),)
> > > +export GAS_BUG_12532:=$(shell if [ $(call binutils-version) -lt 0222 ] ; then echo y; else echo n; fi)
> >
> > Please don't squash out whitespace, just break this out into a
> > multi-line test ala the others in the toplevel config.mk.
>
> Ok
>
> > > +ifeq ($(GAS_BUG_12532),y)
> > > +$(warning *** disabling sibling call optimzation because binutils version < 2.22)
> > > +$(warning *** code size may be slightly larger)
> > > +endif
> > > +endif
> > > +ifeq ($(GAS_BUG_12532),y)
> > > +PLATFORM_RELFLAGS += -fno-optimize-sibling-calls
> > > +endif
> > > +endif
> >
> > This seems a bit longer than needed. Just check that it's y once and do
> > both things. Also, I _think_ we should be able to squish this down to:
> > ifeq ($(CONFIG_SYS_THUMB_BUILD),y)
> > GAS_BUG_12532 := $(shell if [ $(call binutils-version) -lt 0222 ] ; \
> > then echo y; else echo n; fi)
> > ifeq ($(GAS_BUG_125320),y)
> > $(warning ...)
> > $(warning ...)
> > PLATFORM_RELFLAGS += ...
> > endif
> > endif
> >
> > But I haven't tested it.
>
> I wrote it the way I did because I only want the expensive
> shell/binutils-version to get evaluated once per "make". I think what
> you proposed would cause it to get re-evaluated every time the build
> goes down into a subdir.
It should still get evaluated once, I think. Kluding the
binutils-version script to echo 1 >> /tmp/test every time it's run would
tell tho for sure :)
--
Tom
next prev parent reply other threads:[~2012-07-10 17:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-10 17:00 [U-Boot] [PATCH v2 1/2] tools, config.mk: add binutils-version Allen Martin
2012-07-10 17:00 ` [U-Boot] [PATCH v2 2/2] arm: work around assembler bug Allen Martin
2012-07-10 17:25 ` Tom Rini
2012-07-10 17:44 ` Allen Martin
2012-07-10 17:50 ` Tom Rini [this message]
2012-07-10 18:04 ` Allen Martin
2012-07-10 18:11 ` Tom Rini
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