[klibc] fwd: fix up ARM assembly to use 'bx lr' in place of 'mov pc, lr'.
steve.langasek at linaro.org
Wed Feb 16 19:01:44 EST 2011
Thanks for forwarding this on, maks.
On Thu, Feb 17, 2011 at 01:50:19AM +0200, Kirill A. Shutemov wrote:
> > Date: Wed, 16 Feb 2011 22:05:42 -0000
> > From: Steve Langasek <steve.langasek at canonical.com>
> > Subject: [Bug 527720] Re: thumb2 porting issues identified: klibc uses mov.*pc
> > I've also touched it up to be mergeable with Debian (support v4t builds
> > with #ifdef).
> > Confirmed that installing the resulting klibc packages on my beagleboard
> > gives me a successfully-booting initramfs with klibc; and the
> > vfork/setjmptest test cases all pass in the klibc package tree.
> > Fixes: https://bugs.launchpad.net/ubuntu/+source/klibc/+bug/527720
> > --- klibc-1.5.20.orig/usr/klibc/arch/arm/vfork.S
> > +++ klibc-1.5.20/usr/klibc/arch/arm/vfork.S
> > @@ -25,7 +25,11 @@ vfork:
> > ldrcs r3, 1f
> > mvncs r0, #0
> > strcs r2, [r3]
> > +#if defined (___ARM_ARCH_4T__) || defined (__ARM_ARCH_4__)
> NAK. ARMv4T supports bx intruction. ARMv4 doesn't.
I see from
that you are correct - but then in
the recommendation given is to use exactly this guard for backwards
I'm cc:ing Dave Martin from ARM who drafted this porting guide. Dave, was
there some other reason besides instruction compatibility to prefer the
original "mov pc,lr" on armv4t, or is this simply a miscopy?
> > mov pc, lr
> > +#else
> > + bx lr
> > +#endif
Steve Langasek Give me a lever long enough and a Free OS
Debian Developer to set it on, and I can move the world.
Ubuntu Developer http://www.debian.org/
slangasek at ubuntu.com vorlon at debian.org
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