From: steve.langasek@linaro.org (Steve Langasek)
To: linux-arm-kernel@lists.infradead.org
Subject: [klibc] fwd: fix up ARM assembly to use 'bx lr' in place of 'mov pc, lr'.
Date: Wed, 16 Feb 2011 16:01:44 -0800 [thread overview]
Message-ID: <20110217000144.GA6995@virgil.dodds.net> (raw)
In-Reply-To: <20110216235019.GA17674@shutemov.name>
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@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
https://wiki.ubuntu.com/ARM/Thumb2PortingHowto#Identifying%20the%20Target%20Architecture
that you are correct - but then in
https://wiki.ubuntu.com/ARM/Thumb2PortingHowto#Detailed%20Instruction%20Behaviour
the recommendation given is to use exactly this guard for backwards
compatibility.
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
Thanks,
--
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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next prev parent reply other threads:[~2011-02-17 0:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-16 23:06 fwd: [klibc] fix up ARM assembly to use 'bx lr' in place of 'mov pc, lr' maximilian attems
2011-02-16 23:50 ` [klibc] fwd: " Kirill A. Shutemov
2011-02-17 0:01 ` Steve Langasek [this message]
2011-02-17 0:18 ` Kirill A. Shutemov
2011-02-17 0:03 ` Khem Raj
2011-02-17 0:42 ` Kirill A. Shutemov
2011-02-17 3:17 ` Khem Raj
2011-02-17 9:39 ` Dave Martin
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