[klibc] fwd: fix up ARM assembly to use 'bx lr' in place of 'mov pc, lr'.
From: Steve Langasek <hidden>
Date: 2011-02-17 00:01:44
Thanks for forwarding this on, maks. On Thu, Feb 17, 2011 at 01:50:19AM +0200, Kirill A. Shutemov wrote:
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Date: Wed, 16 Feb 2011 22:05:42 -0000 From: Steve Langasek <redacted> Subject: [Bug 527720] Re: thumb2 porting issues identified: klibc uses mov.*pc
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I've also touched it up to be mergeable with Debian (support v4t builds with #ifdef).
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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.
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--- 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?
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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 -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 828 bytes Desc: Digital signature URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20110216/ff3d096d/attachment.sig>