[klibc] fwd: fix up ARM assembly to use 'bx lr' in place of 'mov pc, lr'.

[Khem Raj]

On Wed, Feb 16, 2011 at 4:03 PM, Khem Raj <raj.khem at gmail.com> wrote:
> On Wed, Feb 16, 2011 at 3:50 PM, Kirill A. Shutemov
> <kirill at shutemov.name> wrote:
>> On Thu, Feb 17, 2011 at 12:06:48AM +0100, maximilian attems wrote:
>>> hello vorlon,
>>>
>>> got notified of your patch,
>>> will apply next days upstream unless some critiques are voiced on ml.
>>> thanks.
>>>
>>> --
>>> maks
>>>
>>>
>>> ----- Forwarded message from Steve Langasek <steve.langasek at canonical.com> -----
>>>
>>> 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.
>
> Does ARMv4t support BX lr ?

hmm yes it does. I confused it with blx <Rm> which is unpredictable in
thumb mode on architectures < armv5t

>
>
>>
>>>       mov     pc, lr
>>> +#else
>>> +     bx      lr
>>> +#endif
>>>
>>>       .balign 4
>>>  1:
>>> @@ -49,7 +53,11 @@ vfork:
>>>       str     r2, [r1]
>>>       neg     r0, r0
>>>  1:
>>> +#if defined (___ARM_ARCH_4T__) || defined (__ARM_ARCH_4__)
>>>       mov     pc, lr
>>> +#else
>>> +     bx      lr
>>> +#endif
>>>
>>>       .balign 4
>>>  2:
>>> --- klibc-1.5.20.orig/usr/klibc/arch/arm/setjmp.S
>>> +++ klibc-1.5.20/usr/klibc/arch/arm/setjmp.S
>>> @@ -29,7 +29,11 @@
>>>  setjmp:
>>>       stmia   r0, {r4, r5, r6, r7, r8, r9, r10, fp, sp, lr}
>>>       mov     r0, #0
>>> +#if defined (___ARM_ARCH_4T__) || defined (__ARM_ARCH_4__)
>>>       mov     pc, lr
>>> +#else
>>> +     bx      lr
>>> +#endif
>>>       .size setjmp,.-setjmp
>>>
>>>       .text
>>> @@ -39,7 +43,11 @@ setjmp:
>>>  longjmp:
>>>       ldmia   r0, {r4, r5, r6, r7, r8, r9, r10, fp, sp, lr}
>>>       mov     r0, r1
>>> +#if defined (___ARM_ARCH_4T__) || defined (__ARM_ARCH_4__)
>>>       mov     pc, lr
>>> +#else
>>> +     bx      lr
>>> +#endif
>>>       .size longjmp,.-longjmp
>>>
>>>  #else /* __thumb__ */
>>> @@ -75,7 +83,11 @@ setjmp:
>>>       mov     r7, sp
>>>       stmia   r0!, {r3, r4, r5, r6, r7}
>>>       mov     r0, #0
>>> +#if defined (___ARM_ARCH_4T__) || defined (__ARM_ARCH_4__)
>>>       mov     pc, lr
>>> +#else
>>> +     bx      lr
>>> +#endif
>>>       .size setjmp,.-setjmp
>>>
>>>       .text
>>> @@ -96,7 +108,11 @@ longjmp:
>>>       mov     r0, r1
>>>       bne     1f
>>>       mov     r0, #1
>>> +#if defined (___ARM_ARCH_4T__) || defined (__ARM_ARCH_4__)
>>>  1:   mov     pc, r3
>>> +#else
>>> +1:   bx      r3
>>> +#endif
>>>       .size longjmp,.-longjmp
>>>
>>>  #endif /* __thumb__ */
>>>
>>> _______________________________________________
>>> klibc mailing list
>>> klibc at zytor.com
>>> http://www.zytor.com/mailman/listinfo/klibc
>>
>> --
>>  Kirill A. Shutemov
>>
>> _______________________________________________
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>> linux-arm-kernel at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>
>