linux-2.6.18-xen.hg compilation issue with gcc 4.3

linux-2.6.18-xen.hg compilation issue with gcc 4.3

[Guillaume Rousse]

Hello.

The linux-2.6.18-xen.hg kernel fails to build with gcc 4.3, in linking 
stage:

arch/i386/kernel/built-in.o: In function `sync_xen_wallclock':
time-xen.c:(.text+0x6141): undefined reference to `__udivdi3'
time-xen.c:(.text+0x618a): undefined reference to `__udivdi3'
arch/i386/kernel/built-in.o: In function `do_settimeofday':
(.text+0x63bd): undefined reference to `__udivdi3'
arch/i386/kernel/built-in.o: In function `do_settimeofday':
(.text+0x640b): undefined reference to `__udivdi3'
arch/i386/kernel/built-in.o: In function `do_settimeofday':
(.text+0x6489): undefined reference to `__udivdi3'
arch/i386/kernel/built-in.o:(.text+0x64d2): more undefined references to 
`__udivdi3' follow


According to LKM, this is a known issue:
http://www.nabble.com/undefined-reference-to-__udivdi3-(gcc-4.3)-td17045078.html

However, I couldn't find any loop susceptible to be wrongly optimised in 
incriminated code (sync_xen_wallclock in arch/i386/kernel/time-xen.c). 
Any hint welcome.
-- 
Guillaume Rousse
Moyens Informatiques - INRIA Futurs
Tel: 01 69 35 69 62

Re: linux-2.6.18-xen.hg compilation issue with gcc 4.3

[Keir Fraser]

On 21/5/08 14:19, "Guillaume Rousse" <Guillaume.Rousse@inria.fr> wrote:

> However, I couldn't find any loop susceptible to be wrongly optimised in
> incriminated code (sync_xen_wallclock in arch/i386/kernel/time-xen.c).
> Any hint welcome.

It's hidden in the __normalize_time() macro. Could you backport Jeremy's
upstream fix to the 2.6.18 kernel?

 -- Keir

Re: linux-2.6.18-xen.hg compilation issue with gcc 4.3

[Jan Beulich]

>However, I couldn't find any loop susceptible to be wrongly optimised in 
>incriminated code (sync_xen_wallclock in arch/i386/kernel/time-xen.c). 
>Any hint welcome.

__normalize_time()?

Re: linux-2.6.18-xen.hg compilation issue with gcc 4.3

[Guillaume Rousse]

Keir Fraser a écrit :
> On 21/5/08 14:19, "Guillaume Rousse" <Guillaume.Rousse@inria.fr> wrote:
> 
>> However, I couldn't find any loop susceptible to be wrongly optimised in
>> incriminated code (sync_xen_wallclock in arch/i386/kernel/time-xen.c).
>> Any hint welcome.
> 
> It's hidden in the __normalize_time() macro. Could you backport Jeremy's
> upstream fix to the 2.6.18 kernel?
Ok, it works. Thanks.

-- 
Guillaume Rousse
Moyens Informatiques - INRIA Futurs
Tel: 01 69 35 69 62

Re: linux-2.6.18-xen.hg compilation issue with gcc 4.3

[Keir Fraser]

On 21/5/08 16:22, "Guillaume Rousse" <Guillaume.Rousse@inria.fr> wrote:

>>> However, I couldn't find any loop susceptible to be wrongly optimised in
>>> incriminated code (sync_xen_wallclock in arch/i386/kernel/time-xen.c).
>>> Any hint welcome.
>> 
>> It's hidden in the __normalize_time() macro. Could you backport Jeremy's
>> upstream fix to the 2.6.18 kernel?
> Ok, it works. Thanks.

Could you post the patch so we can check it in? With a signed-off-by line?

 Thanks,
 Keir

Re: linux-2.6.18-xen.hg compilation issue with gcc 4.3

[Guillaume Rousse]

[-- Attachment #1: Type: text/plain, Size: 593 bytes --]

Keir Fraser a écrit :
> 
> 
> On 21/5/08 16:22, "Guillaume Rousse" <Guillaume.Rousse@inria.fr> wrote:
> 
>>>> However, I couldn't find any loop susceptible to be wrongly optimised in
>>>> incriminated code (sync_xen_wallclock in arch/i386/kernel/time-xen.c).
>>>> Any hint welcome.
>>> It's hidden in the __normalize_time() macro. Could you backport Jeremy's
>>> upstream fix to the 2.6.18 kernel?
>> Ok, it works. Thanks.
> 
> Could you post the patch so we can check it in? With a signed-off-by line?
here it is.

-- 
Guillaume Rousse
Moyens Informatiques - INRIA Futurs
Tel: 01 69 35 69 62

[-- Attachment #2: xen-3.2.0-gcc4.3.patch --]
[-- Type: text/plain, Size: 671 bytes --]

Signed-off-by: Guillaume Rousse <Guillaume.Rousse@inria.fr>

diff -Naur --exclude '*~' linux-2.6.18-xen.hg/arch/i386/kernel/time-xen.c linux-2.6.18-xen.hg-gcc.4.3/arch/i386/kernel/time-xen.c
--- linux-2.6.18-xen.hg/arch/i386/kernel/time-xen.c	2008-02-06 22:18:37.000000000 +0100
+++ linux-2.6.18-xen.hg-gcc.4.3/arch/i386/kernel/time-xen.c	2008-05-21 16:23:42.000000000 +0200
@@ -140,10 +140,12 @@
 static inline void __normalize_time(time_t *sec, s64 *nsec)
 {
 	while (*nsec >= NSEC_PER_SEC) {
+        asm("" : "+r"(*nsec));
 		(*nsec) -= NSEC_PER_SEC;
 		(*sec)++;
 	}
 	while (*nsec < 0) {
+        asm("" : "+r"(*nsec));
 		(*nsec) += NSEC_PER_SEC;
 		(*sec)--;
 	}

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