[PATCH] xen: relax signature check

[PATCH] xen: relax signature check

[Jeremy Fitzhardinge]

Some versions of Xen 3.x set their magic number to "xen-3.[12]", so
relax the test to match them.

[ Linus: Please apply for 2.6.24. Thanks - J ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>

---
 arch/x86/xen/enlighten.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

===================================================================
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1131,7 +1131,7 @@ asmlinkage void __init xen_start_kernel(
 	if (!xen_start_info)
 		return;
 
-	BUG_ON(memcmp(xen_start_info->magic, "xen-3.0", 7) != 0);
+	BUG_ON(memcmp(xen_start_info->magic, "xen-3", 5) != 0);
 
 	/* Install Xen paravirt ops */
 	pv_info = xen_info;

Re: [PATCH] xen: relax signature check

[Bodo Eggert]

Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Some versions of Xen 3.x set their magic number to "xen-3.[12]", so
> relax the test to match them.


> -     BUG_ON(memcmp(xen_start_info->magic, "xen-3.0", 7) != 0);
> +     BUG_ON(memcmp(xen_start_info->magic, "xen-3", 5) != 0);

Not BUG_ON(memcmp(xen_start_info->magic, "xen-3.", 6) != 0); ?
I don't thin Xen version 32 will be compatible ...

Re: [PATCH] xen: relax signature check

[Jeremy Fitzhardinge]

Bodo Eggert wrote:
> Not BUG_ON(memcmp(xen_start_info->magic, "xen-3.", 6) != 0); ?
> I don't thin Xen version 32 will be compatible ...
>   

It had better be; if it loads the kernel, it should present a xen-3
compatible ABI.

But this is just a sanity check to make sure things are basically OK;
BUG_ON is hardly nice error reporting (not that there's much else we can
do at that point).

    J

Re: [PATCH] xen: relax signature check

[Anthony Liguori]

Jeremy Fitzhardinge wrote:
> Bodo Eggert wrote:
>> Not BUG_ON(memcmp(xen_start_info->magic, "xen-3.", 6) != 0); ?
>> I don't thin Xen version 32 will be compatible ...
>>   
> 
> It had better be; if it loads the kernel, it should present a xen-3
> compatible ABI.

If xen-32.0 should be compatible than wouldn't xen-24.0 be compatible 
too?  I think the point was that you should either be checking for 
'xen-3.x' or something more general that would accept anything >= xen-3.0.

Regards,

Anthony Liguori

> But this is just a sanity check to make sure things are basically OK;
> BUG_ON is hardly nice error reporting (not that there's much else we can
> do at that point).
> 
>     J

Re: [PATCH] xen: relax signature check

[Jeremy Fitzhardinge]

Anthony Liguori wrote:
> If xen-32.0 should be compatible than wouldn't xen-24.0 be compatible
> too?  I think the point was that you should either be checking for
> 'xen-3.x' or something more general that would accept anything >=
> xen-3.0.

The signature is supposed to be an ABI signature, so regardless of the
actual hypervisor version, it should always present "xen-3.0"
(presumably backwards compat if it also supports other versions of the
ABI).  There was a bug in some versions where it puts the actual
hypervisor version in there, requiring this patch.  Technically that
means that looking for "xen-3." is more accurate, but frankly not
important enough to bother raising a patch over.

    J