Re: [PATCH 4/4] x86: check for canonical address before doing page walks

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 10/10/13 15:10, Jan Beulich wrote:
>>>> On 10.10.13 at 16:01, Andrew Cooper <andrew.cooper3@citrix.com> wrote:
>> On 10/10/13 14:55, Jan Beulich wrote:
>>> --- a/xen/arch/x86/x86_64/traps.c
>>> +++ b/xen/arch/x86/x86_64/traps.c
>>> @@ -170,6 +170,8 @@ void show_page_walk(unsigned long addr)
>>>      l1_pgentry_t l1e, *l1t;
>>>  
>>>      printk("Pagetable walk from %016lx:\n", addr);
>>> +    if ( !is_canonical_address(addr) )
>>> +        return;
>>>  
>>>      l4t = map_domain_page(mfn);
>>>      l4e = l4t[l4_table_offset(addr)];
>>>
>> I was intending something a little more like
>>
>> if ( !is_canonical_address(addr) )
>> {
>>     printk(" Not canonical\n");
>>     return;
>> }
>>
>> So it doesn't appear on the console that show_page_walk() got stuck
>> somewhere.
> Seems pretty pointless - the address is being printed, and anyone
> (I would hope) can easily see whether it is non-canonical.
>
> Jan
>

True I suppose, although it would start getting harder if/when the
non-canonical section shrinks in size.

I would prefer the printk(), but am not overly fussed and the other fix
is certainly good, so

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>