On 23.04.2024 16:31, Roger Pau Monné wrote:
> On Tue, Apr 23, 2024 at 03:51:31PM +0200, Jan Beulich wrote:
>> On 23.04.2024 15:12, Roger Pau Monne wrote:
>>> Ensure the entries of a payload exception table only apply to text regions
>>> in
>>> the payload itself. Since the payload exception table needs to be loaded
>>> and
>>> active even before a patch is applied (because hooks might already rely on
>>> it),
>>> make sure the exception table (if any) only contains fixups for the payload
>>> text section.
>>>
>>> Signed-off-by: Roger Pau Monné <roger....@citrix.com>
>>
>> In principle
>> Reviewed-by: Jan Beulich <jbeul...@suse.com>
>> Still two comments:
>>
>>> --- a/xen/arch/x86/extable.c
>>> +++ b/xen/arch/x86/extable.c
>>> @@ -228,3 +228,21 @@ unsigned long asmlinkage
>>> search_pre_exception_table(struct cpu_user_regs *regs)
>>> }
>>> return fixup;
>>> }
>>> +
>>> +#ifdef CONFIG_LIVEPATCH
>>> +bool extable_is_between_bounds(const struct exception_table_entry
>>> *ex_start,
>>
>> s/between/in/ or even s/is_between/in/? "Between", to me at least, reads
>> very much like meaning "exclusive at both ends".
>
> Oh, OK, I don't associate any boundary inclusion with 'between' or
> 'in'. The result is shorter, so I like it.
>
>>> + const struct exception_table_entry *ex_end,
>>> + const void *start, const void *end)
>>> +{
>>> + for ( ; ex_start < ex_end; ex_start++ )
>>> + {
>>> + const void *addr = (void *)ex_addr(ex_start);
>>> + const void *cont = (void *)ex_cont(ex_start);
>>
>> Might be nicer to use _p() here, or not do the comparisons with pointers, but
>> instead with unsigned long-s.
>
> No strong opinion regarding whether to use unsigned longs or pointers.
> I've used pointers because I think the function parameters should be
> pointers, and that avoided doing a cast in the comparison with
> obfuscates it (or introducing yet another local variable).
>
> I can switch to _p(), that's indeed better.
>
> Let me know if you have a strong opinion for using unsigned longs,
> otherwise my preference would be to leave it with pointers.
Especially if you want to stick to pointer function arguments - no, no
strong opinion.
Jan
