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Re: [Xen-devel] [PATCH v3 5/7] x86/livepatch: Fail the build if duplicate symbols exist
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Wed, 30 Oct 2019 10:37:43 +0000
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- Cc: Juergen Gross <jgross@xxxxxxxx>, Wei Liu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, Norbert Manthey <nmanthey@xxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Wed, 30 Oct 2019 10:37:50 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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On 30/10/2019 08:41, Jan Beulich wrote:
> On 29.10.2019 18:06, Andrew Cooper wrote:
>> On 24/10/2019 13:03, Jan Beulich wrote:
>>> On 23.10.2019 15:58, Andrew Cooper wrote:
>>>> --- a/xen/common/Kconfig
>>>> +++ b/xen/common/Kconfig
>>>> @@ -361,9 +361,23 @@ config FAST_SYMBOL_LOOKUP
>>>>
>>>> If unsure, say Y.
>>>>
>>>> +config ENFORCE_UNIQUE_SYMBOLS
>>>> + bool "Enforce unique symbols" if LIVEPATCH
>>>> + default y if LIVEPATCH
>>> Instead of two identical "if", why not "depends on LIVEPATCH"?
>>>
>>>> + ---help---
>>>> + Multiple symbols with the same name aren't generally a problem
>>>> + unless Live patching is to be used.
>>>> +
>>>> + Livepatch loading involves resolving relocations against symbol
>>>> + names, and attempting to a duplicate symbol in a livepatch will
>>>> + result in incorrect livepatch application.
>>>> +
>>>> + This option should be used to ensure that a build of Xen can have a
>>>> + livepatch build and apply correctly.
>>>> +
>>>> config SUPPRESS_DUPLICATE_SYMBOL_WARNINGS
>>>> - bool "Suppress duplicate symbol warnings" if !LIVEPATCH
>>>> - default y if !LIVEPATCH
>>>> + bool "Suppress duplicate symbol warnings" if !ENFORCE_UNIQUE_SYMBOLS
>>>> + default y if !ENFORCE_UNIQUE_SYMBOLS
>>> Similarly here then. With this changed, or with a proper reason
>>> supplied
>>> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
>> That's a question for the author of c/s 064a2652233 to answer... I'm
>> merely following the prevailing style.
> "Prevailing style" seems a little bold considering that according to
> my grep-ing there's exactly on other such instance (VGA). I.e. you'd
> grow the "badness" by 50% when you could equally well shrink it by
> this same percentage.
Allow me to be less subtle.
*You* are the author of the code, in this form.
As a consequence, I expect there is a deliberate reason.
And seeing as I've had to reverse engineer the reason myself, it looks
to be related to the fact that other options in the build select these,
so they need not to be dependent on livepatching in the first place.
~Andrew
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