Fixing the glibc adobe flash incompatibility

[Andrew Haley]

On 11/17/2010 03:17 PM, Magnus Glantz wrote:
> On 11/17/2010 11:36 AM, nodata wrote:
>> On 17/11/10 10:20, drago01 wrote:
>>> On Wed, Nov 17, 2010 at 10:17 AM, nodata<lsof at nodata.co.uk>   wrote:
>>>> On 17/11/10 08:57, Hans de Goede wrote:
>>>>> Hi all,
>>>>>
>>>>> For those who do not know it yet, recent Fedora glibc updates include
>>>>> an optimized memcpy (which gets used on some processors) which breaks the
>>>>> 64 bit adobe flash plugin.
>>>>>
>>>>> The problem has been analyzed and is known, as well as a fix for it, see:
>>>>> https://bugzilla.redhat.com/show_bug.cgi?id=638477
>>>>>
>>>>> The problem still exists however. The glibc developers say that this is
>>>>> not a glibc bug, but a flash plugin bug. And technically they are 100%
>>>>> correct, and the adobe flash plugin is a buggy .... (no surprise there).
>>>>> To be specific the flash plugin is doing overlapping memcpy-s which is
>>>>> clearly not how memcpy is supposed to be used. But the way the flash
>>>>> plugin does overlapping memcpy's happens to work fine as long as one as
>>>>> the c library does the memcpy-s in forward direction. And the new memcpy
>>>>> implementation does the memcpy in backward direction.
>>>>>
>>>>> The glibc developers being technically 100% correct is not helping our
>>>>> end users in this case though. So we (The Fedora project) need to come up
>>>>> with a solution to help our end users, many of whom want to use the adobe
>>>>> flash plugin.
>>>>>
>>>>> This solution could be reverting the problem causing glibc change, or
>>>>> maybe changing it to do forward memcpy's while still using the new SSE
>>>>> instructions, or something more specific to the flash plugin, as long
>>>>> as it will automatically fix things with a yum upgrade without requiring
>>>>> any further user intervention.
>>>>>
>>>>> I would also like to point out that if this were to happen in Ubuntu
>>>>> which we sometimes look at jealously for getting more attention / users
>>>>> then us, the glibc change would likely be reverted immediately, as that
>>>>> is the right thing to do from an end user pov.
>>>>>
>>>>> I've filed a ticket for FESCo to look into this, as I believe this
>>>>> makes us look really bad, and the glibc maintainers do not seem to be
>>>>> willing to fix it without some sort of intervention:
>>>>> https://fedorahosted.org/fesco/ticket/501
>>>>>
>>>>> Regards,
>>>>>
>>>>> Hans
>>>> Is someone talking to Adobe about this?
>>> Yes, see https://bugs.adobe.com/jira/browse/FP-5739
>> Adobe benefits from Flash in Linux. So it seems sensible to:
>>
>> 1. Get Adobe to commit to a fix soon WITH A $DATE
>> 2. Agree to patch the change until $DATE
>> 3. Adobe updates Flash, we revert the patch, everyone is happy
> I've e-mailed a with Shu Wang at Adobe (who is the assigned contact for 
> this issue) about a date when they can have this fixed.
> You've got the e-mail thread regarding this below:

So we should be able simply to patch glibc, right?  Can't see any reason
not to.

Andrew.