[PATCH 2/4] S390: Use own tbegin macro instead of __builtin_tbegin.

[Florian Weimer]

On 01/13/2017 12:28 PM, Torvald Riegel wrote:
> On Thu, 2017-01-12 at 16:45 +0100, Florian Weimer wrote:
>> On 01/10/2017 05:34 PM, Torvald Riegel wrote:
>>
>>> (2) This introduces a facility to probe memory for being accessible or
>>> not, considering that you say it masks segfaults.  It seems that this
>>> probing may not be visible to the same extent as possible if a signal
>>> handler were installed.  Is this relevant from a security perspective?
>>
>> If the fallback implementation has essentially the same behavior, I
>> don't think there is a transaction-specific security problem.
>
> We don't know what the fallback implementation in the user code does.
> It can detect whether it is running in a HW transaction and run
> different code depending on that.

Is this really supported?  I assumed that if you acquire a lock (which 
might use elision), hardware transactions are off limits because glibc 
might require their use internally.

Thanks,
Florian