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


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


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