Hi Marek

Thanks for pointing this out. Typically we expect any timing sensitive secure operations to be implemented at Secure-EL1 or lower, which the current code does protect. However, you are correct that all secure world code including EL3 should not expose timing information. A fix is in progress to address this.

Regards

Dan.

-----Original Message----- From: TF-A tf-a-bounces@lists.trustedfirmware.org On Behalf Of Marek Bykowski via TF-A Sent: 03 August 2019 07:37 To: tf-a@lists.trustedfirmware.org; David Cunado David.Cunado@arm.com Subject: [TF-A] Advisory TFV 5 to CVE-2017-15031 only saves/stores the PMCR_EL0 across world switching

Hi David/ATF Support,

An excerpt from the commit message to CVE-2017-15031 is "Additionally, PMCR_EL0 is added to the list of registers that are saved and restored during a world switch."

My question is why it is only being saved/restored across the world switch and not during a "normal" SMC call? When I do modify the PMCR_EL0 in EL2 or NonSecure-EL1 and run the smc call the PMCCNTR counter counts during the smc call and does expose secure world timing information to NonSecure in that matter.

Thanks, Marek -- TF-A mailing list TF-A@lists.trustedfirmware.org https://lists.trustedfirmware.org/mailman/listinfo/tf-a

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