On 18/10/2021 16:50, Mathieu Poirier wrote:

Good morning,

On Thu, Oct 14, 2021 at 11:31:14PM +0100, Suzuki K Poulose wrote:

quoted

Arm Neoverse-N2 and Cortex-A710 cores are affected by an erratum where the
trbe, under some circumstances, might write upto 64bytes to an address after

Checkpatch gives me a warning about this line...

quoted

the Limit as programmed by the TRBLIMITR_EL1.LIMIT. This might -

   - Corrupt a page in the ring buffer, which may corrupt trace from a
     previous session, consumed by userspace.
   - Hit the guard page at the end of the vmalloc area and raise a fault.

To keep the handling simpler, we always leave the last page from the
range, which TRBE is allowed to write. This can be achieved by ensuring
that we always have more than a PAGE worth space in the range, while
calculating the LIMIT for TRBE. And then the LIMIT pointer can be adjusted
to leave the PAGE (TRBLIMITR.LIMIT -= PAGE_SIZE), out of the TRBE range
while enabling it. This makes sure that the TRBE will only write to an area
within its allowed limit (i.e, [head-head+size]) and we do not have to handle

I'm pretty sure this line will also be flagged.

Thanks for pointing them out. I have fixed it now.

Suzuki

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