[PATCH] aarch64: MTE compatible strncmp

Szabolcs Nagy szabolcs.nagy@arm.com
Thu Jun 11 13:03:14 GMT 2020


The 06/09/2020 16:03, Alex Butler wrote:
> 
> This patch passes the tests with no regressions.
> 

here it fails with

FAIL: string/tst-cmp

it seems strncmp("","0",SIZE_MAX) is not handled correctly
in the unaligned inputs case.

this should be fixed.

> 8< --- 8< --- 8<
> Add support for MTE to strncmp. Regression tested with xcheck and benchmarked
> with glibc's benchtests on the Cortex-A53, Cortex-A72, and Neoverse N1.
> 
> The existing implementation assumes that any access to the pages in which the
> string resides is safe. This assumption is not true when MTE is enabled. This
> patch updates the algorithm to ensure that accesses remain within the bounds
> of an MTE tag (16-byte chunks) and improves overall performance.
> 
> Co-authored-by: Branislav Rankov <branislav.rankov@arm.com>



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