[PATCH v5 4/6] kselftest/arm64/mte: preparation for mtefar test

[Mark Brown]

On Tue, Jun 10, 2025 at 04:01:42PM +0100, Yeoreum Yun wrote:
> If FEAT_MTE_TAGGED_FAR (Armv8.9) is supported, bits 63:60 of the fault address
> are preserved in response to synchronous tag check faults (SEGV_MTESERR).
> 
> This patch is preparation for testing FEAT_MTE_TAGGED_FAR.
> It shouldn't change the test result.

I'm not clear from the above what the change is intended to do (ie, how
does it prepare for testing FEAT_MTE_TAGGED_FAR).  I think this could
usefully be split out into multiple commits (eg, adding logging of the
additional si_ fields separately, or splitting the renaming MT_CLEAR_TAG
to MT_CLEAR_TAGS), it's kind of hard to review as is.

> @@ -45,13 +64,18 @@ void mte_default_handler(int signum, siginfo_t *si, void *uc)
>  		}
>  		/* Compare the context for precise error */
>  		else if (si->si_code == SEGV_MTESERR) {
> +		 	if ((!mtefar_support && si_atag) || (si_atag != MT_FETCH_ATAG(cur_mte_cxt.trig_addr))) {
> +			  ksft_print_msg("Invalid MTE synchronous exception caught for address tag! si_tag=%x, si_atag: %x\n", si_tag, si_atag);
> +			  exit(1);
> +			}

We should really exit with a kselftest error rather than just a number,
though I see this is just copying the existing style for the file so
*shrug*.
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