linux-kernel - Re: [PATCH v6 5/9] kselftest/arm64/mte: check MTE

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Message-ID: <916e2064-efa9-4b69-b561-51b0378158c0@sirena.org.uk>
Date: Wed, 11 Jun 2025 12:52:04 +0100
From: Mark Brown <broonie@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, pcc@...gle.com, will@...nel.org,
	anshuman.khandual@....com, joey.gouly@....com,
	yury.khrustalev@....com, maz@...nel.org, oliver.upton@...ux.dev,
	frederic@...nel.org, akpm@...ux-foundation.org, surenb@...gle.com,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v6 5/9] kselftest/arm64/mte: check MTE_FAR feature is
 supported

On Wed, Jun 11, 2025 at 10:41:03AM +0100, Yeoreum Yun wrote:
> --- a/tools/testing/selftests/arm64/mte/mte_common_util.c
> +++ b/tools/testing/selftests/arm64/mte/mte_common_util.c
> @@ -6,6 +6,7 @@
>  #include <signal.h>
>  #include <stdio.h>
>  #include <stdlib.h>
> +#include <time.h>
>  #include <unistd.h>

Not sure why we'd be including time.h here?

>  
>  #include <linux/auxvec.h>
> @@ -26,6 +27,7 @@
>  #define INIT_BUFFER_SIZE       256
>  
>  struct mte_fault_cxt cur_mte_cxt;
> +bool mtefar_support;

This is a non-static variable so won't have a defined default value...

> @@ -273,6 +275,7 @@ void mte_initialize_current_context(int mode, uintptr_t ptr, ssize_t range)
>  	cur_mte_cxt.fault_valid = false;
>  	cur_mte_cxt.trig_addr = ptr;
>  	cur_mte_cxt.trig_range = range;
> +
>  	if (mode == MTE_SYNC_ERR)
>  		cur_mte_cxt.trig_si_code = SEGV_MTESERR;
>  	else if (mode == MTE_ASYNC_ERR)

Unrelated whitespace change.

>  	if (!(hwcaps2 & HWCAP2_MTE))
>  		ksft_exit_skip("MTE features unavailable\n");
>  
> +	if (hwcaps3 & HWCAP3_MTE_FAR)
> +		mtefar_support = true;
> +

...this will only set mtefar_support if the hwcap is present, leaving it
undefined if not.  If you just make this

	mtefar_support = hwcap3 & HWCAP3_MTE_FAR

that should avoid the issue.

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