linux-kernel - Re: [PATCH v7 37/39] kselftest/arm64: Add a GCS stress test

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Message-ID: <87zfyex1l9.fsf@linaro.org>
Date:   Tue, 12 Dec 2023 23:45:06 -0300
From:   Thiago Jung Bauermann <thiago.bauermann@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <shuah@...nel.org>,
        "Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
        Deepak Gupta <debug@...osinc.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>,
        "H.J. Lu" <hjl.tools@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Florian Weimer <fweimer@...hat.com>,
        Christian Brauner <brauner@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v7 37/39] kselftest/arm64: Add a GCS stress test


I'm going a bit out-of-order to report a build failure in a test:

Mark Brown <broonie@...nel.org> writes:

> +// Recurse x20 times
> +.macro recurse id

I get an assembler error here:

gcc -nostdlib gcs-stress-thread.S -o /home/thiago.bauermann/src/linux/tools/testing/selftests/arm64/gcs/gcs-stress-thread
gcs-stress-thread.S: Assembler messages:
gcs-stress-thread.S:236: Error: unexpected end of file in macro `recurse' definition
make[2]: *** [Makefile:24: /home/thiago.bauermann/src/linux/tools/testing/selftests/arm64/gcs/gcs-stress-thread] Error 1

This is with gas from Ubuntu 22.04, which ships binutils 2.38.

> +function recurse\id
> +	stp	x29, x30, [sp, #-16]!
> +	mov	x29, sp
> +
> +	cmp	x20, 0
> +	beq	1f
> +	sub	x20, x20, 1
> +	bl	recurse\id
> +
> +1:
> +	ldp	x29, x30, [sp], #16
> +
> +	// Do a syscall immediately prior to returning to try to provoke
> +	// scheduling and migration at a point where coherency issues
> +	// might trigger.
> +	mov	x8, #__NR_getpid
> +	svc	#0
> +
> +	ret
> +endfunction
> +.endmacro
> +
> +// Generate and use two copies so we're changing the GCS contents
> +recurse 1
> +recurse 2

-- 
Thiago