From: Suzuki K Poulose <Suzuki.Poulose@arm.com>
To: Dave Martin <Dave.Martin@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com,
ryan.arnold@linaro.org, sid@reserved-bit.com, aph@redhat.com,
catalin.marinas@arm.com, will.deacon@arm.com,
linux-kernel@vger.kernel.org, marc.zyngier@arm.com,
adhemerval.zanella@linaro.org
Subject: Re: [sample] A sample program for MRS emulation
Date: Tue, 3 Jan 2017 15:37:22 +0000 [thread overview]
Message-ID: <008f25f9-662c-fbed-1623-520f424b74d6@arm.com> (raw)
In-Reply-To: <20161130162720.GN1574@e103592.cambridge.arm.com>
On 30/11/16 16:27, Dave Martin wrote:
> On Wed, Nov 30, 2016 at 03:15:01PM +0000, Suzuki K Poulose wrote:
>> Here is a sample program which demonstrates how to use mrs
>> emulation to fetch the ID registers.
>
> Are we planning to add this in Documentation/? If so, we might want
> some tweaks (noted below).
Dave,
Thanks for taking a look. Apologies for the late response. We could
either add it to the Documentation or stick it into samples/. I prefer
the Documentation, as it would help the text.
>
>>
>> ----8>----
>> /*
>> * Sample program to demonstrate the MRS emulation
>> * ABI.
>
> overwrapped?
will fix it.
>
>> int main()
>
> (void)
>
>> {
>
> We don't wan't people using the MRS emulation without checking for its
> availability first.
>
> Something like this may work (untested), with the caveat that getauxval()
> is a GNU libc extension, and other environments may require a different
> mechanism to obtain the hwcaps.
>
Makes sense.
> --8<--
>
> #include <sys/auxv.h>
> #include <asm/hwcap.h>
>
> /* ... */
>
> if (!getauxval(AT_HWCAP) & HWCAP_CPUID) {
> fputs("CPUID registers unavailable\n", stderr);
> return 1;
> }
>
> -->8--
Cheers
Suzuki
prev parent reply other threads:[~2017-01-03 15:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-30 15:14 [PATCH v2 0/9] arm64: Expose CPUID registers via emulation Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 1/9] arm64: cpufeature: treat unknown fields as RES0 Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 2/9] arm64: cpufeature: remove explicit RAZ fields Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 3/9] arm64: cpufeature: Cleanup feature bit tables Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 4/9] arm64: cpufeature: Document the rules of safe value for features Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 5/9] arm64: cpufeature: Define helpers for sys_reg id Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 6/9] arm64: Add helper to decode register from instruction Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 7/9] arm64: cpufeature: Track user visible fields Suzuki K Poulose
2016-11-30 15:14 ` [PATCH v2 8/9] arm64: cpufeature: Expose CPUID registers by emulation Suzuki K Poulose
2016-11-30 15:15 ` [PATCH v2 9/9] arm64: Documentation - Expose CPU feature registers Suzuki K Poulose
2016-11-30 15:15 ` [sample] A sample program for MRS emulation Suzuki K Poulose
2016-11-30 16:27 ` Dave Martin
2017-01-03 15:37 ` Suzuki K Poulose [this message]
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