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Date:   Thu, 13 Jun 2019 13:28:21 +0100
From:   Catalin Marinas <catalin.marinas@arm.com>
To:     Dave Martin <Dave.Martin@arm.com>
Cc:     Vincenzo Frascino <vincenzo.frascino@arm.com>,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        Szabolcs Nagy <szabolcs.nagy@arm.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        Will Deacon <will.deacon@arm.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-kselftest@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 1/2] arm64: Define
 Documentation/arm64/tagged-address-abi.txt
Message-ID: <20190613122821.GS28951@C02TF0J2HF1T.local>
References: <cover.1560339705.git.andreyknvl@google.com>
 <20190612142111.28161-1-vincenzo.frascino@arm.com>
 <20190612142111.28161-2-vincenzo.frascino@arm.com>
 <20190612153538.GL28951@C02TF0J2HF1T.local>
 <141c740a-94c2-2243-b6d1-b44ffee43791@arm.com>
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On Thu, Jun 13, 2019 at 12:37:32PM +0100, Dave P Martin wrote:
> On Thu, Jun 13, 2019 at 11:15:34AM +0100, Vincenzo Frascino wrote:
> > On 12/06/2019 16:35, Catalin Marinas wrote:
> > > On Wed, Jun 12, 2019 at 03:21:10PM +0100, Vincenzo Frascino wrote:
> > >> +  - PR_GET_TAGGED_ADDR_CTRL: can be used to check the status of the Tagged
> > >> +                             Address ABI.
[...]
> Is there a canonical way to detect whether this whole API/ABI is
> available?  (i.e., try to call this prctl / check for an HWCAP bit,
> etc.)

The canonical way is a prctl() call. HWCAP doesn't make sense since it's
not a hardware feature. If you really want a different way of detecting
this (which I don't think it's worth), we can reinstate the AT_FLAGS
bit.

-- 
Catalin