linux-kernel - Re: [PATCH v6 1/2] arm64: Define Documentation/arm64/tagged-address-abi.rst

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Message-ID: <b74e7ce7-d58a-68a0-2f28-6648ec6302c0@intel.com>
Date:   Wed, 31 Jul 2019 09:43:46 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-arch@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Szabolcs Nagy <szabolcs.nagy@....com>
Subject: Re: [PATCH v6 1/2] arm64: Define
 Documentation/arm64/tagged-address-abi.rst

On 7/25/19 6:50 AM, Vincenzo Frascino wrote:
> With the relaxed ABI proposed through this document, it is now possible
> to pass tagged pointers to the syscalls, when these pointers are in
> memory ranges obtained by an anonymous (MAP_ANONYMOUS) mmap().

I don't see a lot of description of why this restriction is necessary.
What's the problem with supporting MAP_SHARED?