linux-kernel - Re: [PATCH v5 11/17] arm64: docs: document pointer authentication

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Message-ID: <7f9c1bc4-2e82-e930-7d00-c26791ab9eef@arm.com>
Date:   Fri, 2 Nov 2018 09:46:47 +0000
From:   Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>
To:     Kees Cook <keescook@...omium.org>,
        Kristina Martsenko <Kristina.Martsenko@....com>
CC:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Adam Wallis <awallis@...eaurora.org>,
        Amit Kachhap <Amit.Kachhap@....com>,
        Andrew Jones <drjones@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Christoffer Dall <Christoffer.Dall@....com>,
        Dave P Martin <Dave.Martin@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Marc Zyngier <Marc.Zyngier@....com>,
        Mark Rutland <Mark.Rutland@....com>,
        Suzuki Poulose <Suzuki.Poulose@....com>,
        Will Deacon <Will.Deacon@....com>,
        "kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
        linux-arch <linux-arch@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, nd <nd@....com>
Subject: Re: [PATCH v5 11/17] arm64: docs: document pointer authentication


>> +
>> +When CONFIG_ARM64_PTR_AUTH is selected, and relevant HW support is
>> +present, the kernel will assign a random APIAKey value to each process
>> +at exec*() time. This key is shared by all threads within the process,
>> +and the key is preserved across fork(). Presence of functionality using
>> +APIAKey is advertised via HWCAP_APIA.
> 
> It might be useful to include documentation here on how many bits of
> the address are being used for the PAC bits (I'm assuming it's 7?)


the number of bits available depends on the VA size, so you can't really 
document a number.

Ramana

> 
> -Kees
>