linux-kernel - Re: [RFC PATCH v3] sparc64: Add support for Application Data Integrity (ADI)

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Date:   Wed, 4 Jan 2017 15:44:56 -0800
From:   Rob Gardner <rob.gardner@...cle.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Khalid Aziz <khalid.aziz@...cle.com>, davem@...emloft.net,
        corbet@....net, arnd@...db.de, akpm@...ux-foundation.org
Cc:     hpa@...or.com, viro@...iv.linux.org.uk, nitin.m.gupta@...cle.com,
        chris.hyser@...cle.com, tushar.n.dave@...cle.com,
        sowmini.varadhan@...cle.com, mike.kravetz@...cle.com,
        adam.buchbinder@...il.com, minchan@...nel.org, hughd@...gle.com,
        kirill.shutemov@...ux.intel.com, keescook@...omium.org,
        allen.pais@...cle.com, aryabinin@...tuozzo.com,
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        vdavydov.dev@...il.com, hannes@...xchg.org, namit@...are.com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-arch@...r.kernel.org,
        x86@...nel.org, linux-mm@...ck.org,
        Khalid Aziz <khalid@...ehiking.org>
Subject: Re: [RFC PATCH v3] sparc64: Add support for Application Data
 Integrity (ADI)

On 01/04/2017 03:40 PM, Dave Hansen wrote:
> On 01/04/2017 03:35 PM, Rob Gardner wrote:
>> Tags are not cleared at all when memory is freed, but rather, lazily
>> (and automatically) cleared when memory is allocated.
> What does "allocated" mean in this context?  Physical or virtual? What
> does this do, for instance?

The first time a virtual page is touched by a process after the malloc, 
the kernel does clear_user_page() or something similar, which zeroes the 
memory. At the same time, the memory tags are cleared.

Rob


>
> 	ptr = malloc(PAGE_SIZE);
> 	set_tag(ptr, 14);
> 	madvise(ptr, PAGE_SIZE, MADV_FREE);
> 	printf("tag: %d\n", get_tag(ptr));
> 	free(ptr);
> --
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