linux-kernel - Re: POWER: Unexpected fault when writing to brk-allocated memory

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Message-ID: <20171107111658.ifkbeg4dnlheabnr@node.shutemov.name>
Date:   Tue, 7 Nov 2017 14:16:58 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-mm <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arch@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: POWER: Unexpected fault when writing to brk-allocated memory

On Tue, Nov 07, 2017 at 09:15:21AM +0100, Florian Weimer wrote:
> MAP_FIXED is near-impossible to use correctly.  I hope you don't expect
> applications to do that.  If you want address-based opt in, it should work
> without MAP_FIXED.  Sure, in obscure cases, applications might still see
> out-of-range addresses, but I expected a full opt-out based on RLIMIT_AS
> would be sufficient for them.

Just use mmap(-1), without MAP_FIXED to get full address space.

-- 
 Kirill A. Shutemov