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

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Florian Weimer <fweimer@redhat.com>
Cc: Nicholas Piggin <npiggin@gmail.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linuxppc-dev@lists.ozlabs.org, linux-mm <linux-mm@kvack.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Dave Hansen <dave.hansen@intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-arch@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: POWER: Unexpected fault when writing to brk-allocated memory
Date: Tue, 7 Nov 2017 14:16:58 +0300	[thread overview]
Message-ID: <20171107111658.ifkbeg4dnlheabnr@node.shutemov.name> (raw)
In-Reply-To: <b7348864-533a-ef40-e66f-b14d0f422c04@redhat.com>

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