Re: parisc: fix mmap(MAP_FIXED|MAP_SHARED) to already mmapped address

From: John David Anglin <dave.anglin@bell.net>
To: Aaro Koskinen <aaro.koskinen@iki.fi>,
	Helge Deller <deller@gmx.de>,
	linux-parisc@vger.kernel.org
Subject: Re: parisc: fix mmap(MAP_FIXED|MAP_SHARED) to already mmapped address
Date: Thu, 19 Dec 2013 14:44:40 -0500	[thread overview]
Message-ID: <BLU0-SMTP47556722282C83F98582B797C50@phx.gbl> (raw)
In-Reply-To: <20131219191750.GC2881@blackmetal.musicnaut.iki.fi>

On 12/19/2013 2:17 PM, Aaro Koskinen wrote:
> Hi,
>
> This commit (0576da2c08e3d332f1b0653030d28ab804585ab6) and the current
> mainline kernel (3.13-rc4) gives me the following with GLIBC 2.18:
>
> $ localedef -c -i en_US -f UTF-8 en_US.UTF-8
> cannot map archive header: Invalid argument
>
> strace looks like this:
>
> mmap2(NULL, 536870912, PROT_NONE, MAP_SHARED, 3, 0) = 0x42f34000
> mmap2(0x43000000, 1607632, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, 3, 0) = -1 EINVAL (Invalid argument)
>
> With the patch reverted, it works:
>
> mmap2(NULL, 536870912, PROT_NONE, MAP_SHARED, 3, 0) = 0x42d74000
> mmap2(0x43000000, 1607632, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, 3, 0) = 0x43000000
>
> BTW, note that for GLIBC 2.18 some changes were done regarding this:
> https://sourceware.org/bugzilla/show_bug.cgi?id=10283
Are you sure the glibc changes are correct?  PARISC addresses are not 
strictly aligned to SHMLBA.
There's also a page offset and "random" offset derived from the kernel 
address of the mapping struct.

Helge is still looking at this to try and improve the allocation density 
of small maps as we run out of
memory far too quickly.

Dave

-- 
John David Anglin    dave.anglin@bell.net