Linux-Next Archive on lore.kernel.org
 help / color / Atom feed
From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Michal Hocko <mhocko@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
	Joel Stanley <joel@jms.id.au>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-Next Mailing List <linux-next@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Abdul Haleem <abdhalee@linux.vnet.ibm.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	"James E.J. Bottomley" <jejb@parisc-linux.org>,
	Helge Deller <deller@gmx.de>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	"David S. Miller" <davem@davemloft.net>,
	Chris Zankel <chris@zankel.net>,
	Max Filippov <jcmvbkbc@gmail.com>,
	linux-arm-kernel@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org, linux-mips@linux-mips.org
Subject: Re: linux-next: Tree for Nov 7
Date: Mon, 13 Nov 2017 15:48:13 +0000
Message-ID: <20171113154811.GM12318@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20171113151641.yfqrecpcxllpn5mq@dhcp22.suse.cz>

On Mon, Nov 13, 2017 at 04:16:41PM +0100, Michal Hocko wrote:
> On Mon 13-11-17 13:00:57, Michal Hocko wrote:
> [...]
> > Yes, I have mentioned that in the previous email but the amount of code
> > would be even larger. Basically every arch which reimplements
> > arch_get_unmapped_area would have to special case new MAP_FIXED flag to
> > do vma lookup.
> 
> It turned out that this might be much more easier than I thought after
> all. It seems we can really handle that in the common code. This would
> mean that we are exposing a new functionality to the userspace though.
> Myabe this would be useful on its own though. Just a quick draft (not
> even compile tested) whether this makes sense in general. I would be
> worried about unexpected behavior when somebody set other bit without a
> good reason and we might fail with ENOMEM for such a call now.
> 
> Elf loader would then use MAP_FIXED_SAFE rather than MAP_FIXED.
> ---
> diff --git a/arch/alpha/include/uapi/asm/mman.h b/arch/alpha/include/uapi/asm/mman.h
> index 3b26cc62dadb..d021c21f9b01 100644
> --- a/arch/alpha/include/uapi/asm/mman.h
> +++ b/arch/alpha/include/uapi/asm/mman.h
> @@ -31,6 +31,9 @@
>  #define MAP_STACK	0x80000		/* give out an address that is best suited for process/thread stacks */
>  #define MAP_HUGETLB	0x100000	/* create a huge page mapping */
>  
> +#define MAP_KEEP_MAPPING 0x2000000
> +#define MAP_FIXED_SAFE	MAP_FIXED|MAP_KEEP_MAPPING /* enforce MAP_FIXED without clobbering an existing mapping */

A few things...

1. Does this need to be exposed to userland?
2. Can it end up in include/uapi/asm-generic/mman*.h ?
3. The definition of MAP_FIXED_SAFE should really have parens around it.

> @@ -1365,6 +1365,13 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
>  	if (offset_in_page(addr))
>  		return addr;
>  
> +	if ((flags & MAP_FIXED_SAFE) == MAP_FIXED_SAFE) {

I'm surprised this doesn't warn - since this effectively expands to:

	flags & MAP_FIXED | MAP_KEEP_MAPPING

hence why MAP_FIXED_SAFE needs parens.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-07  5:22 Stephen Rothwell
2017-11-07 22:22 ` Joel Stanley
2017-11-08 14:20   ` Michal Hocko
2017-11-10 12:30     ` Michal Hocko
2017-11-12  1:08       ` Joel Stanley
2017-11-13  9:20         ` Michal Hocko
2017-11-13  9:34           ` Russell King - ARM Linux
2017-11-13  9:42           ` Michal Hocko
2017-11-13 11:34             ` Michael Ellerman
2017-11-13 12:00               ` Michal Hocko
2017-11-13 15:16                 ` Michal Hocko
2017-11-13 15:48                   ` Russell King - ARM Linux [this message]
2017-11-13 15:59                     ` Michal Hocko
2017-11-13 15:49                   ` Michal Hocko
2017-11-13 16:06                     ` Michal Hocko
2017-11-13 16:35                       ` Khalid Aziz
2017-11-14  7:07                         ` Michal Hocko
2017-11-14  9:18                       ` Michael Ellerman
2017-11-14  9:29                         ` Michal Hocko
2017-11-14  9:02                   ` Michael Ellerman
2017-11-14  8:54                 ` Michael Ellerman
2017-11-14  9:04                   ` Michal Hocko
2017-11-14 14:52                     ` Khalid Aziz
2017-11-13 14:11           ` Michal Hocko
2017-11-13 15:09             ` Russell King - ARM Linux
2017-11-13 15:31               ` Michal Hocko
2017-11-14  0:03         ` Andrew Morton
2017-11-14  0:36           ` Stephen Rothwell
  -- strict thread matches above, loose matches on Subject: below --
2019-11-07  8:07 Stephen Rothwell
2018-11-07  3:16 Stephen Rothwell
2013-11-07  7:31 Stephen Rothwell
2012-11-07  5:15 Stephen Rothwell

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20171113154811.GM12318@n2100.armlinux.org.uk \
    --to=linux@armlinux.org.uk \
    --cc=abdhalee@linux.vnet.ibm.com \
    --cc=akpm@linux-foundation.org \
    --cc=benh@kernel.crashing.org \
    --cc=chris@zankel.net \
    --cc=dalias@libc.org \
    --cc=davem@davemloft.net \
    --cc=deller@gmx.de \
    --cc=jcmvbkbc@gmail.com \
    --cc=jejb@parisc-linux.org \
    --cc=joel@jms.id.au \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mips@linux-mips.org \
    --cc=linux-next@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mhocko@kernel.org \
    --cc=mpe@ellerman.id.au \
    --cc=ralf@linux-mips.org \
    --cc=sfr@canb.auug.org.au \
    --cc=ysato@users.sourceforge.jp \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Next Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-next/0 linux-next/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-next linux-next/ https://lore.kernel.org/linux-next \
		linux-next@vger.kernel.org
	public-inbox-index linux-next

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-next


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git