Re: [PATCH 00/10] Enhance /dev/mem to allow read/write of arbitrary

Christoph Hellwig
2011-07-01T13:47:05Z

On Fri, Jul 01, 2011 at 02:58:02PM +0200, Ingo Molnar wrote:
> So what was not mentioned in your series, what is *your* motivation
> and your usecase? Enabling closed-source userspace drivers? Enabling
> the crash utility?

He stated it pretty clearly in the thread, it's the crash utility.

>
> If the former then shame on you, if the latter then how do you
> explain that distros appear to disable the RAM aspect of /dev/mem:
>
> $ grep DEVMEM $(rpm -ql kernel-2.6.38-0.rc7.git2.3.fc16.x86_64 | grep config-2.6 )
> CONFIG_STRICT_DEVMEM=y
>
> So the crash utility use-case does not work on unpatched, default
> kernels, right?

Not if you have highmem. That's why Redhat or Fedora to quote your
example patch in the /dev/crash driver, which totally defeats the
CONFIG_STRICT_DEVMEM setting. But apparently it's good enough that no
one either noticed or at least doesn't care.