Thread (13 messages) 13 messages, 6 authors, 2014-04-29

ARM: mm: Could I change module space size or place modules in vmalloc area?

From: Gioh Kim <hidden>
Date: 2014-03-12 06:38:44
Also in: linux-mm

I am sorry to read your mail so late.
My module had been a proprietary driver so that I requested to strip it and
got small size driver.

Thank you for attention.

-----Original Message-----
From: Arnd Bergmann [mailto:arnd at arndb.de]
Sent: Friday, January 03, 2014 10:24 PM
To: linux-arm-kernel at lists.infradead.org
Cc: Russell King - ARM Linux; HyoJun Im; linux-mm at kvack.org; Gioh Kim
Subject: Re: ARM: mm: Could I change module space size or place modules in
vmalloc area?

On Friday 03 January 2014, Russell King - ARM Linux wrote:
quoted
On Fri, Jan 03, 2014 at 01:10:09PM +0100, Arnd Bergmann wrote:
quoted
Aside from the good comments that Russell made, I would remark that
the fact that you need multiple megabytes worth of modules indicates
that you are doing something wrong. Can you point to a git tree
containing those modules?
From the comments which have been made, one point that seems to have
been identified is that if this module is first stripped and then
loaded, it can load, but if it's unstripped, it's too big.  This
sounds suboptimal to me - the debug info shouldn't be loaded into the
kernel.

Reading the layout_and_allocate() function, that is probably the intention
already, and if something goes wrong there on ARM, it could be fixed up in
an arch specific module_frob_arch_sections() function.
quoted
However, I guess there's bad interactions with module signing if you
don't do this and the module was signed with the debug info present,
so I don't think there's a good solution for this.
My point was another anyway: I can't think of any good reason why you
would end up with this many modules on any sane system. The only cases
I've seen so far are

- modules written in C++, with libstdc++ linked into the module
- a closed-source platform port hidden in a loadable module that
  contains all the device drivers and subsystems while ignoring the
  infrastructure we have in the kernel, and the possible legal
  implications.
- a bug in the module using large arrays that should just be
  dynamically allocated.
- device firmware statically linked into the module rather than
  loaded using request_firmware.

In each of these cases, the real answer is to fix the code they are trying
to load to do things in a more common way, especially if the intention is
to eventually merge the code upstream. It is of course possible that they
are indeed trying something valid, that's why I asked to see the source
code.

	Arnd
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