[PATCH] ARM: Avoid discarding sections that might have SMP_ON_UP fixups

[Russell King - ARM Linux]

On Thu, Feb 10, 2011 at 06:29:41PM +0000, Dave Martin wrote:
> On Thu, Feb 10, 2011 at 2:46 PM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
> > On Thu, Feb 10, 2011 at 02:13:13PM +0000, Dave Martin wrote:
> >> Note that this tree contains some extra patches (though I believe
> >> nothing is there which should cause the problem), and does not contain
> >> everything from rmk/devel -- so it's possible this has been fixed in
> >> the meantime or no longer occurs for some other reason...
> >
> > No need - I now have some modules which contain SMP alternatives, so we
> > do need to fix the module loader for this, and keep the SMP alternatives
> > replacement code around.  It's not worth eliminating the code as if we
> > include an informative printk() to say why we're refusing to load the
> > module, the string would be larger than the code it eliminates.  So, I
> > think we need to merge the patch below to avoid run-time problems.
> 
> I thought the problem was not caused by removal of the fixup code, but
> rather by the removal of code referenced by fixups?

It is.  But:

arm-linux-objdump -h sound/core/snd-timer.ko

sound/core/snd-timer.ko:     file format elf32-littlearm

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .text         00002f34  00000000  00000000  00000034  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  1 .exit.text    00000070  00000000  00000000  00002f68  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  2 .init.text    000001b4  00000000  00000000  00002fd8  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  3 .rodata       000000bc  00000000  00000000  0000318c  2**2
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
  4 .rodata.str1.1 00000156  00000000  00000000  00003248  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  5 .alt.smp.init 00000088  00000000  00000000  0000339e  2**0
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
...

Here we have a module which contains the spin_unlock assembly, which
contains the SMP alternatives.  If we insert that into a kernel also
built with SMP alternatives support, but which is running on a UP
system, we need to run these fixups as well when the module is loaded.