Re: [PATCH] Add non-zero module sections to sysfs

[John David Anglin]

On 6-Apr-13, at 6:52 AM, James Bottomley wrote:

> On Sat, 2013-04-06 at 15:22 +1030, Rusty Russell wrote:
> > > The problem is our assumption that section names be unique.  This
> > > assumption is wrong.  The ELF spec says (version 1.1 page 1-15): "An
> > > object file may have more than one section with the same name."   
> > > We need
> > > to fix the kernel not to rely on a bogus assumption ... but we had  
> > > no
> > > idea how to do that in a way that preserved the backwards  
> > > compatibility
> > > of sections subdirectory.
> > >
> > > I admit that 35dead4235e2b67da7275b4122fed37099c2f462 is a hack,  
> > > but now
> > > the problem has got attention, can we fix it properly?
> >
> > Yep.  The original patch didn't go through me, or we would have had  
> > this
> > discussion back then...
> >
> > The use of section names in sysfs goes back to one Mr. Corbet.  Why  
> > did
> > he do it that way?  Because gdb's add-symbol-file makes the same
> > assumption.  So if we fixed the sysfs somehow, it still wouldn't be
> > useful, since there's no way to tell gdb :(
> >
> > The real answer don't use -ffunction-sections on modules: probably  
> > not
> > as important as the rest of the kernel.  And the new shiny is
> > -flto anyway.
> >
> > And that leaves us with a PA-RISC specific issue, for which we should
> > move the fix to PA-RISC.
> >
> > Thoughts?
>
> Well, we don't have much of a choice.  Our ELF stub jump on 32 bits  
> is a
> PCREL17.  That means once a module size is over 128k there's a  
> chance we
> might not be able to link it because the jump is too big for the
> instruction.  IPV6 is one such big module today, but I'm sure there  
> are
> others.  The only way I know to fix this is to allow the linker to
> insert stubs between functions, so we only fail at linking if a single
> function is >128k big.  The way to do this is -ffunction-sections,
> unless there's something else we could do (all we really need is a way
> to ensure we can insert ELF stubs every 128k).

There is now a config work around for this.  See:
http://www.spinics.net/lists/linux-parisc/msg04521.html

Dave
--
John David Anglin	dave.anglin@xxxxxxxx



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