linux-kernel - Re: Help needed to fix section mismatch warnings

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Date:	Sat, 19 Jan 2008 22:22:42 +0100
From:	Sam Ravnborg <sam@...nborg.org>
To:	Randy Dunlap <randy.dunlap@...cle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	akpm <akpm@...ux-foundation.org>
Subject: Re: Help needed to fix section mismatch warnings

On Sat, Jan 19, 2008 at 11:52:55AM -0800, Randy Dunlap wrote:
> On Sun, 6 Jan 2008 15:07:28 +0100 Sam Ravnborg wrote:
> 
> > kbuild emit section mismatch warnings when it detects that someone does a
> > call from a non-init section to a init section.
> > The rationale here is that the init section are discarded at runtime and
> > if this call happens after the init section has gone we have an oops.
> > 
> > This check is planned to be turned into an error soon but we still
> > see a bit too many warnings.
> > 
> > To see the list below build a kernel like this:
> > 
> > make allyesconfig
> > Set CONFIG_HOTPLUG to n
> > (In General Setup | Configure standard kernel features | Support for hot-plugable devices)
> > 
> > Then build the kernel like this:
> > make KCFLAGS=-fno-unit-at-a-time
> > 
> > The flag "-fno-unit-at-a-time" tell gcc to avoid additional inlining which
> > otherwise would hide several section mismatch warnings.
> > 
> > With latest kernel I got 113 warnings and most should fixable.
> > Try to look at how other section mismatch warnings has been fixed for inspiration.
> > 
> > Patches can be cc:ed to me but always send it to the maintainer and lkml.
> > 
> > 	Sam
> > 
> > This is the current list of warnings
> > 
> > WARNING: vmlinux.o(.text+0x1ffd0): Section mismatch: reference to .init.text:register_cpu (between 'arch_register_cpu' and 'arch_unregister_cpu')
> 
> > WARNING: vmlinux.o(.text+0x21a39): Section mismatch: reference to .init.text:absent_pages_in_range (between 'reserve_hotadd' and 'unparse_node')
> > WARNING: vmlinux.o(.text+0x21ae9): Section mismatch: reference to .init.data: (between 'unparse_node' and 'null_slit_node_compare')
> 
> > WARNING: vmlinux.o(.text+0x38b43): Section mismatch: reference to .init.text:idle_regs (between 'fork_idle' and 'fork_traceflag')
> 
> Above 4 seem to be mostly fixed in -mm.  I made patches for them
> and then checked -mm, so I won't post the patches...
> 
> 
> > WARNING: vmlinux.o(.text+0x43524): Section mismatch: reference to .init.text: (between 'timer_cpu_notify' and 'msleep')
> > WARNING: vmlinux.o(.text+0x4c6f6): Section mismatch: reference to .init.text: (between 'rcu_cpu_notify' and 'wakeme_after_rcu')
> > WARNING: vmlinux.o(.text+0x51cbe): Section mismatch: reference to .init.text: (between 'hrtimer_cpu_notify' and 'down_read_trylock')
> 
> I'll post patches for the 3 above.  However, the rcu code in -mm
> is quite different, so the rcu patch may have a short life.

Hi Randy.

Thanks for your efforts!

	Sam
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