Re: missing .data.shared_align placement in vmlinux

From: Sam Ravnborg
Date: Wed Aug 04 2010 - 07:57:08 EST

On Fri, May 21, 2010 at 04:58:53PM -0400, Mike Frysinger wrote:
> am i missing something or does the .data.shared_align section lack
> definition in and all arch files ?
> with the recent change "net: remove time limit in process_backlog()",
> the softnet_data variable changed from "DEFINE_PER_CPU()" to
> "DEFINE_PER_CPU_ALIGNED()" which moved it from the .data section to
> the .data.shared_align section. i'm not saying this patch is wrong,
> just that is what caused me to notice this larger problem. no one
> else in the kernel is using this aligned macro variant, so i imagine
> that's why no one has noticed yet.
> since .data.shared_align isnt declared in any vmlinux files that i can
> see, the linker just places it last. this "just works" for most
> people, but when building a ROM kernel on Blackfin systems, it causes
> section overlap errors:
> bfin-uclinux-ld.real: section [00000000202e06b8 ->
> 00000000202e48b7] overlaps section .data.shared_aligned
> [00000000202e06b8 -> 00000000202e0723]
> i imagine other arches which support the ROM config option and thus do
> funky placement would see similar issues ...
> on x86, it is stuck in a dedicated section:
> [ 8] .data PROGBITS ffffffff810ec000 2ec000
> 0303a8 00 WA 0 0 4096
> [ 9] .data.shared_alig PROGBITS ffffffff8111c3c0 31c3c0
> 0000c8 00 WA 0 0 64
> the ifdef forest in asm-generic/percpu.h is beyond a quick glance &
> fix, so i leave it up to someone else ;)

as there any resolution on this?
I briefly looked at it some time ago.
And it looks like a plain oversight.

But I was also a bit lost in the forest of ifdef land...

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