Messages in this thread Patch in this message | | | Date | Wed, 4 Aug 2010 22:28:06 +0200 | From | Sam Ravnborg <> | Subject | Re: missing .data.shared_align placement in vmlinux |
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On Wed, Aug 04, 2010 at 02:12:03PM -0400, Mike Frysinger wrote: > On Wed, Aug 4, 2010 at 07:56, Sam Ravnborg wrote: > > 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 vmlinux.lds.h and all arch vmlinux.lds.S 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 .init.data [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. > > no, it's still broken in 2.6.35 :( > $ make ARCH=blackfin BF537-STAMP_defconfig > $ make ARCH=blackfin -s -j4 > $ readelf -WS vmlinux | grep '\<data\>' > [10] .data PROGBITS 0018369c 17269c 012964 00 WA 0 0 4 > [11] .data..shared_aligned PROGBITS 00196000 185000 00006c 00 > WA 0 0 4
Following simple patch should deal with it. Jeremy - you introduced this in ("x86/i386: Put aligned stack-canary in percpu shared_aligned section") 53f824520b6d84ca5b4a8fd71addc91dbf64357e
Does the following simple fix look correct to you?
Sam
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 030a954..e87260f 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -150,6 +150,7 @@ #define DATA_DATA \ *(.data) \ *(.ref.data) \ + *(.data..shared_aligned) /* percpu related */ \ DEV_KEEP(init.data) \ DEV_KEEP(exit.data) \ CPU_KEEP(init.data) \ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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