lkml.org 
[lkml]   [2010]   [Aug]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: missing .data.shared_align placement in vmlinux
    [Resend - this time with Jeremy included in To: ]

    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?
    [See below]

    Sam

    >
    On Wed, Aug 04, 2010 at 10:28:06PM +0200, Sam Ravnborg wrote:
    > 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
    >

    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/
    \
     
     \ /
      Last update: 2010-08-04 22:43    [W:0.023 / U:32.472 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site