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    SubjectRe: [PATCH 4/6] Add support for LZO-compressed kernels for ARM
    On Fri, Aug 07, 2009 at 03:27:00PM +0200, Matthieu CASTET wrote :
    > Albin Tonnerre a écrit :
    > > On Fri, Aug 07, 2009 at 01:50:03PM +0200, Matthieu CASTET wrote :
    > >> Albin Tonnerre a écrit :
    > >>> On Fri, Aug 07, 2009 at 11:36:56AM +0200, Alain Knaff wrote :
    > >>>> On 08/07/09 11:24, Albin Tonnerre wrote:

    > >>>>> Regards,

    > >>>> Could it be that the patches that remove division (zutil.h and inflate.c)
    > >>>> have somehow not been applied?

    > >>> Indeed, they've not been applied. However, I'd rather try to understand why
    > >>> exactly this is an issue when compiling with -Os and not -O2 instead of working
    > >>> around it by removing the divisions.

    > >> Look at the generated code.

    > >> Arm doesn't have division instruction.
    > >> May be at -Os gcc emit a call to the software division, but at -O2 it
    > >> manage to optimise the division (transform it in shift, inline some
    > >> builtin, ...).

    > > Yes, I figured that out. What I don't get, though, is that it fails while the
    > > software division symbol (__aeabi_uidivmod here) does seem to be provided by
    > > libgcc.

    > AFAIK we don't link the kernel with libgcc.
    > That's why the kernel provide __aeabi_* in arch/arm/lib

    That's true for the actual kernel image, but not for the bootstrap code we use
    when compiling compressed kernels. arch/arm/boot/compressed/Makefile uses
    libgcc, unless I'm overlooking something here:

    arm-unknown-linux-uclibcgnueabi-ld -EL --defsym zreladdr=0x20008000
    --defsym initrd_phys=0x20410000 --defsym params_phys=0x20000100 -p
    --no-undefined -X
    -T arch/arm/boot/compressed/ arch/arm/boot/compressed/head.o
    arch/arm/boot/compressed/piggy.gzip.o arch/arm/boot/compressed/misc.o -o

    Albin Tonnerre, Free Electrons
    Kernel, drivers and embedded Linux development,
    consulting, training and support.
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      Last update: 2009-08-07 15:57    [W:0.022 / U:69.372 seconds]
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