Subject: [PATCH] ARM: kvm: implement replacement for ld's LOG2CEIL()

From: [email-masked] (Will Deacon)
Date: Mon, 23 Mar 2015 11:40:01 +0000

On Mon, Mar 23, 2015 at 10:52:57AM +0000, Ard Biesheuvel wrote:
> Commit 06f75a1f6200 ("ARM, arm64: kvm: get rid of the bounce
> page") uses ld's builtin function LOG2CEIL() to align the
> KVM init code to a log2 upper bound of its size. However,
> this function turns out to be a fairly recent addition to
> binutils, which breaks the build for older toolchains.
> 
> So instead, implement a replacement LOG2_ROUNDUP() using
> the C preprocessor.
> 
> Signed-off-by: Ard Biesheuvel <[email-masked]>
> ---
> 
> Linker map output after applying this patch:
> 
>                 0xc09a2590                __idmap_text_end = .
>                 [...]
>  *fill*         0xc09a2590       0x70 
>                 0xc09a2600                __hyp_idmap_text_start = .
>  *(.hyp.idmap.text)
>  .hyp.idmap.text
>                 0xc09a2600      0x100 arch/arm/kvm/built-in.o
>                 0xc09a2600                __kvm_hyp_init
>                 0xc09a26ec                __kvm_hyp_init_end
>                 0xc09a2700                __hyp_idmap_text_end = .
> 
> which confirms that the alignemnt is correct. The size of the region
> is 0xec bytes, and 0x70 bytes of padding are emitted to align it at
> a 0x100 byte boundary
> 
>  arch/arm/kernel/vmlinux.lds.S | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)

Thanks Ard. I pushed this on top of kvm-bounce-page and re-generated
for-next/core.

Will