Re: [PATCH v2 2/3] efi/libstub: add random.c to ARM build

From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org
Cc: Ard Biesheuvel
	<ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	"linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>,
	Matt Fleming
	<matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>,
	Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>
Subject: Re: [PATCH v2 2/3] efi/libstub: add random.c to ARM build
Date: Tue, 15 Nov 2016 16:11:03 +0100	[thread overview]
Message-ID: <2189664.D28O3TYR8x@wuerfel> (raw)
In-Reply-To: <CAKv+Gu_=et=2zHBTYOr9thz2kS0cXHHYg96oWGRdD3D10fqXtw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Wednesday, November 2, 2016 9:37:13 AM CET Ard Biesheuvel wrote:
> @@ -98,7 +100,7 @@
>                 efi_memory_desc_t *md = (void *)memory_map + map_offset;
>                 unsigned long slots;
> 
> -               slots = get_entry_num_slots(md, size, align);
> +               slots = get_entry_num_slots(md, size, ilog2(align));
>                 MD_NUM_SLOTS(md) = slots;
>                 total_slots += slots;
>         }
> """
> 
> This is because ARM does not have a division routine in the
> decompressor, and the fact that the division by 'align' should always
> involve a power of 2 is not visible to the compiler.
> 
> If nobody objects, I will fold this in when applying
> 
> 

I'm getting a link error here when building with -Os:

drivers/firmware/efi/libstub/random.stub.o: In function `efi_random_alloc':
random.c:(.text.efi_random_alloc+0x264): undefined reference to `__aeabi_llsr'

If I compile this with -O2, the ilog2 gets inlined and everything
works.

	Arnd