Re: [PATCH v2] ARM: atags_to_fdt: don't warn about stack size

From: Nicolas Pitre
Date: Thu Feb 18 2016 - 12:14:15 EST


On Thu, 18 Feb 2016, Arnd Bergmann wrote:

> The merge_fdt_bootargs() function by definition consumes more than 1024
> bytes of stack because it has a 1024 byte command line on the stack,
> meaning that we always get a warning when building this file:
>
> arch/arm/boot/compressed/atags_to_fdt.c: In function 'merge_fdt_bootargs':
> arch/arm/boot/compressed/atags_to_fdt.c:98:1: warning: the frame size of 1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>
> However, as this is the decompressor and we know that it has a very shallow
> call chain, and we do not actually risk overflowing the kernel stack
> at runtime here.
>
> This just shuts up the warning by slightly increasing the limit for this
> file.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>

Acked-by: Nicolas Pitre <nico@xxxxxxxxxx>


> ---
> On Thursday 18 February 2016 11:13:52 Nicolas Pitre wrote:
> > What about setting the warning to 2048 instead?
>
> Sure, actually 1280 is more than enough I think.
>
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 7a6a58ef8aaf..2cc63038d6c8 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -85,6 +85,8 @@ $(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/
> $(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \
> $(addprefix $(obj)/,$(libfdt_hdrs))
>
> +CFLAGS_atags_to_fdt.o += -Wframe-larger-than=1280
> +
> ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y)
> OBJS += $(libfdt_objs) atags_to_fdt.o
> endif
>
>