[issue report] ARM: compile error of frame size

[Geert Uytterhoeven]

Hi Morimoto-san,

CC Arnd

On Tue, 29 Jul 2025 at 02:12, Kuninori Morimoto
<kuninori.morimoto.gx at renesas.com> wrote:
> > >         > grep CONFIG_FRAME_WARN .config
> > >         CONFIG_FRAME_WARN=2040
> > >
> > >         > git diff
> > >         diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> > >         index d61369b1eabe..c5173bd82380 100644
> > >         --- a/arch/arm/boot/compressed/Makefile
> > >         +++ b/arch/arm/boot/compressed/Makefile
> > >         @@ -80,7 +80,7 @@ libfdt_objs := fdt_rw.o fdt_ro.o fdt_wip.o fdt.o
> > >
> > >          ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y)
> > >          CFLAGS_REMOVE_atags_to_fdt.o += -Wframe-larger-than=${CONFIG_FRAME_WARN}
> > > -        CFLAGS_atags_to_fdt.o += -Wframe-larger-than=1280
> > > +        CFLAGS_atags_to_fdt.o += -Wframe-larger-than=2040
> > >          OBJS   += $(libfdt_objs) atags_to_fdt.o
> > >          endif
> > >          ifeq ($(CONFIG_USE_OF),y)
> (snip)
> > Yes it is.  And it is hard to fix, according to the maple_tree maintainer:
>
> Hmm...
> Actually I have tried to same solution (= remove or fix the big node), but
> noticed there are many such code. My suggested was very simple solution
> I guess, but I'm not sure detail of ARM limitation, and/or it can solve all
> cases, etc...
>
> But other CPU (like ARM64) doesn't have this issue, so we can follow same
> way (= allow large frame) I guess.

I do see it in one my arm64 builds, it depends on your kernel config:

    lib/maple_tree.c: In function ‘mas_wr_spanning_store’:
    lib/maple_tree.c:3812:1: warning: the frame size of 1040 bytes is
larger than 1024 bytes [-Wframe-larger-than=] 3812 | }

I guess Arnd has seen it in his randconfig builds, too...

> Does ARM has some reason which can't use large frame ? If not, do you think
> we can allow to use it on ARM ?

(stacked) Large frames may cause kernel stack overflow.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds