Re: [PATCH 7/7 v4] sh: mcount.S: fix build error when PRINTK is not enabled

[Geert Uytterhoeven]

Hi Adrian,

On Sun, Mar 19, 2023 at 9:49 PM John Paul Adrian Glaubitz
<glaubitz@xxxxxxxxxxxxxxxxxxx> wrote:
> On Sun, 2023-03-05 at 20:00 -0800, Randy Dunlap wrote:
> > Fix a build error in mcount.S when CONFIG_PRINTK is not enabled.
> > Fixes this build error:
> >
> > sh2-linux-ld: arch/sh/lib/mcount.o: in function `stack_panic':
> > (.text+0xec): undefined reference to `dump_stack'
> >
> > Fixes: e460ab27b6c3 ("sh: Fix up stack overflow check with ftrace disabled.")
> > Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> > Cc: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
> > Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Rich Felker <dalias@xxxxxxxx>
> > Suggested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> > v2: add PRINTK to STACK_DEBUG dependency (thanks, Geert)
> > v3: skipped
> > v4: refresh & resend
> >
> >  arch/sh/Kconfig.debug |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff -- a/arch/sh/Kconfig.debug b/arch/sh/Kconfig.debug
> > --- a/arch/sh/Kconfig.debug
> > +++ b/arch/sh/Kconfig.debug
> > @@ -15,7 +15,7 @@ config SH_STANDARD_BIOS
> >
> >  config STACK_DEBUG
> >       bool "Check for stack overflows"
> > -     depends on DEBUG_KERNEL
> > +     depends on DEBUG_KERNEL && PRINTK
> >       help
> >         This option will cause messages to be printed if free stack space
> >         drops below a certain limit. Saying Y here will add overhead to
>
> I can't really test this change as the moment I am enabling CONFIG_STACK_DEBUG,
> the build fails with:
>
>   CC      scripts/mod/devicetable-offsets.s
> sh4-linux-gcc: error: -pg and -fomit-frame-pointer are incompatible
> make[1]: *** [scripts/Makefile.build:252: scripts/mod/empty.o] Error 1
> make[1]: *** Waiting for unfinished jobs....
> sh4-linux-gcc: error: -pg and -fomit-frame-pointer are incompatible
> make[1]: *** [scripts/Makefile.build:114: scripts/mod/devicetable-offsets.s] Error 1
> make: *** [Makefile:1286: prepare0] Error 2
>
> So, I assume we need to strip -fomit-frame-pointer from KBUILD_CFLAGS, correct?
>
> I tried this change, but that doesn't fix it for me:
>
> diff --git a/arch/sh/Makefile b/arch/sh/Makefile
> index 5c8776482530..83f535b73835 100644
> --- a/arch/sh/Makefile
> +++ b/arch/sh/Makefile
> @@ -173,6 +173,7 @@ KBUILD_AFLAGS               += $(cflags-y)
>
>  ifeq ($(CONFIG_MCOUNT),y)
>    KBUILD_CFLAGS += -pg
> +  KBUILD_CFLAGS := $(subst -fomit-frame-pointer,,$(KBUILD_CFLAGS))
>  endif
>
>  ifeq ($(CONFIG_DWARF_UNWINDER),y)
>
> Any ideas?

Please try with "+=" instead of ":=".

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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