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

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Message-ID: <01f84314b2499b6859a4826ecf7363635e66a4fc.camel@physik.fu-berlin.de>
Date:   Mon, 20 Mar 2023 10:13:30 +0100
From:   John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>, stable@...r.kernel.org
Subject: Re: [PATCH 7/7 v4] sh: mcount.S: fix build error when PRINTK is not
 enabled

Hi Geert!

On Mon, 2023-03-20 at 09:16 +0100, Geert Uytterhoeven wrote:
> Hi Adrian,
> 
> On Sun, Mar 19, 2023 at 9:49 PM John Paul Adrian Glaubitz
> <glaubitz@...sik.fu-berlin.de> 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@...radead.org>
> > > Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
> > > Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> > > Cc: Rich Felker <dalias@...c.org>
> > > Suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > Cc: stable@...r.kernel.org
> > > ---
> > > 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 ":=".

That doesn't work either. I tried the following, but that didn't strip -fomit-frame-pointer:

diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index 5c8776482530..9eef6f6ffc8b 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -172,7 +172,7 @@ KBUILD_CPPFLAGS             += $(cflags-y)
 KBUILD_AFLAGS          += $(cflags-y)
 
 ifeq ($(CONFIG_MCOUNT),y)
-  KBUILD_CFLAGS += -pg
+  KBUILD_CFLAGS := $(subst -fomit-frame-pointer,,$(KBUILD_CFLAGS)) -pg
 endif
 
 ifeq ($(CONFIG_DWARF_UNWINDER),y)

I will have to do some more digging tonight.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
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