linux-kernel - Re: [PATCH 1/2] sh: mcount.S: fix build error when PRINTK is not enabled

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Date:   Mon, 15 Nov 2021 11:10:42 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH 1/2] sh: mcount.S: fix build error when PRINTK is not enabled

Hi Randy,

On Mon, Nov 15, 2021 at 7:41 AM Randy Dunlap <rdunlap@...radead.org> 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: e460ab27b6c3e ("sh: Fix up stack overflow check with ftrace disabled.")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>

Thanks for your patch!

> Possibly even more of this function should conditionally not be built...

What about making STACK_DEBUG depend on PRINTK instead?
It doesn't make much sense to enable the former, if you won't print
any output...

> --- linux-next-20211112.orig/arch/sh/lib/mcount.S
> +++ linux-next-20211112/arch/sh/lib/mcount.S
> @@ -257,9 +257,11 @@ return_to_handler:
>  #ifdef CONFIG_STACK_DEBUG
>         .globl  stack_panic
>  stack_panic:
> +#ifdef CONFIG_PRINTK
>         mov.l   .Ldump_stack, r0
>         jsr     @r0
>          nop
> +#endif
>
>         mov.l   .Lpanic, r0
>         jsr     @r0
> @@ -277,8 +279,10 @@ stack_panic:
>         .long   panic
>  .Lpanic_s:
>         .long   .Lpanic_str
> +#ifdef CONFIG_PRINTK
>  .Ldump_stack:
>         .long   dump_stack
> +#endif
>
>         .section        .rodata
>         .align 2

Gr{oetje,eeting}s,

                        Geert

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