Re: [PATCH] sh: machvec: Use char[] for section boundaries

Rich Felker
2022-09-08T22:31:03Z

On Wed, Sep 07, 2022 at 04:43:45PM -0700, Kees Cook wrote:
> As done for other sections, define the extern as a character array,
> which relaxes many of the compiler-time object size checks, which would
> otherwise assume it's a single long. Solves the following build error:
>
> arch/sh/kernel/machvec.c: error: array subscript 'struct sh_machine_vector[0]' is partly outside array bounds of 'long int[1]' [-Werror=array-bounds]: => 105:33

LGMT. This is the approach I recommend for this general type of
mechanism. So,

Acked-by: Rich Felker <dalias@libc.org>

Since I haven't been on top of collating patches for upstreaming, I'd
be happy if anyone else wants to take this in their tree before I get
back to it.

Rich

> Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
> Cc: Rich Felker <dalias@libc.org>
> Cc: linux-sh@vger.kernel.org
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Link: https://lore.kernel.org/lkml/alpine.DEB.2.22.394.2209050944290.964530@ramsan.of.borg/
> Fixes: 9655ad03af2d ("sh: Fixup machvec support.")
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> arch/sh/include/asm/sections.h | 2 +-
> arch/sh/kernel/machvec.c | 10 +++++-----
> 2 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/sh/include/asm/sections.h b/arch/sh/include/asm/sections.h
> index 8edb824049b9..0cb0ca149ac3 100644
> --- a/arch/sh/include/asm/sections.h
> +++ b/arch/sh/include/asm/sections.h
> @@ -4,7 +4,7 @@
>
> #include <asm-generic/sections.h>
>
> -extern long __machvec_start, __machvec_end;
> +extern char __machvec_start[], __machvec_end[];
> extern char __uncached_start, __uncached_end;
> extern char __start_eh_frame[], __stop_eh_frame[];
>
> diff --git a/arch/sh/kernel/machvec.c b/arch/sh/kernel/machvec.c
> index d606679a211e..57efaf5b82ae 100644
> --- a/arch/sh/kernel/machvec.c
> +++ b/arch/sh/kernel/machvec.c
> @@ -20,8 +20,8 @@
> #define MV_NAME_SIZE 32
>
> #define for_each_mv(mv) \
> - for ((mv) = (struct sh_machine_vector *)&__machvec_start; \
> - (mv) && (unsigned long)(mv) < (unsigned long)&__machvec_end; \
> + for ((mv) = (struct sh_machine_vector *)__machvec_start; \
> + (mv) && (unsigned long)(mv) < (unsigned long)__machvec_end; \
> (mv)++)
>
> static struct sh_machine_vector * __init get_mv_byname(const char *name)
> @@ -87,8 +87,8 @@ void __init sh_mv_setup(void)
> if (!machvec_selected) {
> unsigned long machvec_size;
>
> - machvec_size = ((unsigned long)&__machvec_end -
> - (unsigned long)&__machvec_start);
> + machvec_size = ((unsigned long)__machvec_end -
> + (unsigned long)__machvec_start);
>
> /*
> * Sanity check for machvec section alignment. Ensure
> @@ -102,7 +102,7 @@ void __init sh_mv_setup(void)
> * vector (usually the only one) from .machvec.init.
> */
> if (machvec_size >= sizeof(struct sh_machine_vector))
> - sh_mv = *(struct sh_machine_vector *)&__machvec_start;
> + sh_mv = *(struct sh_machine_vector *)__machvec_start;
> }
>
> pr_notice("Booting machvec: %s\n", get_system_type());
> --
> 2.34.1