linux-kernel - Re: [PATCH] kbuild: do not generate .tmp_vmlinux*.map when CONFIG_VMLINUX

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Message-ID: <CAGnOC3Y9OYZKB+7aQsDcq5pN4jJYkL8QRwXgH3jpLQkVwD-kTQ@mail.gmail.com>
Date: Thu, 13 Mar 2025 11:40:54 +0100
From: Ard Biesheuvel <ardb@...gle.com>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Ard Biesheuvel <ardb+git@...gle.com>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>
Subject: Re: [PATCH] kbuild: do not generate .tmp_vmlinux*.map when CONFIG_VMLINUX_MAP=y

On Thu, Mar 13, 2025 at 11:26 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Commit 5cc124720461 ("kbuild: add CONFIG_VMLINUX_MAP expert option")
> mentioned that "the .map file can be rather large (several MB), and
> that's a waste of space when one isn't interested in these things."
>
> If that is the case, generating map files for the intermediate
> tmp_vmlinux* files is also a waste of space. It is unlikely that
> anyone would be interested in the .tmp_vmlinux.map* files.
>
> This commit stops passing the -Map= option when linking the .tmp_vmlinux*
> intermediates.
>
> I also hard-coded the file name 'vmlinux.map' instead of ${output}.map
> because a later commit will introduce vmlinux.unstripped but I want to
> keep the name of the map file.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Acked-by: Ard Biesheuvel <ardb@...nel.org>

> ---
>
>  scripts/link-vmlinux.sh | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
> index e55026128e05..7cbbfa3efbca 100755
> --- a/scripts/link-vmlinux.sh
> +++ b/scripts/link-vmlinux.sh
> @@ -98,8 +98,8 @@ vmlinux_link()
>                 ldflags="${ldflags} ${wl}--strip-debug"
>         fi
>
> -       if is_enabled CONFIG_VMLINUX_MAP; then
> -               ldflags="${ldflags} ${wl}-Map=${output}.map"
> +       if [ -n "${generate_map}" ];  then
> +               ldflags="${ldflags} ${wl}-Map=vmlinux.map"
>         fi
>
>         ${ld} ${ldflags} -o ${output}                                   \
> @@ -211,6 +211,7 @@ fi
>  btf_vmlinux_bin_o=
>  kallsymso=
>  strip_debug=
> +generate_map=
>
>  if is_enabled CONFIG_KALLSYMS; then
>         true > .tmp_vmlinux0.syms
> @@ -279,6 +280,10 @@ fi
>
>  strip_debug=
>
> +if is_enabled CONFIG_VMLINUX_MAP; then
> +       generate_map=1
> +fi
> +
>  vmlinux_link "${VMLINUX}"
>
>  # fill in BTF IDs
> --
> 2.43.0
>