Re: [PATCH] kbuild: do not generate .tmp_vmlinux*.map when CONFIG_VMLINUX_MAP=y

[Ard Biesheuvel]

On Thu, Mar 13, 2025 at 11:26 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> 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@xxxxxxxxxx>

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

> ---
>
>  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
>