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    SubjectRe: [PATCH 09/13] kbuild: do not create built-in.a.symversions or lib.a.symversions
    On Thu, Aug 19, 2021 at 09:57:40AM +0900, Masahiro Yamada wrote:
    > Merge all *.o.symversions in scripts/link-vmlinux.sh instead of
    > merging them in the unit of built-in.a or lib.a.
    >
    > This is a preparation for further code cleanups.

    Looks good, though I wonder about this becoming serialized during the
    link phase rather than doing the work per-target. I mean, it always had
    to collect them all during the link phase (with "cat"), but before it
    wasn't running $(AR) serially to do it.

    I'll ponder how this might be made a little more parallel. But for now:

    Reviewed-by: Kees Cook <keescook@chromium.org>

    -Kees

    >
    > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
    > ---
    >
    > scripts/Makefile.build | 10 ++--------
    > scripts/link-vmlinux.sh | 22 ++++++++++++++++++----
    > 2 files changed, 20 insertions(+), 12 deletions(-)
    >
    > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
    > index 585dae34746a..37d6f6da34d6 100644
    > --- a/scripts/Makefile.build
    > +++ b/scripts/Makefile.build
    > @@ -430,11 +430,8 @@ endif
    > quiet_cmd_ar_builtin = AR $@
    > cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
    >
    > -quiet_cmd_ar_and_symver = AR $@
    > - cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
    > -
    > $(obj)/built-in.a: $(real-obj-y) FORCE
    > - $(call if_changed,ar_and_symver)
    > + $(call if_changed,ar_builtin)
    >
    > #
    > # Rule to create modules.order file
    > @@ -454,11 +451,8 @@ $(obj)/modules.order: $(obj-m) FORCE
    > #
    > # Rule to compile a set of .o files into one .a file (with symbol table)
    > #
    > -quiet_cmd_ar_lib = AR $@
    > - cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
    > -
    > $(obj)/lib.a: $(lib-y) FORCE
    > - $(call if_changed,ar_lib)
    > + $(call if_changed,ar)
    >
    > # NOTE:
    > # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
    > diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
    > index d74cee5c4326..17976609c2d8 100755
    > --- a/scripts/link-vmlinux.sh
    > +++ b/scripts/link-vmlinux.sh
    > @@ -52,6 +52,13 @@ gen_initcalls()
    > > .tmp_initcalls.lds
    > }
    >
    > +append_symversion()
    > +{
    > + if [ -f ${1}.symversions ]; then
    > + cat ${1}.symversions >> .tmp_symversions.lds
    > + fi
    > +}
    > +
    > # If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
    > # .tmp_symversions.lds
    > gen_symversions()
    > @@ -59,10 +66,17 @@ gen_symversions()
    > info GEN .tmp_symversions.lds
    > rm -f .tmp_symversions.lds
    >
    > - for o in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
    > - if [ -f ${o}.symversions ]; then
    > - cat ${o}.symversions >> .tmp_symversions.lds
    > - fi
    > + for a in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
    > + case $a in
    > + *.a)
    > + for o in $(${AR} t ${a}); do
    > + append_symversion ${o}
    > + done
    > + ;;
    > + *)
    > + append_symversion ${a}
    > + ;;
    > + esac
    > done
    > }
    >
    > --
    > 2.30.2
    >

    --
    Kees Cook

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