Re: [PATCH 7/7] kbuild: read *.mod to get objects passed to $(LD) or $(AR)

From: Jeff Johnson
Date: Wed Apr 06 2022 - 15:39:10 EST


On 4/6/2022 8:30 AM, Masahiro Yamada wrote:
ld and ar support @file, which command-line options are read from.

Now that *.mod lists the member objects in the correct order, without
duplication, it is ready to be passed to ld and ar.

By using the @file syntax, people will not be worried about the pitfall
described in the NOTE.

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---

scripts/Makefile.build | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 3da731cf6978..f6a506318795 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -450,22 +450,18 @@ quiet_cmd_ar_lib = AR $@
$(obj)/lib.a: $(lib-y) FORCE
$(call if_changed,ar_lib)
-# NOTE:
-# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
-# module is turned into a multi object module, $^ will contain header file
-# dependencies recorded in the .*.cmd file.
ifneq ($(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT),)
quiet_cmd_link_multi-m = AR [M] $@
cmd_link_multi-m = \
$(cmd_update_lto_symversions); \
rm -f $@; \
- $(AR) cDPrsT $@ $(filter %.o,$^)
+ $(AR) cDPrsT $@ @$(patsubst %.o,%.mod,$@)
else
quiet_cmd_link_multi-m = LD [M] $@
- cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^)
+ cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ @$(patsubst %.o,%.mod,$@)
endif
-$(multi-obj-m): FORCE
+$(multi-obj-m): %.o: %.mod FORCE
$(call if_changed,link_multi-m)
$(call multi_depend, $(multi-obj-m), .o, -objs -y -m)

Looks like this also addresses the out-of-tree issue described in <https://lore.kernel.org/linux-kbuild/1610500731-30960-2-git-send-email-jjohnson@xxxxxxxxxxxxxx/>

:)

/jeff