[PATCH v7 11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link

Hari Bathini
2024-10-30T07:10:12Z

On powerpc, we would like to be able to make a pass on vmlinux.o and
generate a new object file to be linked into vmlinux. Add a generic pass
in Makefile.vmlinux that architectures can use for this purpose.

Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
provide arch/<arch>/tools/Makefile with .arch.vmlinux.o target, which
will be invoked prior to the final vmlinux link step.

Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

Changes in v7:
* Changed 'arch_vmlinux_o=""' to 'arch_vmlinux_o='.
* Added Masahiro's Acked-by.

arch/Kconfig | 6 ++++++
scripts/Makefile.vmlinux | 7 +++++++
scripts/link-vmlinux.sh | 7 ++++++-
3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 8af374ea1adc..a1538927c8c1 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1684,4 +1684,10 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
config ARCH_NEED_CMPXCHG_1_EMU
bool

+config ARCH_WANTS_PRE_LINK_VMLINUX
+ bool
+ help
+ An architecture can select this if it provides arch/<arch>/tools/Makefile
+ with .arch.vmlinux.o target to be linked into vmlinux.
+
endmenu
diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux
index 1284f05555b9..dddad554e912 100644
--- a/scripts/Makefile.vmlinux
+++ b/scripts/Makefile.vmlinux
@@ -22,6 +22,13 @@ targets += .vmlinux.export.o
vmlinux: .vmlinux.export.o
endif

+ifdef CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX
+vmlinux: arch/$(SRCARCH)/tools/vmlinux.arch.o
+
+arch/$(SRCARCH)/tools/vmlinux.arch.o: vmlinux.o FORCE
+ $(Q)$(MAKE) $(build)=arch/$(SRCARCH)/tools $@
+endif
+
ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)

# Final link of vmlinux with optional arch pass after final link
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index a9b3f34a78d2..a3c634b2f348 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -100,7 +100,7 @@ vmlinux_link()
${ld} ${ldflags} -o ${output} \
${wl}--whole-archive ${objs} ${wl}--no-whole-archive \
${wl}--start-group ${libs} ${wl}--end-group \
- ${kallsymso} ${btf_vmlinux_bin_o} ${ldlibs}
+ ${kallsymso} ${btf_vmlinux_bin_o} ${arch_vmlinux_o} ${ldlibs}
}

# generate .BTF typeinfo from DWARF debuginfo
@@ -198,6 +198,11 @@ fi

${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init init/version-timestamp.o

+arch_vmlinux_o=
+if is_enabled CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX; then
+ arch_vmlinux_o=arch/${SRCARCH}/tools/vmlinux.arch.o
+fi
+
btf_vmlinux_bin_o=
kallsymso=
strip_debug=
--
2.47.0