[RFC PATCH v2 4/5] kbuild: Add generic hook for architectures to use before the final vmlinux link

[Naveen N Rao]

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 link-vmlinux.sh that architectures can use for this purpose.
Architectures need to select CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX and must
provide arch/<arch>/tools/vmlinux_o.sh, which will be invoked prior to
the final vmlinux link step.

Signed-off-by: Naveen N Rao <nav...@kernel.org>
---
 arch/Kconfig            |  3 +++
 scripts/link-vmlinux.sh | 18 +++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 975dd22a2dbd..649f0903e7ef 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1643,4 +1643,7 @@ config CC_HAS_SANE_FUNCTION_ALIGNMENT
 config ARCH_NEED_CMPXCHG_1_EMU
        bool
 
+config ARCH_WANTS_PRE_LINK_VMLINUX
+       def_bool n
+
 endmenu
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 46ce5d04dbeb..07f70e105d82 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -122,7 +122,7 @@ gen_btf()
                return 1
        fi
 
-       vmlinux_link ${1}
+       vmlinux_link ${1} ${arch_vmlinux_o}
 
        info "BTF" ${2}
        LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
@@ -178,7 +178,7 @@ kallsyms_step()
        kallsymso=${kallsyms_vmlinux}.o
        kallsyms_S=${kallsyms_vmlinux}.S
 
-       vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" 
${btf_vmlinux_bin_o}
+       vmlinux_link ${kallsyms_vmlinux} "${kallsymso_prev}" 
${btf_vmlinux_bin_o} ${arch_vmlinux_o}
        mksysmap ${kallsyms_vmlinux} ${kallsyms_vmlinux}.syms
        kallsyms ${kallsyms_vmlinux}.syms ${kallsyms_S}
 
@@ -203,6 +203,7 @@ sorttable()
 
 cleanup()
 {
+       rm -f .arch.vmlinux.*
        rm -f .btf.*
        rm -f System.map
        rm -f vmlinux
@@ -223,6 +224,17 @@ 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.vmlinux.o
+       info "ARCH" ${arch_vmlinux_o}
+       if ! ${srctree}/arch/${SRCARCH}/tools/vmlinux_o.sh ${arch_vmlinux_o} ; 
then
+               echo >&2 "Failed to generate ${arch_vmlinux_o}"
+               echo >&2 "Try to disable CONFIG_ARCH_WANTS_PRE_LINK_VMLINUX"
+               exit 1
+       fi
+fi
+
 btf_vmlinux_bin_o=""
 if is_enabled CONFIG_DEBUG_INFO_BTF; then
        btf_vmlinux_bin_o=.btf.vmlinux.bin.o
@@ -273,7 +285,7 @@ if is_enabled CONFIG_KALLSYMS; then
        fi
 fi
 
-vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o}
+vmlinux_link vmlinux "${kallsymso}" ${btf_vmlinux_bin_o} ${arch_vmlinux_o}
 
 # fill in BTF IDs
 if is_enabled CONFIG_DEBUG_INFO_BTF && is_enabled CONFIG_BPF; then
-- 
2.45.2