[v6,11/17] kbuild: Add generic hook for architectures to use before the final vmlinux link

Commit Message

Hari Bathini Oct. 18, 2024, 5:36 p.m. UTC

From: Naveen N Rao <[e-mail]>

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.

Signed-off-by: Naveen N Rao <[e-mail]>
Signed-off-by: Hari Bathini <[e-mail]>
---

Changes in v6:
* Intermediate files named vmlinux.arch.* instead of .vmlinux.arch.*
* Used 'bool' instead of 'def_bool n'
* Missing FORCE added for vmlinux.arch.o


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

Comments

Masahiro Yamada Oct. 27, 2024, 9:14 a.m. UTC | #1

On Sat, Oct 19, 2024 at 2:37 AM Hari Bathini <[e-mail]> wrote:
>
> From: Naveen N Rao <[e-mail]>
>
> 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.
>
> Signed-off-by: Naveen N Rao <[e-mail]>
> Signed-off-by: Hari Bathini <[e-mail]>


> --- 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=""

Nit:  unnecessary double quotes.

arch_vmlinux_o=

is enough.


Other than that,

Acked-by: Masahiro Yamada <[e-mail]>








--
Best Regards
Masahiro Yamada

Patch

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..7acf4e31e51c 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=