[PATCH 22/28] efi/libstub: avoid linking libstub/lib-ksyms.o into vmlinux

[Ard Biesheuvel]

From: Masahiro Yamada <masahiroy@xxxxxxxxxx>

drivers/firmware/efi/libstub/Makefile builds a static library, which
is not linked into the main vmlinux target in the ordinary way [arm64],
or at all [ARM, x86].

Since commit 7f2084fa55e6 ("[kbuild] handle exports in lib-y objects
reliably"), any Makefile using lib-y generates lib-ksyms.o which is
linked into vmlinux.

In this case, the following garbage object is linked into vmlinux.

  drivers/firmware/efi/libstub/lib-ksyms.o

We do not want to follow the default linking rules for static libraries
built under libstub/ so using subdir-y instead of obj-y is the correct
way to descend into this directory.

Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200305055047.6097-1-masahiroy@xxxxxxxxxx
[ardb: update commit log to clarify that arm64 deviates in this respect]
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
---
 drivers/firmware/efi/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index 317a05cd388b..7a216984552b 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -20,7 +20,7 @@ obj-$(CONFIG_EFI_VARS_PSTORE)		+= efi-pstore.o
 obj-$(CONFIG_UEFI_CPER)			+= cper.o
 obj-$(CONFIG_EFI_RUNTIME_MAP)		+= runtime-map.o
 obj-$(CONFIG_EFI_RUNTIME_WRAPPERS)	+= runtime-wrappers.o
-obj-$(CONFIG_EFI_STUB)			+= libstub/
+subdir-$(CONFIG_EFI_STUB)		+= libstub
 obj-$(CONFIG_EFI_FAKE_MEMMAP)		+= fake_map.o
 obj-$(CONFIG_EFI_BOOTLOADER_CONTROL)	+= efibc.o
 obj-$(CONFIG_EFI_TEST)			+= test/
-- 
2.17.1