[PATCH v6 19/29] arm/build: Warn on orphan section placement

[Kees Cook]

We don't want to depend on the linker's orphan section placement
heuristics as these can vary between linkers, and may change between
versions. All sections need to be explicitly handled in the linker
script.

Specifically, this would have made a recently fixed bug very obvious:

ld: warning: orphan section `.fixup' from `arch/arm/lib/copy_from_user.o' being placed in section `.fixup'

With all sections handled, enable orphan section warning.

Reviewed-by: Nick Desaulniers <ndesaulniers at google.com>
Signed-off-by: Kees Cook <keescook at chromium.org>
---
 arch/arm/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 4e877354515f..0aa133c4ddec 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -16,6 +16,10 @@ LDFLAGS_vmlinux	+= --be8
 KBUILD_LDFLAGS_MODULE	+= --be8
 endif
 
+# We never want expected sections to be placed heuristically by the
+# linker. All sections should be explicitly named in the linker script.
+LDFLAGS_vmlinux += --orphan-handling=warn
+
 ifeq ($(CONFIG_ARM_MODULE_PLTS),y)
 KBUILD_LDS_MODULE	+= $(srctree)/arch/arm/kernel/module.lds
 endif
-- 
2.25.1