[tip: core/build] arm/build: Warn on orphan section placement

[tip-bot2 for Kees Cook]

The following commit has been merged into the core/build branch of tip:

Commit-ID:     5a17850e251a55bba6d65aefbfeacfa9888cd2cd
Gitweb:        https://git.kernel.org/tip/5a17850e251a55bba6d65aefbfeacfa9888cd2cd
Author:        Kees Cook <keescook@xxxxxxxxxxxx>
AuthorDate:    Tue, 01 Sep 2020 19:53:44 -07:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Thu, 03 Sep 2020 10:28:35 +02:00

arm/build: Warn on orphan section placement

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.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200902025347.2504702-3-keescook@xxxxxxxxxxxx
---
 arch/arm/Makefile | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 4e87735..e589da3 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 += $(call ld-option, --orphan-handling=warn)
+
 ifeq ($(CONFIG_ARM_MODULE_PLTS),y)
 KBUILD_LDS_MODULE	+= $(srctree)/arch/arm/kernel/module.lds
 endif