lkdtm: add function for testing .rodata section

This adds a function that lives in the .rodata section. The section
flags are corrected using objcopy since there is no way with gcc to
declare section flags in an architecture-agnostic way.

Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index c3cb6ad..7d45ed4 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -59,3 +59,11 @@
 obj-$(CONFIG_PANEL)             += panel.o
 
 lkdtm-$(CONFIG_LKDTM)		+= lkdtm_core.o
+lkdtm-$(CONFIG_LKDTM)		+= lkdtm_rodata_objcopy.o
+
+OBJCOPYFLAGS :=
+OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \
+			--set-section-flags .text=alloc,readonly \
+			--rename-section .text=.rodata
+$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o
+	$(call if_changed,objcopy)