powerpc: Check for unsupported relocs when using CONFIG_RELOCATABLE

When using CONFIG_RELOCATABLE, we build the kernel as a position
independent executable. The kernel then uses a little bit of relocation
code to relocate itself. That code only deals with R_PPC64_RELATIVE
relocations though. If for some reason you use assembly constructs
such as LOAD_REG_IMMEDIATE() to load the address of a symbol, you'll
generate different kinds of relocations that won't be processed properly
and bad things will happen. (We have 2 such bugs today).

The perl script tries to filter out "known" bad ones. It's possible
that we are missing some in the case of a weak function that nobody
implements, we'll see if we get false positive and fix it.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index aacf629c1a9f..1a54a3b3a3fa 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -164,6 +164,17 @@ PHONY += $(BOOT_TARGETS)
 
 boot := arch/$(ARCH)/boot
 
+ifeq ($(CONFIG_RELOCATABLE),y)
+quiet_cmd_relocs_check = CALL    $<
+      cmd_relocs_check = perl $< "$(OBJDUMP)" "$(obj)/vmlinux"
+
+PHONY += relocs_check
+relocs_check: arch/powerpc/relocs_check.pl vmlinux
+        $(call cmd,relocs_check)
+
+zImage: relocs_check
+endif
+
 $(BOOT_TARGETS): vmlinux
         $(Q)$(MAKE) ARCH=ppc64 $(build)=$(boot) $(patsubst %,$(boot)/%,$@)