MIPS: Generate relocation table when CONFIG_RELOCATABLE

When CONFIG_RELOCATABLE is enabled (added in later patch) add
--emit-relocs to vmlinux LDFLAGS so that fully linked vmlinux contains
relocation information.

Run the previously added relocs tool to fill in the .data.relocs section
of vmlinux with a table of relocations. The relocs tool will also remove
(mark as 0 length) the relocation sections added to vmlinux.

When vmlinux is passed to the boot makefile for conversion into a boot
image the now empty relocation sections will be removed and the
populated relocation table will be included in the binary image.

Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: kernel-hardening@lists.openwall.com
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12983/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index a61031e7c06f34b267a6fea433e07dfdcd5cf49c..c0b002a09befe4d80701b736411fa207893969d0 100644 (file)
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -96,6 +96,10 @@ LDFLAGS_vmlinux                      += -G 0 -static -n -nostdlib
 KBUILD_AFLAGS_MODULE           += -mlong-calls
 KBUILD_CFLAGS_MODULE           += -mlong-calls
 
+ifeq ($(CONFIG_RELOCATABLE),y)
+LDFLAGS_vmlinux                        += --emit-relocs
+endif
+
 #
 # pass -msoft-float to GAS if it supports it.  However on newer binutils
 # (specifically newer than 2.24.51.20140728) we then also need to explicitly
@@ -313,6 +317,10 @@ rom.bin rom.sw: vmlinux
                $(bootvars-y) $@
 endif
 
+CMD_RELOCS = arch/mips/boot/tools/relocs
+quiet_cmd_relocs = RELOCS  $<
+      cmd_relocs = $(CMD_RELOCS) $<
+
 #
 # Some machines like the Indy need 32-bit ELF binaries for booting purposes.
 # Other need ECOFF, so we build a 32-bit ELF binary for them which we then
@@ -321,6 +329,11 @@ endif
 quiet_cmd_32 = OBJCOPY $@
        cmd_32 = $(OBJCOPY) -O $(32bit-bfd) $(OBJCOPYFLAGS) $< $@
 vmlinux.32: vmlinux
+ifeq ($(CONFIG_RELOCATABLE)$(CONFIG_64BIT),yy)
+# Currently, objcopy fails to handle the relocations in the elf64
+# So the relocs tool must be run here to remove them first
+       $(call cmd,relocs)
+endif
        $(call cmd,32)
 
 #
@@ -336,6 +349,9 @@ all:        $(all-y)
 
 # boot
 $(boot-y): $(vmlinux-32) FORCE
+ifeq ($(CONFIG_RELOCATABLE)$(CONFIG_32BIT),yy)
+       $(call cmd,relocs)
+endif
        $(Q)$(MAKE) $(build)=arch/mips/boot VMLINUX=$(vmlinux-32) \
                $(bootvars-y) arch/mips/boot/$@