[kernel-hardening] [PATCH v2 04/11] MIPS: Generate relocation table when CONFIG_RELOCATABLE

Matt Redfearn
2016-03-31T09:05:35Z

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>
---

Changes in v2: None

arch/mips/Makefile | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index fa25d60bc717..8388ef6a0044 100644
--- 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) \
$(bootvars-y) arch/mips/boot/$@

--
2.5.0