powerpc/boot: Allow building the zImage wrapper as a relocatable ET_DYN
This patch adds code, linker script and makefile support to allow
building the zImage wrapper around the kernel as a position independent
executable. This results in an ET_DYN instead of an ET_EXEC ELF output
file, which can be loaded at any location by the firmware and will
process its own relocations to work correctly at the loaded address.
This is of interest particularly since the standard ePAPR image format
must be an ET_DYN (although this patch alone is not sufficient to
produce a fully ePAPR compliant boot image).
Note for now we don't enable building with -pie for anything.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/boot/wrapper b/arch/powerpc/boot/wrapper
index cb97e75..fef5278 100755
--- a/arch/powerpc/boot/wrapper
+++ b/arch/powerpc/boot/wrapper
@@ -39,6 +39,7 @@
cacheit=
binary=
gzip=.gz
+pie=
# cross-compilation prefix
CROSS=
@@ -157,9 +158,10 @@
platformo=$object/of.o
;;
coff)
- platformo=$object/of.o
+ platformo="$object/crt0.o $object/of.o"
lds=$object/zImage.coff.lds
link_address='0x500000'
+ pie=
;;
miboot|uboot)
# miboot and U-boot want just the bare bits, not an ELF binary
@@ -208,6 +210,7 @@
ksection=.kernel:vmlinux.bin
isection=.kernel:initrd
link_address=''
+ pie=
;;
ep88xc|ep405|ep8248e)
platformo="$object/fixed-head.o $object/$platform.o"
@@ -310,9 +313,9 @@
if [ "$platform" != "miboot" ]; then
if [ -n "$link_address" ] ; then
- text_start="-Ttext $link_address --defsym _start=$link_address"
+ text_start="-Ttext $link_address"
fi
- ${CROSS}ld -m elf32ppc -T $lds $text_start -o "$ofile" \
+ ${CROSS}ld -m elf32ppc -T $lds $text_start $pie -o "$ofile" \
$platformo $tmp $object/wrapper.a
rm $tmp
fi