powerpc/boot: Add support for 64bit little endian wrapper

The code is only slightly modified : entry points now use the
FIXUP_ENDIAN trampoline to switch endian order. The 32bit wrapper
is kept for big endian kernels and 64bit is enforced for little
endian kernels with a PPC64_BOOT_WRAPPER config option.

The linker script is generated using the kernel preprocessor flags
to make use of the CONFIG_* definitions and the wrapper script is
modified to take into account the new elf64ppc format.

Finally, the zImage file is compiled as a position independent
executable (-pie) which makes it loadable at any address by the
firmware.

Signed-off-by: Cédric Le Goater <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>

arch/powerpc/boot/Makefile

···
 BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		 -fno-strict-aliasing -Os -msoft-float -pipe \
 		 -fomit-frame-pointer -fno-builtin -fPIC -nostdinc \
-		 -isystem $(shell $(CROSS32CC) -print-file-name=include) \
-		 -mbig-endian
+		 -isystem $(shell $(CROSS32CC) -print-file-name=include)
+ifdef CONFIG_PPC64_BOOT_WRAPPER
+BOOTCFLAGS	+= -m64
+endif
+ifdef CONFIG_CPU_BIG_ENDIAN
+BOOTCFLAGS	+= -mbig-endian
+endif
+
 BOOTAFLAGS	:= -D__ASSEMBLY__ $(BOOTCFLAGS) -traditional -nostdinc
 
 ifdef CONFIG_DEBUG_INFO
···
 $(obj)/empty.c:
 	@touch $@
 
-$(obj)/zImage.lds $(obj)/zImage.coff.lds $(obj)/zImage.ps3.lds: $(obj)/%: $(srctree)/$(src)/%.S
+$(obj)/zImage.lds: $(obj)/%: $(srctree)/$(src)/%.S
+	$(CROSS32CC) $(cpp_flags) -E -Wp,-MD,$(depfile) -P -Upowerpc \
+		-D__ASSEMBLY__ -DLINKER_SCRIPT -o $@ $<
+
+$(obj)/zImage.coff.lds $(obj)/zImage.ps3.lds : $(obj)/%: $(srctree)/$(src)/%.S
 	@cp $< $@
 
 clean-files := $(zlib) $(zlibheader) $(zliblinuxheader) \

arch/powerpc/boot/crt0.S

···
 	rfid
 
 1:	/* Return from OF */
+	FIXUP_ENDIAN
 
 	/* Restore registers and return. */
 	rldicl  r1,r1,0,32

arch/powerpc/boot/ppc_asm.h

···
 #define SPRN_TBRL	268
 #define SPRN_TBRU	269
 
+#define FIXUP_ENDIAN						   \
+	tdi   0, 0, 0x48; /* Reverse endian of b . + 8		*/ \
+	b     $+36;	  /* Skip trampoline if endian is good	*/ \
+	.long 0x05009f42; /* bcl 20,31,$+4			*/ \
+	.long 0xa602487d; /* mflr r10				*/ \
+	.long 0x1c004a39; /* addi r10,r10,28			*/ \
+	.long 0xa600607d; /* mfmsr r11				*/ \
+	.long 0x01006b69; /* xori r11,r11,1			*/ \
+	.long 0xa6035a7d; /* mtsrr0 r10				*/ \
+	.long 0xa6037b7d; /* mtsrr1 r11				*/ \
+	.long 0x2400004c  /* rfid				*/
+
 #endif /* _PPC64_PPC_ASM_H */

arch/powerpc/boot/pseries-head.S

···
+#include "ppc_asm.h"
+
 	.text
 
 	.globl _zimage_start
 _zimage_start:
+	FIXUP_ENDIAN
 	b _zimage_start_lib

arch/powerpc/boot/wrapper

···
 binary=
 gzip=.gz
 pie=
+format=
 
 # cross-compilation prefix
 CROSS=
···
     kernel=vmlinux
 fi
 
+elfformat="`${CROSS}objdump -p "$kernel" | grep 'file format' | awk '{print $4}'`"
+case "$elfformat" in
+    elf64-powerpcle)	format=elf64lppc	;;
+    elf64-powerpc)	format=elf32ppc	;;
+    elf32-powerpc)	format=elf32ppc	;;
+esac
+
+
 platformo=$object/"$platform".o
 lds=$object/zImage.lds
 ext=strip
···
 pseries)
     platformo="$object/pseries-head.o $object/of.o $object/epapr.o"
     link_address='0x4000000'
+    if [ "$format" != "elf32ppc" ]; then
+	link_address=
+	pie=-pie
+    fi
     make_space=n
     ;;
 maple)
···
     if [ -n "$link_address" ] ; then
         text_start="-Ttext $link_address"
     fi
-    ${CROSS}ld -m elf32ppc -T $lds $text_start $pie -o "$ofile" \
+    ${CROSS}ld -m $format -T $lds $text_start $pie -o "$ofile" \
 	$platformo $tmp $object/wrapper.a
     rm $tmp
 fi

arch/powerpc/boot/zImage.lds.S

···
+#include <asm-generic/vmlinux.lds.h>
+
+#ifdef CONFIG_PPC64_BOOT_WRAPPER
+OUTPUT_ARCH(powerpc:common64)
+#else
 OUTPUT_ARCH(powerpc:common)
+#endif
 ENTRY(_zimage_start)
 EXTERN(_zimage_start)
 SECTIONS
···
     *(.rodata*)
     *(.data*)
     *(.sdata*)
+#ifndef CONFIG_PPC64_BOOT_WRAPPER
     *(.got2)
+#endif
   }
   .dynsym : { *(.dynsym) }
   .dynstr : { *(.dynstr) }
···
   }
   .hash : { *(.hash) }
   .interp : { *(.interp) }
-  .rela.dyn : { *(.rela*) }
+  .rela.dyn :
+  {
+#ifdef CONFIG_PPC64_BOOT_WRAPPER
+    __rela_dyn_start = .;
+#endif
+    *(.rela*)
+  }
 
   . = ALIGN(8);
   .kernel:dtb :
···
     *(.kernel:initrd)
     _initrd_end =  .;
   }
+
+#ifdef CONFIG_PPC64_BOOT_WRAPPER
+  .got :
+  {
+    __toc_start = .;
+    *(.got)
+    *(.toc)
+  }
+#endif
 
   . = ALIGN(4096);
   .bss       :

arch/powerpc/platforms/Kconfig.cputype

···
 
 config CPU_LITTLE_ENDIAN
 	bool "Build little endian kernel"
+	select PPC64_BOOT_WRAPPER
 	help
 	  Build a little endian kernel.
 
···
 	  little endian powerpc.
 
 endchoice
+
+config PPC64_BOOT_WRAPPER
+	def_bool n
+	depends on CPU_LITTLE_ENDIAN