Subject: [RFC v3 PATCH 2/4] Build files needed for relocation support

From: Mohan Kumar M <[email-masked]>
Date: Fri, 18 Jul 2008 00:12:19 +0530

Build files needed for relocation

This patch builds vmlinux file with relocation sections and contents so
that relocs user space program can extract the required relocation
offsets. This packs final relocatable vmlinux kernel as following:
earlier part of relocation apply code, vmlinux, rest of relocation apply
code.

TODO:
Relocatable vmlinux image is built in arch/powerpc/boot as vmlinux.reloc.
But it should be built in top level directory of kernel source as vmlinux
instead of vmlinux.reloc

Signed-off-by: Mohan Kumar M <[email-masked]>
---
 arch/powerpc/Kconfig            |   15 ++++++++++++---
 arch/powerpc/Makefile           |    9 +++++++--
 arch/powerpc/boot/Makefile      |   39 ++++++++++++++++++++++++++++++++++++---
 arch/powerpc/boot/vmlinux.lds.S |   28 ++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 8 deletions(-)

Index: linux-2.6.26/arch/powerpc/Kconfig
===================================================================
--- linux-2.6.26.orig/arch/powerpc/Kconfig
+++ linux-2.6.26/arch/powerpc/Kconfig
@@ -317,6 +317,15 @@ config CRASH_DUMP
 
 	  Don't change this unless you know what you are doing.
 
+config RELOCATABLE_PPC64
+	bool "Build a relocatable kernel (EXPERIMENTAL)"
+	depends on PPC_MULTIPLATFORM && PPC64 && CRASH_DUMP && EXPERIMENTAL
+	help
+	  Build a kernel suitable for use as regular kernel and kdump capture
+	  kernel.
+
+	  Don't change this unless you know what you are doing.
+
 config PHYP_DUMP
 	bool "Hypervisor-assisted dump (EXPERIMENTAL)"
 	depends on PPC_PSERIES && EXPERIMENTAL
@@ -656,7 +665,7 @@ config LOWMEM_SIZE
 	default "0x30000000"
 
 config RELOCATABLE
-	bool "Build a relocatable kernel (EXPERIMENTAL)"
+	bool "Build relocatable kernel (EXPERIMENTAL)"
 	depends on EXPERIMENTAL && ADVANCED_OPTIONS && FLATMEM && FSL_BOOKE
 	help
 	  This builds a kernel image that is capable of running at the
@@ -776,11 +785,11 @@ config PAGE_OFFSET
 	default "0xc000000000000000"
 config KERNEL_START
 	hex
-	default "0xc000000002000000" if CRASH_DUMP
+	default "0xc000000002000000" if CRASH_DUMP && !RELOCATABLE_PPC64
 	default "0xc000000000000000"
 config PHYSICAL_START
 	hex
-	default "0x02000000" if CRASH_DUMP
+	default "0x02000000" if CRASH_DUMP && !RELOCATABLE_PPC64
 	default "0x00000000"
 endif
 
Index: linux-2.6.26/arch/powerpc/Makefile
===================================================================
--- linux-2.6.26.orig/arch/powerpc/Makefile
+++ linux-2.6.26/arch/powerpc/Makefile
@@ -69,7 +69,7 @@ override CC	+= -m$(CONFIG_WORD_SIZE)
 override AR	:= GNUTARGET=elf$(CONFIG_WORD_SIZE)-powerpc $(AR)
 endif
 
-LDFLAGS_vmlinux	:= -Bstatic
+LDFLAGS_vmlinux	:= --emit-relocs
 
 CFLAGS-$(CONFIG_PPC64)	:= -mminimal-toc -mtraceback=none  -mcall-aixdesc
 CFLAGS-$(CONFIG_PPC32)	:= -ffixed-r2 -mmultiple
@@ -152,11 +152,16 @@ core-$(CONFIG_KVM) 		+= arch/powerpc/kvm
 drivers-$(CONFIG_OPROFILE)	+= arch/powerpc/oprofile/
 
 # Default to zImage, override when needed
+
+ifneq ($(CONFIG_RELOCATABLE_PPC64),y)
 all: zImage
+else
+all: zImage vmlinux.reloc
+endif
 
 CPPFLAGS_vmlinux.lds	:= -Upowerpc
 
-BOOT_TARGETS = zImage zImage.initrd uImage zImage% dtbImage% treeImage.% cuImage.% simpleImage.%
+BOOT_TARGETS = zImage vmlinux.reloc zImage.initrd uImage zImage% dtbImage% treeImage.% cuImage.% simpleImage.%
 
 PHONY += $(BOOT_TARGETS)
 
Index: linux-2.6.26/arch/powerpc/boot/Makefile
===================================================================
--- linux-2.6.26.orig/arch/powerpc/boot/Makefile
+++ linux-2.6.26/arch/powerpc/boot/Makefile
@@ -17,7 +17,7 @@
 #	CROSS32_COMPILE is setup as a prefix just like CROSS_COMPILE
 #	in the toplevel makefile.
 
-all: $(obj)/zImage
+all: $(obj)/zImage $(obj)/vmlinux.reloc
 
 BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
 		 -fno-strict-aliasing -Os -msoft-float -pipe \
@@ -120,18 +120,51 @@ $(patsubst %.S,%.o, $(filter %.S, $(src-
 $(obj)/wrapper.a: $(obj-wlib) FORCE
 	$(call if_changed,bootar)
 
-hostprogs-y	:= addnote addRamDisk hack-coff mktree dtc
+hostprogs-y	:= addnote addRamDisk hack-coff mktree dtc relocs
 
 targets		+= $(patsubst $(obj)/%,%,$(obj-boot) wrapper.a)
 extra-y		:= $(obj)/wrapper.a $(obj-plat) $(obj)/empty.o \
 		   $(obj)/zImage.lds $(obj)/zImage.coff.lds $(obj)/zImage.ps3.lds
 
+ifeq ($(CONFIG_RELOCATABLE_PPC64),y)
+extra-y		+= $(obj)/vmlinux.lds
+endif
+
 dtstree		:= $(srctree)/$(src)/dts
 
 wrapper		:=$(srctree)/$(src)/wrapper
-wrapperbits	:= $(extra-y) $(addprefix $(obj)/,addnote hack-coff mktree dtc) \
+wrapperbits	:= $(extra-y) $(addprefix $(obj)/,addnote hack-coff mktree dtc relocs) \
 			$(wrapper) FORCE
 
+ifeq ($(CONFIG_RELOCATABLE_PPC64),y)
+
+targets +=  vmlinux.offsets vmlinux.bin vmlinux.bin.all vmlinux.reloc.elf vmlinux.reloc reloc_apply.o vmlinux.lds
+
+OBJCOPYFLAGS_vmlinux.bin :=  -O binary -R .note -R .comment -S
+$(obj)/vmlinux.bin: vmlinux FORCE
+	$(call if_changed,objcopy)
+
+quiet_cmd_relocbin = BUILD   $@
+      cmd_relocbin = cat $(filter-out FORCE,$^) > $@
+
+quiet_cmd_relocs = RELOCS   $@
+    cmd_relocs = $(obj)/relocs $< > $@
+
+$(obj)/vmlinux.offsets: vmlinux $(obj)/relocs FORCE
+	$(call if_changed,relocs)
+
+$(obj)/vmlinux.bin.all: $(obj)/vmlinux.bin $(obj)/vmlinux.offsets FORCE
+	$(call if_changed,relocbin)
+
+LDFLAGS_vmlinux.reloc.elf := -T $(obj)/vmlinux.reloc.scr -r --format binary --oformat elf64-powerpc
+$(obj)/vmlinux.reloc.elf: $(obj)/vmlinux.bin.all FORCE
+	$(call if_changed,ld)
+
+LDFLAGS_vmlinux.reloc := -T $(obj)/vmlinux.lds
+$(obj)/vmlinux.reloc: $(obj)/reloc_apply.o $(obj)/vmlinux.reloc.elf FORCE
+	$(call if_changed,ld)
+endif
+
 #############
 # Bits for building dtc
 # DTC_GENPARSER      := 1    # Uncomment to rebuild flex/bison output
Index: linux-2.6.26/arch/powerpc/boot/vmlinux.lds.S
===================================================================
--- /dev/null
+++ linux-2.6.26/arch/powerpc/boot/vmlinux.lds.S
@@ -0,0 +1,28 @@
+#include <asm/page.h>
+#include <asm-generic/vmlinux.lds.h>
+
+ENTRY(start_wrap)
+
+OUTPUT_ARCH(powerpc:common64)
+SECTIONS
+{
+	. = KERNELBASE;
+
+/*
+ * Text, read only data and other permanent read-only sections
+ */
+	/* Text and gots */
+	.text : {
+		_head = .;
+		*(.text.head)
+		_ehead = .;
+
+		_text = .;
+		*(.vmlinux)
+		_etext = .;
+
+		_reloc = .;
+		*(.text.reloc)
+		_ereloc = .;
+	}
+}