ARM: Auto calculate ZRELADDR and provide option for exceptions

As long as the zImage is placed within the 128MB range from the start of
memory, ZRELADDR (Address where the decompressed kernel will be placed,
usually == PHYS_OFFSET + TEXT_OFFSET) can be determined at run-time by
masking PC with 0xf80000000.

Running through all the Makefile.boot, all those zreladdr-y
addresses == 0x[0-f][08]00_0000 + TEXT_OFFSET can be determined at
run-time.

Option CONFIG_AUTO_ZRELADDR and CONFIG_ZRELADDR are introduced,
CONFIG_ZRELADDR _must_ be explicitly specified if:

- ((zreladdr-y - TEXT_OFFSET) & ~0xf8000000) != 0, which means
  masking PC with 0xf8000000 will result in an incorrect address.
  Currently this is only a problem on u300.

- or the assumption of the zImage being loaded by the bootloader within
  the first 128MB of RAM is incorrect

- or when ZBOOT_ROM is used, where the above assumption is usually wrong.

[ukleinek: changed mask from 0xf0000000 to 0xf8000000 for mx1 and shark
+ some review fixes from the mailing list]

Original-Idea-and-Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Eric Miao <eric.miao@canonical.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

3 files changed, 13 insertions, 10 deletions

diff --git a/arch/arm/boot/Makefile b/arch/arm/boot/Makefile
index 4a590f4..f705213 100644
--- a/arch/arm/boot/Makefile
+++ b/arch/arm/boot/Makefile
@@ -14,18 +14,16 @@
 MKIMAGE         := $(srctree)/scripts/mkuboot.sh
 
 ifneq ($(MACHINE),)
-include $(srctree)/$(MACHINE)/Makefile.boot
+-include $(srctree)/$(MACHINE)/Makefile.boot
 endif
 
 # Note: the following conditions must always be true:
-#   ZRELADDR == virt_to_phys(PAGE_OFFSET + TEXT_OFFSET)
 #   PARAMS_PHYS must be within 4MB of ZRELADDR
 #   INITRD_PHYS must be in RAM
-ZRELADDR    := $(zreladdr-y)
 PARAMS_PHYS := $(params_phys-y)
 INITRD_PHYS := $(initrd_phys-y)
 
-export ZRELADDR INITRD_PHYS PARAMS_PHYS
+export INITRD_PHYS PARAMS_PHYS
 
 targets := Image zImage xipImage bootpImage uImage
 
@@ -67,7 +65,7 @@ quiet_cmd_uimage = UIMAGE  $@
 ifeq ($(CONFIG_ZBOOT_ROM),y)
 $(obj)/uImage: LOADADDR=$(CONFIG_ZBOOT_ROM_TEXT)
 else
-$(obj)/uImage: LOADADDR=$(ZRELADDR)
+$(obj)/uImage: LOADADDR=$(CONFIG_ZRELADDR)
 endif
 
 ifeq ($(CONFIG_THUMB2_KERNEL),y)
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 2a80c9d..cc8380b 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -4,6 +4,7 @@
 # create a compressed vmlinuz image from the original vmlinux
 #
 
+AFLAGS_head.o += -DTEXT_OFFSET=$(TEXT_OFFSET)
 HEAD	= head.o
 OBJS	= misc.o decompress.o
 FONTC	= $(srctree)/drivers/video/console/font_acorn_8x8.c
@@ -79,8 +80,6 @@ endif
 EXTRA_CFLAGS  := -fpic -fno-builtin
 EXTRA_AFLAGS  := -Wa,-march=all
 
-# Supply ZRELADDR to the decompressor via a linker symbol.
-LDFLAGS_vmlinux := --defsym zreladdr=$(ZRELADDR)
 ifeq ($(CONFIG_CPU_ENDIAN_BE8),y)
 LDFLAGS_vmlinux += --be8
 endif
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index d27faa1..abf4d65 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -170,9 +170,16 @@ not_angel:
 
 		.text
 		adr	r0, LC0
- ARM(		ldmia	r0, {r1, r2, r3, r4, r5, r6, r11, ip, sp})
- THUMB(		ldmia	r0, {r1, r2, r3, r4, r5, r6, r11, ip}	)
+ ARM(		ldmia	r0, {r1, r2, r3, r5, r6, r11, ip, sp})
+ THUMB(		ldmia	r0, {r1, r2, r3, r5, r6, r11, ip}	)
  THUMB(		ldr	sp, [r0, #32]				)
+#ifdef CONFIG_AUTO_ZRELADDR
+		@ determine final kernel image address
+		and	r4, pc, #0xf8000000
+		add	r4, r4, #TEXT_OFFSET
+#else
+		ldr	r4, =CONFIG_ZRELADDR
+#endif
 		subs	r0, r0, r1		@ calculate the delta offset
 
 						@ if delta is zero, we are
@@ -310,7 +317,6 @@ wont_overwrite:	mov	r0, r4
 LC0:		.word	LC0			@ r1
 		.word	__bss_start		@ r2
 		.word	_end			@ r3
-		.word	zreladdr		@ r4
 		.word	_start			@ r5
 		.word	_image_size		@ r6
 		.word	_got_start		@ r11