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>

2 files changed, 10 insertions, 5 deletions

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 2a80c9de6eaf..cc8380b879fe 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 d27faa131796..abf4d65acf62 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