ARM: zImage: no need to get the decompressed size from the filesystem

In commit d239b1dc093d the hardcoded 4x estimate for the decompressed
kernel size was replaced by the exact Image file size and passed to
the linker as a symbol value.  Turns out that this is unneeded as the
size is already included at the end of the compressed piggy data.
For those compressed formats that don't include this data, the build
system already takes care of appending it using size_append in
scripts/Makefile.lib.  So let's use that instead.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Tony Lindgren <tony@atomide.com>

2 files changed, 16 insertions, 4 deletions

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 0c6852d93506..79b5c62746df 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -98,8 +98,6 @@ endif
 ccflags-y := -fpic -fno-builtin
 asflags-y := -Wa,-march=all
 
-# Provide size of uncompressed kernel to the decompressor via a linker symbol.
-LDFLAGS_vmlinux = --defsym _image_size=$(shell stat -c "%s" $(obj)/../Image)
 # Supply ZRELADDR to the decompressor via a linker symbol.
 ifneq ($(CONFIG_AUTO_ZRELADDR),y)
 LDFLAGS_vmlinux += --defsym zreladdr=$(ZRELADDR)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index d1fd1cfca9c2..b541217bd040 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -187,7 +187,7 @@ not_angel:
                 bl      cache_on
 
 restart:        adr     r0, LC0
-                ldmia   r0, {r1, r2, r3, r6, r9, r11, r12}
+                ldmia   r0, {r1, r2, r3, r6, r10, r11, r12}
                 ldr     sp, [r0, #28]
 
                 /*
@@ -196,6 +196,20 @@ restart:	adr	r0, LC0
                  */
                 sub     r0, r0, r1              @ calculate the delta offset
                 add     r6, r6, r0              @ _edata
+                add     r10, r10, r0            @ inflated kernel size location
+
+                /*
+                 * The kernel build system appends the size of the
+                 * decompressed kernel at the end of the compressed data
+                 * in little-endian form.
+                 */
+                ldrb    r9, [r10, #0]
+                ldrb    lr, [r10, #1]
+                orr     r9, r9, lr, lsl #8
+                ldrb    lr, [r10, #2]
+                ldrb    r10, [r10, #3]
+                orr     r9, r9, lr, lsl #16
+                orr     r9, r9, r10, lsl #24
 
 #ifndef CONFIG_ZBOOT_ROM
                 /* malloc space is above the relocated stack (64k max) */
@@ -355,7 +369,7 @@ LC0:		.word	LC0			@ r1
                 .word   __bss_start             @ r2
                 .word   _end                    @ r3
                 .word   _edata                  @ r6
-                .word   _image_size             @ r9
+                .word   input_data_end - 4      @ r10 (inflated size location)
                 .word   _got_start              @ r11
                 .word   _got_end                @ ip
                 .word   user_stack_end          @ sp