Subject: [PATCH v4 3/5] ARM: decompressor: defer loading of the contents of the LC0 structure

From: Ard Biesheuvel <[email-masked]>
Date: Tue, 19 May 2020 18:26:43 +0200

The remaining contents of LC0 are only used after the point in the
decompressor startup code where we enter via 'wont_overwrite'. So
move the loading of the LC0 structure after it. This will allow us
to jump to wont_overwrite directly from the EFI stub, and execute
the decompressor in place at the offset it was loaded by the UEFI
firmware.

Signed-off-by: Ard Biesheuvel <[email-masked]>
Reviewed-by: Geert Uytterhoeven <[email-masked]>
Reviewed-by: Nicolas Pitre <[email-masked]>
---
 arch/arm/boot/compressed/head.S | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 5d712e2c0001..ce442ec5028a 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -299,10 +299,6 @@ restart:	adr	r0, LC1
 		add	sp, sp, r0
 		add	r6, r6, r0
 
-		adr	r0, LC0
-		ldmia	r0, {r1, r2, r3, r11, r12}
-		sub	r0, r0, r1		@ calculate the delta offset
-
 		get_inflated_image_size	r9, r10, lr
 
 #ifndef CONFIG_ZBOOT_ROM
@@ -320,9 +316,6 @@ restart:	adr	r0, LC1
 		mov	r5, #0			@ init dtb size to 0
 #ifdef CONFIG_ARM_APPENDED_DTB
 /*
- *   r0  = delta
- *   r2  = BSS start
- *   r3  = BSS end
  *   r4  = final kernel address (possibly with LSB set)
  *   r5  = appended dtb size (still unknown)
  *   r6  = _edata
@@ -330,8 +323,6 @@ restart:	adr	r0, LC1
  *   r8  = atags/device tree pointer
  *   r9  = size of decompressed image
  *   r10 = end of this image, including  bss/stack/malloc space if non XIP
- *   r11 = GOT start
- *   r12 = GOT end
  *   sp  = stack pointer
  *
  * if there are device trees (dtb) appended to zImage, advance r10 so that the
@@ -379,7 +370,6 @@ restart:	adr	r0, LC1
 		/* temporarily relocate the stack past the DTB work space */
 		add	sp, sp, r5
 
-		stmfd	sp!, {r0-r3, ip, lr}
 		mov	r0, r8
 		mov	r1, r6
 		mov	r2, r5
@@ -398,7 +388,6 @@ restart:	adr	r0, LC1
 		mov	r2, r5
 		bleq	atags_to_fdt
 
-		ldmfd	sp!, {r0-r3, ip, lr}
 		sub	sp, sp, r5
 #endif
 
@@ -535,6 +524,10 @@ dtb_check_done:
 		mov	pc, r0
 
 wont_overwrite:
+		adr	r0, LC0
+		ldmia	r0, {r1, r2, r3, r11, r12}
+		sub	r0, r0, r1		@ calculate the delta offset
+
 /*
  * If delta is zero, we are running at the address we were linked at.
  *   r0  = delta
-- 
2.17.1

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