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Date: Sun,  3 Sep 2017 13:07:39 +0100
From: Ard Biesheuvel <ard.biesheuvel@...aro.org>
To: linux-arm-kernel@...ts.infradead.org,
	kernel-hardening@...ts.openwall.com
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Nicolas Pitre <nico@...aro.org>,
	Russell King <linux@...linux.org.uk>,
	Kees Cook <keescook@...omium.org>,
	Thomas Garnier <thgarnie@...gle.com>,
	Marc Zyngier <marc.zyngier@....com>,
	Mark Rutland <mark.rutland@....com>,
	Tony Lindgren <tony@...mide.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Dave Martin <dave.martin@....com>
Subject: [PATCH v2 11/29] ARM: head.S: use PC relative insn sequence to calculate PHYS_OFFSET

Replace the open coded arithmetic with a simple adr_l/sub pair. This
ensures these quantities are invariant under runtime relocation.

Cc: Russell King <linux@...linux.org.uk>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 arch/arm/kernel/head.S | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index f607e290ef4b..62c961849035 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -106,10 +106,8 @@ ENTRY(stext)
 #endif
 
 #ifndef CONFIG_XIP_KERNEL
-	adr	r3, 2f
-	ldmia	r3, {r4, r8}
-	sub	r4, r3, r4			@ (PHYS_OFFSET - PAGE_OFFSET)
-	add	r8, r8, r4			@ PHYS_OFFSET
+	adr_l	r8, _text			@ __pa(_text)
+	sub	r8, r8, #TEXT_OFFSET		@ PHYS_OFFSET
 #else
 	ldr	r8, =PLAT_PHYS_OFFSET		@ always constant in this case
 #endif
@@ -161,10 +159,6 @@ ENTRY(stext)
 1:	b	__enable_mmu
 ENDPROC(stext)
 	.ltorg
-#ifndef CONFIG_XIP_KERNEL
-2:	.long	.
-	.long	PAGE_OFFSET
-#endif
 
 /*
  * Setup the initial page tables.  We only setup the barest
-- 
2.11.0

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