linux-kernel - [PATCH 5/8] arm64: kernel: replace early 64-bit literal loads with move-immediates

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Date:	Mon, 18 Apr 2016 17:09:45 +0200
From:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	will.deacon@....com, mark.rutland@....com, james.morse@....com
Cc:	catalin.marinas@....com, Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [PATCH 5/8] arm64: kernel: replace early 64-bit literal loads with move-immediates

When building a relocatable kernel, we currently rely on the fact that
early 64-bit literal loads need to be deferred to after the relocation
has been performed only if they involve symbol references, and not if
they involve assemble time constants. While this is not an unreasonable
assumption to make, it is better to switch to movk/movz sequences, since
these are guaranteed to be resolved at link time, simply because there are
no dynamic relocation types to describe them.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 arch/arm64/kernel/head.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 0d487d90d221..dae9cabaadf5 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -337,7 +337,7 @@ __create_page_tables:
 	cmp	x0, x6
 	b.lo	1b
 
-	ldr	x7, =SWAPPER_MM_MMUFLAGS
+	mov	x7, SWAPPER_MM_MMUFLAGS
 
 	/*
 	 * Create the identity mapping.
@@ -393,7 +393,7 @@ __create_page_tables:
 	 * Map the kernel image (starting with PHYS_OFFSET).
 	 */
 	mov	x0, x26				// swapper_pg_dir
-	ldr	x5, =KIMAGE_VADDR
+	mov_q	x5, KIMAGE_VADDR
 	add	x5, x5, x23			// add KASLR displacement
 	create_pgd_entry x0, x5, x3, x6
 	ldr	w6, =kernel_img_size
@@ -631,7 +631,7 @@ ENTRY(secondary_holding_pen)
 	bl	el2_setup			// Drop to EL1, w20=cpu_boot_mode
 	bl	set_cpu_boot_mode_flag
 	mrs	x0, mpidr_el1
-	ldr     x1, =MPIDR_HWID_BITMASK
+	mov_q	x1, MPIDR_HWID_BITMASK
 	and	x0, x0, x1
 	adr_l	x3, secondary_holding_pen_release
 pen:	ldr	x4, [x3]
@@ -773,7 +773,7 @@ __primary_switch:
 	ldr	w9, =__rela_offset		// offset to reloc table
 	ldr	w10, =__rela_size		// size of reloc table
 
-	ldr	x11, =KIMAGE_VADDR		// default virtual offset
+	mov_q	x11, KIMAGE_VADDR		// default virtual offset
 	add	x11, x11, x23			// actual virtual offset
 	add	x8, x8, x11			// __va(.dynsym)
 	add	x9, x9, x11			// __va(.rela)
-- 
2.5.0