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Commit f88f06e1 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Greg Kroah-Hartman
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arm64: assembler: make adr_l work in modules under KASLR 




[ Upstream commit 41c066f2c4d436c535616fe182331766c57838f0 ]

When CONFIG_RANDOMIZE_MODULE_REGION_FULL=y, the offset between loaded
modules and the core kernel may exceed 4 GB, putting symbols exported
by the core kernel out of the reach of the ordinary adrp/add instruction
pairs used to generate relative symbol references. So make the adr_l
macro emit a movz/movk sequence instead when executing in module context.

While at it, remove the pointless special case for the stack pointer.

Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarSasha Levin <alexander.levin@verizon.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent aabb797b

arch/arm64/include/asm/assembler.h

+27 −9
Original line number Diff line number Diff line
@@ -155,22 +155,25 @@ lr .req x30 // link register 


/*

 * Pseudo-ops for PC-relative adr/ldr/str <reg>, <symbol> where

 * <symbol> is within the range +/- 4 GB of the PC.

 * <symbol> is within the range +/- 4 GB of the PC when running

 * in core kernel context. In module context, a movz/movk sequence

 * is used, since modules may be loaded far away from the kernel

 * when KASLR is in effect.

 */

	/*

	 * @dst: destination register (64 bit wide)

	 * @sym: name of the symbol

	 * @tmp: optional scratch register to be used if <dst> == sp, which

	 *       is not allowed in an adrp instruction

	 */

	.macro	adr_l, dst, sym, tmp=

	.ifb	\tmp

	.macro	adr_l, dst, sym

#ifndef MODULE

	adrp	\dst, \sym

	add	\dst, \dst, :lo12:\sym

	.else

	adrp	\tmp, \sym

	add	\dst, \tmp, :lo12:\sym

	.endif

#else

	movz	\dst, #:abs_g3:\sym

	movk	\dst, #:abs_g2_nc:\sym

	movk	\dst, #:abs_g1_nc:\sym

	movk	\dst, #:abs_g0_nc:\sym

#endif

	.endm



	/*
@@ -181,6 +184,7 @@ lr .req x30 // link register 
	 *       the address

	 */

	.macro	ldr_l, dst, sym, tmp=

#ifndef MODULE

	.ifb	\tmp

	adrp	\dst, \sym

	ldr	\dst, [\dst, :lo12:\sym]
@@ -188,6 +192,15 @@ lr .req x30 // link register 
	adrp	\tmp, \sym

	ldr	\dst, [\tmp, :lo12:\sym]

	.endif

#else

	.ifb	\tmp

	adr_l	\dst, \sym

	ldr	\dst, [\dst]

	.else

	adr_l	\tmp, \sym

	ldr	\dst, [\tmp]

	.endif

#endif

	.endm



	/*
@@ -197,8 +210,13 @@ lr .req x30 // link register 
	 *       while <src> needs to be preserved.

	 */

	.macro	str_l, src, sym, tmp

#ifndef MODULE

	adrp	\tmp, \sym

	str	\src, [\tmp, :lo12:\sym]

#else

	adr_l	\tmp, \sym

	str	\src, [\tmp]

#endif

	.endm



	/*