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arm64: assembler: make adr_l work in modules under KASLR 

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: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Ard Biesheuvel 2017-01-11 14:54:53 +00:00 committed by Catalin Marinas
parent 69d012345a
commit 41c066f2c4
1 changed files with 27 additions and 9 deletions
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36
arch/arm64/include/asm/assembler.h
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@ -164,22 +164,25 @@ 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
/*
@ -190,6 +193,7 @@ 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]
@ -197,6 +201,15 @@ 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
/*
@ -206,8 +219,13 @@ 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
/*