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s390/boot: fix use of expolines in the DMA code

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The DMA code section of the decompressor must be compiled with expolines
if Spectre V2 mitigation has been enabled for the decompressed kernel.
This is required because although the decompressor's image contains
the DMA code section, it is handed over to the decompressed kernel for use.

Because the DMA code is already slow w/o expolines, use expolines always
regardless whether the decompressed kernel is using them or not. This
simplifies the DMA code by dropping the conditional compilation of
expolines.

Fixes: bf72630130 ("s390: use proper expoline sections for .dma code")
Cc: <stable@vger.kernel.org> # 5.2
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Alexander Egorenkov 2021-07-16 22:00:22 +02:00 committed by Heiko Carstens
parent f8c2602733
commit 463f36c76f
1 changed files with 4 additions and 15 deletions
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19
arch/s390/boot/text_dma.S
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@ -9,16 +9,6 @@
#include <asm/errno.h>
#include <asm/sigp.h>
#ifdef CC_USING_EXPOLINE
.pushsection .dma.text.__s390_indirect_jump_r14,"axG"
__dma__s390_indirect_jump_r14:
larl %r1,0f
ex 0,0(%r1)
j .
0: br %r14
.popsection
#endif
.section .dma.text,"ax"
/*
* Simplified version of expoline thunk. The normal thunks can not be used here,
@ -27,11 +17,10 @@ __dma__s390_indirect_jump_r14:
* affects a few functions that are not performance-relevant.
*/
.macro BR_EX_DMA_r14
#ifdef CC_USING_EXPOLINE
jg __dma__s390_indirect_jump_r14
#else
br %r14
#endif
larl %r1,0f
ex 0,0(%r1)
j .
0: br %r14
.endm
/*