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linux-next/drivers/s390
Martin Schwidefsky f19fbd5ed6 s390: introduce execute-trampolines for branches
Add CONFIG_EXPOLINE to enable the use of the new -mindirect-branch= and
-mfunction_return= compiler options to create a kernel fortified against
the specte v2 attack.

With CONFIG_EXPOLINE=y all indirect branches will be issued with an
execute type instruction. For z10 or newer the EXRL instruction will
be used, for older machines the EX instruction. The typical indirect
call

	basr	%r14,%r1

is replaced with a PC relative call to a new thunk

	brasl	%r14,__s390x_indirect_jump_r1

The thunk contains the EXRL/EX instruction to the indirect branch

__s390x_indirect_jump_r1:
	exrl	0,0f
	j	.
0:	br	%r1

The detour via the execute type instruction has a performance impact.
To get rid of the detour the new kernel parameter "nospectre_v2" and
"spectre_v2=[on,off,auto]" can be used. If the parameter is specified
the kernel and module code will be patched at runtime.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2018-02-07 15:57:02 +01:00
..
block Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2018-02-01 09:31:04 -08:00
char s390: introduce execute-trampolines for branches 2018-02-07 15:57:02 +01:00
cio s390/cio: fix kernel-doc usage 2018-02-05 07:34:52 +01:00
crypto treewide: Use DEVICE_ATTR_RO 2018-01-09 16:34:34 +01:00
net s390/qeth: support early setup for z/VM NICs 2018-01-02 13:52:23 -05:00
scsi s390: add a few more SPDX identifiers 2017-12-05 07:51:09 +01:00
virtio s390: drivers: Remove redundant license text 2017-11-24 14:28:47 +01:00
Makefile s390: add a few more SPDX identifiers 2017-12-05 07:51:09 +01:00