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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2018-04-27 07:36:55 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-04-29 07:50:03 +0200
commitbbf89d7832ed4b94b7d689165f90dc38bba350ca (patch)
tree7e79bad6f23886f7d279874ec23c6f5079db6bef /arch
parentf3303788c0514ef43151b7272c7309740ed88dc8 (diff)
s390: do not bypass BPENTER for interrupt system calls
[ Upstream commit d5feec04fe578c8dbd9e2e1439afc2f0af761ed4 ] The system call path can be interrupted before the switch back to the standard branch prediction with BPENTER has been done. The critical section cleanup code skips forward to .Lsysc_do_svc and bypasses the BPENTER. In this case the kernel and all subsequent code will run with the limited branch prediction. Fixes: eacf67eb9b32 ("s390: run user space and KVM guests with modified branch prediction") Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/kernel/entry.S3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index beda1c33ca12..2c71cdf2a4f0 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -1299,7 +1299,8 @@ cleanup_critical:
srag %r9,%r9,23
jz 0f
mvc __TI_last_break(8,%r12),16(%r11)
-0: # set up saved register r11
+0: BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP
+ # set up saved register r11
lg %r15,__LC_KERNEL_STACK
la %r9,STACK_FRAME_OVERHEAD(%r15)
stg %r9,24(%r11) # r11 pt_regs pointer