[S390] ftrace: fix kernel stack backchain walking

With CONFIG_IRQSOFF_TRACER the trace_hardirqs_off() function includes
a call to __builtin_return_address(1). But we calltrace_hardirqs_off()
from early entry code. There we have just a single stack frame.
So this results in a kernel stack backchain walk that would walk beyond
the kernel stack. Following the NULL terminated backchain this results
in a lowcore read access.

To fix this we simply call trace_hardirqs_off_caller() and pass the
current instruction pointer.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/arch/s390/kernel/entry64.S b/arch/s390/kernel/entry64.S
index d7ce150453f2..41aca06682aa 100644
--- a/arch/s390/kernel/entry64.S
+++ b/arch/s390/kernel/entry64.S
@@ -61,19 +61,22 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
 
 #ifdef CONFIG_TRACE_IRQFLAGS
         .macro  TRACE_IRQS_ON
-         brasl  %r14,trace_hardirqs_on
+         basr   %r2,%r0
+         brasl  %r14,trace_hardirqs_on_caller
         .endm
 
         .macro  TRACE_IRQS_OFF
-         brasl  %r14,trace_hardirqs_off
+         basr   %r2,%r0
+         brasl  %r14,trace_hardirqs_off_caller
         .endm
 
         .macro TRACE_IRQS_CHECK
+        basr    %r2,%r0
         tm      SP_PSW(%r15),0x03       # irqs enabled?
         jz      0f
-        brasl   %r14,trace_hardirqs_on
+        brasl   %r14,trace_hardirqs_on_caller
         j       1f
-0:      brasl   %r14,trace_hardirqs_off
+0:      brasl   %r14,trace_hardirqs_off_caller
 1:
         .endm
 #else