[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, 11 insertions, 7 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 5f0c4fba87c3..08844fc24a2e 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -61,22 +61,25 @@ STACK_SIZE  = 1 << STACK_SHIFT
 
 #ifdef CONFIG_TRACE_IRQFLAGS
         .macro  TRACE_IRQS_ON
-        l       %r1,BASED(.Ltrace_irq_on)
+        basr    %r2,%r0
+        l       %r1,BASED(.Ltrace_irq_on_caller)
         basr    %r14,%r1
         .endm
 
         .macro  TRACE_IRQS_OFF
-        l       %r1,BASED(.Ltrace_irq_off)
+        basr    %r2,%r0
+        l       %r1,BASED(.Ltrace_irq_off_caller)
         basr    %r14,%r1
         .endm
 
         .macro  TRACE_IRQS_CHECK
+        basr    %r2,%r0
         tm      SP_PSW(%r15),0x03       # irqs enabled?
         jz      0f
-        l       %r1,BASED(.Ltrace_irq_on)
+        l       %r1,BASED(.Ltrace_irq_on_caller)
         basr    %r14,%r1
         j       1f
-0:      l       %r1,BASED(.Ltrace_irq_off)
+0:      l       %r1,BASED(.Ltrace_irq_off_caller)
         basr    %r14,%r1
 1:
         .endm
@@ -1113,9 +1116,10 @@ cleanup_io_leave_insn:
 .Lschedtail:    .long   schedule_tail
 .Lsysc_table:   .long   sys_call_table
 #ifdef CONFIG_TRACE_IRQFLAGS
-.Ltrace_irq_on: .long   trace_hardirqs_on
-.Ltrace_irq_off:
-                .long   trace_hardirqs_off
+.Ltrace_irq_on_caller:
+                .long   trace_hardirqs_on_caller
+.Ltrace_irq_off_caller:
+                .long   trace_hardirqs_off_caller
 #endif
 #ifdef CONFIG_LOCKDEP
 .Llockdep_sys_exit: