[S390] ftrace: add function trace mcount test support

Add support for early test if the function tracer is enabled or
disabled. Saves some extra function calls.

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

2 files changed, 27 insertions, 12 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index b674e79044a0..480590f21570 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -82,6 +82,7 @@ config S390
         select USE_GENERIC_SMP_HELPERS if SMP
         select HAVE_SYSCALL_WRAPPERS
         select HAVE_FUNCTION_TRACER
+        select HAVE_FUNCTION_TRACE_MCOUNT_TEST
         select HAVE_FTRACE_MCOUNT_RECORD
         select HAVE_DYNAMIC_FTRACE
         select HAVE_DEFAULT_NO_SPIN_MUTEXES
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index de274996f640..0aa85ec94d08 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -21,6 +21,9 @@ _mcount:
 
         .globl ftrace_caller
 ftrace_caller:
+        larl    %r1,function_trace_stop
+        icm     %r1,0xf,0(%r1)
+        bnzr    %r14
         stmg    %r2,%r5,32(%r15)
         stg     %r14,112(%r15)
         lgr     %r1,%r15
@@ -46,6 +49,9 @@ ftrace_dyn_func:
 
         .globl _mcount
 _mcount:
+        larl    %r1,function_trace_stop
+        icm     %r1,0xf,0(%r1)
+        bnzr    %r14
         stmg    %r2,%r5,32(%r15)
         stg     %r14,112(%r15)
         lgr     %r1,%r15
@@ -74,21 +80,25 @@ _mcount:
         .globl ftrace_caller
 ftrace_caller:
         stm     %r2,%r5,16(%r15)
+        bras    %r1,2f
+0:      .long   ftrace_trace_function
+1:      .long   function_trace_stop
+2:      l       %r2,1b-0b(%r1)
+        icm     %r2,0xf,0(%r2)
+        jnz     3f
         st      %r14,56(%r15)
-        lr      %r1,%r15
+        lr      %r0,%r15
         ahi     %r15,-96
         l       %r3,100(%r15)
         la      %r2,0(%r14)
-        st      %r1,__SF_BACKCHAIN(%r15)
+        st      %r0,__SF_BACKCHAIN(%r15)
         la      %r3,0(%r3)
-        bras    %r14,0f
-        .long   ftrace_dyn_func
-0:      l       %r14,0(%r14)
+        l       %r14,0b-0b(%r1)
         l       %r14,0(%r14)
         basr    %r14,%r14
         ahi     %r15,96
-        lm      %r2,%r5,16(%r15)
         l       %r14,56(%r15)
+3:      lm      %r2,%r5,16(%r15)
         br      %r14
 
         .data
@@ -102,21 +112,25 @@ ftrace_dyn_func:
         .globl _mcount
 _mcount:
         stm     %r2,%r5,16(%r15)
+        bras    %r1,2f
+0:      .long   ftrace_trace_function
+1:      .long   function_trace_stop
+2:      l       %r2,1b-0b(%r1)
+        icm     %r2,0xf,0(%r2)
+        jnz     3f
         st      %r14,56(%r15)
-        lr      %r1,%r15
+        lr      %r0,%r15
         ahi     %r15,-96
         l       %r3,100(%r15)
         la      %r2,0(%r14)
-        st      %r1,__SF_BACKCHAIN(%r15)
+        st      %r0,__SF_BACKCHAIN(%r15)
         la      %r3,0(%r3)
-        bras    %r14,0f
-        .long   ftrace_trace_function
-0:      l       %r14,0(%r14)
+        l       %r14,0b-0b(%r1)
         l       %r14,0(%r14)
         basr    %r14,%r14
         ahi     %r15,96
-        lm      %r2,%r5,16(%r15)
         l       %r14,56(%r15)
+3:      lm      %r2,%r5,16(%r15)
         br      %r14
 
 #endif /* CONFIG_DYNAMIC_FTRACE */