sparc64: Add HAVE_FUNCTION_TRACE_MCOUNT_TEST and tidy up.

Check function_trace_stop at ftrace_caller

Toss mcount_call and dummy call of ftrace_stub, unnecessary.

Document problems we'll have if the final kernel image link
ever turns on relaxation.

Properly size 'ftrace_call' so it looks right when inspecting
instructions under gdb et al.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 7 deletions

diff --git a/arch/sparc/lib/mcount.S b/arch/sparc/lib/mcount.S
index 24b8b12deed2..7047997be0eb 100644
--- a/arch/sparc/lib/mcount.S
+++ b/arch/sparc/lib/mcount.S
@@ -96,13 +96,12 @@ mcount:
 #endif
 #ifdef CONFIG_FUNCTION_TRACER
 #ifdef CONFIG_DYNAMIC_FTRACE
-        mov             %o7, %o0
-        .globl          mcount_call
-mcount_call:
-        call            ftrace_stub
-         mov            %o0, %o7
+        /* Do nothing, the retl/nop below is all we need.  */
 #else
-        sethi           %hi(ftrace_trace_function), %g1
+        sethi           %hi(function_trace_stop), %g1
+        lduw            [%g1 + %lo(function_trace_stop)], %g2
+        brnz,pn         %g2, 1f
+         sethi          %hi(ftrace_trace_function), %g1
         sethi           %hi(ftrace_stub), %g2
         ldx             [%g1 + %lo(ftrace_trace_function)], %g1
         or              %g2, %lo(ftrace_stub), %g2
@@ -131,14 +130,23 @@ ftrace_stub:
         .globl          ftrace_caller
         .type           ftrace_caller,#function
 ftrace_caller:
+        sethi           %hi(function_trace_stop), %g1
         mov             %i7, %o1
-        mov             %o7, %o0
+        lduw            [%g1 + %lo(function_trace_stop)], %g2
+        brnz,pn         %g2, ftrace_stub
+         mov            %o7, %o0
         .globl          ftrace_call
 ftrace_call:
+        /* If the final kernel link ever turns on relaxation, we'll need
+         * to do something about this tail call.  Otherwise the linker
+         * will rewrite the call into a branch and nop out the move
+         * instruction.
+         */
         call            ftrace_stub
          mov            %o0, %o7
         retl
          nop
+        .size           ftrace_call,.-ftrace_call
         .size           ftrace_caller,.-ftrace_caller
 #endif
 #endif