tile: ftrace: fix function_graph tracer issues

- Add support for ARCH_SUPPORTS_FTRACE_OPS
- Replace the instruction in ftrace_call with the bundle {move r10, lr;
jal ftrace_stub}, so that the lr contains the right value after returning
from ftrace_stub.  An alternative fix might be to leave the instruction
in ftrace_call alone when it is being updated with ftrace_stub.

Signed-off-by: Tony Lu <zlu@ezchip.com>
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>

3 files changed, 13 insertions, 2 deletions

diff --git a/arch/tile/include/asm/ftrace.h b/arch/tile/include/asm/ftrace.h
index 13a9bb81a8ab..738d239b792f 100644
--- a/arch/tile/include/asm/ftrace.h
+++ b/arch/tile/include/asm/ftrace.h
@@ -23,6 +23,8 @@
 #ifndef __ASSEMBLY__
 extern void __mcount(void);
 
+#define ARCH_SUPPORTS_FTRACE_OPS 1
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
diff --git a/arch/tile/kernel/ftrace.c b/arch/tile/kernel/ftrace.c
index 8d52d83cc516..0c0996175b1e 100644
--- a/arch/tile/kernel/ftrace.c
+++ b/arch/tile/kernel/ftrace.c
@@ -74,7 +74,11 @@ static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
                         create_JumpOff_X1(pcrel_by_instr);
         }
 
-        if (addr == FTRACE_ADDR) {
+        /*
+         * Also put { move r10, lr; jal ftrace_stub } in a bundle, which
+         * is used to replace the instruction in address ftrace_call.
+         */
+        if (addr == FTRACE_ADDR || addr == (unsigned long)ftrace_stub) {
                 /* opcode: or r10, lr, zero */
                 opcode_x0 =
                         create_Dest_X0(10) |
diff --git a/arch/tile/kernel/mcount_64.S b/arch/tile/kernel/mcount_64.S
index 3c2b8d5e1d1a..6c6702451962 100644
--- a/arch/tile/kernel/mcount_64.S
+++ b/arch/tile/kernel/mcount_64.S
@@ -81,7 +81,12 @@ STD_ENTRY(ftrace_caller)
 
         /* arg1: self return address */
         /* arg2: parent's return address */
-        { move  r0, lr; move    r1, r10 }
+        /* arg3: ftrace_ops */
+        /* arg4: regs (but make it NULL) */
+        { move  r0, lr;  moveli        r2, hw2_last(function_trace_op) }
+        { move  r1, r10; shl16insli    r2, r2, hw1(function_trace_op) }
+        { movei r3, 0;   shl16insli    r2, r2, hw0(function_trace_op) }
+        ld      r2,r2
 
         .global ftrace_call
 ftrace_call: