riscv/ftrace: Add dynamic function graph tracer support

Once the function_graph tracer is enabled, a filtered function has the
following call sequence:

* ftracer_caller         ==> on/off by ftrace_make_call/ftrace_make_nop
* ftrace_graph_caller
* ftrace_graph_call      ==> on/off by ftrace_en/disable_ftrace_graph_caller
* prepare_ftrace_return

Considering the following DYNAMIC_FTRACE_WITH_REGS feature, it would be
more extendable to have a ftrace_graph_caller function, instead of
calling prepare_ftrace_return directly in ftrace_caller.

Cc: Greentime Hu <greentime@andestech.com>
Signed-off-by: Alan Kao <alankao@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index be4b243..5bbe1af 100644 (file)
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -139,4 +139,57 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
                return;
        *parent = return_hooker;
 }
-#endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+int ftrace_enable_ftrace_graph_caller(void)
+{
+       unsigned int call[2];
+       static int init_graph = 1;
+       int ret;
+
+       make_call(&ftrace_graph_call, &ftrace_stub, call);
+
+       /*
+        * When enabling graph tracer for the first time, ftrace_graph_call
+        * should contains a call to ftrace_stub.  Once it has been disabled,
+        * the 8-bytes at the position becomes NOPs.
+        */
+       if (init_graph) {
+               ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
+                                               call);
+               init_graph = 0;
+       } else {
+               ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
+                                               NULL);
+       }
+
+       if (ret)
+               return ret;
+
+       return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
+                                   (unsigned long)&prepare_ftrace_return, true);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+       unsigned int call[2];
+       int ret;
+
+       make_call(&ftrace_graph_call, &prepare_ftrace_return, call);
+
+       /*
+        * This is to make sure that ftrace_enable_ftrace_graph_caller
+        * did the right thing.
+        */
+       ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
+                                       call);
+
+       if (ret)
+               return ret;
+
+       return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
+                                   (unsigned long)&prepare_ftrace_return, false);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index a3ebead..739e07a 100644 (file)
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -14,18 +14,62 @@
        .text
 
        .macro SAVE_ABI_STATE
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+       addi    sp, sp, -48
+       sd      s0, 32(sp)
+       sd      ra, 40(sp)
+       addi    s0, sp, 48
+       sd      t0, 24(sp)
+       sd      t1, 16(sp)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+       sd      t2, 8(sp)
+#endif
+#else
        addi    sp, sp, -16
        sd      s0, 0(sp)
        sd      ra, 8(sp)
        addi    s0, sp, 16
+#endif
        .endm
 
        .macro RESTORE_ABI_STATE
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+       ld      s0, 32(sp)
+       ld      ra, 40(sp)
+       addi    sp, sp, 48
+#else
        ld      ra, 8(sp)
        ld      s0, 0(sp)
        addi    sp, sp, 16
+#endif
        .endm
 
+       .macro RESTORE_GRAPH_ARGS
+       ld      a0, 24(sp)
+       ld      a1, 16(sp)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+       ld      a2, 8(sp)
+#endif
+       .endm
+
+ENTRY(ftrace_graph_caller)
+       addi    sp, sp, -16
+       sd      s0, 0(sp)
+       sd      ra, 8(sp)
+       addi    s0, sp, 16
+ftrace_graph_call:
+       .global ftrace_graph_call
+       /*
+        * Calling ftrace_enable/disable_ftrace_graph_caller would overwrite the
+        * call below.  Check ftrace_modify_all_code for details.
+        */
+       call    ftrace_stub
+       ld      ra, 8(sp)
+       ld      s0, 0(sp)
+       addi    sp, sp, 16
+       ret
+ENDPROC(ftrace_graph_caller)
+
 ENTRY(ftrace_caller)
        /*
         * a0: the address in the caller when calling ftrace_caller
@@ -33,6 +77,20 @@ ENTRY(ftrace_caller)
         */
        ld      a1, -8(s0)
        addi    a0, ra, -MCOUNT_INSN_SIZE
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+       /*
+        * the graph tracer (specifically, prepare_ftrace_return) needs these
+        * arguments but for now the function tracer occupies the regs, so we
+        * save them in temporary regs to recover later.
+        */
+       addi    t0, s0, -8
+       mv      t1, a0
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+       ld      t2, -16(s0)
+#endif
+#endif
+
        SAVE_ABI_STATE
 ftrace_call:
        .global ftrace_call
@@ -45,6 +103,12 @@ ftrace_call:
         * Check ftrace_modify_all_code for details.
         */
        call    ftrace_stub
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+       RESTORE_GRAPH_ARGS
+       call    ftrace_graph_caller
+#endif
+
        RESTORE_ABI_STATE
        ret
 ENDPROC(ftrace_caller)