4 files changed, 72 insertions, 21 deletions

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 7def9fd5c1e6..958af86186c4 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1174,6 +1174,11 @@ ftrace_call:
         popl %edx
         popl %ecx
         popl %eax
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl ftrace_graph_call
+ftrace_graph_call:
+        jmp ftrace_stub
+#endif
 
 .globl ftrace_stub
 ftrace_stub:
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 26b2d92d48b3..7ef914e6a2f6 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -111,7 +111,6 @@ static void ftrace_mod_code(void)
          */
         mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
                                              MCOUNT_INSN_SIZE);
-
 }
 
 void ftrace_nmi_enter(void)
@@ -325,7 +324,51 @@ int __init ftrace_dyn_arch_init(void *data)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
-#ifndef CONFIG_DYNAMIC_FTRACE
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+
+static int ftrace_mod_jmp(unsigned long ip,
+                          int old_offset, int new_offset)
+{
+        unsigned char code[MCOUNT_INSN_SIZE];
+
+        if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
+                return -EFAULT;
+
+        if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
+                return -EINVAL;
+
+        *(int *)(&code[1]) = new_offset;
+
+        if (do_ftrace_mod_code(ip, &code))
+                return -EPERM;
+
+        return 0;
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+        unsigned long ip = (unsigned long)(&ftrace_graph_call);
+        int old_offset, new_offset;
+
+        old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
+        new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
+
+        return ftrace_mod_jmp(ip, old_offset, new_offset);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+        unsigned long ip = (unsigned long)(&ftrace_graph_call);
+        int old_offset, new_offset;
+
+        old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
+        new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
+
+        return ftrace_mod_jmp(ip, old_offset, new_offset);
+}
+
+#else /* CONFIG_DYNAMIC_FTRACE */
 
 /*
  * These functions are picked from those used on
@@ -343,6 +386,7 @@ void ftrace_nmi_exit(void)
 {
         atomic_dec(&in_nmi);
 }
+
 #endif /* !CONFIG_DYNAMIC_FTRACE */
 
 /* Add a function return address to the trace stack on thread info.*/
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index fc2d54987198..f9792c0d73f6 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -117,6 +117,11 @@ extern void ftrace_call(void);
 extern void mcount_call(void);
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 extern void ftrace_graph_caller(void);
+extern int ftrace_enable_ftrace_graph_caller(void);
+extern int ftrace_disable_ftrace_graph_caller(void);
+#else
+static inline int ftrace_enable_ftrace_graph_caller(void) { return 0; }
+static inline int ftrace_disable_ftrace_graph_caller(void) { return 0; }
 #endif
 
 /**
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 00d98c65fad0..5f7c8642d58b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -281,6 +281,8 @@ enum {
         FTRACE_UPDATE_TRACE_FUNC        = (1 << 2),
         FTRACE_ENABLE_MCOUNT            = (1 << 3),
         FTRACE_DISABLE_MCOUNT           = (1 << 4),
+        FTRACE_START_FUNC_RET           = (1 << 5),
+        FTRACE_STOP_FUNC_RET            = (1 << 6),
 };
 
 static int ftrace_filtered;
@@ -465,14 +467,7 @@ __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
         unsigned long ip, fl;
         unsigned long ftrace_addr;
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-        if (ftrace_tracing_type == FTRACE_TYPE_ENTER)
-                ftrace_addr = (unsigned long)ftrace_caller;
-        else
-                ftrace_addr = (unsigned long)ftrace_graph_caller;
-#else
         ftrace_addr = (unsigned long)ftrace_caller;
-#endif
 
         ip = rec->ip;
 
@@ -605,6 +600,11 @@ static int __ftrace_modify_code(void *data)
         if (*command & FTRACE_UPDATE_TRACE_FUNC)
                 ftrace_update_ftrace_func(ftrace_trace_function);
 
+        if (*command & FTRACE_START_FUNC_RET)
+                ftrace_enable_ftrace_graph_caller();
+        else if (*command & FTRACE_STOP_FUNC_RET)
+                ftrace_disable_ftrace_graph_caller();
+
         return 0;
 }
 
@@ -629,10 +629,8 @@ static void ftrace_startup_enable(int command)
         ftrace_run_update_code(command);
 }
 
-static void ftrace_startup(void)
+static void ftrace_startup(int command)
 {
-        int command = 0;
-
         if (unlikely(ftrace_disabled))
                 return;
 
@@ -645,10 +643,8 @@ static void ftrace_startup(void)
         mutex_unlock(&ftrace_start_lock);
 }
 
-static void ftrace_shutdown(void)
+static void ftrace_shutdown(int command)
 {
-        int command = 0;
-
         if (unlikely(ftrace_disabled))
                 return;
 
@@ -1453,8 +1449,9 @@ device_initcall(ftrace_nodyn_init);
 
 static inline int ftrace_init_dyn_debugfs(struct dentry *d_tracer) { return 0; }
 static inline void ftrace_startup_enable(int command) { }
-# define ftrace_startup()               do { } while (0)
-# define ftrace_shutdown()              do { } while (0)
+/* Keep as macros so we do not need to define the commands */
+# define ftrace_startup(command)        do { } while (0)
+# define ftrace_shutdown(command)       do { } while (0)
 # define ftrace_startup_sysctl()        do { } while (0)
 # define ftrace_shutdown_sysctl()       do { } while (0)
 #endif /* CONFIG_DYNAMIC_FTRACE */
@@ -1585,7 +1582,7 @@ int register_ftrace_function(struct ftrace_ops *ops)
         }
 
         ret = __register_ftrace_function(ops);
-        ftrace_startup();
+        ftrace_startup(0);
 
 out:
         mutex_unlock(&ftrace_sysctl_lock);
@@ -1604,7 +1601,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
 
         mutex_lock(&ftrace_sysctl_lock);
         ret = __unregister_ftrace_function(ops);
-        ftrace_shutdown();
+        ftrace_shutdown(0);
         mutex_unlock(&ftrace_sysctl_lock);
 
         return ret;
@@ -1751,7 +1748,7 @@ int register_ftrace_graph(trace_func_graph_ret_t retfunc,
         ftrace_tracing_type = FTRACE_TYPE_RETURN;
         ftrace_graph_return = retfunc;
         ftrace_graph_entry = entryfunc;
-        ftrace_startup();
+        ftrace_startup(FTRACE_START_FUNC_RET);
 
 out:
         mutex_unlock(&ftrace_sysctl_lock);
@@ -1765,7 +1762,7 @@ void unregister_ftrace_graph(void)
         atomic_dec(&ftrace_graph_active);
         ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;
         ftrace_graph_entry = (trace_func_graph_ent_t)ftrace_stub;
-        ftrace_shutdown();
+        ftrace_shutdown(FTRACE_STOP_FUNC_RET);
         /* Restore normal tracing type */
         ftrace_tracing_type = FTRACE_TYPE_ENTER;