1 files changed, 133 insertions, 0 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index cff58e288a22..d9e75ec7def5 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -392,6 +392,139 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
 #endif
 
 /*
+ * General tracing related utility functions - trace_printk(),
+ * tracing_on/tracing_off and tracing_start()/tracing_stop
+ *
+ * Use tracing_on/tracing_off when you want to quickly turn on or off
+ * tracing. It simply enables or disables the recording of the trace events.
+ * This also corresponds to the user space debugfs/tracing/tracing_on
+ * file, which gives a means for the kernel and userspace to interact.
+ * Place a tracing_off() in the kernel where you want tracing to end.
+ * From user space, examine the trace, and then echo 1 > tracing_on
+ * to continue tracing.
+ *
+ * tracing_stop/tracing_start has slightly more overhead. It is used
+ * by things like suspend to ram where disabling the recording of the
+ * trace is not enough, but tracing must actually stop because things
+ * like calling smp_processor_id() may crash the system.
+ *
+ * Most likely, you want to use tracing_on/tracing_off.
+ */
+#ifdef CONFIG_RING_BUFFER
+void tracing_on(void);
+void tracing_off(void);
+/* trace_off_permanent stops recording with no way to bring it back */
+void tracing_off_permanent(void);
+int tracing_is_on(void);
+#else
+static inline void tracing_on(void) { }
+static inline void tracing_off(void) { }
+static inline void tracing_off_permanent(void) { }
+static inline int tracing_is_on(void) { return 0; }
+#endif
+#ifdef CONFIG_TRACING
+extern void tracing_start(void);
+extern void tracing_stop(void);
+extern void ftrace_off_permanent(void);
+
+extern void
+ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3);
+
+static inline void __attribute__ ((format (printf, 1, 2)))
+____trace_printk_check_format(const char *fmt, ...)
+{
+}
+#define __trace_printk_check_format(fmt, args...)                       \
+do {                                                                    \
+        if (0)                                                          \
+                ____trace_printk_check_format(fmt, ##args);             \
+} while (0)
+
+/**
+ * trace_printk - printf formatting in the ftrace buffer
+ * @fmt: the printf format for printing
+ *
+ * Note: __trace_printk is an internal function for trace_printk and
+ *       the @ip is passed in via the trace_printk macro.
+ *
+ * This function allows a kernel developer to debug fast path sections
+ * that printk is not appropriate for. By scattering in various
+ * printk like tracing in the code, a developer can quickly see
+ * where problems are occurring.
+ *
+ * This is intended as a debugging tool for the developer only.
+ * Please refrain from leaving trace_printks scattered around in
+ * your code.
+ */
+
+#define trace_printk(fmt, args...)                                      \
+do {                                                                    \
+        __trace_printk_check_format(fmt, ##args);                       \
+        if (__builtin_constant_p(fmt)) {                                \
+                static const char *trace_printk_fmt                     \
+                  __attribute__((section("__trace_printk_fmt"))) =      \
+                        __builtin_constant_p(fmt) ? fmt : NULL;         \
+                                                                        \
+                __trace_bprintk(_THIS_IP_, trace_printk_fmt, ##args);   \
+        } else                                                          \
+                __trace_printk(_THIS_IP_, fmt, ##args);         \
+} while (0)
+
+extern int
+__trace_bprintk(unsigned long ip, const char *fmt, ...)
+        __attribute__ ((format (printf, 2, 3)));
+
+extern int
+__trace_printk(unsigned long ip, const char *fmt, ...)
+        __attribute__ ((format (printf, 2, 3)));
+
+/*
+ * The double __builtin_constant_p is because gcc will give us an error
+ * if we try to allocate the static variable to fmt if it is not a
+ * constant. Even with the outer if statement.
+ */
+#define ftrace_vprintk(fmt, vargs)                                      \
+do {                                                                    \
+        if (__builtin_constant_p(fmt)) {                                \
+                static const char *trace_printk_fmt                     \
+                  __attribute__((section("__trace_printk_fmt"))) =      \
+                        __builtin_constant_p(fmt) ? fmt : NULL;         \
+                                                                        \
+                __ftrace_vbprintk(_THIS_IP_, trace_printk_fmt, vargs);  \
+        } else                                                          \
+                __ftrace_vprintk(_THIS_IP_, fmt, vargs);                \
+} while (0)
+
+extern int
+__ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap);
+
+extern int
+__ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
+
+extern void ftrace_dump(void);
+#else
+static inline void
+ftrace_special(unsigned long arg1, unsigned long arg2, unsigned long arg3) { }
+static inline int
+trace_printk(const char *fmt, ...) __attribute__ ((format (printf, 1, 2)));
+
+static inline void tracing_start(void) { }
+static inline void tracing_stop(void) { }
+static inline void ftrace_off_permanent(void) { }
+static inline int
+trace_printk(const char *fmt, ...)
+{
+        return 0;
+}
+static inline int
+ftrace_vprintk(const char *fmt, va_list ap)
+{
+        return 0;
+}
+static inline void ftrace_dump(void) { }
+#endif /* CONFIG_TRACING */
+
+/*
  *      Display an IP address in readable format.
  */