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Subject[PATCH] ftrace: Add debug_print trace to print data from kernel to userspace
Date
The trace add a new interface dp_printk() which can be used
to dump data from kernel to user space using ftrace framework.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

---
include/linux/debug_print.h | 12 +++++
kernel/trace/Kconfig | 7 +++
kernel/trace/Makefile | 1 +
kernel/trace/trace_debugprint.c | 90 +++++++++++++++++++++++++++++++++++++++
4 files changed, 110 insertions(+), 0 deletions(-)
diff --git a/include/linux/debug_print.h b/include/linux/debug_print.h
new file mode 100644
index 0000000..db4397b
--- /dev/null
+++ b/include/linux/debug_print.h
@@ -0,0 +1,12 @@
+#ifndef _LINUX_DEBUGPRINT_H
+#define _LINUX_DEBUGPRINT_H
+#include <linux/marker.h>
+
+#ifdef CONFIG_DEBUG_PRINT
+extern int do_dp_printk(const char *fmt, ...);
+#define dp_printk(fmt, arg...) \
+ do_dp_printk(fmt, ##arg)
+#else
+#define dp_printk(fmt, arg...)
+#endif
+#endif /* _LINUX_DEBUGPRINT_H */
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 9c89526..30eccc8 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -254,4 +254,11 @@ config FTRACE_STARTUP_TEST
functioning properly. It will do tests on all the configured
tracers of ftrace.

+config DEBUG_PRINT
+ bool "Trace based printk support"
+ depends on DEBUG_KERNEL
+ select TRACING
+ help
+ This tracer can be used for printk style debugging.
+
endmenu
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index 1a8c925..86e5869 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -31,5 +31,6 @@ obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
obj-$(CONFIG_BOOT_TRACER) += trace_boot.o
obj-$(CONFIG_FUNCTION_RET_TRACER) += trace_functions_return.o
obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
+obj-$(CONFIG_DEBUG_PRINT) += trace_debugprint.o

libftrace-y := ftrace.o
diff --git a/kernel/trace/trace_debugprint.c b/kernel/trace/trace_debugprint.c
new file mode 100644
index 0000000..2c3ac3d
--- /dev/null
+++ b/kernel/trace/trace_debugprint.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright IBM Corporation, 2008
+ * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/ftrace.h>
+
+#include "trace.h"
+
+static int __read_mostly dp_tracer_enabled;
+
+int do_dp_printk(const char *fmt, ...)
+{
+ int ret;
+ va_list args;
+
+ if (!dp_tracer_enabled)
+ return 0;
+
+ va_start(args, fmt);
+ ret = trace_vprintk(0, fmt, args);
+ va_end(args);
+ return ret;
+}
+EXPORT_SYMBOL(do_dp_printk);
+
+static void dp_reset(struct trace_array *tr)
+{
+ int cpu;
+
+ tr->time_start = ftrace_now(tr->cpu);
+
+ for_each_online_cpu(cpu)
+ tracing_reset(tr, cpu);
+}
+
+static void dp_trace_start(struct trace_array *tr)
+{
+ dp_reset(tr);
+ dp_tracer_enabled = 1;
+}
+
+static void dp_trace_stop(struct trace_array *tr)
+{
+ dp_tracer_enabled = 0;
+ /* Nothing to do! */
+}
+
+static void dp_trace_init(struct trace_array *tr)
+{
+ /*
+ * enable the trace during init if
+ * we have enabled flag already set
+ */
+ if (tracing_is_enabled())
+ dp_trace_start(tr);
+}
+
+static void dp_trace_reset(struct trace_array *tr)
+{
+ if (dp_tracer_enabled)
+ dp_trace_stop(tr);
+}
+
+struct tracer dp_trace __read_mostly =
+{
+ .name = "debug_print",
+ .init = dp_trace_init,
+ .reset = dp_trace_reset,
+ .start = dp_trace_start,
+ .stop = dp_trace_stop,
+};
+
+__init static int init_dp_trace(void)
+{
+ return register_tracer(&dp_trace);
+}
+device_initcall(init_dp_trace);
--
tg: (bfb3409..) an/ftrace-dp-printk.patch (depends on: an/ftrace-dump-iterator.patch)

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