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Date: Fri, 14 Nov 2008 16:16:05 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: rostedt@...dmis.org, mingo@...e.hu, akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH 2/3] ftrace: Add debug_print trace to print data from kernel to userspace
The trace add a new interface debug_print() which can be used
to dump data from kernel to user space using ftrace framework.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
include/linux/debug_print.h | 12 ++++
kernel/trace/Kconfig | 7 ++
kernel/trace/Makefile | 1 +
kernel/trace/trace_debugprint.c | 134 +++++++++++++++++++++++++++++++++++++++
4 files changed, 154 insertions(+), 0 deletions(-)
create mode 100644 include/linux/debug_print.h
create mode 100644 kernel/trace/trace_debugprint.c
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 b58f43b..9b832e0 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -195,4 +195,11 @@ 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 c8228b1..afbf059 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -24,5 +24,6 @@ obj-$(CONFIG_NOP_TRACER) += trace_nop.o
obj-$(CONFIG_STACK_TRACER) += trace_stack.o
obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
obj-$(CONFIG_BOOT_TRACER) += trace_boot.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..feb38d8
--- /dev/null
+++ b/kernel/trace/trace_debugprint.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright IBM Corporation, 2008
+ * Author Aneesh Kumar K.V <aneesh.kumar@...ux.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 struct trace_array *ctx_trace;
+static int __read_mostly tracer_enabled;
+
+int do_dp_printk(const char *fmt, ...)
+{
+ int ret;
+ va_list args;
+
+ if (!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 start_dp_trace(struct trace_array *tr)
+{
+ dp_reset(tr);
+ tracer_enabled = 1;
+}
+
+static void stop_dp_trace(struct trace_array *tr)
+{
+ tracer_enabled = 0;
+ /* Nothing to do! */
+}
+
+static void dp_trace_init(struct trace_array *tr)
+{
+ ctx_trace = tr;
+
+ if (tr->ctrl)
+ start_dp_trace(tr);
+}
+
+static void dp_trace_reset(struct trace_array *tr)
+{
+ if (tr->ctrl)
+ stop_dp_trace(tr);
+}
+
+static void dp_trace_ctrl_update(struct trace_array *tr)
+{
+ /* When starting a new trace, reset the buffers */
+ if (tr->ctrl)
+ start_dp_trace(tr);
+ else
+ stop_dp_trace(tr);
+}
+
+#ifdef CONFIG_NOP_TRACER
+int
+trace_selftest_startup_dp(struct tracer *trace, struct trace_array *tr)
+{
+ /* What could possibly go wrong? */
+ return 0;
+}
+#endif
+
+static enum print_line_t debug_print_line(struct trace_iterator *iter)
+{
+ struct trace_seq *s = &iter->seq;
+ struct trace_entry *entry;
+
+ entry = iter->ent;
+ switch (entry->type) {
+ case TRACE_PRINT: {
+ struct print_entry *field;
+ trace_assign_type(field, entry);
+
+ trace_seq_printf(s, "%s", field->buf);
+ if (entry->flags & TRACE_FLAG_CONT)
+ trace_seq_print_cont(s, iter);
+ break;
+ }
+ default:
+ printk(KERN_INFO "Unsupported type in debug_print\n");
+ return TRACE_TYPE_UNHANDLED;
+ }
+
+ return TRACE_TYPE_HANDLED;
+}
+
+struct tracer dp_trace __read_mostly =
+{
+ .name = "debug_print",
+ .init = dp_trace_init,
+ .reset = dp_trace_reset,
+ .ctrl_update = dp_trace_ctrl_update,
+#ifdef CONFIG_FTRACE_SELFTEST
+ .selftest = trace_selftest_startup_dp,
+#endif
+ .print_line = debug_print_line,
+};
+
+__init static int init_dp_trace(void)
+{
+ return register_tracer(&dp_trace);
+}
+device_initcall(init_dp_trace);
--
1.6.0.4.608.ga9645
--
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