[RFC PATCH 2/3] Generic Trace Setup and Control (GTSC) code

[Tom Zanussi <zanussi@us.ibm.com>]

The Generic Tracing and Control Interface (GTSC) code.

Signed-off-by: Tom Zanussi <zanussi@us.ibm.com>
Signed-off-by: David Wilder <dwilder@us.ibm.com>
---
 include/linux/gtsc.h |  104 +++++++++
 lib/Kconfig          |   10 
 lib/Makefile         |    2 
 lib/gtsc.c           |  558 +++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 674 insertions(+)

diff --git a/include/linux/gtsc.h b/include/linux/gtsc.h
new file mode 100644
index 0000000..cbb2601
--- /dev/null
+++ b/include/linux/gtsc.h
@@ -0,0 +1,104 @@
+/*
+ * GTSC defines and function prototypes
+ *
+ * Copyright (C) 2006 IBM Inc.
+ *
+ *	Tom Zanussi <zanussi@us.ibm.com>
+ *	Martin Hunt <hunt@redhat.com>
+ *	David Wilder <dwilder@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+#ifndef _LINUX_GTSC_H
+#define _LINUX_GTSC_H
+
+#include <linux/relay.h>
+
+/*
+ * GTSC channel flags
+ */
+#define TRACE_GLOBAL_CHANNEL	0x01
+#define TRACE_FLIGHT_CHANNEL	0x02
+#define TRACE_DISABLE_STATE	0x04
+
+enum trace_state {
+	TRACE_SETUP,
+	TRACE_RUNNING,
+	TRACE_STOPPED,
+};
+
+#define TRACE_ROOT_NAME_SIZE	64	/* Max root dir identifier */
+#define TRACE_NAME_SIZE		64	/* Max trace identifier */
+
+/*
+ * Global root user information
+ */
+struct trace_root {
+	struct list_head list;
+	char name[TRACE_ROOT_NAME_SIZE];
+	struct dentry *root;
+	unsigned int users;
+};
+
+/*
+ * Client information
+ */
+struct trace_info {
+	enum trace_state state;
+	struct dentry *state_file;
+	struct rchan *rchan;
+	struct dentry *dir;
+	struct dentry *dropped_file;
+	struct dentry *reset_consumed_file;
+	struct dentry *nr_sub_file;
+	struct dentry *sub_size_file;
+	atomic_t dropped;
+	struct trace_root *root;
+	void *private_data;
+	unsigned int flags;
+	unsigned int buf_size;
+	unsigned int buf_nr;
+};
+
+#ifdef CONFIG_GTSC
+static inline int trace_running(struct trace_info *trace)
+{
+	return trace->state == TRACE_RUNNING;
+}
+struct trace_info *trace_setup(const char *root, const char *name,
+			       u32 buf_size, u32 buf_nr, u32 flags);
+int trace_start(struct trace_info *trace);
+int trace_stop(struct trace_info *trace);
+void trace_cleanup_channel(struct trace_info *gt);
+void trace_cleanup(struct trace_info *gt);
+unsigned long long trace_timestamp(void);
+#else
+static inline struct trace_info *trace_setup(const char *root,
+					     const char *name,
+					     u32 buf_size,
+					     u32 buf_nr,
+					     u32 flags)
+{
+	return NULL;
+}
+static inline int trace_running(struct trace_info *trace) { return 0; }
+static inline int trace_start(struct trace_info *trace) { return -EINVAL; }
+static inline int trace_stop(struct trace_info *trace) {}
+static inline void trace_cleanup_channel(struct trace_info *trace) {}
+static inline void trace_cleanup(struct trace_info *trace) {}
+static inline unsigned long long trace_timestamp(void) { return 0; }
+#endif
+
+#endif
diff --git a/lib/Kconfig b/lib/Kconfig
index 2e7ae6b..b3931f3 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -124,4 +124,14 @@ config HAS_DMA
 	depends on !NO_DMA
 	default y
 
+config GTSC
+	bool "Generic Trace Setup and Control"
+	select RELAY
+	select DEBUG_FS
+	help
+	  This option provides support for the setup, teardown and control
+	  of tracing channels from kernel code.  It also provides trace
+	  information and control to userspace via a set of debugfs control
+	  files.  If unsure, say N.
+
 endmenu
diff --git a/lib/Makefile b/lib/Makefile
index c8c8e20..d9e68fa 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -62,6 +62,8 @@ obj-$(CONFIG_FAULT_INJECTION) += fault-inject.o
 
 lib-$(CONFIG_GENERIC_BUG) += bug.o
 
+obj-$(CONFIG_GTSC) += gtsc.o
+
 hostprogs-y	:= gen_crc32table
 clean-files	:= crc32table.h
 
diff --git a/lib/gtsc.c b/lib/gtsc.c
new file mode 100644
index 0000000..ecd0ddf
--- /dev/null
+++ b/lib/gtsc.c
@@ -0,0 +1,558 @@
+/*
+ * Based on blktrace code, Copyright (C) 2006 Jens Axboe <axboe@suse.de>
+ * Moved to utt.c by Tom Zanussi <zanussi@us.ibm.com>, 2006
+ * Additional contributions by:
+ * Martin Hunt <hunt@redhat.com>, 2007
+ * David Wilder <dwilder@us.ibm.com>, 2007
+ * Renamed to gtsc <dwilder.ibm.com>, 2007
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/debugfs.h>
+#include <linux/gtsc.h>
+
+static LIST_HEAD(trace_roots);
+static DEFINE_MUTEX(trace_mutex);
+
+static int state_open(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+
+	return 0;
+}
+
+static ssize_t state_read(struct file *filp, char __user *buffer,
+			  size_t count, loff_t *ppos)
+{
+	struct trace_info *trace = filp->private_data;
+	char *buf = "trace not started\n";
+
+	if (trace->state == TRACE_STOPPED)
+		buf = "stopped\n";
+	else if (trace->state == TRACE_RUNNING)
+		buf = "running\n";
+	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
+}
+
+
+static ssize_t state_write(struct file *filp, const char __user *buffer,
+			   size_t count, loff_t *ppos)
+{
+	struct trace_info *trace = filp->private_data;
+	char buf[16] = { '\0' };
+	int ret;
+
+	if (trace->flags & TRACE_DISABLE_STATE)
+		return -EINVAL;
+	
+	if (count > sizeof(buf) - 1)
+		return -EINVAL;
+
+	if (copy_from_user(buf, buffer, count))
+		return -EFAULT;
+
+	buf[count] = '\0';
+	
+	if (strncmp(buf, "start", strlen("start")) == 0 ) {
+		ret = trace_start(trace);
+		if (ret)
+			return ret;
+	} else if (strncmp(buffer, "stop", strlen("stop")) == 0)
+		trace_stop(trace);
+	else
+		return -EINVAL;
+
+	return count;
+}
+
+
+static struct file_operations state_fops = {
+	.owner	= THIS_MODULE,
+	.open	= state_open,
+	.read	= state_read,
+	.write	= state_write,
+};
+
+
+static void remove_root(struct trace_info *trace)
+{
+	if (trace->root->root && simple_empty(trace->root->root)) {
+		debugfs_remove(trace->root->root);
+		list_del(&trace->root->list);
+		kfree(trace->root);
+		trace->root = NULL;
+	}
+}
+
+
+static void remove_tree(struct trace_info *trace)
+{
+	mutex_lock(&trace_mutex);
+
+	debugfs_remove(trace->dir);
+
+	if (--trace->root->users == 0)
+		remove_root(trace);
+
+	mutex_unlock(&trace_mutex);
+}
+
+
+static struct trace_root *lookup_root(const char *root)
+{
+	struct list_head *pos;
+	struct trace_root *r;
+
+	list_for_each(pos, &trace_roots) {
+		r = list_entry(pos, struct trace_root, list);
+		if (!strcmp(r->name, root))
+			return r;
+	}
+
+	r = kzalloc(sizeof(struct trace_root), GFP_KERNEL);
+	if (!r)
+		return NULL;
+
+	strlcpy(r->name, root, sizeof(r->name));
+
+	r->root = debugfs_create_dir(root, NULL);
+	if (r->root)
+		list_add(&r->list, &trace_roots);
+
+	return r;
+}
+
+
+static struct dentry *create_tree(struct trace_info *trace,
+				  const char *root,
+				  const char *name)
+{
+	struct dentry *dir = NULL;
+
+	if (root == NULL || name == NULL)
+		return NULL;
+	
+	mutex_lock(&trace_mutex);
+
+	trace->root = lookup_root(root);
+	if (!trace->root)
+		goto err;
+
+	dir = debugfs_create_dir(name, trace->root->root);
+	if (dir)
+		trace->root->users++;
+	else
+		remove_root(trace);
+
+err:
+	mutex_unlock(&trace_mutex);
+
+	return dir;
+}
+
+
+static int dropped_open(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+
+	return 0;
+}
+
+
+static ssize_t dropped_read(struct file *filp, char __user *buffer,
+			    size_t count, loff_t *ppos)
+{
+	struct trace_info *trace = filp->private_data;
+	char buf[16];
+
+	snprintf(buf, sizeof(buf), "%u\n", atomic_read(&trace->dropped));
+
+	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
+}
+
+
+static struct file_operations dropped_fops = {
+	.owner	= THIS_MODULE,
+	.open	= dropped_open,
+	.read	= dropped_read,
+};
+
+static int reset_consumed_open(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+
+	return 0;
+}
+
+static ssize_t reset_consumed_write(struct file *filp,
+				    const char __user *buffer,
+				    size_t count,
+				    loff_t *ppos)
+{
+	struct trace_info *trace = filp->private_data;
+
+	relay_reset_consumed(trace->rchan);
+
+	return count;
+}
+
+struct file_operations reset_consumed_fops = {
+	.owner	= THIS_MODULE,
+	.open	= reset_consumed_open,
+	.write	= reset_consumed_write
+};
+
+static int sub_size_open(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+
+	return 0;
+}
+
+static ssize_t sub_size_read(struct file *filp, char __user *buffer,
+			     size_t count, loff_t *ppos)
+{
+	struct trace_info *trace = filp->private_data;
+	char buf[32];
+
+	snprintf(buf, sizeof(buf), "%u\n",
+		 (unsigned int)trace->rchan->subbuf_size);
+
+	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
+}
+
+struct file_operations sub_size_fops = {
+	.owner	= THIS_MODULE,
+	.open	= sub_size_open,
+	.read	= sub_size_read,
+};
+
+static int nr_sub_open(struct inode *inode, struct file *filp)
+{
+	filp->private_data = inode->i_private;
+	return 0;
+}
+
+static ssize_t nr_sub_read(struct file *filp, char __user *buffer,
+			   size_t count, loff_t *ppos)
+{
+	struct trace_info *trace = filp->private_data;
+	char buf[32];
+
+	snprintf(buf, sizeof(buf), "%u\n",
+		 (unsigned int)trace->rchan->n_subbufs);
+
+	return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
+}
+
+struct file_operations nr_sub_fops = {
+	.owner	= THIS_MODULE,
+	.open	= nr_sub_open,
+	.read	= nr_sub_read,
+};
+
+/*
+ * Keep track of how many times we encountered a full subbuffer, to aid
+ * the user space app in telling how many lost events there were.
+ */
+static int subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
+				 void *prev_subbuf, size_t prev_padding)
+{
+	struct trace_info *trace = buf->chan->private_data;
+	
+	if (trace->flags & TRACE_FLIGHT_CHANNEL)
+		return 1;
+	
+	if (!relay_buf_full(buf))
+		return 1;
+
+	atomic_inc(&trace->dropped);
+
+	return 0;
+}
+
+
+static int remove_buf_file_callback(struct dentry *dentry)
+{
+	debugfs_remove(dentry);
+
+	return 0;
+}
+
+
+static struct dentry *create_buf_file_callback(const char *filename,
+					       struct dentry *parent,
+					       int mode,
+					       struct rchan_buf *buf,
+					       int *is_global)
+{
+	return debugfs_create_file(filename, mode, parent, buf,
+				   &relay_file_operations);
+}
+
+
+static struct dentry *create_global_buf_file_callback(const char *filename,
+						      struct dentry *parent,
+						      int mode,
+						      struct rchan_buf *buf,
+						      int *is_global)
+{
+	*is_global = 1;
+
+	return debugfs_create_file(filename, mode, parent, buf,
+				   &relay_file_operations);
+}
+
+
+static struct rchan_callbacks relay_callbacks = {
+	.subbuf_start		= subbuf_start_callback,
+	.create_buf_file	= create_buf_file_callback,
+	.remove_buf_file	= remove_buf_file_callback,
+};
+static struct rchan_callbacks relay_callbacks_global = {
+	.subbuf_start		= subbuf_start_callback,
+	.create_buf_file	= create_global_buf_file_callback,
+	.remove_buf_file	= remove_buf_file_callback,
+};
+
+
+static void remove_controls(struct trace_info *trace)
+{
+	if (trace->state_file)
+		debugfs_remove(trace->state_file);
+	if (trace->dropped_file)
+		debugfs_remove(trace->dropped_file);
+	if (trace->reset_consumed_file)
+		debugfs_remove(trace->reset_consumed_file);
+	if (trace->nr_sub_file)
+		debugfs_remove(trace->nr_sub_file);
+	if (trace->sub_size_file)
+		debugfs_remove(trace->sub_size_file);
+	if (trace->dir)
+		remove_tree(trace);
+}
+
+/*
+ * Setup controls for tracing.
+ */
+static struct trace_info *setup_controls(const char *root,
+					 const char *name, u32 flags)
+{
+	struct trace_info *trace = NULL;
+
+	trace = kzalloc(sizeof(*trace), GFP_KERNEL);
+	if (!trace)
+		goto err;
+
+	trace->dir = create_tree(trace, root, name);
+	if (!trace->dir)
+		goto err;
+
+	trace->state_file = debugfs_create_file("state", 0444, trace->dir,
+						trace, &state_fops);
+	if (!trace->state_file)
+		goto err;
+
+	if (!flags & TRACE_FLIGHT_CHANNEL) {
+		trace->dropped_file = debugfs_create_file("dropped", 0444,
+							  trace->dir,
+							  trace,
+							  &dropped_fops);
+		if (!trace->dropped_file)
+			goto err;
+	}
+
+	if (flags & TRACE_FLIGHT_CHANNEL) {
+		trace->reset_consumed_file = debugfs_create_file("rewind",
+								 0444,
+								 trace->dir,
+								 trace,
+								 &reset_consumed_fops);
+		if (!trace->reset_consumed_file)
+			goto err;
+	}
+
+	trace->nr_sub_file = debugfs_create_file("nr_sub", 0444,
+						 trace->dir, trace,
+						 &nr_sub_fops);
+	if (!trace->nr_sub_file)
+		goto err;
+
+	trace->sub_size_file = debugfs_create_file("sub_size", 0444,
+						   trace->dir, trace,
+						   &sub_size_fops);
+	if (!trace->sub_size_file)
+		goto err;
+
+	return trace;
+err:
+	if (trace) {
+		remove_controls(trace);
+		kfree(trace);
+	}
+
+	return NULL;
+}
+
+
+int trace_setup_channel(struct trace_info *trace, u32 buf_size, u32 buf_nr,
+			u32 flags)
+{
+	if (!buf_size || !buf_nr)
+		return -EINVAL;
+
+	if (flags & TRACE_GLOBAL_CHANNEL)
+		trace->rchan = relay_open("trace", trace->dir, buf_size,
+					  buf_nr, &relay_callbacks_global,
+					  trace);
+	else
+		trace->rchan = relay_open("trace", trace->dir, buf_size,
+					  buf_nr, &relay_callbacks, trace);
+	
+	if (!trace->rchan)
+		return -ENOMEM;
+
+	trace->flags = flags;
+	trace->state = TRACE_SETUP;
+
+	return 0;
+}
+
+
+/**
+ *	trace_setup: create a new gtsc trace handle
+ *
+ *	@root: The root directory name in the root of the debugfs
+ *	       to place trace directories. Created as needed.
+ *	@name: Trace directory name, created in @root
+ *	@buf_size: size of the relay sub-buffers
+ *	@buf_nr: number of relay sub-buffers
+ *	@flags: Option selection (see GTSC channel flags definitions)
+ *		default values when flags=0 are: use per-CPU buffering,
+ *		use non-overwrite mode. See Documentation/gtsc.txt for details.
+ *
+ *	returns a gtsc_trace handle or NULL, if setup failed.
+ */
+struct trace_info *trace_setup(const char *root, const char *name,
+			       u32 buf_size, u32 buf_nr, u32 flags)
+{
+	struct trace_info *trace = NULL;
+
+	trace = setup_controls(root, name, flags);
+	if (!trace)
+		return NULL;
+
+	trace->buf_size = buf_size;
+	trace->buf_nr = buf_nr;
+	trace->flags = flags;
+	trace->state = TRACE_SETUP;
+
+	return trace;
+}
+EXPORT_SYMBOL_GPL(trace_setup);
+
+
+/**
+ *	trace_start: start tracing
+ *
+ *	@trace: gtsc trace handle to start or stop.
+ *
+ *	returns 0 if successful.
+ */
+int trace_start(struct trace_info *trace)
+{
+	/*
+	 * For starting a trace, we can transition from a setup or stopped
+	 * trace.
+	 */
+	if (trace->state == TRACE_RUNNING)
+		return -EINVAL;
+
+	if (trace->state == TRACE_SETUP) {
+		int ret;
+
+		ret = trace_setup_channel(trace, trace->buf_size,
+					  trace->buf_nr, trace->flags);
+		if (ret)
+			return ret;
+	}
+
+	trace->state = TRACE_RUNNING;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(trace_start);
+
+/**
+ *	trace_stop: stop tracing
+ *
+ *	@trace: gtsc trace handle to start or stop.
+ */
+int trace_stop(struct trace_info *trace)
+{
+	int ret = -EINVAL;
+	
+	/*
+	 * For stopping a trace, the state must be running
+	 */
+	if (trace->state == TRACE_RUNNING) {
+		trace->state = TRACE_STOPPED;
+		relay_flush(trace->rchan);
+		ret = 0;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(trace_stop);
+
+
+/**
+ *	trace_cleanup_channel: destroys the gtsc channel only
+ *
+ *	@trace: gtsc trace handle to cleanup
+ */
+void trace_cleanup_channel(struct trace_info *trace)
+{
+	if (trace->rchan)
+		relay_close(trace->rchan);
+	trace->rchan = NULL;
+}
+EXPORT_SYMBOL_GPL(trace_cleanup_channel);
+
+
+/**
+ *	trace_cleanup: destroys the gtsc channel, control files and dir
+ *
+ *	@trace: gtsc trace handle to cleanup
+ */
+void trace_cleanup(struct trace_info *trace)
+{
+	trace_cleanup_channel(trace);
+	remove_controls(trace);
+	kfree(trace);
+}
+EXPORT_SYMBOL_GPL(trace_cleanup);
+
+
+unsigned long long trace_timestamp(void)
+{
+	return sched_clock();
+}
+EXPORT_SYMBOL_GPL(trace_timestamp);