lkml.org 
[lkml]   [2008]   [May]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC Patch 1/1] trace_printk and trace_dump interface - v2
ACK

trace_printk() and trace_dump() will be very usefully. This simplified
interface to trace is a needed improvement. Among other features it
makes it easy to convert from printk to trace and provides separate
streams for debugging data. For many subsystems a conversion from
printk to trace only requires changing a #define.

Dave.

K.Prasad wrote:
> This patch introduces two new interfaces called trace_printk and
> trace_dump which can be used to print to the debugfs mount directly.
> It uses the 'trace' infrastructure underneath and is a patch over it.
> A sample file is also created to demonstrate its ease of use.
>
> Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
> ---
> Documentation/trace.txt | 22 ++++
> include/linux/trace.h | 57 +++++++++++
> lib/trace.c | 204
> +++++++++++++++++++++++++++++++++++++++--
> samples/trace/Makefile | 2
> samples/trace/fork_new_trace.c | 99 +++++++++++++++++++
> 5 files changed, 378 insertions(+), 6 deletions(-)
>
> Index: linux-blktrace-many/include/linux/trace.h
> ===================================================================
> --- linux-blktrace-many.orig/include/linux/trace.h
> +++ linux-blktrace-many/include/linux/trace.h
> @@ -39,10 +39,22 @@ enum trace_state {
> TRACE_STOPPED,
> };
>
> +enum trace_dir_state {
> + TRACE_PARENT_DIR_ABSENT,
> + TRACE_PARENT_DIR_EXISTS,
> + TRACE_DIR_EXISTS
> +};
> +
> #define TRACE_ROOT_NAME_SIZE 64 /* Max root dir identifier */
> #define TRACE_NAME_SIZE 64 /* Max trace identifier */
>
> /*
> + * Buffers for use by trace_printk
> + */
> +#define DEFAULT_TRACE_BUF_SIZE 4096
> +#define DEFAULT_TRACE_SUB_BUF_NR 40
> +
> +/*
> * Global root user information
> */
> struct trace_root {
> @@ -71,6 +83,28 @@ struct trace_info {
> unsigned int flags;
> unsigned int buf_size;
> unsigned int buf_nr;
> + spinlock_t trace_lock;
> +};
> +
> +struct trace_printk_data {
> + char *parent_dir;
> + char *dir;
> + int exists;
> + int buf_size;
> + int sub_buf_size;
> + unsigned long flags;
> + struct trace_info *ti;
> +};
> +
> +/*
> + * Information about every trace directory
> + */
> +struct trace_dir {
> + struct list_head trace_dir_list;
> + char trace_dir_name[TRACE_NAME_SIZE];
> + struct dentry *trace_root;
> + struct dentry *trace_dir;
> + struct trace_info *ti;
> };
>
> #ifdef CONFIG_TRACE
> @@ -83,6 +117,12 @@ struct trace_info *trace_setup(const cha
> int trace_start(struct trace_info *trace);
> int trace_stop(struct trace_info *trace);
> void trace_cleanup(struct trace_info *trace);
> +int trace_exists(const char *parent_dir, const char *dir,
> + struct trace_info **ti);
> +void trace_cleanup_all(const char *parent_dir);
> +int trace_printk(struct trace_printk_data *dpk, char *format, ...);
> +int trace_dump(struct trace_printk_data *dpk, const void *output,
> + const int output_len);
> #else
> static inline struct trace_info *trace_setup(const char *root,
> const char *name, u32 buf_size,
> @@ -94,6 +134,23 @@ static inline int trace_start(struct tra
> static inline int trace_stop(struct trace_info *trace) { return -EINVAL; }
> static inline int trace_running(struct trace_info *trace) { return 0; }
> static inline void trace_cleanup(struct trace_info *trace) {}
> +static inline int trace_exists(const char *parent_dir, const char *dir,
> + struct trace_info **ti)
> +{
> + return -EINVAL;
> +}
> +static inline void trace_cleanup_all(const char *parent_dir) {}
> +static inline int trace_printk(struct trace_printk_data *dpk, char
> *format,
> + ...)
> +{
> + return -EINVAL;
> +}
> +int trace_dump(struct trace_printk_data *dpk, const void *output,
> + const int output_len)
> +{
> + return -EINVAL;
> +}
> +
> #endif
>
> #endif
> Index: linux-blktrace-many/lib/trace.c
> ===================================================================
> --- linux-blktrace-many.orig/lib/trace.c
> +++ linux-blktrace-many/lib/trace.c
> @@ -29,6 +29,7 @@
> #include <linux/trace.h>
>
> static LIST_HEAD(trace_roots);
> +static LIST_HEAD(trace_dirs);
> static DEFINE_MUTEX(trace_mutex);
>
> static int state_open(struct inode *inode, struct file *filp)
> @@ -99,9 +100,19 @@ static void remove_root(struct trace_inf
>
> static void remove_tree(struct trace_info *trace)
> {
> + struct list_head *pos, *temp;
> + struct trace_dir *dr = NULL;
> +
> mutex_lock(&trace_mutex);
> debugfs_remove(trace->dir);
>
> + list_for_each_safe(pos, temp, &trace_dirs) {
> + dr = list_entry(pos, struct trace_dir, trace_dir_list);
> + if (dr->ti == trace) {
> + list_del(pos);
> + kfree(dr);
> + }
> + }
> if (trace->root) {
> if (--trace->root->users == 0)
> remove_root(trace);
> @@ -142,11 +153,17 @@ static struct trace_root *lookup_root(co
> static struct dentry *create_tree(struct trace_info *trace, const char
> *root,
> const char *name)
> {
> - struct dentry *dir = NULL;
> + struct trace_dir *temp;
>
> if (root == NULL || name == NULL)
> return ERR_PTR(-EINVAL);
>
> + temp = kzalloc(sizeof(struct trace_dir), GFP_KERNEL);
> + if ((temp == NULL) || (strlen(name) > TRACE_NAME_SIZE))
> + return ERR_PTR(-ENOMEM);
> +
> + strlcpy(temp->trace_dir_name, name, sizeof(temp->trace_dir_name));
> +
> mutex_lock(&trace_mutex);
>
> trace->root = lookup_root(root);
> @@ -155,17 +172,49 @@ static struct dentry *create_tree(struct
> goto err;
> }
>
> - dir = debugfs_create_dir(name, trace->root->root);
> - if (IS_ERR(dir))
> + temp->trace_root = trace->root->root;
> + temp->trace_dir = debugfs_create_dir(name, trace->root->root);
> +
> + if (IS_ERR(temp->trace_dir))
> remove_root(trace);
> - else
> + else {
> trace->root->users++;
> + temp->ti = trace;
> + list_add_tail(&temp->trace_dir_list, &trace_dirs);
> + }
>
> err:
> mutex_unlock(&trace_mutex);
> - return dir;
> + return temp->trace_dir;
> }
>
> +int trace_exists(const char *parent_dir, const char *dir,
> + struct trace_info **ti)
> +{
> + struct list_head *pos;
> + struct trace_root *r;
> + struct trace_dir *temp;
> +
> + list_for_each(pos, &trace_roots) {
> + r = list_entry(pos, struct trace_root, list);
> + if (!strcmp(parent_dir, r->name))
> + goto search_dir;
> + }
> + return TRACE_PARENT_DIR_ABSENT;
> +
> + search_dir:
> + list_for_each(pos, &trace_dirs) {
> + temp = list_entry(pos, struct trace_dir, trace_dir_list);
> +
> + if (!strcmp(dir, temp->trace_dir_name)) {
> + *ti = temp->ti;
> + return TRACE_DIR_EXISTS;
> + }
> + }
> + return TRACE_PARENT_DIR_EXISTS;
> +}
> +EXPORT_SYMBOL_GPL(trace_exists);
> +
> static int dropped_open(struct inode *inode, struct file *filp)
> {
> filp->private_data = inode->i_private;
> @@ -561,3 +610,148 @@ void trace_cleanup(struct trace_info *tr
> kfree(trace);
> }
> EXPORT_SYMBOL_GPL(trace_cleanup);
> +
> +/**
> + * trace_cleanup_all - Removes all trace directories under a parent_dir
> + * @parent_dir: Name of the parent directory
> + */
> +void trace_cleanup_all(const char *parent_dir)
> +{
> + struct list_head *pos, *pos_temp;
> + struct trace_dir *temp;
> +
> + list_for_each_safe(pos, pos_temp, &trace_dirs) {
> + temp = list_entry(pos, struct trace_dir, trace_dir_list);
> + if (!strncmp(parent_dir, temp->trace_root->d_iname,
> strlen(parent_dir)))
> + trace_cleanup(temp->ti);
> + }
> +}
> +EXPORT_SYMBOL_GPL(trace_cleanup_all);
> +
> +/*
> + * Send formatted trace data to trace channel.
> + */
> +static int trace_printf(struct trace_info *trace, const char *format,
> + va_list ap)
> +{
> + va_list aq;
> + char *record;
> + int len, ret = 0;
> +
> + if (trace_running(trace)) {
> + va_copy(aq, ap);
> + len = vsnprintf(NULL, 0, format, aq);
> + va_end(aq);
> + record = relay_reserve(trace->rchan, ++len);
> + if (record)
> + ret = vsnprintf(record, len, format, ap);
> + }
> + return ret;
> +}
> +
> +static inline int init_trace_interface(struct trace_printk_data *tpk)
> +{
> + int ret = 0;
> + tpk->exists = trace_exists(tpk->parent_dir, tpk->dir, &tpk->ti);
> +
> + switch(tpk->exists) {
> +
> + case TRACE_PARENT_DIR_EXISTS:
> + case TRACE_PARENT_DIR_ABSENT:
> + if(!tpk->buf_size)
> + tpk->buf_size = DEFAULT_TRACE_BUF_SIZE;
> + if(!tpk->sub_buf_size)
> + tpk->sub_buf_size = DEFAULT_TRACE_SUB_BUF_NR;
> + tpk->ti = trace_setup(tpk->parent_dir, tpk->dir,
> + tpk->buf_size, tpk->sub_buf_size, tpk->flags);
> + printk(KERN_INFO "Trace interface %s setup\n",
> + tpk->ti->dir->d_iname);
> + if (IS_ERR(tpk->ti)) {
> + printk(KERN_ERR "Error initialising %s interface\n",
> + tpk->ti->dir->d_iname);
> + return -EPERM;
> + }
> + /* Fall through */
> + case TRACE_DIR_EXISTS:
> + if (tpk->ti->state == TRACE_SETUP)
> + ret = trace_start(tpk->ti);
> + else
> + ret = -EPERM;
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * trace_printk - Output a string to debugfs mount 'directly' using
> 'trace'
> + * @tpk: Structure containing info such as parent_dir and directory
> + * @format: String containing format string specifiers
> + * @ap: List of arguments
> + */
> +int trace_printk(struct trace_printk_data *tpk, char *format, ...)
> +{
> + int ret = 0;
> + va_list(ap);
> + unsigned long flags = 0;
> +
> + va_start(ap, format);
> +
> + ret = init_trace_interface(tpk);
> + if (unlikely(ret))
> + return ret;
> +
> + /* Now do the actual printing */
> + /* Take an RCU Lock over the trace_info state */
> + rcu_read_lock();
> + /* Take a spinlock for the global buffer used by relay */
> + if (tpk->flags & TRACE_GLOBAL_CHANNEL)
> + spin_lock_irqsave(&tpk->ti->trace_lock, flags);
> + ret = trace_printf(tpk->ti, format, ap);
> + if (tpk->flags & TRACE_GLOBAL_CHANNEL)
> + spin_unlock_irqrestore(&tpk->ti->trace_lock, flags);
> + rcu_read_unlock();
> +
> + va_end(ap);
> + return ret;
> +}
> +EXPORT_SYMBOL(trace_printk);
> +
> +/**
> + * trace_dump - Output binary into debugfs mount 'directly' using 'trace'
> + * @tpk: Structure containing info such as parent_dir and directory
> + * @output: Data that needs to be output
> + * @output_len: Length of the output data
> + */
> +int trace_dump(struct trace_printk_data *tpk, const void *output,
> + const int output_len)
> +{
> + char *record;
> + unsigned long flags = 0;
> + int ret = 0;
> +
> + ret = init_trace_interface(tpk);
> + if (unlikely(ret))
> + return ret;
> +
> + /* Now do the actual printing */
> + rcu_read_lock();
> + /* Take a spinlock for the global buffer used by relay */
> + if (tpk->flags & TRACE_GLOBAL_CHANNEL)
> + spin_lock_irqsave(&tpk->ti->trace_lock, flags);
> + record = relay_reserve(tpk->ti->rchan, output_len);
> +
> + if (record && trace_running(tpk->ti))
> + memcpy(record, output, output_len);
> + else {
> + if(record)
> + ret = -EPERM;
> + else
> + ret = -ENOMEM;
> + }
> + if (tpk->flags & TRACE_GLOBAL_CHANNEL)
> + spin_unlock_irqrestore(&tpk->ti->trace_lock, flags);
> + rcu_read_unlock();
> +
> + return ret;
> +}
> +EXPORT_SYMBOL(trace_dump);
> Index: linux-blktrace-many/samples/trace/fork_new_trace.c
> ===================================================================
> --- /dev/null
> +++ linux-blktrace-many/samples/trace/fork_new_trace.c
> @@ -0,0 +1,99 @@
> +/*
> + * An example of using trace in a kprobes module
> + *
> + * Copyright (C) 2008 IBM Inc.
> + *
> + * K.Prasad <prasad@linux.vnet.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
> + *
> + * -------
> + * This module creates a trace channel and places a kprobe
> + * on the function do_fork(). The value of current->pid is written to
> + * the trace channel each time the kprobe is hit..
> + *
> + * How to run the example:
> + * $ mount -t debugfs /debug
> + * $ insmod fork_new_trace.ko
> + *
> + * To view the data produced by the module:
> + * $ cat /debug/trace_example/do_fork/trace0
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/kprobes.h>
> +#include <linux/trace.h>
> +
> +#define SAMPLE_PARENT_DIR "trace_new_example"
> +#define PROBE_POINT "do_fork"
> +
> +static struct kprobe kp;
> +static struct trace_printk_data *tpk;
> +
> +static int handler_pre(struct kprobe *p, struct pt_regs *regs)
> +{
> + trace_printk(tpk, "%d\n", current->pid);
> + return 0;
> +}
> +
> +int init_module(void)
> +{
> + int ret = 0;
> + int len_parent_dir, len_dir;
> +
> + /* setup the kprobe */
> + kp.pre_handler = handler_pre;
> + kp.post_handler = NULL;
> + kp.fault_handler = NULL;
> + kp.symbol_name = PROBE_POINT;
> + ret = register_kprobe(&kp);
> + if (ret) {
> + printk(KERN_ERR "fork_trace: register_kprobe failed\n");
> + return ret;
> + }
> +
> + len_parent_dir = strlen(SAMPLE_PARENT_DIR) + 1;
> + /* Initialising len_dir to the larger of the two dir names */
> + len_dir = strlen("kprobe_struct") + 1;
> +
> + tpk = kzalloc(sizeof(*tpk), GFP_KERNEL);
> + if(!tpk)
> + ret = 1;
> +
> + tpk->parent_dir = SAMPLE_PARENT_DIR;
> +
> + /* Let's do a binary dump of struct kprobe using trace_dump */
> + tpk->dir = "kprobes_struct";
> + tpk->flags = TRACE_GLOBAL_CHANNEL;
> + trace_dump(tpk, &kp, sizeof(kp));
> +
> + /* Now change the directory to collect fork pid data */
> + tpk->dir = PROBE_POINT;
> +
> + if(ret)
> + printk(KERN_ERR "Unable to find required free memory. "
> + "Trace new sample module loading aborted");
> + return ret;
> +}
> +
> +void cleanup_module(void)
> +{
> + unregister_kprobe(&kp);
> +
> + /* Just a single cleanup call passing the parent dir string */
> + trace_cleanup_all(SAMPLE_PARENT_DIR);
> +}
> +MODULE_LICENSE("GPL");
> Index: linux-blktrace-many/samples/trace/Makefile
> ===================================================================
> --- linux-blktrace-many.orig/samples/trace/Makefile
> +++ linux-blktrace-many/samples/trace/Makefile
> @@ -1,4 +1,4 @@
> # builds the trace example kernel modules;
> # then to use (as root): insmod <fork_trace.ko>
>
> -obj-$(CONFIG_SAMPLE_TRACE) := fork_trace.o
> +obj-$(CONFIG_SAMPLE_TRACE) := fork_trace.o fork_new_trace.o
> Index: linux-blktrace-many/Documentation/trace.txt
> ===================================================================
> --- linux-blktrace-many.orig/Documentation/trace.txt
> +++ linux-blktrace-many/Documentation/trace.txt
> @@ -150,6 +150,28 @@ The steps a kernel data provider takes t
> 5) Destroy the trace channel and underlying relay channel -
> trace_cleanup().
>
> +Alternatively the user may choose to make use of two new interfaces --
> +trace_printk() and trace_dump() -- to setup trace interface and
> +trace_cleanup_all() to tear-down the same.
> +
> +Steps to use:
> +1) Create and populate an instance of trace_printk_data structure. The
> fields
> + parent_dir and dir are mandatory. The fields buf_size, sub_buf_size
> and flags
> + are optional and will take default values if not populated. The field
> + 'exists' and ti are for the trace infrastructure to use. The pointer
> to the
> + 'struct trace_info' i.e. ti may be used to perform fine granular
> operations
> + such as determine the state of the 'trace', stop individual traces,
> etc.
> +2) Default values for buf_size and sub_buf_size are 4096, 40 respectively.
> +3) Use trace_dump() to output binary data which may be acted upon by a
> + high-level program (say dumping a structure). trace_printk() can be
> used
> + for string output. Pass a pointer to the instance of trace_printk_data
> + structure to these functions along with other parameters. The output
> from
> + these functions can be found at
> + <debugfs_mount>/<parent_dir>/<dir>/trace<0..n>.
> +4) trace_cleanup_all() for a given parent directory will cleanup and
> remove all
> + trace directories created under the specified directory.
> +5) Sample code for the same can be found in samples/trace/fork_new_trace.c
> +
> Kernel Configuration
> --------------------
> To use trace, configure your kernel with CONFIG_TRACE=y. Trace depends on
>



\
 
 \ /
  Last update: 2008-05-19 22:07    [W:0.063 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site