Messages in this thread | | | Date | Mon, 19 May 2008 13:02:42 -0700 | From | David Wilder <> | Subject | Re: [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 >
| |