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    SubjectRe: [PATCH 4/4] tracing: add per-subsystem filtering
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    Hi,

    On Mon, 2009-03-23 at 14:24 -0400, Steven Rostedt wrote:
    > On Sun, 22 Mar 2009, Tom Zanussi wrote:
    > >
    > > +struct event_subsystem {
    > > + struct list_head list;
    > > + const char *name;
    > > + struct dentry *entry;
    > > + struct filter_pred **preds;
    > > +};
    > > +
    > > +#define events_for_each(event) \
    > > + for (event = __start_ftrace_events; \
    > > + (unsigned long)event < (unsigned long)__stop_ftrace_events; \
    > > + event++)
    > > +
    > > #define MAX_FILTER_PRED 8
    > >
    > > struct filter_pred;
    > > @@ -832,6 +844,9 @@ extern int filter_add_pred(struct ftrace_event_call *call,
    > > struct filter_pred *pred);
    > > extern void filter_free_preds(struct ftrace_event_call *call);
    > > extern int filter_match_preds(struct ftrace_event_call *call, void *rec);
    > > +extern void filter_free_subsystem_preds(struct event_subsystem *system);
    > > +extern int filter_add_subsystem_pred(struct event_subsystem *system,
    > > + struct filter_pred *pred);
    > >
    > > void event_trace_printk(unsigned long ip, const char *fmt, ...);
    > > extern struct ftrace_event_call __start_ftrace_events[];
    > > diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
    > > index 97470c4..97d4daa 100644
    > > --- a/kernel/trace/trace_events.c
    > > +++ b/kernel/trace/trace_events.c
    > > @@ -524,6 +524,71 @@ event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
    > > return cnt;
    > > }
    > >
    > > +static ssize_t
    > > +subsystem_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
    > > + loff_t *ppos)
    > > +{
    > > + struct event_subsystem *system = filp->private_data;
    > > + struct trace_seq *s;
    >
    > Again, trace_seq is not used, might as well use your own buffer.
    >
    > > + int r;
    > > +
    > > + if (*ppos)
    > > + return 0;
    > > +
    > > + s = kmalloc(sizeof(*s), GFP_KERNEL);
    > > + if (!s)
    > > + return -ENOMEM;
    > > +
    > > + trace_seq_init(s);
    > > +
    > > + r = filter_print_preds(system->preds, s->buffer);
    > > + r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, r);
    > > +
    > > + kfree(s);
    > > +
    > > + return r;
    > > +}
    > > +
    > > +static ssize_t
    > > +subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
    > > + loff_t *ppos)
    > > +{
    > > + struct event_subsystem *system = filp->private_data;
    > > + char buf[64], *pbuf = buf;
    > > + struct filter_pred *pred;
    > > + int err;
    > > +
    > > + if (cnt >= sizeof(buf))
    > > + return -EINVAL;
    > > +
    > > + if (copy_from_user(&buf, ubuf, cnt))
    > > + return -EFAULT;
    > > +
    > > + pred = kzalloc(sizeof(*pred), GFP_KERNEL);
    > > + if (!pred)
    > > + return -ENOMEM;
    > > +
    > > + err = filter_parse(&pbuf, pred);
    > > + if (err < 0) {
    > > + filter_free_pred(pred);
    > > + return err;
    > > + }
    > > +
    > > + if (pred->clear) {
    > > + filter_free_subsystem_preds(system);
    >
    > is "system" correct here?

    Do you mean the naming i.e. would be better as "subsystem"? Otherwise,
    I think it's correct.

    >
    > > + return cnt;
    > > + }
    > > +
    > > + if (filter_add_subsystem_pred(system, pred)) {
    > > + filter_free_pred(pred);
    > > + return -EINVAL;
    > > + }
    > > +
    > > + *ppos += cnt;
    > > +
    > > + return cnt;
    > > +}
    > > +
    > > static const struct seq_operations show_event_seq_ops = {
    > > .start = t_start,
    > > .next = t_next,
    > > @@ -575,6 +640,12 @@ static const struct file_operations ftrace_event_filter_fops = {
    > > .write = event_filter_write,
    > > };
    > >
    > > +static const struct file_operations ftrace_subsystem_filter_fops = {
    > > + .open = tracing_open_generic,
    > > + .read = subsystem_filter_read,
    > > + .write = subsystem_filter_write,
    > > +};
    > > +
    > > static struct dentry *event_trace_events_dir(void)
    > > {
    > > static struct dentry *d_tracer;
    > > @@ -595,18 +666,13 @@ static struct dentry *event_trace_events_dir(void)
    > > return d_events;
    > > }
    > >
    > > -struct event_subsystem {
    > > - struct list_head list;
    > > - const char *name;
    > > - struct dentry *entry;
    > > -};
    > > -
    > > static LIST_HEAD(event_subsystems);
    > >
    > > static struct dentry *
    > > event_subsystem_dir(const char *name, struct dentry *d_events)
    > > {
    > > struct event_subsystem *system;
    > > + struct dentry *entry;
    > >
    > > /* First see if we did not already create this dir */
    > > list_for_each_entry(system, &event_subsystems, list) {
    > > @@ -633,6 +699,14 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
    > > system->name = name;
    > > list_add(&system->list, &event_subsystems);
    > >
    > > + system->preds = NULL;
    > > +
    > > + entry = debugfs_create_file("filter", 0444, system->entry, system,
    > > + &ftrace_subsystem_filter_fops);
    > > + if (!entry)
    > > + pr_warning("Could not create debugfs "
    > > + "'%s/filter' entry\n", name);
    > > +
    > > return system->entry;
    > > }
    > >
    > > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
    > > index 8e8c5fa..1ab20ce 100644
    > > --- a/kernel/trace/trace_events_filter.c
    > > +++ b/kernel/trace/trace_events_filter.c
    > > @@ -181,6 +181,27 @@ void filter_free_preds(struct ftrace_event_call *call)
    > > }
    > > }
    > >
    > > +void filter_free_subsystem_preds(struct event_subsystem *system)
    > > +{
    > > + struct ftrace_event_call *call = __start_ftrace_events;
    > > + int i;
    > > +
    > > + if (system->preds) {
    > > + for (i = 0; i < MAX_FILTER_PRED; i++)
    > > + filter_free_pred(system->preds[i]);
    > > + kfree(system->preds);
    > > + system->preds = NULL;
    > > + }
    > > +
    > > + events_for_each(call) {
    > > + if (!call->name || !call->regfunc)
    > > + continue;
    > > +
    > > + if (!strcmp(call->system, system->name))
    > > + filter_free_preds(call);
    > > + }
    > > +}
    > > +
    > > static int __filter_add_pred(struct ftrace_event_call *call,
    > > struct filter_pred *pred)
    > > {
    > > @@ -250,6 +271,65 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
    > > return __filter_add_pred(call, pred);
    > > }
    > >
    > > +static struct filter_pred *copy_pred(struct filter_pred *pred)
    > > +{
    > > + struct filter_pred *new_pred = kmalloc(sizeof(*pred), GFP_KERNEL);
    > > + if (!new_pred)
    > > + return NULL;
    > > +
    > > + memcpy(new_pred, pred, sizeof(*pred));
    > > + if (pred->str_val) {
    > > + new_pred->str_val = kstrdup(pred->str_val, GFP_KERNEL);
    > > + new_pred->field_name = kstrdup(pred->field_name, GFP_KERNEL);
    > > + if (!new_pred->str_val) {
    > > + kfree(new_pred);
    >
    > Shouldn't there be a check for field_name too?
    >

    Yes - I posted a patch to copy_pred() yesterday to fix that.

    Tom

    > -- Steve
    >
    > > + return NULL;
    > > + }
    > > + }
    > > +
    > > + return new_pred;
    > > +}
    > > +



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