tracing/kprobes: Support ftrace_event_file base multibuffer

Support multi-buffer on kprobe-based dynamic events by
using ftrace_event_file.

Link: http://lkml.kernel.org/r/20130509054449.30398.88343.stgit@mhiramat-M0-7522

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 214 insertions, 36 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 9ca44fc3fb0b..fee865d8a7c4 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -27,7 +27,6 @@
 /**
  * Kprobe event core functions
  */
-
 struct trace_probe {
         struct list_head        list;
         struct kretprobe        rp;     /* Use rp.kp for kprobe use */
@@ -36,6 +35,7 @@ struct trace_probe {
         const char              *symbol;        /* symbol name */
         struct ftrace_event_class       class;
         struct ftrace_event_call        call;
+        struct ftrace_event_file        **files;
         ssize_t                 size;           /* trace entry size */
         unsigned int            nr_args;
         struct probe_arg        args[];
@@ -183,12 +183,57 @@ static struct trace_probe *find_trace_probe(const char *event,
         return NULL;
 }
 
-/* Enable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
-static int enable_trace_probe(struct trace_probe *tp, int flag)
+static int trace_probe_nr_files(struct trace_probe *tp)
+{
+        struct ftrace_event_file **file = tp->files;
+        int ret = 0;
+
+        if (file)
+                while (*(file++))
+                        ret++;
+
+        return ret;
+}
+
+static DEFINE_MUTEX(probe_enable_lock);
+
+/*
+ * Enable trace_probe
+ * if the file is NULL, enable "perf" handler, or enable "trace" handler.
+ */
+static int
+enable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
 {
         int ret = 0;
 
-        tp->flags |= flag;
+        mutex_lock(&probe_enable_lock);
+
+        if (file) {
+                struct ftrace_event_file **new, **old = tp->files;
+                int n = trace_probe_nr_files(tp);
+
+                /* 1 is for new one and 1 is for stopper */
+                new = kzalloc((n + 2) * sizeof(struct ftrace_event_file *),
+                              GFP_KERNEL);
+                if (!new) {
+                        ret = -ENOMEM;
+                        goto out_unlock;
+                }
+                memcpy(new, old, n * sizeof(struct ftrace_event_file *));
+                new[n] = file;
+                /* The last one keeps a NULL */
+
+                rcu_assign_pointer(tp->files, new);
+                tp->flags |= TP_FLAG_TRACE;
+
+                if (old) {
+                        /* Make sure the probe is done with old files */
+                        synchronize_sched();
+                        kfree(old);
+                }
+        } else
+                tp->flags |= TP_FLAG_PROFILE;
+
         if (trace_probe_is_enabled(tp) && trace_probe_is_registered(tp) &&
             !trace_probe_has_gone(tp)) {
                 if (trace_probe_is_return(tp))
@@ -197,19 +242,83 @@ static int enable_trace_probe(struct trace_probe *tp, int flag)
                         ret = enable_kprobe(&tp->rp.kp);
         }
 
+ out_unlock:
+        mutex_unlock(&probe_enable_lock);
+
         return ret;
 }
 
-/* Disable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
-static void disable_trace_probe(struct trace_probe *tp, int flag)
+static int
+trace_probe_file_index(struct trace_probe *tp, struct ftrace_event_file *file)
+{
+        int i;
+
+        if (tp->files) {
+                for (i = 0; tp->files[i]; i++)
+                        if (tp->files[i] == file)
+                                return i;
+        }
+
+        return -1;
+}
+
+/*
+ * Disable trace_probe
+ * if the file is NULL, disable "perf" handler, or disable "trace" handler.
+ */
+static int
+disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
 {
-        tp->flags &= ~flag;
+        int ret = 0;
+
+        mutex_lock(&probe_enable_lock);
+
+        if (file) {
+                struct ftrace_event_file **new, **old = tp->files;
+                int n = trace_probe_nr_files(tp);
+                int i, j;
+
+                if (n == 0 || trace_probe_file_index(tp, file) < 0) {
+                        ret = -EINVAL;
+                        goto out_unlock;
+                }
+
+                if (n == 1) {   /* Remove the last file */
+                        tp->flags &= ~TP_FLAG_TRACE;
+                        new = NULL;
+                } else {
+                        new = kzalloc(n * sizeof(struct ftrace_event_file *),
+                                      GFP_KERNEL);
+                        if (!new) {
+                                ret = -ENOMEM;
+                                goto out_unlock;
+                        }
+
+                        /* This copy & check loop copies the NULL stopper too */
+                        for (i = 0, j = 0; j < n && i < n + 1; i++)
+                                if (old[i] != file)
+                                        new[j++] = old[i];
+                }
+
+                rcu_assign_pointer(tp->files, new);
+
+                /* Make sure the probe is done with old files */
+                synchronize_sched();
+                kfree(old);
+        } else
+                tp->flags &= ~TP_FLAG_PROFILE;
+
         if (!trace_probe_is_enabled(tp) && trace_probe_is_registered(tp)) {
                 if (trace_probe_is_return(tp))
                         disable_kretprobe(&tp->rp);
                 else
                         disable_kprobe(&tp->rp.kp);
         }
+
+ out_unlock:
+        mutex_unlock(&probe_enable_lock);
+
+        return ret;
 }
 
 /* Internal register function - just handle k*probes and flags */
@@ -724,7 +833,8 @@ static __kprobes void store_trace_args(int ent_size, struct trace_probe *tp,
 
 /* Kprobe handler */
 static __kprobes void
-kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)
+__kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs,
+                    struct ftrace_event_file *ftrace_file)
 {
         struct kprobe_trace_entry_head *entry;
         struct ring_buffer_event *event;
@@ -733,14 +843,17 @@ kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)
         unsigned long irq_flags;
         struct ftrace_event_call *call = &tp->call;
 
+        WARN_ON(call != ftrace_file->event_call);
+
         local_save_flags(irq_flags);
         pc = preempt_count();
 
         dsize = __get_data_size(tp, regs);
         size = sizeof(*entry) + tp->size + dsize;
 
-        event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
-                                                  size, irq_flags, pc);
+        event = trace_event_buffer_lock_reserve(&buffer, ftrace_file,
+                                                call->event.type,
+                                                size, irq_flags, pc);
         if (!event)
                 return;
 
@@ -753,10 +866,23 @@ kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)
                                                 irq_flags, pc, regs);
 }
 
+static __kprobes void
+kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs)
+{
+        struct ftrace_event_file **file = tp->files;
+
+        /* Note: preempt is already disabled around the kprobe handler */
+        while (*file) {
+                __kprobe_trace_func(tp, regs, *file);
+                file++;
+        }
+}
+
 /* Kretprobe handler */
 static __kprobes void
-kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
-                     struct pt_regs *regs)
+__kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
+                       struct pt_regs *regs,
+                       struct ftrace_event_file *ftrace_file)
 {
         struct kretprobe_trace_entry_head *entry;
         struct ring_buffer_event *event;
@@ -765,14 +891,17 @@ kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
         unsigned long irq_flags;
         struct ftrace_event_call *call = &tp->call;
 
+        WARN_ON(call != ftrace_file->event_call);
+
         local_save_flags(irq_flags);
         pc = preempt_count();
 
         dsize = __get_data_size(tp, regs);
         size = sizeof(*entry) + tp->size + dsize;
 
-        event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
-                                                  size, irq_flags, pc);
+        event = trace_event_buffer_lock_reserve(&buffer, ftrace_file,
+                                                call->event.type,
+                                                size, irq_flags, pc);
         if (!event)
                 return;
 
@@ -786,6 +915,19 @@ kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
                                                 irq_flags, pc, regs);
 }
 
+static __kprobes void
+kretprobe_trace_func(struct trace_probe *tp, struct kretprobe_instance *ri,
+                     struct pt_regs *regs)
+{
+        struct ftrace_event_file **file = tp->files;
+
+        /* Note: preempt is already disabled around the kprobe handler */
+        while (*file) {
+                __kretprobe_trace_func(tp, ri, regs, *file);
+                file++;
+        }
+}
+
 /* Event entry printers */
 enum print_line_t
 print_kprobe_event(struct trace_iterator *iter, int flags,
@@ -1041,20 +1183,19 @@ int kprobe_register(struct ftrace_event_call *event,
                     enum trace_reg type, void *data)
 {
         struct trace_probe *tp = (struct trace_probe *)event->data;
+        struct ftrace_event_file *file = data;
 
         switch (type) {
         case TRACE_REG_REGISTER:
-                return enable_trace_probe(tp, TP_FLAG_TRACE);
+                return enable_trace_probe(tp, file);
         case TRACE_REG_UNREGISTER:
-                disable_trace_probe(tp, TP_FLAG_TRACE);
-                return 0;
+                return disable_trace_probe(tp, file);
 
 #ifdef CONFIG_PERF_EVENTS
         case TRACE_REG_PERF_REGISTER:
-                return enable_trace_probe(tp, TP_FLAG_PROFILE);
+                return enable_trace_probe(tp, NULL);
         case TRACE_REG_PERF_UNREGISTER:
-                disable_trace_probe(tp, TP_FLAG_PROFILE);
-                return 0;
+                return disable_trace_probe(tp, NULL);
         case TRACE_REG_PERF_OPEN:
         case TRACE_REG_PERF_CLOSE:
         case TRACE_REG_PERF_ADD:
@@ -1190,11 +1331,24 @@ static __used int kprobe_trace_selftest_target(int a1, int a2, int a3,
         return a1 + a2 + a3 + a4 + a5 + a6;
 }
 
+static struct ftrace_event_file *
+find_trace_probe_file(struct trace_probe *tp, struct trace_array *tr)
+{
+        struct ftrace_event_file *file;
+
+        list_for_each_entry(file, &tr->events, list)
+                if (file->event_call == &tp->call)
+                        return file;
+
+        return NULL;
+}
+
 static __init int kprobe_trace_self_tests_init(void)
 {
         int ret, warn = 0;
         int (*target)(int, int, int, int, int, int);
         struct trace_probe *tp;
+        struct ftrace_event_file *file;
 
         target = kprobe_trace_selftest_target;
 
@@ -1204,31 +1358,43 @@ static __init int kprobe_trace_self_tests_init(void)
                                   "$stack $stack0 +0($stack)",
                                   create_trace_probe);
         if (WARN_ON_ONCE(ret)) {
-                pr_warning("error on probing function entry.\n");
+                pr_warn("error on probing function entry.\n");
                 warn++;
         } else {
                 /* Enable trace point */
                 tp = find_trace_probe("testprobe", KPROBE_EVENT_SYSTEM);
                 if (WARN_ON_ONCE(tp == NULL)) {
-                        pr_warning("error on getting new probe.\n");
+                        pr_warn("error on getting new probe.\n");
                         warn++;
-                } else
-                        enable_trace_probe(tp, TP_FLAG_TRACE);
+                } else {
+                        file = find_trace_probe_file(tp, top_trace_array());
+                        if (WARN_ON_ONCE(file == NULL)) {
+                                pr_warn("error on getting probe file.\n");
+                                warn++;
+                        } else
+                                enable_trace_probe(tp, file);
+                }
         }
 
         ret = traceprobe_command("r:testprobe2 kprobe_trace_selftest_target "
                                   "$retval", create_trace_probe);
         if (WARN_ON_ONCE(ret)) {
-                pr_warning("error on probing function return.\n");
+                pr_warn("error on probing function return.\n");
                 warn++;
         } else {
                 /* Enable trace point */
                 tp = find_trace_probe("testprobe2", KPROBE_EVENT_SYSTEM);
                 if (WARN_ON_ONCE(tp == NULL)) {
-                        pr_warning("error on getting new probe.\n");
+                        pr_warn("error on getting 2nd new probe.\n");
                         warn++;
-                } else
-                        enable_trace_probe(tp, TP_FLAG_TRACE);
+                } else {
+                        file = find_trace_probe_file(tp, top_trace_array());
+                        if (WARN_ON_ONCE(file == NULL)) {
+                                pr_warn("error on getting probe file.\n");
+                                warn++;
+                        } else
+                                enable_trace_probe(tp, file);
+                }
         }
 
         if (warn)
@@ -1239,27 +1405,39 @@ static __init int kprobe_trace_self_tests_init(void)
         /* Disable trace points before removing it */
         tp = find_trace_probe("testprobe", KPROBE_EVENT_SYSTEM);
         if (WARN_ON_ONCE(tp == NULL)) {
-                pr_warning("error on getting test probe.\n");
+                pr_warn("error on getting test probe.\n");
                 warn++;
-        } else
-                disable_trace_probe(tp, TP_FLAG_TRACE);
+        } else {
+                file = find_trace_probe_file(tp, top_trace_array());
+                if (WARN_ON_ONCE(file == NULL)) {
+                        pr_warn("error on getting probe file.\n");
+                        warn++;
+                } else
+                        disable_trace_probe(tp, file);
+        }
 
         tp = find_trace_probe("testprobe2", KPROBE_EVENT_SYSTEM);
         if (WARN_ON_ONCE(tp == NULL)) {
-                pr_warning("error on getting 2nd test probe.\n");
+                pr_warn("error on getting 2nd test probe.\n");
                 warn++;
-        } else
-                disable_trace_probe(tp, TP_FLAG_TRACE);
+        } else {
+                file = find_trace_probe_file(tp, top_trace_array());
+                if (WARN_ON_ONCE(file == NULL)) {
+                        pr_warn("error on getting probe file.\n");
+                        warn++;
+                } else
+                        disable_trace_probe(tp, file);
+        }
 
         ret = traceprobe_command("-:testprobe", create_trace_probe);
         if (WARN_ON_ONCE(ret)) {
-                pr_warning("error on deleting a probe.\n");
+                pr_warn("error on deleting a probe.\n");
                 warn++;
         }
 
         ret = traceprobe_command("-:testprobe2", create_trace_probe);
         if (WARN_ON_ONCE(ret)) {
-                pr_warning("error on deleting a probe.\n");
+                pr_warn("error on deleting a probe.\n");
                 warn++;
         }