tracing/uprobes: Support ftrace_event_file base multibuffer

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

This patch is based kprobe-based dynamic events multibuffer
support work initially, commited by Masami(commit 41a7dd420c),
but revised as below:

Oleg changed the kprobe-based multibuffer design from
array-pointers of ftrace_event_file into simple list,
so this patch also change to the list design.

rcu_read_lock/unlock added into uprobe_trace_func/uretprobe_trace_func,
to synchronize with ftrace_event_file list add and delete.

Even though we allow multi-uprobes instances now,
but TP_FLAG_PROFILE/TP_FLAG_TRACE are still mutually exclusive
in probe_event_enable currently, this means we cannot allow
one user is using uprobe-tracer, and another user is using
perf-probe on same uprobe concurrently.
(Perhaps this will be fix in future, kprobe don't have this
limitation now)

Link: http://lkml.kernel.org/r/1389946120-19610-4-git-send-email-namhyung@kernel.org

Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 84 insertions, 21 deletions

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index d83155e0da78..349c6df9e332 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -260,6 +260,7 @@ alloc_trace_uprobe(const char *group, const char *event, int nargs, bool is_ret)
                 goto error;
 
         INIT_LIST_HEAD(&tu->list);
+        INIT_LIST_HEAD(&tu->tp.files);
         tu->consumer.handler = uprobe_dispatcher;
         if (is_ret)
                 tu->consumer.ret_handler = uretprobe_dispatcher;
@@ -760,7 +761,8 @@ static void uprobe_buffer_put(struct uprobe_cpu_buffer *ucb)
 
 static void __uprobe_trace_func(struct trace_uprobe *tu,
                                 unsigned long func, struct pt_regs *regs,
-                                struct uprobe_cpu_buffer *ucb, int dsize)
+                                struct uprobe_cpu_buffer *ucb, int dsize,
+                                struct ftrace_event_file *ftrace_file)
 {
         struct uprobe_trace_entry_head *entry;
         struct ring_buffer_event *event;
@@ -769,13 +771,15 @@ static void __uprobe_trace_func(struct trace_uprobe *tu,
         int size, esize;
         struct ftrace_event_call *call = &tu->tp.call;
 
+        WARN_ON(call != ftrace_file->event_call);
+
         if (WARN_ON_ONCE(tu->tp.size + dsize > PAGE_SIZE))
                 return;
 
         esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));
         size = esize + tu->tp.size + dsize;
-        event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
-                                                  size, 0, 0);
+        event = trace_event_buffer_lock_reserve(&buffer, ftrace_file,
+                                                call->event.type, size, 0, 0);
         if (!event)
                 return;
 
@@ -799,8 +803,16 @@ static void __uprobe_trace_func(struct trace_uprobe *tu,
 static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs,
                              struct uprobe_cpu_buffer *ucb, int dsize)
 {
-        if (!is_ret_probe(tu))
-                __uprobe_trace_func(tu, 0, regs, ucb, dsize);
+        struct event_file_link *link;
+
+        if (is_ret_probe(tu))
+                return 0;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(link, &tu->tp.files, list)
+                __uprobe_trace_func(tu, 0, regs, ucb, dsize, link->file);
+        rcu_read_unlock();
+
         return 0;
 }
 
@@ -808,7 +820,12 @@ static void uretprobe_trace_func(struct trace_uprobe *tu, unsigned long func,
                                  struct pt_regs *regs,
                                  struct uprobe_cpu_buffer *ucb, int dsize)
 {
-        __uprobe_trace_func(tu, func, regs, ucb, dsize);
+        struct event_file_link *link;
+
+        rcu_read_lock();
+        list_for_each_entry_rcu(link, &tu->tp.files, list)
+                __uprobe_trace_func(tu, func, regs, ucb, dsize, link->file);
+        rcu_read_unlock();
 }
 
 /* Event entry printers */
@@ -855,12 +872,31 @@ typedef bool (*filter_func_t)(struct uprobe_consumer *self,
                                 struct mm_struct *mm);
 
 static int
-probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
+probe_event_enable(struct trace_uprobe *tu, struct ftrace_event_file *file,
+                   filter_func_t filter)
 {
-        int ret = 0;
+        bool enabled = trace_probe_is_enabled(&tu->tp);
+        struct event_file_link *link = NULL;
+        int ret;
+
+        if (file) {
+                if (tu->tp.flags & TP_FLAG_PROFILE)
+                        return -EINTR;
 
-        if (trace_probe_is_enabled(&tu->tp))
-                return -EINTR;
+                link = kmalloc(sizeof(*link), GFP_KERNEL);
+                if (!link)
+                        return -ENOMEM;
+
+                link->file = file;
+                list_add_tail_rcu(&link->list, &tu->tp.files);
+
+                tu->tp.flags |= TP_FLAG_TRACE;
+        } else {
+                if (tu->tp.flags & TP_FLAG_TRACE)
+                        return -EINTR;
+
+                tu->tp.flags |= TP_FLAG_PROFILE;
+        }
 
         ret = uprobe_buffer_enable();
         if (ret < 0)
@@ -868,24 +904,49 @@ probe_event_enable(struct trace_uprobe *tu, int flag, filter_func_t filter)
 
         WARN_ON(!uprobe_filter_is_empty(&tu->filter));
 
-        tu->tp.flags |= flag;
+        if (enabled)
+                return 0;
+
         tu->consumer.filter = filter;
         ret = uprobe_register(tu->inode, tu->offset, &tu->consumer);
-        if (ret)
-                tu->tp.flags &= ~flag;
+        if (ret) {
+                if (file) {
+                        list_del(&link->list);
+                        kfree(link);
+                        tu->tp.flags &= ~TP_FLAG_TRACE;
+                } else
+                        tu->tp.flags &= ~TP_FLAG_PROFILE;
+        }
 
         return ret;
 }
 
-static void probe_event_disable(struct trace_uprobe *tu, int flag)
+static void
+probe_event_disable(struct trace_uprobe *tu, struct ftrace_event_file *file)
 {
         if (!trace_probe_is_enabled(&tu->tp))
                 return;
 
+        if (file) {
+                struct event_file_link *link;
+
+                link = find_event_file_link(&tu->tp, file);
+                if (!link)
+                        return;
+
+                list_del_rcu(&link->list);
+                /* synchronize with u{,ret}probe_trace_func */
+                synchronize_sched();
+                kfree(link);
+
+                if (!list_empty(&tu->tp.files))
+                        return;
+        }
+
         WARN_ON(!uprobe_filter_is_empty(&tu->filter));
 
         uprobe_unregister(tu->inode, tu->offset, &tu->consumer);
-        tu->tp.flags &= ~flag;
+        tu->tp.flags &= file ? ~TP_FLAG_TRACE : ~TP_FLAG_PROFILE;
 
         uprobe_buffer_disable();
 }
@@ -1077,25 +1138,27 @@ static void uretprobe_perf_func(struct trace_uprobe *tu, unsigned long func,
 }
 #endif  /* CONFIG_PERF_EVENTS */
 
-static
-int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type, void *data)
+static int
+trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
+                      void *data)
 {
         struct trace_uprobe *tu = event->data;
+        struct ftrace_event_file *file = data;
 
         switch (type) {
         case TRACE_REG_REGISTER:
-                return probe_event_enable(tu, TP_FLAG_TRACE, NULL);
+                return probe_event_enable(tu, file, NULL);
 
         case TRACE_REG_UNREGISTER:
-                probe_event_disable(tu, TP_FLAG_TRACE);
+                probe_event_disable(tu, file);
                 return 0;
 
 #ifdef CONFIG_PERF_EVENTS
         case TRACE_REG_PERF_REGISTER:
-                return probe_event_enable(tu, TP_FLAG_PROFILE, uprobe_perf_filter);
+                return probe_event_enable(tu, NULL, uprobe_perf_filter);
 
         case TRACE_REG_PERF_UNREGISTER:
-                probe_event_disable(tu, TP_FLAG_PROFILE);
+                probe_event_disable(tu, NULL);
                 return 0;
 
         case TRACE_REG_PERF_OPEN: