1 files changed, 30 insertions, 9 deletions

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index a7f946094128..4945d1c99864 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -649,6 +649,7 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
  *      struct ftrace_event_call *event_call = &event_<call>;
  *      extern void perf_tp_event(int, u64, u64, void *, int);
  *      struct ftrace_raw_##call *entry;
+ *      struct perf_trace_buf *trace_buf;
  *      u64 __addr = 0, __count = 1;
  *      unsigned long irq_flags;
  *      struct trace_entry *ent;
@@ -673,14 +674,25 @@ __attribute__((section("_ftrace_events"))) event_##call = {		\
  *      __cpu = smp_processor_id();
  *
  *      if (in_nmi())
- *              raw_data = rcu_dereference(trace_profile_buf_nmi);
+ *              trace_buf = rcu_dereference(perf_trace_buf_nmi);
  *      else
- *              raw_data = rcu_dereference(trace_profile_buf);
+ *              trace_buf = rcu_dereference(perf_trace_buf);
  *
- *      if (!raw_data)
+ *      if (!trace_buf)
  *              goto end;
  *
- *      raw_data = per_cpu_ptr(raw_data, __cpu);
+ *      trace_buf = per_cpu_ptr(trace_buf, __cpu);
+ *
+ *      // Avoid recursion from perf that could mess up the buffer
+ *      if (trace_buf->recursion++)
+ *              goto end_recursion;
+ *
+ *      raw_data = trace_buf->buf;
+ *
+ *      // Make recursion update visible before entering perf_tp_event
+ *      // so that we protect from perf recursions.
+ *
+ *      barrier();
  *
  *      //zero dead bytes from alignment to avoid stack leak to userspace:
  *      *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;
@@ -713,8 +725,9 @@ static void ftrace_profile_##call(proto)				\
 {                                                                       \
         struct ftrace_data_offsets_##call __maybe_unused __data_offsets;\
         struct ftrace_event_call *event_call = &event_##call;           \
-        extern void perf_tp_event(int, u64, u64, void *, int);  \
+        extern void perf_tp_event(int, u64, u64, void *, int);          \
         struct ftrace_raw_##call *entry;                                \
+        struct perf_trace_buf *trace_buf;                               \
         u64 __addr = 0, __count = 1;                                    \
         unsigned long irq_flags;                                        \
         struct trace_entry *ent;                                        \
@@ -739,14 +752,20 @@ static void ftrace_profile_##call(proto)				\
         __cpu = smp_processor_id();                                     \
                                                                         \
         if (in_nmi())                                                   \
-                raw_data = rcu_dereference(trace_profile_buf_nmi);              \
+                trace_buf = rcu_dereference(perf_trace_buf_nmi);        \
         else                                                            \
-                raw_data = rcu_dereference(trace_profile_buf);          \
+                trace_buf = rcu_dereference(perf_trace_buf);            \
                                                                         \
-        if (!raw_data)                                                  \
+        if (!trace_buf)                                                 \
                 goto end;                                               \
                                                                         \
-        raw_data = per_cpu_ptr(raw_data, __cpu);                        \
+        trace_buf = per_cpu_ptr(trace_buf, __cpu);                      \
+        if (trace_buf->recursion++)                                     \
+                goto end_recursion;                                     \
+                                                                        \
+        barrier();                                                      \
+                                                                        \
+        raw_data = trace_buf->buf;                                      \
                                                                         \
         *(u64 *)(&raw_data[__entry_size - sizeof(u64)]) = 0ULL;         \
         entry = (struct ftrace_raw_##call *)raw_data;                   \
@@ -761,6 +780,8 @@ static void ftrace_profile_##call(proto)				\
         perf_tp_event(event_call->id, __addr, __count, entry,           \
                              __entry_size);                             \
                                                                         \
+end_recursion:                                                          \
+        trace_buf->recursion--;                                         \
 end:                                                                    \
         local_irq_restore(irq_flags);                                   \
                                                                         \