1 files changed, 70 insertions, 8 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 42ca822fc701..b20428c5efe2 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -20,13 +20,24 @@
 
 #define STACK_TRACE_ENTRIES 500
 
+#ifdef CC_USING_FENTRY
+# define fentry         1
+#else
+# define fentry         0
+#endif
+
 static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] =
          { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX };
 static unsigned stack_dump_index[STACK_TRACE_ENTRIES];
 
+/*
+ * Reserve one entry for the passed in ip. This will allow
+ * us to remove most or all of the stack size overhead
+ * added by the stack tracer itself.
+ */
 static struct stack_trace max_stack_trace = {
-        .max_entries            = STACK_TRACE_ENTRIES,
-        .entries                = stack_dump_trace,
+        .max_entries            = STACK_TRACE_ENTRIES - 1,
+        .entries                = &stack_dump_trace[1],
 };
 
 static unsigned long max_stack_size;
@@ -39,25 +50,34 @@ static DEFINE_MUTEX(stack_sysctl_mutex);
 int stack_tracer_enabled;
 static int last_stack_tracer_enabled;
 
-static inline void check_stack(void)
+static inline void
+check_stack(unsigned long ip, unsigned long *stack)
 {
         unsigned long this_size, flags;
         unsigned long *p, *top, *start;
+        static int tracer_frame;
+        int frame_size = ACCESS_ONCE(tracer_frame);
         int i;
 
-        this_size = ((unsigned long)&this_size) & (THREAD_SIZE-1);
+        this_size = ((unsigned long)stack) & (THREAD_SIZE-1);
         this_size = THREAD_SIZE - this_size;
+        /* Remove the frame of the tracer */
+        this_size -= frame_size;
 
         if (this_size <= max_stack_size)
                 return;
 
         /* we do not handle interrupt stacks yet */
-        if (!object_is_on_stack(&this_size))
+        if (!object_is_on_stack(stack))
                 return;
 
         local_irq_save(flags);
         arch_spin_lock(&max_stack_lock);
 
+        /* In case another CPU set the tracer_frame on us */
+        if (unlikely(!frame_size))
+                this_size -= tracer_frame;
+
         /* a race could have already updated it */
         if (this_size <= max_stack_size)
                 goto out;
@@ -70,10 +90,18 @@ static inline void check_stack(void)
         save_stack_trace(&max_stack_trace);
 
         /*
+         * Add the passed in ip from the function tracer.
+         * Searching for this on the stack will skip over
+         * most of the overhead from the stack tracer itself.
+         */
+        stack_dump_trace[0] = ip;
+        max_stack_trace.nr_entries++;
+
+        /*
          * Now find where in the stack these are.
          */
         i = 0;
-        start = &this_size;
+        start = stack;
         top = (unsigned long *)
                 (((unsigned long)start & ~(THREAD_SIZE-1)) + THREAD_SIZE);
 
@@ -97,6 +125,18 @@ static inline void check_stack(void)
                                 found = 1;
                                 /* Start the search from here */
                                 start = p + 1;
+                                /*
+                                 * We do not want to show the overhead
+                                 * of the stack tracer stack in the
+                                 * max stack. If we haven't figured
+                                 * out what that is, then figure it out
+                                 * now.
+                                 */
+                                if (unlikely(!tracer_frame) && i == 1) {
+                                        tracer_frame = (p - stack) *
+                                                sizeof(unsigned long);
+                                        max_stack_size -= tracer_frame;
+                                }
                         }
                 }
 
@@ -113,6 +153,7 @@ static void
 stack_trace_call(unsigned long ip, unsigned long parent_ip,
                  struct ftrace_ops *op, struct pt_regs *pt_regs)
 {
+        unsigned long stack;
         int cpu;
 
         preempt_disable_notrace();
@@ -122,7 +163,26 @@ stack_trace_call(unsigned long ip, unsigned long parent_ip,
         if (per_cpu(trace_active, cpu)++ != 0)
                 goto out;
 
-        check_stack();
+        /*
+         * When fentry is used, the traced function does not get
+         * its stack frame set up, and we lose the parent.
+         * The ip is pretty useless because the function tracer
+         * was called before that function set up its stack frame.
+         * In this case, we use the parent ip.
+         *
+         * By adding the return address of either the parent ip
+         * or the current ip we can disregard most of the stack usage
+         * caused by the stack tracer itself.
+         *
+         * The function tracer always reports the address of where the
+         * mcount call was, but the stack will hold the return address.
+         */
+        if (fentry)
+                ip = parent_ip;
+        else
+                ip += MCOUNT_INSN_SIZE;
+
+        check_stack(ip, &stack);
 
  out:
         per_cpu(trace_active, cpu)--;
@@ -322,7 +382,7 @@ static const struct file_operations stack_trace_filter_fops = {
         .open = stack_trace_filter_open,
         .read = seq_read,
         .write = ftrace_filter_write,
-        .llseek = ftrace_regex_lseek,
+        .llseek = ftrace_filter_lseek,
         .release = ftrace_regex_release,
 };
 
@@ -371,6 +431,8 @@ static __init int stack_trace_init(void)
         struct dentry *d_tracer;
 
         d_tracer = tracing_init_dentry();
+        if (!d_tracer)
+                return 0;
 
         trace_create_file("stack_max_size", 0644, d_tracer,
                         &max_stack_size, &stack_max_size_fops);