Merge tag 'trace-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux...

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / kernel / trace / trace_stack.c

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 83a8b5b7bd35fa01a5e0302d83bf3d33d81f9557..b20428c5efe26ba54ef2a6e83bb9ad711a9f85b5 100644 (file)
--- 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;
@@ -69,11 +89,19 @@ 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)--;
@@ -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);