tracing/function-return-tracer: store return stack into task_struct and allocate it dynamically

Impact: use deeper function tracing depth safely

Some tests showed that function return tracing needed a more deeper depth
of function calls. But it could be unsafe to store these return addresses
to the stack.

So these arrays will now be allocated dynamically into task_struct of current
only when the tracer is activated.

Typical scheme when tracer is activated:
- allocate a return stack for each task in global list.
- fork: allocate the return stack for the newly created task
- exit: free return stack of current
- idle init: same as fork

I chose a default depth of 50. I don't have overruns anymore.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 0 insertions, 29 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index e90e81ef6ab9..0921b4018c11 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -40,36 +40,8 @@ struct thread_info {
                                                 */
         __u8                    supervisor_stack[0];
 #endif
-
-#ifdef CONFIG_FUNCTION_RET_TRACER
-        /* Index of current stored adress in ret_stack */
-        int             curr_ret_stack;
-        /* Stack of return addresses for return function tracing */
-        struct ftrace_ret_stack ret_stack[FTRACE_RET_STACK_SIZE];
-        /*
-         * Number of functions that haven't been traced
-         * because of depth overrun.
-         */
-        atomic_t        trace_overrun;
-#endif
 };
 
-#ifdef CONFIG_FUNCTION_RET_TRACER
-#define INIT_THREAD_INFO(tsk)                   \
-{                                               \
-        .task           = &tsk,                 \
-        .exec_domain    = &default_exec_domain, \
-        .flags          = 0,                    \
-        .cpu            = 0,                    \
-        .preempt_count  = 1,                    \
-        .addr_limit     = KERNEL_DS,            \
-        .restart_block = {                      \
-                .fn = do_no_restart_syscall,    \
-        },                                      \
-        .curr_ret_stack = -1,\
-        .trace_overrun  = ATOMIC_INIT(0)        \
-}
-#else
 #define INIT_THREAD_INFO(tsk)                   \
 {                                               \
         .task           = &tsk,                 \
@@ -82,7 +54,6 @@ struct thread_info {
                 .fn = do_no_restart_syscall,    \
         },                                      \
 }
-#endif
 
 #define init_thread_info        (init_thread_union.thread_info)
 #define init_stack              (init_thread_union.stack)