[POC,V2 2/5] task_struct : add additional member for sframe state

[Indu Bhagat <indu.bhagat@oracle.com>]

[Changes in V2]
  - No changes yet.
  - ATM, it is understood that this POC is broken because accessing
    SFrame sections may fault while the perf event is being handled in
    the NMI context. The changes in this patch will likely be reworked.
[End of Changes in V2]

Add a new member to keep track of the SFrame sections for the current
task (program and its DSOs).

The definition of struct sframe_state is owned by the SFrame unwinder,
and added in a later commit.  Regarding the state management of the
task_struct.sframe_state:
  - Allocation and initialization is done at the task initialization
    time in the kernel.
  - Update: Not clear. We need to be able to track dlopen/dlclose, or
    additional shared libraries loaded via the dynamic linker at the
    task execution time.

Signed-off-by: Indu Bhagat <indu.bhagat@oracle.com>
---
 include/linux/sched.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index eed5d65b8d1f..fc0b0c720979 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -71,6 +71,7 @@ struct signal_struct;
 struct task_delay_info;
 struct task_group;
 struct user_event_mm;
+struct sframe_state;
 
 /*
  * Task state bitmask. NOTE! These bits are also
@@ -1534,6 +1535,10 @@ struct task_struct {
 	struct user_event_mm		*user_event_mm;
 #endif
 
+#ifdef CONFIG_USER_UNWINDER_SFRAME
+	struct sframe_state		*sframe_state;
+#endif
+
 	/*
 	 * New fields for task_struct should be added above here, so that
 	 * they are included in the randomized portion of task_struct.
-- 
2.39.2