[PATCH 1/2] ps: Add support to "ps -l" to properly display process list

[Austin Kim <austindh.kim@xxxxxxxxx>]

Sometimes kernel image is generated without CONFIG_SCHED_STAT or CONFIG_SCHED_INFO.

Running crash-utility with above kernel image,
"ps -l" options cannot display all processes sorted with most recently-run process

crash> ps -l
ps: last-run timestamps do not exist in this kernel
Usage:
  ps [-k|-u|-G] [-s] [-p|-c|-t|-[l|m][-C cpu]|-a|-g|-r|-S]
     [pid | task | command] ...
Enter "help ps" for details.

This is because output of 'ps -l' depends on task_struct.sched_info.last_arrival.
Without CONFIG_SCHED_STAT or CONFIG_SCHED_INFO, 'sched_info' field is not included
in task_struct.

So we make 'ps -e' option to access 'exec_start' field of sched_entity.
where 'exec_start' is task_struct.se.exec_start.

With this patch, "ps -l" option works well without CONFIG_SCHED_STAT or 
CONFIG_SCHED_INFO.

The history of CONFIG_SCHED_INFO and CONFIG_SCHED_STAT is as below;

  - CONFIG_SCHED_INFO: KERNEL_VERSION >= LINUX(4,2,0)
  - CONFIG_SCHED_STAT: KERNEL_VERSION < LINUX(4,2,0)

Signed-off-by: Austin Kim <austindh.kim@xxxxxxxxx>
---
 defs.h    |  2 ++
 symbols.c |  2 ++
 task.c    | 17 ++++++++++++++---
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/defs.h b/defs.h
index 7d386d2..ed2f5ca 100644
--- a/defs.h
+++ b/defs.h
@@ -1768,6 +1768,8 @@ struct offset_table {                    /* stash of commonly-used offsets */
 	long vcpu_struct_rq;
 	long task_struct_sched_info;
 	long sched_info_last_arrival;
+	long task_struct_sched_entity;
+	long se_exec_start;
 	long page_objects;
 	long kmem_cache_oo;
 	long char_device_struct_cdev;
diff --git a/symbols.c b/symbols.c
index 97fb778..5e2032a 100644
--- a/symbols.c
+++ b/symbols.c
@@ -8892,6 +8892,8 @@ dump_offset_table(char *spec, ulong makestruct)
                 OFFSET(sched_rt_entity_run_list));
 	fprintf(fp, "       sched_info_last_arrival: %ld\n",
                 OFFSET(sched_info_last_arrival));
+		fprintf(fp, "       se_exec_start: %ld\n",
+				OFFSET(se_exec_start));
         fprintf(fp, "       task_struct_thread_info: %ld\n",
                 OFFSET(task_struct_thread_info));
         fprintf(fp, "             task_struct_stack: %ld\n",
diff --git a/task.c b/task.c
index 864c838..e6fde74 100644
--- a/task.c
+++ b/task.c
@@ -334,9 +334,15 @@ task_init(void)
 	if (VALID_MEMBER(task_struct_sched_info))
 		MEMBER_OFFSET_INIT(sched_info_last_arrival, 
 			"sched_info", "last_arrival");
+	MEMBER_OFFSET_INIT(task_struct_sched_entity, "task_struct", "se");
+	if (VALID_MEMBER(task_struct_sched_entity)) {
+		STRUCT_SIZE_INIT(sched_entity, "sched_entity");
+		MEMBER_OFFSET_INIT(se_exec_start, "sched_entity", "exec_start");
+	}
 	if (VALID_MEMBER(task_struct_last_run) || 
 	    VALID_MEMBER(task_struct_timestamp) ||
-	    VALID_MEMBER(sched_info_last_arrival)) {
+	    VALID_MEMBER(sched_info_last_arrival) ||
+	    VALID_MEMBER(se_exec_start)) {
 		char buf[BUFSIZE];
 	        strcpy(buf, "alias last ps -l");
         	alias_init(buf);
@@ -3574,7 +3580,8 @@ cmd_ps(void)
 		case 'l':
 			if (INVALID_MEMBER(task_struct_last_run) &&
 			    INVALID_MEMBER(task_struct_timestamp) &&
-			    INVALID_MEMBER(sched_info_last_arrival)) {
+			    INVALID_MEMBER(sched_info_last_arrival) &&
+			    INVALID_MEMBER(se_exec_start)) {
 				error(INFO, 
                             "last-run timestamps do not exist in this kernel\n");
 				argerrs++;
@@ -6020,7 +6027,11 @@ task_last_run(ulong task)
         	timestamp = tt->last_task_read ?  ULONGLONG(tt->task_struct + 
 			OFFSET(task_struct_sched_info) + 
 			OFFSET(sched_info_last_arrival)) : 0;
-	
+	else if (VALID_MEMBER(se_exec_start))
+			timestamp = tt->last_task_read ?  ULONGLONG(tt->task_struct +
+			OFFSET(task_struct_sched_entity) +
+			OFFSET(se_exec_start)) : 0;
+
         return timestamp;
 }
 
-- 
2.20.1

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