[Crash-utility] [PATCH 1/1] Handle task_struct cpu member changes in linux-next

[Alexander Egorenkov]

Kernel commit bcf9033e5449bdcaa9bed46467a7141a8049dadb
("sched: move CPU field back into thread_info if THREAD_INFO_IN_TASK=y")
moved the member cpu of task_struct back into thread_info.

https://lkml.org/lkml/2021/9/30/517

This fixes the following problem:

please wait... (gathering task table data)
crash: invalid structure member offset: task_struct_cpu
       FILE: task.c  LINE: 2904  FUNCTION: add_context()

[/usr/bin/crash] error trace: 114840a => 115560a => 114e360 => 11d6394

  11d6394: (undetermined)
  114e360: (undetermined)
  115560a: (undetermined)
  114840a: task_init+4634

Signed-off-by: Alexander Egorenkov <egorenar at linux.ibm.com>
---
 task.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/task.c b/task.c
index 672b41697e75..bb6a5da8ad33 100644
--- a/task.c
+++ b/task.c
@@ -278,8 +278,10 @@ task_init(void)
 	} else if (VALID_MEMBER(task_struct_stack))
 		MEMBER_OFFSET_INIT(task_struct_thread_info, "task_struct", "stack");
 
+	MEMBER_OFFSET_INIT(task_struct_cpu, "task_struct", "cpu");
+
 	if (VALID_MEMBER(task_struct_thread_info)) {
-		if (tt->flags & THREAD_INFO_IN_TASK) {
+		if (tt->flags & THREAD_INFO_IN_TASK && VALID_MEMBER(task_struct_cpu)) {
 			MEMBER_OFFSET_INIT(thread_info_flags, "thread_info", "flags");
 			/* (unnecessary) reminders */
 			ASSIGN_OFFSET(thread_info_task) = INVALID_OFFSET;
@@ -315,7 +317,6 @@ task_init(void)
         MEMBER_OFFSET_INIT(task_struct_has_cpu, "task_struct", "has_cpu");
         MEMBER_OFFSET_INIT(task_struct_cpus_runnable,  
 		"task_struct", "cpus_runnable");
-	MEMBER_OFFSET_INIT(task_struct_cpu, "task_struct", "cpu");
 	MEMBER_OFFSET_INIT(task_struct_active_mm, "task_struct", "active_mm");
 	MEMBER_OFFSET_INIT(task_struct_next_run, "task_struct", "next_run");
 	MEMBER_OFFSET_INIT(task_struct_flags, "task_struct", "flags");
@@ -2900,7 +2901,7 @@ add_context(ulong task, char *tp)
 		else
 			tc->thread_info = ULONG(tp + OFFSET(task_struct_thread_info));
 		fill_thread_info(tc->thread_info);
-		if (tt->flags & THREAD_INFO_IN_TASK)
+		if (tt->flags & THREAD_INFO_IN_TASK && VALID_MEMBER(task_struct_cpu))
                 	processor_addr = (int *) (tp + OFFSET(task_struct_cpu));
 		else
 			processor_addr = (int *) (tt->thread_info + 
-- 
2.31.1