linux-kernel - Re: crash binary for latest unreleased kernel

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Date:   Wed, 31 Jan 2018 17:03:53 +0100
From:   Mike Galbraith <efault@....de>
To:     Joe Smith <codesoldier1@...il.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: crash binary for latest unreleased kernel

On Wed, 2018-01-31 at 04:51 +0100, Mike Galbraith wrote:
> On Sun, 2018-01-28 at 12:19 -0800, Joe Smith wrote:
> > Thanks a lot, Mike. Following your suggestions worked !!!!
> 
> Until Monday happened :)

And during a rare non-lazy-sod moment...

---
 task.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

--- a/task.c
+++ b/task.c
@@ -438,8 +438,21 @@ task_init(void)
 			len = SIZE(task_union));
 		machdep->stacksize = len;
 	} else if (VALID_SIZE(thread_union) && 
-	    	((len = SIZE(thread_union)) != STACKSIZE())) 
+		   ((len = SIZE(thread_union)) != STACKSIZE())) {
 		machdep->stacksize = len;
+	} else {
+		/*
+		 * Post kernel commit 0500871f21b2, init_thread_union size
+		 * became zero.  Use __end_init_task - __start_init_task.
+		 */
+		if (kernel_symbol_exists("__start_init_task") &&
+		    kernel_symbol_exists("__end_init_task")) {
+			len = symbol_value("__end_init_task");
+			len -= symbol_value("__start_init_task");
+			ASSIGN_SIZE(thread_union) = len;
+			machdep->stacksize = len;
+		}
+	}
 
 	MEMBER_OFFSET_INIT(pid_namespace_idr, "pid_namespace", "idr");
 	MEMBER_OFFSET_INIT(idr_idr_rt, "idr", "idr_rt");