Re: [PATCH] kdump: Fix gdb macros work work with newer and 64-bit kernels

[Baoquan He]

Hi Corey,

I am trying to review this patch now, and these fixes contained are very
great. Just several concerns are added in inline comment.

By the way, did you run this in your side?

Hi Vivek,

Member variable was added into task_struct in below commit replacing
pids[PIDTYPE_TGID], and from then on nobody complained about it. Seems
people rarely use this utility.

commit 47e65328a7b1cdfc4e3102e50d60faf94ebba7d3
Author: Oleg Nesterov <oleg@xxxxxxxxxx>
Date:   Tue Mar 28 16:11:25 2006 -0800

    [PATCH] pids: kill PIDTYPE_TGID



On 04/27/16 at 07:21am, Corey Minyard wrote:
> Any comments on this?  If no one else cares I'd be willing to take over
> maintenance of this.
> 
> -corey
> 
> On 02/25/2016 07:51 AM, minyard@xxxxxxx wrote:
> >From: Corey Minyard <cminyard@xxxxxxxxxx>
> >
> >Lots of little changes needed to be made to clean these up, remove the
> >four byte pointer assumption and traverse the pid queue properly.
> >Also consolidate the traceback code into a single function instead
> >of having three copies of it.
> >
> >Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
> >---
> >  Documentation/kdump/gdbmacros.txt | 90 +++++++++++++++++----------------------
> >  1 file changed, 40 insertions(+), 50 deletions(-)
> >
> >I sent this earlier, but I didn't get a response.  These are clearly
> >wrong.  I'd be happy to take over maintenance of these macros.  It
> >might be better to move them someplace else, too, since they are also
> >useful for kgdb.
> >
> >diff --git a/Documentation/kdump/gdbmacros.txt b/Documentation/kdump/gdbmacros.txt
> >index 9b9b454..e5bbd8d 100644
> >--- a/Documentation/kdump/gdbmacros.txt
> >+++ b/Documentation/kdump/gdbmacros.txt
> >@@ -15,14 +15,14 @@
> >  define bttnobp
> >  	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
> >-	set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
> >+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)

This is a quite nice fix.

> >  	set $init_t=&init_task
> >  	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
> >  	while ($next_t != $init_t)
> >  		set $next_t=(struct task_struct *)$next_t
> >  		printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
> >  		printf "===================\n"
> >-		set var $stackp = $next_t.thread.esp
> >+		set var $stackp = $next_t.thread.sp
> >  		set var $stack_top = ($stackp & ~4095) + 4096
> >  		while ($stackp < $stack_top)
> >@@ -31,12 +31,12 @@ define bttnobp
> >  			end
> >  			set $stackp += 4
> >  		end
> >-		set $next_th=(((char *)$next_t->pids[1].pid_list.next) - $pid_off)
> >+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
> >  		while ($next_th != $next_t)
> >  			set $next_th=(struct task_struct *)$next_th
> >  			printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
> >  			printf "===================\n"
> >-			set var $stackp = $next_t.thread.esp
> >+			set var $stackp = $next_t.thread.sp
> >  			set var $stack_top = ($stackp & ~4095) + 4096
> >  			while ($stackp < $stack_top)
> >@@ -45,7 +45,7 @@ define bttnobp
> >  				end
> >  				set $stackp += 4
> >  			end
> >-			set $next_th=(((char *)$next_th->pids[1].pid_list.next) - $pid_off)
> >+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
> >  		end
> >  		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
> >  	end
> >@@ -54,42 +54,43 @@ document bttnobp
> >  	dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
> >  end
> >+define btthreadstruct

This is a nice wrapping, but I guess you want to name it as
btthreadstack, right? Since I didn't get at all why it's related to
thread_struct except of getting 'sp'.

> >+	set var $pid_task = $arg0
> >+
> >+	printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
> >+	printf "task struct: "
> >+	print $pid_task
> >+	printf "===================\n"
> >+	set var $stackp = $pid_task.thread.sp
> >+	set var $stack_top = ($stackp & ~4095) + 4096
> >+	set var $stack_bot = ($stackp & ~4095)
> >+
> >+	set $stackp = *((unsigned long *) $stackp)
> >+	while (($stackp < $stack_top) && ($stackp > $stack_bot))
> >+		set var $addr = *(((unsigned long *) $stackp) + 1)
> >+		info symbol $addr
> >+		set $stackp = *((unsigned long *) $stackp)
> >+	end
> >+end
> >+document btthreadstruct
> >+	 dump a thread stack using the given task structure pointer
> >+end
> >+
> >+
> >  define btt
> >  	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
> >-	set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
> >+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
> >  	set $init_t=&init_task
> >  	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
> >  	while ($next_t != $init_t)
> >  		set $next_t=(struct task_struct *)$next_t
> >-		printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
> >-		printf "===================\n"
> >-		set var $stackp = $next_t.thread.esp
> >-		set var $stack_top = ($stackp & ~4095) + 4096
> >-		set var $stack_bot = ($stackp & ~4095)
> >+		btthreadstruct $next_t
> >-		set $stackp = *($stackp)
> >-		while (($stackp < $stack_top) && ($stackp > $stack_bot))
> >-			set var $addr = *($stackp + 4)
> >-			info symbol $addr
> >-			set $stackp = *($stackp)
> >-		end
> >-
> >-		set $next_th=(((char *)$next_t->pids[1].pid_list.next) - $pid_off)
> >+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
> >  		while ($next_th != $next_t)
> >  			set $next_th=(struct task_struct *)$next_th
> >-			printf "\npid %d; comm %s:\n", $next_t.pid, $next_t.comm
> >-			printf "===================\n"
> >-			set var $stackp = $next_t.thread.esp
> >-			set var $stack_top = ($stackp & ~4095) + 4096
> >-			set var $stack_bot = ($stackp & ~4095)
> >-
> >-			set $stackp = *($stackp)
> >-			while (($stackp < $stack_top) && ($stackp > $stack_bot))
> >-				set var $addr = *($stackp + 4)
> >-				info symbol $addr
> >-				set $stackp = *($stackp)
> >-			end
> >-			set $next_th=(((char *)$next_th->pids[1].pid_list.next) - $pid_off)
> >+			btthreadstruct $next_th
> >+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
> >  		end
> >  		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
> >  	end
> >@@ -101,7 +102,7 @@ end
> >  define btpid
> >  	set var $pid = $arg0
> >  	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
> >-	set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
> >+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
> >  	set $init_t=&init_task
> >  	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
> >  	set var $pid_task = 0
> >@@ -113,29 +114,18 @@ define btpid
> >  			set $pid_task = $next_t
> >  		end
> >-		set $next_th=(((char *)$next_t->pids[1].pid_list.next) - $pid_off)
> >+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
> >  		while ($next_th != $next_t)
> >  			set $next_th=(struct task_struct *)$next_th
> >  			if ($next_th.pid == $pid)
> >  				set $pid_task = $next_th
> >  			end
> >-			set $next_th=(((char *)$next_th->pids[1].pid_list.next) - $pid_off)
> >+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
> >  		end
> >  		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
> >  	end
> >-	printf "\npid %d; comm %s:\n", $pid_task.pid, $pid_task.comm
> >-	printf "===================\n"
> >-	set var $stackp = $pid_task.thread.esp
> >-	set var $stack_top = ($stackp & ~4095) + 4096
> >-	set var $stack_bot = ($stackp & ~4095)
> >-
> >-	set $stackp = *($stackp)
> >-	while (($stackp < $stack_top) && ($stackp > $stack_bot))
> >-		set var $addr = *($stackp + 4)
> >-		info symbol $addr
> >-		set $stackp = *($stackp)
> >-	end
> >+	btthreadstruct $pid_task
> >  end
> >  document btpid
> >  	backtrace of pid
> >@@ -145,7 +135,7 @@ end
> >  define trapinfo
> >  	set var $pid = $arg0
> >  	set $tasks_off=((size_t)&((struct task_struct *)0)->tasks)
> >-	set $pid_off=((size_t)&((struct task_struct *)0)->pids[1].pid_list.next)
> >+	set $pid_off=((size_t)&((struct task_struct *)0)->thread_group.next)
> >  	set $init_t=&init_task
> >  	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
> >  	set var $pid_task = 0
> >@@ -157,13 +147,13 @@ define trapinfo
> >  			set $pid_task = $next_t
> >  		end
> >-		set $next_th=(((char *)$next_t->pids[1].pid_list.next) - $pid_off)
> >+		set $next_th=(((char *)$next_t->thread_group.next) - $pid_off)
> >  		while ($next_th != $next_t)
> >  			set $next_th=(struct task_struct *)$next_th
> >  			if ($next_th.pid == $pid)
> >  				set $pid_task = $next_th
> >  			end
> >-			set $next_th=(((char *)$next_th->pids[1].pid_list.next) - $pid_off)
> >+			set $next_th=(((char *)$next_th->thread_group.next) - $pid_off)
> >  		end
> >  		set $next_t=(char *)($next_t->tasks.next) - $tasks_off
> >  	end