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Date:	Mon, 16 May 2016 17:44:27 +0800
From:	Baoquan He <bhe@...hat.com>
To:	minyard@....org
Cc:	Corey Minyard <cminyard@...sta.com>, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Haren Myneni <hbabu@...ibm.com>,
	dyoung@...hat.com, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH v2] kdump: Fix gdb macros work work with newer and 64-bit
 kernels

On 05/16/16 at 05:32pm, Baoquan He wrote:
> On 05/10/16 at 07:30pm, minyard@....org wrote:
> > From: Corey Minyard <cminyard@...sta.com>
> > 
> > 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@...sta.com>
> 
> Hi Corey,
> 
> Today I tried gdbmacro.txt and found dmesg doesn't work. I tested it
> on the latest 4.6.0 kernel. And I directly copy /proc/vmcore out
> and use gdb to open it by below command" 
> 
> gdb vmlinux /var/crash/vmcore --"gdbmacros.txt"
		Here I means  --command="gdbmacros.txt"

> 
> All macro functions work well except of dmesg since code inside refer to
> the deprecated variable like "log_end" and "logged_chars". But these
> have been changed since this commit:
> 
> commit 7ff9554bb578ba02166071d2d487b7fc7d860d62
> Author: Kay Sievers <kay@...y.org>
> Date:   Thu May 3 02:29:13 2012 +0200
> 
>     printk: convert byte-buffer to variable-length record buffer
> 
> So invoking dmesg will cause an error message printing out:
> 
> (gdb) dmesg
> No symbol "log_end" in current context.
> 
> Thanks
> Baoquan
> 
> > ---
> > 
> > Changes since v1:
> > 
> > Rename btthreadstruct to btthreadstack
> > 
> > Use sizeof(union thread_union) for the stack size instead of a hardcoded
> > 4096.
> > 
> >  Documentation/kdump/gdbmacros.txt | 96 ++++++++++++++++++---------------------
> >  1 file changed, 44 insertions(+), 52 deletions(-)
> > 
> > diff --git a/Documentation/kdump/gdbmacros.txt b/Documentation/kdump/gdbmacros.txt
> > index 9b9b454..35f6a98 100644
> > --- a/Documentation/kdump/gdbmacros.txt
> > +++ b/Documentation/kdump/gdbmacros.txt
> > @@ -15,15 +15,16 @@
> >  
> >  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)
> >  	set $init_t=&init_task
> >  	set $next_t=(((char *)($init_t->tasks).next) - $tasks_off)
> > +	set var $stacksize = sizeof(union thread_union)
> >  	while ($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 $stackp = $next_t.thread.sp
> > +		set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
> >  
> >  		while ($stackp < $stack_top)
> >  			if (*($stackp) > _stext && *($stackp) < _sinittext)
> > @@ -31,13 +32,13 @@ 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 $stack_top = ($stackp & ~4095) + 4096
> > +			set var $stackp = $next_t.thread.sp
> > +			set var $stack_top = ($stackp & ~($stacksize - 1)) + stacksize
> >  
> >  			while ($stackp < $stack_top)
> >  				if (*($stackp) > _stext && *($stackp) < _sinittext)
> > @@ -45,7 +46,7 @@ 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 +55,44 @@ document bttnobp
> >  	dump all thread stack traces on a kernel compiled with !CONFIG_FRAME_POINTER
> >  end
> >  
> > +define btthreadstack
> > +	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 $stacksize = sizeof(union thread_union)
> > +	set var $stack_top = ($stackp & ~($stacksize - 1)) + $stacksize
> > +	set var $stack_bot = ($stackp & ~($stacksize - 1))
> > +
> > +	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 btthreadstack
> > +	 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)
> > -
> > -		set $stackp = *($stackp)
> > -		while (($stackp < $stack_top) && ($stackp > $stack_bot))
> > -			set var $addr = *($stackp + 4)
> > -			info symbol $addr
> > -			set $stackp = *($stackp)
> > -		end
> > +		btthreadstack $next_t
> >  
> > -		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)
> > +			btthreadstack $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 +104,7 @@ 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 +116,18 @@ 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
> > +	btthreadstack $pid_task
> >  end
> >  document btpid
> >  	backtrace of pid
> > @@ -145,7 +137,7 @@ 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 +149,13 @@ 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
> > -- 
> > 2.7.4
> > 
> > 
> > _______________________________________________
> > kexec mailing list
> > kexec@...ts.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> _______________________________________________
> kexec mailing list
> kexec@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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