Re: [PATCH v2] kdump: Fix gdb macros work work with newer and 64-bit kernels

From: Baoquan He
Date: Mon May 16 2016 - 05:33:25 EST

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On 05/10/16 at 07:30pm, 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>

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"

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@xxxxxxxx>
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
>
>
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Next message: Borislav Petkov: "[PATCH] locking/rwsem: Fix comment on register clobbering"
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Next in thread: Baoquan He: "Re: [PATCH v2] kdump: Fix gdb macros work work with newer and 64-bit kernels"
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