Re: [PATCH v2] uprobes: Add uprobe_task->dup_work/dup_addr

[Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>]

Ping?

Is this already pulled?
I think it is enough discussed and reviewed.

Thank you,

(2013/11/13 4:20), Oleg Nesterov wrote:
> On 11/12, Srikar Dronamraju wrote:
>>
>> Okay, moving to arch_uprobe_task is fine. I probably got confused by
>> "First of all it is not really needed,"
> 
> OK, this doesn't look good, I agree.
> 
> Please see v2 below, I tried to improve the changelog.
> 
>>> OK. How about dup_xol_work/dup_xol_vaddr ?
>>
>> Yes fine with me.
> 
> Done.
> 
> I added your ack optimistically, please let me know if you think I
> should change something else.
> 
> Oleg.
> ---
> 
> Subject: [PATCH] uprobes: Add uprobe_task->dup_xol_work/dup_xol_addr
> 
> uprobe_task->vaddr is a bit strange. The generic code uses it only
> to pass the additional argument to arch_uprobe_pre_xol(), and since
> it is always equal to instruction_pointer() this looks even more
> strange.
> 
> And both utask->vaddr and and utask->autask have the same scope,
> they only have the meaning when the task executes the probed insn
> out-of-line, so it is safe to reuse both in UTASK_RUNNING state.
> 
> This all means that logically ->vaddr belongs to arch_uprobe_task
> and we should probably move it there, arch_uprobe_pre_xol() can
> record instruction_pointer() itself.
> 
> OTOH, it is also used by uprobe_copy_process() and dup_xol_work()
> for another purpose, this doesn't look clean and doesn't allow to
> move this member into arch_uprobe_task.
> 
> This patch adds the union with 2 anonymous structs into uprobe_task.
> 
> The first struct is autask + vaddr, this way we "almost" move vaddr
> into autask.
> 
> The second struct has 2 new members for uprobe_copy_process() paths:
> ->dup_xol_addr which can be used instead ->vaddr, and ->dup_xol_work
> which can be used to avoid kmalloc() and simplify the code.
> 
> Note that this union will likely have another member(s), we need
> something like "private_data_for_handlers" so that the tracing
> handlers could use it to communicate with call_fetch() methods.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
>  include/linux/uprobes.h |   21 ++++++++++++++++-----
>  kernel/events/uprobes.c |   16 ++++------------
>  2 files changed, 20 insertions(+), 17 deletions(-)
> 
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 319eae7..2225542 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -26,6 +26,7 @@
>  
>  #include <linux/errno.h>
>  #include <linux/rbtree.h>
> +#include <linux/types.h>
>  
>  struct vm_area_struct;
>  struct mm_struct;
> @@ -72,14 +73,24 @@ enum uprobe_task_state {
>   */
>  struct uprobe_task {
>  	enum uprobe_task_state		state;
> -	struct arch_uprobe_task		autask;
>  
> -	struct return_instance		*return_instances;
> -	unsigned int			depth;
> -	struct uprobe			*active_uprobe;
> +	union {
> +		struct {
> +			struct arch_uprobe_task	autask;
> +			unsigned long		vaddr;
> +		};
> +
> +		struct {
> +			struct callback_head	dup_xol_work;
> +			unsigned long		dup_xol_addr;
> +		};
> +	};
>  
> +	struct uprobe			*active_uprobe;
>  	unsigned long			xol_vaddr;
> -	unsigned long			vaddr;
> +
> +	struct return_instance		*return_instances;
> +	unsigned int			depth;
>  };
>  
>  /*
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 24b7d6c..df4ef09 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1403,12 +1403,10 @@ static void uprobe_warn(struct task_struct *t, const char *msg)
>  
>  static void dup_xol_work(struct callback_head *work)
>  {
> -	kfree(work);
> -
>  	if (current->flags & PF_EXITING)
>  		return;
>  
> -	if (!__create_xol_area(current->utask->vaddr))
> +	if (!__create_xol_area(current->utask->dup_xol_addr))
>  		uprobe_warn(current, "dup xol area");
>  }
>  
> @@ -1419,7 +1417,6 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
>  {
>  	struct uprobe_task *utask = current->utask;
>  	struct mm_struct *mm = current->mm;
> -	struct callback_head *work;
>  	struct xol_area *area;
>  
>  	t->utask = NULL;
> @@ -1441,14 +1438,9 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
>  	if (mm == t->mm)
>  		return;
>  
> -	/* TODO: move it into the union in uprobe_task */
> -	work = kmalloc(sizeof(*work), GFP_KERNEL);
> -	if (!work)
> -		return uprobe_warn(t, "dup xol area");
> -
> -	t->utask->vaddr = area->vaddr;
> -	init_task_work(work, dup_xol_work);
> -	task_work_add(t, work, true);
> +	t->utask->dup_xol_addr = area->vaddr;
> +	init_task_work(&t->utask->dup_xol_work, dup_xol_work);
> +	task_work_add(t, &t->utask->dup_xol_work, true);
>  }
>  
>  /*
> 


-- 
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com