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Message-ID: <5291B694.8040003@hitachi.com>
Date: Sun, 24 Nov 2013 17:19:32 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
Namhyung Kim <namhyung@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] uprobes: Add uprobe_task->dup_work/dup_addr
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@...hat.com>
> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Acked-by: Srikar Dronamraju <srikar@...ux.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@...achi.com
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