(2013/11/09 4:00), Oleg Nesterov wrote:
> uprobe_task->vaddr is a bit strange. First of all it is not really
> needed, we can move it into arch_uprobe_task. 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. This means it is safe to reuse both in UTASK_RUNNING
> state.
>
> 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_addr which can be used instead ->vaddr, and ->dup_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.
OK, those are used in the different phase as a scratchpad.
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Thanks!
> ---
> 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..366b8b2 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_work;
> + unsigned long dup_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..2546a7b 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_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_addr = area->vaddr;
> + init_task_work(&t->utask->dup_work, dup_xol_work);
> + task_work_add(t, &t->utask->dup_work, true);
> }
>
> /*
>
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu...@hitachi.com
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