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Commit 32473431 authored by Oleg Nesterov's avatar Oleg Nesterov
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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: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent caea6cf5

include/linux/uprobes.h

+16 −5
Original line number Diff line number Diff line
@@ -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;



	union {

		struct {

			struct arch_uprobe_task	autask;

			unsigned long		vaddr;

		};



	struct return_instance		*return_instances;

	unsigned int			depth;

	struct uprobe			*active_uprobe;

		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;

};



/*

kernel/events/uprobes.c

+4 −12
Original line number Diff line number Diff line
@@ -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);

}



/*