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Commit 6441ec8b authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes: Introduce __create_xol_area() 



No functional changes, preparation.

Extract the code which actually allocates/installs the new area
into the new helper, __create_xol_area().

While at it remove the unnecessary "ret = ENOMEM" and "ret = 0"
in xol_add_vma(), they both have no effect.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarSrikar Dronamraju <srikar@linux.vnet.ibm.com>
parent b68e0749

kernel/events/uprobes.c

+25 −22
Original line number Diff line number Diff line
@@ -1096,16 +1096,14 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon 
}



/* Slot allocation for XOL */

static int xol_add_vma(struct xol_area *area)

static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)

{

	struct mm_struct *mm = current->mm;

	int ret = -EALREADY;



	down_write(&mm->mmap_sem);

	if (mm->uprobes_state.xol_area)

		goto fail;



	ret = -ENOMEM;

	/* Try to map as high as possible, this is only a hint. */

	area->vaddr = get_unmapped_area(NULL, TASK_SIZE - PAGE_SIZE, PAGE_SIZE, 0, 0);

	if (area->vaddr & ~PAGE_MASK) {
@@ -1120,28 +1118,17 @@ static int xol_add_vma(struct xol_area *area) 


	smp_wmb();	/* pairs with get_xol_area() */

	mm->uprobes_state.xol_area = area;

	ret = 0;

 fail:

	up_write(&mm->mmap_sem);



	return ret;

}



/*

 * get_xol_area - Allocate process's xol_area if necessary.

 * This area will be used for storing instructions for execution out of line.

 *

 * Returns the allocated area or NULL.

 */

static struct xol_area *get_xol_area(void)

static struct xol_area *__create_xol_area(void)

{

	struct mm_struct *mm = current->mm;

	struct xol_area *area;

	uprobe_opcode_t insn = UPROBE_SWBP_INSN;



	area = mm->uprobes_state.xol_area;

	if (area)

		goto ret;

	struct xol_area *area;



	area = kzalloc(sizeof(*area), GFP_KERNEL);

	if (unlikely(!area))
@@ -1155,13 +1142,13 @@ static struct xol_area *get_xol_area(void) 
	if (!area->page)

		goto free_bitmap;



	/* allocate first slot of task's xol_area for the return probes */

	init_waitqueue_head(&area->wq);

	/* Reserve the 1st slot for get_trampoline_vaddr() */

	set_bit(0, area->bitmap);

	copy_to_page(area->page, 0, &insn, UPROBE_SWBP_INSN_SIZE);

	atomic_set(&area->slot_count, 1);

	init_waitqueue_head(&area->wq);

	copy_to_page(area->page, 0, &insn, UPROBE_SWBP_INSN_SIZE);



	if (!xol_add_vma(area))

	if (!xol_add_vma(mm, area))

		return area;



	__free_page(area->page);
@@ -1170,8 +1157,24 @@ static struct xol_area *get_xol_area(void) 
 free_area:

	kfree(area);

 out:

	return NULL;

}



/*

 * get_xol_area - Allocate process's xol_area if necessary.

 * This area will be used for storing instructions for execution out of line.

 *

 * Returns the allocated area or NULL.

 */

static struct xol_area *get_xol_area(void)

{

	struct mm_struct *mm = current->mm;

	struct xol_area *area;



	if (!mm->uprobes_state.xol_area)

		__create_xol_area();



	area = mm->uprobes_state.xol_area;

 ret:

	smp_read_barrier_depends();	/* pairs with wmb in xol_add_vma() */

	return area;

}