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Subject[PATCH 2/5] 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.

Cc: stable@vger.kernel.org # 3.9+
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/events/uprobes.c | 49 ++++++++++++++++++++++++----------------------
1 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index db7a1dc..c09d417 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1096,17 +1096,15 @@ 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. */
+ /* 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) {
ret = area->vaddr;
@@ -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);
@@ -1170,9 +1157,25 @@ 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() */
+ smp_read_barrier_depends(); /* pairs with wmb in xol_add_vma() */
return area;
}

--
1.5.5.1


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