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Subject[PATCH] uprobes: teach build_probe_list() to consider the range
Currently build_probe_list() builds the list of all uprobes attached
to the given inode, and the caller should filter out those who don't
fall into the [start,end) range, this is sub-optimal.

This patch turns find_least_offset_node() into find_node_in_range()
which returns the first node inside the [min,max] range, and changes
build_probe_list() to use this node as a starting point for rb_prev()
and rb_next() to find all other nodes the caller needs. The resulting
list is no longer sorted but we do not care.

This can speed up both build_probe_list() and the callers, but there
is another reason to introduce find_node_in_range(). It can be used
to figure out whether the given vma has uprobes or not, this will be
needed soon.

While at it, shift INIT_LIST_HEAD(tmp_list) into build_probe_list().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/events/uprobes.c | 103 +++++++++++++++++++++++------------------------
1 files changed, 50 insertions(+), 53 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 6194edb..c825404 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -939,59 +939,66 @@ void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consume
put_uprobe(uprobe);
}

-/*
- * Of all the nodes that correspond to the given inode, return the node
- * with the least offset.
- */
-static struct rb_node *find_least_offset_node(struct inode *inode)
+static struct rb_node *
+find_node_in_range(struct inode *inode, loff_t min, loff_t max)
{
- struct uprobe u = { .inode = inode, .offset = 0};
struct rb_node *n = uprobes_tree.rb_node;
- struct rb_node *close_node = NULL;
- struct uprobe *uprobe;
- int match;

while (n) {
- uprobe = rb_entry(n, struct uprobe, rb_node);
- match = match_uprobe(&u, uprobe);
-
- if (uprobe->inode == inode)
- close_node = n;
+ struct uprobe *u = rb_entry(n, struct uprobe, rb_node);

- if (!match)
- return close_node;
-
- if (match < 0)
+ if (inode < u->inode) {
n = n->rb_left;
- else
+ } else if (inode > u->inode) {
n = n->rb_right;
+ } else {
+ if (max < u->offset)
+ n = n->rb_left;
+ else if (min > u->offset)
+ n = n->rb_right;
+ else
+ break;
+ }
}

- return close_node;
+ return n;
}

/*
- * For a given inode, build a list of probes that need to be inserted.
+ * For a given range in vma, build a list of probes that need to be inserted.
*/
-static void build_probe_list(struct inode *inode, struct list_head *head)
+static void build_probe_list(struct inode *inode,
+ struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ struct list_head *head)
{
- struct uprobe *uprobe;
+ loff_t min, max;
unsigned long flags;
- struct rb_node *n;
-
- spin_lock_irqsave(&uprobes_treelock, flags);
-
- n = find_least_offset_node(inode);
+ struct rb_node *n, *t;
+ struct uprobe *u;

- for (; n; n = rb_next(n)) {
- uprobe = rb_entry(n, struct uprobe, rb_node);
- if (uprobe->inode != inode)
- break;
+ INIT_LIST_HEAD(head);
+ min = ((loff_t)vma->vm_pgoff << PAGE_SHIFT) + start - vma->vm_start;
+ max = min + (end - start) - 1;

- list_add(&uprobe->pending_list, head);
- atomic_inc(&uprobe->ref);
+ spin_lock_irqsave(&uprobes_treelock, flags);
+ n = find_node_in_range(inode, min, max);
+ if (n) {
+ for (t = n; t; t = rb_prev(t)) {
+ u = rb_entry(t, struct uprobe, rb_node);
+ if (u->inode != inode || u->offset < min)
+ break;
+ list_add(&u->pending_list, head);
+ atomic_inc(&u->ref);
+ }
+ for (t = n; (t = rb_next(t)); ) {
+ u = rb_entry(t, struct uprobe, rb_node);
+ if (u->inode != inode || u->offset > max)
+ break;
+ list_add(&u->pending_list, head);
+ atomic_inc(&u->ref);
+ }
}
-
spin_unlock_irqrestore(&uprobes_treelock, flags);
}

@@ -1021,9 +1028,8 @@ int uprobe_mmap(struct vm_area_struct *vma)
if (!inode)
return 0;

- INIT_LIST_HEAD(&tmp_list);
mutex_lock(uprobes_mmap_hash(inode));
- build_probe_list(inode, &tmp_list);
+ build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);

ret = 0;
count = 0;
@@ -1032,11 +1038,6 @@ int uprobe_mmap(struct vm_area_struct *vma)
if (!ret) {
loff_t vaddr = vma_address(vma, uprobe->offset);

- if (vaddr < vma->vm_start || vaddr >= vma->vm_end) {
- put_uprobe(uprobe);
- continue;
- }
-
ret = install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
/*
* We can race against uprobe_register(), see the
@@ -1092,21 +1093,17 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon
if (!inode)
return;

- INIT_LIST_HEAD(&tmp_list);
mutex_lock(uprobes_mmap_hash(inode));
- build_probe_list(inode, &tmp_list);
+ build_probe_list(inode, vma, start, end, &tmp_list);

list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
loff_t vaddr = vma_address(vma, uprobe->offset);
-
- if (vaddr >= start && vaddr < end) {
- /*
- * An unregister could have removed the probe before
- * unmap. So check before we decrement the count.
- */
- if (is_swbp_at_addr(vma->vm_mm, vaddr) == 1)
- atomic_dec(&vma->vm_mm->uprobes_state.count);
- }
+ /*
+ * An unregister could have removed the probe before
+ * unmap. So check before we decrement the count.
+ */
+ if (is_swbp_at_addr(vma->vm_mm, vaddr) == 1)
+ atomic_dec(&vma->vm_mm->uprobes_state.count);
put_uprobe(uprobe);
}
mutex_unlock(uprobes_mmap_hash(inode));
--
1.5.5.1



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