uprobes: Rationalize the usage of filter_chain()
filter_chain() was added into install_breakpoint/remove_breakpoint to
simplify the initial changes but this is sub-optimal.
This patch shifts the callsite to the callers, register_for_each_vma()
and uprobe_mmap(). This way:
- It will be easier to add the new arguments. This is the main reason,
we can do more optimizations later.
- register_for_each_vma(is_register => true) can be optimized, we only
need to consult the new consumer. The previous consumers were already
asked when they called uprobe_register().
This patch also moves the MMF_HAS_UPROBES check from remove_breakpoint(),
this allows to avoid the potentionally costly filter_chain(). Note that
register_for_each_vma(is_register => false) doesn't really need to take
->consumer_rwsem, but I don't think it makes sense to optimize this and
introduce filter_chain_lockless().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c3b65d1..3391208 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -579,6 +579,11 @@
return ret;
}
+static inline bool consumer_filter(struct uprobe_consumer *uc)
+{
+ return true; /* TODO: !uc->filter || uc->filter(...) */
+}
+
static bool filter_chain(struct uprobe *uprobe)
{
struct uprobe_consumer *uc;
@@ -586,8 +591,7 @@
down_read(&uprobe->consumer_rwsem);
for (uc = uprobe->consumers; uc; uc = uc->next) {
- /* TODO: ret = uc->filter(...) */
- ret = true;
+ ret = consumer_filter(uc);
if (ret)
break;
}
@@ -603,15 +607,6 @@
bool first_uprobe;
int ret;
- /*
- * If probe is being deleted, unregister thread could be done with
- * the vma-rmap-walk through. Adding a probe now can be fatal since
- * nobody will be able to cleanup. But in this case filter_chain()
- * must return false, all consumers have gone away.
- */
- if (!filter_chain(uprobe))
- return 0;
-
ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
if (ret)
return ret;
@@ -636,12 +631,6 @@
static int
remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
{
- if (!test_bit(MMF_HAS_UPROBES, &mm->flags))
- return 0;
-
- if (filter_chain(uprobe))
- return 0;
-
set_bit(MMF_RECALC_UPROBES, &mm->flags);
return set_orig_insn(&uprobe->arch, mm, vaddr);
}
@@ -781,10 +770,14 @@
vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
goto unlock;
- if (is_register)
- err = install_breakpoint(uprobe, mm, vma, info->vaddr);
- else
- err |= remove_breakpoint(uprobe, mm, info->vaddr);
+ if (is_register) {
+ /* consult only the "caller", new consumer. */
+ if (consumer_filter(uprobe->consumers))
+ err = install_breakpoint(uprobe, mm, vma, info->vaddr);
+ } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
+ if (!filter_chain(uprobe))
+ err |= remove_breakpoint(uprobe, mm, info->vaddr);
+ }
unlock:
up_write(&mm->mmap_sem);
@@ -968,9 +961,14 @@
mutex_lock(uprobes_mmap_hash(inode));
build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
-
+ /*
+ * We can race with uprobe_unregister(), this uprobe can be already
+ * removed. But in this case filter_chain() must return false, all
+ * consumers have gone away.
+ */
list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
- if (!fatal_signal_pending(current)) {
+ if (!fatal_signal_pending(current) &&
+ filter_chain(uprobe)) {
unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
}
