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authorOleg Nesterov <oleg@redhat.com>2012-12-27 18:21:11 +0100
committerOleg Nesterov <oleg@redhat.com>2013-02-08 17:47:10 +0100
commit806a98bdf2a862fef0fc880399d677b35ba525ff (patch)
tree5b322a48c4d22d15e8d1a6c8a6a7e28d77ce62a7 /kernel
parent66d06dffa5ef6f3544997440af63a91ef36a2171 (diff)
downloadlinux-806a98bdf2a862fef0fc880399d677b35ba525ff.tar.bz2
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/uprobes.c44
1 files changed, 21 insertions, 23 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index c3b65d1c8443..33912086d54e 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -579,6 +579,11 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
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 @@ static bool filter_chain(struct uprobe *uprobe)
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 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
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 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
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 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
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 @@ int uprobe_mmap(struct vm_area_struct *vma)
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);
}