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uprobes: Rationalize the usage of filter_chain()

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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>
This commit is contained in:
Oleg Nesterov 2012-12-27 18:21:11 +01:00
parent 66d06dffa5
commit 806a98bdf2
1 changed files with 21 additions and 23 deletions
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44
kernel/events/uprobes.c
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@ -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);
}