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>
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@ -579,6 +579,11 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
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return ret;
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}
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static inline bool consumer_filter(struct uprobe_consumer *uc)
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{
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return true; /* TODO: !uc->filter || uc->filter(...) */
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}
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static bool filter_chain(struct uprobe *uprobe)
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{
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struct uprobe_consumer *uc;
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@ -586,8 +591,7 @@ static bool filter_chain(struct uprobe *uprobe)
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down_read(&uprobe->consumer_rwsem);
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for (uc = uprobe->consumers; uc; uc = uc->next) {
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/* TODO: ret = uc->filter(...) */
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ret = true;
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ret = consumer_filter(uc);
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if (ret)
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break;
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}
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@ -603,15 +607,6 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
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bool first_uprobe;
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int ret;
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/*
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* If probe is being deleted, unregister thread could be done with
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* the vma-rmap-walk through. Adding a probe now can be fatal since
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* nobody will be able to cleanup. But in this case filter_chain()
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* must return false, all consumers have gone away.
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*/
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if (!filter_chain(uprobe))
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return 0;
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ret = prepare_uprobe(uprobe, vma->vm_file, mm, vaddr);
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if (ret)
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return ret;
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@ -636,12 +631,6 @@ install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
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static int
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remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
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{
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if (!test_bit(MMF_HAS_UPROBES, &mm->flags))
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return 0;
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if (filter_chain(uprobe))
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return 0;
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set_bit(MMF_RECALC_UPROBES, &mm->flags);
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return set_orig_insn(&uprobe->arch, mm, vaddr);
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}
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@ -781,10 +770,14 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
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vaddr_to_offset(vma, info->vaddr) != uprobe->offset)
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goto unlock;
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if (is_register)
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err = install_breakpoint(uprobe, mm, vma, info->vaddr);
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else
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err |= remove_breakpoint(uprobe, mm, info->vaddr);
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if (is_register) {
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/* consult only the "caller", new consumer. */
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if (consumer_filter(uprobe->consumers))
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err = install_breakpoint(uprobe, mm, vma, info->vaddr);
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} else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
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if (!filter_chain(uprobe))
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err |= remove_breakpoint(uprobe, mm, info->vaddr);
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}
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unlock:
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up_write(&mm->mmap_sem);
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@ -968,9 +961,14 @@ int uprobe_mmap(struct vm_area_struct *vma)
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mutex_lock(uprobes_mmap_hash(inode));
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build_probe_list(inode, vma, vma->vm_start, vma->vm_end, &tmp_list);
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/*
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* We can race with uprobe_unregister(), this uprobe can be already
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* removed. But in this case filter_chain() must return false, all
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* consumers have gone away.
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*/
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list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
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if (!fatal_signal_pending(current)) {
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if (!fatal_signal_pending(current) &&
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filter_chain(uprobe)) {
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unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
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install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
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}
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