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SubjectRe: [PATCH 2/2] uprobes: Reintroduce uprobe_consumer->filter()
* Oleg Nesterov <oleg@redhat.com> [2012-12-28 19:13:14]:

> Finally add uprobe_consumer->filter() and change consumer_filter()
> to actually call this method.
>
> Note that ->filter() accepts mm_struct, not task_struct. Because:
>
> 1. We do not have for_each_mm_user(mm, task).
>
> 2. Even if we implement for_each_mm_user(), ->filter() can
> use it itself.
>
> 3. It is not clear who will actually need this interface to
> do the "nontrivial" filtering.
>
> Another argument is "enum uprobe_filter_ctx", consumer->filter() can
> use it to figure out why/where it was called. For example, perhaps
> we can add UPROBE_FILTER_PRE_REGISTER used by build_map_info() to
> quickly "nack" the unwanted mm's. In this case consumer should know
> that it is called under ->i_mmap_mutex.
>
> See the previous discussion at http://marc.info/?t=135214229700002
> Perhaps we should pass more arguments, vma/vaddr?
>
> Note: this patch obviously can't help to filter out the child created
> by fork(), this will be addressed later.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
> include/linux/uprobes.h | 9 +++++++++
> kernel/events/uprobes.c | 18 +++++++++++-------
> 2 files changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 83742b9..c2df693 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -35,8 +35,17 @@ struct inode;
> # include <asm/uprobes.h>
> #endif
>
> +enum uprobe_filter_ctx {
> + UPROBE_FILTER_REGISTER,
> + UPROBE_FILTER_UNREGISTER,
> + UPROBE_FILTER_MMAP,
> +};
> +
> struct uprobe_consumer {
> int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
> + bool (*filter)(struct uprobe_consumer *self,
> + enum uprobe_filter_ctx ctx,
> + struct mm_struct *mm);
>
> struct uprobe_consumer *next;
> };
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 60b0a90..e2ebb6f 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -579,19 +579,21 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
> return ret;
> }
>
> -static inline bool consumer_filter(struct uprobe_consumer *uc)
> +static inline bool consumer_filter(struct uprobe_consumer *uc,
> + enum uprobe_filter_ctx ctx, struct mm_struct *mm)
> {
> - return true; /* TODO: !uc->filter || uc->filter(...) */
> + return !uc->filter || uc->filter(uc, ctx, mm);
> }
>
> -static bool filter_chain(struct uprobe *uprobe)
> +static bool filter_chain(struct uprobe *uprobe,
> + enum uprobe_filter_ctx ctx, struct mm_struct *mm)
> {
> struct uprobe_consumer *uc;
> bool ret = false;
>
> down_read(&uprobe->consumer_rwsem);
> for (uc = uprobe->consumers; uc; uc = uc->next) {
> - ret = consumer_filter(uc);
> + ret = consumer_filter(uc, ctx, mm);
> if (ret)
> break;
> }
> @@ -772,10 +774,12 @@ static int register_for_each_vma(struct uprobe *uprobe, bool is_register)
>
> if (is_register) {
> /* consult only the "caller", new consumer. */
> - if (consumer_filter(uprobe->consumers))
> + if (consumer_filter(uprobe->consumers,
> + UPROBE_FILTER_REGISTER, mm))
> err = install_breakpoint(uprobe, mm, vma, info->vaddr);
> } else if (test_bit(MMF_HAS_UPROBES, &mm->flags)) {
> - if (!filter_chain(uprobe))
> + if (!filter_chain(uprobe,
> + UPROBE_FILTER_UNREGISTER, mm))
> err |= remove_breakpoint(uprobe, mm, info->vaddr);
> }
>
> @@ -968,7 +972,7 @@ int uprobe_mmap(struct vm_area_struct *vma)
> */
> list_for_each_entry_safe(uprobe, u, &tmp_list, pending_list) {
> if (!fatal_signal_pending(current) &&
> - filter_chain(uprobe)) {
> + filter_chain(uprobe, UPROBE_FILTER_MMAP, vma->vm_mm)) {
> unsigned long vaddr = offset_to_vaddr(vma, uprobe->offset);
> install_breakpoint(uprobe, vma->vm_mm, vma, vaddr);
> }
> --
> 1.5.5.1
>



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