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    SubjectRe: [PATCH 5/8] trace_uprobe: Support SDT markers having reference count (semaphore)
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    On 03/15/2018 08:00 PM, Oleg Nesterov wrote:
    > On 03/15, Oleg Nesterov wrote:
    >>> +static struct vm_area_struct *
    >>> +sdt_find_vma(struct mm_struct *mm, struct trace_uprobe *tu)
    >>> +{
    >>> + struct vm_area_struct *tmp;
    >>> +
    >>> + for (tmp = mm->mmap; tmp != NULL; tmp = tmp->vm_next)
    >>> + if (sdt_valid_vma(tu, tmp))
    >>> + return tmp;
    >>> +
    >>> + return NULL;
    >> I can't understand the logic... Lets ignore sdt_valid_vma() for now.
    >> The caller has uprobe_map_info, why it can't simply do
    >> vma = find_vma(uprobe_map_info->vaddr)? and then check sdt_valid_vma().
    > Note to mention that sdt_find_vma() can return NULL but the callers do
    > vma_offset_to_vaddr(vma) without any check.

    If the "mm" we are passing to sdt_find_vma() is returned by
    uprobe_build_map_info(ref_ctr_offset), sdt_find_vma() must
    _not_ return NULL.

    Thanks for the review,
    Ravi

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