On Tue, Oct 10, 2023 at 12:00 PM Dave Marchevsky <davemarchevsky@xxxxxx> wrote:
>
> This patch adds kfuncs bpf_iter_task_vma_{new,next,destroy} which allow
> creation and manipulation of struct bpf_iter_task_vma in open-coded
> iterator style. BPF programs can use these kfuncs directly or through
> bpf_for_each macro for natural-looking iteration of all task vmas.
>
> The implementation borrows heavily from bpf_find_vma helper's locking -
> differing only in that it holds the mmap_read lock for all iterations
> while the helper only executes its provided callback on a maximum of 1
> vma. Aside from locking, struct vma_iterator and vma_next do all the
> heavy lifting.
>
> A pointer to an inner data struct, struct bpf_iter_task_vma_data, is the
> only field in struct bpf_iter_task_vma. This is because the inner data
> struct contains a struct vma_iterator (not ptr), whose size is likely to
> change under us. If bpf_iter_task_vma_kern contained vma_iterator directly
> such a change would require change in opaque bpf_iter_task_vma struct's
> size. So better to allocate vma_iterator using BPF allocator, and since
> that alloc must already succeed, might as well allocate all iter fields,
> thereby freezing struct bpf_iter_task_vma size.
>
> Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
> Cc: Nathan Slingerland <slinger@xxxxxxxx>
> ---
> kernel/bpf/helpers.c | 3 ++
> kernel/bpf/task_iter.c | 85 ++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 88 insertions(+)
>
LGTM.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index d2840dd5b00d..62a53ebfedf9 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
[...]
