On Wed, Nov 6, 2024 at 11:39 AM Juntong Deng <juntong.deng@xxxxxxxxxxx> wrote:
>
> This patch adds the open-coded iterator style process file iterator
> kfuncs bpf_iter_task_file_{new,next,destroy} that iterates over all
> files opened by the specified process.
This is ok.
> In addition, this patch adds bpf_iter_task_file_get_fd() getter to get
> the file descriptor corresponding to the file in the current iteration.
Unnecessary. Use CORE to read iter internal fields.
> The reference to struct file acquired by the previous
> bpf_iter_task_file_next() is released in the next
> bpf_iter_task_file_next(), and the last reference is released in the
> last bpf_iter_task_file_next() that returns NULL.
>
> In the bpf_iter_task_file_destroy(), if the iterator does not iterate to
> the end, then the last struct file reference is released at this time.
>
> Signed-off-by: Juntong Deng <juntong.deng@xxxxxxxxxxx>
> ---
> kernel/bpf/helpers.c | 4 ++
> kernel/bpf/task_iter.c | 96 ++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 100 insertions(+)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 395221e53832..1f0f7ca1c47a 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -3096,6 +3096,10 @@ BTF_ID_FLAGS(func, bpf_iter_css_destroy, KF_ITER_DESTROY)
> BTF_ID_FLAGS(func, bpf_iter_task_new, KF_ITER_NEW | KF_TRUSTED_ARGS | KF_RCU_PROTECTED)
> BTF_ID_FLAGS(func, bpf_iter_task_next, KF_ITER_NEXT | KF_RET_NULL)
> BTF_ID_FLAGS(func, bpf_iter_task_destroy, KF_ITER_DESTROY)
> +BTF_ID_FLAGS(func, bpf_iter_task_file_new, KF_ITER_NEW | KF_TRUSTED_ARGS)
> +BTF_ID_FLAGS(func, bpf_iter_task_file_next, KF_ITER_NEXT | KF_RET_NULL)
> +BTF_ID_FLAGS(func, bpf_iter_task_file_get_fd)
> +BTF_ID_FLAGS(func, bpf_iter_task_file_destroy, KF_ITER_DESTROY)
> BTF_ID_FLAGS(func, bpf_dynptr_adjust)
> BTF_ID_FLAGS(func, bpf_dynptr_is_null)
> BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly)
> diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> index 5af9e130e500..32e15403a5a6 100644
> --- a/kernel/bpf/task_iter.c
> +++ b/kernel/bpf/task_iter.c
> @@ -1031,6 +1031,102 @@ __bpf_kfunc void bpf_iter_task_destroy(struct bpf_iter_task *it)
> {
> }
>
> +struct bpf_iter_task_file {
> + __u64 __opaque[3];
> +} __aligned(8);
> +
> +struct bpf_iter_task_file_kern {
> + struct task_struct *task;
> + struct file *file;
> + int fd;
> +} __aligned(8);
> +
> +/**
> + * bpf_iter_task_file_new() - Initialize a new task file iterator for a task,
> + * used to iterate over all files opened by a specified task
> + *
> + * @it: the new bpf_iter_task_file to be created
> + * @task: a pointer pointing to a task to be iterated over
> + */
> +__bpf_kfunc int bpf_iter_task_file_new(struct bpf_iter_task_file *it,
> + struct task_struct *task)
> +{
> + struct bpf_iter_task_file_kern *kit = (void *)it;
> +
> + BUILD_BUG_ON(sizeof(struct bpf_iter_task_file_kern) > sizeof(struct bpf_iter_task_file));
> + BUILD_BUG_ON(__alignof__(struct bpf_iter_task_file_kern) !=
> + __alignof__(struct bpf_iter_task_file));
> +
> + kit->task = task;
This is broken, since task refcnt can drop while iter is running.
Before doing any of that I'd like to see a long term path for crib.
All these small additions are ok if they're generic and useful elsewhere.
I'm afraid there is no path forward for crib itself though.
pw-bot: cr
