On Sun, May 3, 2020 at 11:29 PM Yonghong Song <yhs@xxxxxx> wrote:
>
> A new bpf command BPF_ITER_CREATE is added.
>
> The anonymous bpf iterator is seq_file based.
> The seq_file private data are referenced by targets.
> The bpf_iter infrastructure allocated additional space
> at seq_file->private before the space used by targets
> to store some meta data, e.g.,
> prog: prog to run
> session_id: an unique id for each opened seq_file
> seq_num: how many times bpf programs are queried in this session
> do_stop: an internal state to decide whether bpf program
> should be called in seq_ops->stop() or not
>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 6 ++
> kernel/bpf/bpf_iter.c | 128 +++++++++++++++++++++++++++++++++
> kernel/bpf/syscall.c | 26 +++++++
> tools/include/uapi/linux/bpf.h | 6 ++
> 5 files changed, 167 insertions(+)
>
[...]
> /* The description below is an attempt at providing documentation to eBPF
> diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
> index 2674c9cbc3dc..2a9f939be6e6 100644
> --- a/kernel/bpf/bpf_iter.c
> +++ b/kernel/bpf/bpf_iter.c
> @@ -2,6 +2,7 @@
> /* Copyright (c) 2020 Facebook */
>
> #include <linux/fs.h>
> +#include <linux/anon_inodes.h>
> #include <linux/filter.h>
> #include <linux/bpf.h>
>
> @@ -20,12 +21,26 @@ struct bpf_iter_link {
> struct bpf_iter_target_info *tinfo;
> };
>
> +struct bpf_iter_priv_data {
> + struct {
nit: anon struct seems unnecessary here? is it just for visual grouping?
> + struct bpf_iter_target_info *tinfo;
> + struct bpf_prog *prog;
> + u64 session_id;
> + u64 seq_num;
> + u64 do_stop;
> + };
> + u8 target_private[] __aligned(8);
> +};
> +
> static struct list_head targets = LIST_HEAD_INIT(targets);
> static DEFINE_MUTEX(targets_mutex);
>
> /* protect bpf_iter_link changes */
> static DEFINE_MUTEX(link_mutex);
>
> +/* incremented on every opened seq_file */
> +static atomic64_t session_id;
> +
> /* bpf_seq_read, a customized and simpler version for bpf iterator.
> * no_llseek is assumed for this file.
> * The following are differences from seq_read():
> @@ -154,6 +169,31 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
> goto Done;
> }
>
> +static int iter_release(struct inode *inode, struct file *file)
> +{
> + struct bpf_iter_priv_data *iter_priv;
> + void *file_priv = file->private_data;
> + struct seq_file *seq;
> +
> + seq = file_priv;
seq might be NULL, if anon_inode_getfile succeeded, but then
prepare_seq_file failed, so you need to handle that.
Also, file_priv is redundant, assign to seq directly from file->private_data?
> + iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
> + target_private);
> +
> + if (iter_priv->tinfo->fini_seq_private)
> + iter_priv->tinfo->fini_seq_private(seq->private);
> +
> + bpf_prog_put(iter_priv->prog);
> + seq->private = iter_priv;
> +
> + return seq_release_private(inode, file);
> +}
> +
> +static const struct file_operations bpf_iter_fops = {
> + .llseek = no_llseek,
> + .read = bpf_seq_read,
> + .release = iter_release,
> +};
> +
> int bpf_iter_reg_target(struct bpf_iter_reg *reg_info)
> {
> struct bpf_iter_target_info *tinfo;
> @@ -289,3 +329,91 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
>
> return bpf_link_settle(&link_primer);
> }
> +
> +static void init_seq_meta(struct bpf_iter_priv_data *priv_data,
> + struct bpf_iter_target_info *tinfo,
> + struct bpf_prog *prog)
> +{
> + priv_data->tinfo = tinfo;
> + priv_data->prog = prog;
> + priv_data->session_id = atomic64_add_return(1, &session_id);
nit: atomic64_inc_return?
> + priv_data->seq_num = 0;
> + priv_data->do_stop = 0;
> +}
> +
[...]
