On 5/5/20 1:11 PM, Andrii Nakryiko wrote:
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?
Yes, this is just for virtual grouping. Not 100% sure whether this
is needed or not.
+ 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.
Thanks for catching this. Missed this case.
Also, file_priv is redundant, assign to seq directly from file->private_data?
Ack.
+ 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?
Ack.
+ priv_data->seq_num = 0;
+ priv_data->do_stop = 0;
+}
+
[...]
