@@ -9,6 +9,9 @@
/* file_operations for kernfs file system */
+/* Command for removing a kernfs entry */
+#define REMOVE_CMD "rm"
+
/* Handler when the watched inode is freed. */
static void kn_watch_free_inode(void *obj, enum bpf_type type, void *kn)
{
@@ -22,8 +25,27 @@ static const struct notify_ops notify_ops = {
.free_inode = kn_watch_free_inode,
};
+static ssize_t bpf_generic_write(struct kernfs_open_file *of, char *buf,
+ size_t bytes, loff_t off)
+{
+ if (sysfs_streq(buf, REMOVE_CMD)) {
+ kernfs_remove_self(of->kn);
+ return bytes;
+ }
+
+ return -EINVAL;
+}
+
+static ssize_t bpf_generic_read(struct kernfs_open_file *of, char *buf,
+ size_t bytes, loff_t off)
+{
+ return -EIO;
+}
+
/* Kernfs file operations for bpf created files. */
static const struct kernfs_ops bpf_generic_ops = {
+ .write = bpf_generic_write,
+ .read = bpf_generic_read,
};
/* Test whether a given dentry is a kernfs entry. */
When a bpf object has been exposed in kernfs, there should be a way to remove it. Kernfs doesn't implement unlink, therefore one can not remove the entry in a normal way. To remove the file, we can allow writing a special command to the new entry, which can trigger a remove_self() for removal. So far there are two ways to remove an entry that is created by pinning bpf objects in kernfs: 1. unpin the object from bpffs. 2. write a special command to the kernfs entry. Signed-off-by: Hao Luo <haoluo@google.com> --- kernel/bpf/kernfs_node.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+)