linux-kernel - [PATCH bpf-next v2 3/4] bpf/crib: Add struct file related CRIB kfuncs

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Message-ID:
 <AM6PR03MB584858690D5A02162502A02099542@AM6PR03MB5848.eurprd03.prod.outlook.com>
Date: Wed, 30 Oct 2024 00:14:56 +0000
From: Juntong Deng <juntong.deng@...look.com>
To: ast@...nel.org,
	daniel@...earbox.net,
	john.fastabend@...il.com,
	andrii@...nel.org,
	martin.lau@...ux.dev,
	eddyz87@...il.com,
	song@...nel.org,
	yonghong.song@...ux.dev,
	kpsingh@...nel.org,
	sdf@...ichev.me,
	haoluo@...gle.com,
	jolsa@...nel.org,
	memxor@...il.com,
	snorcht@...il.com
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH bpf-next v2 3/4] bpf/crib: Add struct file related CRIB kfuncs

This patch adds struct file related CRIB kfuncs.

bpf_fget_task() is used to get a pointer to the struct file
corresponding to the task file descriptor. Note that this function
acquires a reference to struct file.

bpf_get_file_ops_type() is used to determine what exactly this file
is based on the file operations, such as socket, eventfd, timerfd,
pipe, etc, in order to perform different checkpoint/restore processing
for different file types. This function currently has only one return
value, FILE_OPS_UNKNOWN, but will increase with the file types that
CRIB supports for checkpoint/restore.

Signed-off-by: Juntong Deng <juntong.deng@...look.com>
---
 kernel/bpf/crib/crib.c  |  4 ++++
 kernel/bpf/crib/files.c | 44 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/kernel/bpf/crib/crib.c b/kernel/bpf/crib/crib.c
index e6536ee9a845..78ddd19d5693 100644
--- a/kernel/bpf/crib/crib.c
+++ b/kernel/bpf/crib/crib.c
@@ -14,6 +14,10 @@ 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_fget_task, KF_ACQUIRE | KF_TRUSTED_ARGS | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_get_file_ops_type, KF_TRUSTED_ARGS)
+BTF_ID_FLAGS(func, bpf_put_file, KF_RELEASE)
+
 BTF_KFUNCS_END(bpf_crib_kfuncs)
 
 static const struct btf_kfunc_id_set bpf_crib_kfunc_set = {
diff --git a/kernel/bpf/crib/files.c b/kernel/bpf/crib/files.c
index ececf150303f..8e0e29877359 100644
--- a/kernel/bpf/crib/files.c
+++ b/kernel/bpf/crib/files.c
@@ -5,6 +5,14 @@
 #include <linux/fdtable.h>
 #include <linux/net.h>
 
+/**
+ * This enum will grow with the file types that CRIB supports for
+ * checkpoint/restore.
+ */
+enum {
+	FILE_OPS_UNKNOWN = 0
+};
+
 struct bpf_iter_task_file {
 	__u64 __opaque[3];
 } __aligned(8);
@@ -102,4 +110,40 @@ __bpf_kfunc void bpf_iter_task_file_destroy(struct bpf_iter_task_file *it)
 		fput(kit->file);
 }
 
+/**
+ * bpf_fget_task() - Get a pointer to the struct file corresponding to
+ * the task file descriptor
+ *
+ * Note that this function acquires a reference to struct file.
+ *
+ * @task: the specified struct task_struct
+ * @fd: the file descriptor
+ *
+ * @returns the corresponding struct file pointer if found,
+ * otherwise returns NULL
+ */
+__bpf_kfunc struct file *bpf_fget_task(struct task_struct *task, unsigned int fd)
+{
+	struct file *file;
+
+	file = fget_task(task, fd);
+	return file;
+}
+
+/**
+ * bpf_get_file_ops_type() - Determine what exactly this file is based on
+ * the file operations, such as socket, eventfd, timerfd, pipe, etc
+ *
+ * This function will grow with the file types that CRIB supports for
+ * checkpoint/restore.
+ *
+ * @file: a pointer to the struct file
+ *
+ * @returns the file operations type
+ */
+__bpf_kfunc unsigned int bpf_get_file_ops_type(struct file *file)
+{
+	return FILE_OPS_UNKNOWN;
+}
+
 __bpf_kfunc_end_defs();
-- 
2.39.5