linux-kernel - [PATCH bpf-next v3 3/4] bpf/crib: Add struct file related CRIB kfuncs

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Message-ID:
 <AM6PR03MB584840534BA4A82407DFB50D99532@AM6PR03MB5848.eurprd03.prod.outlook.com>
Date: Wed,  6 Nov 2024 19:38:47 +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,
	brauner@...nel.org
Cc: bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH bpf-next v3 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.

Since the struct file_operations of most file types are currently
static (e.g., socket_file_ops) and cannot be directly accessed in
crib/files.c, the future plan is to add functions like
is_socket_file_fops() to the corresponding files (e.g., net/socket.c).

Signed-off-by: Juntong Deng <juntong.deng@...look.com>
---
 kernel/bpf/Makefile      |  1 +
 kernel/bpf/crib/Makefile |  3 +++
 kernel/bpf/crib/crib.c   | 28 +++++++++++++++++++++
 kernel/bpf/crib/files.c  | 54 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 86 insertions(+)
 create mode 100644 kernel/bpf/crib/Makefile
 create mode 100644 kernel/bpf/crib/crib.c
 create mode 100644 kernel/bpf/crib/files.c

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 105328f0b9c0..933d36264e5e 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -53,3 +53,4 @@ obj-$(CONFIG_BPF_SYSCALL) += relo_core.o
 obj-$(CONFIG_BPF_SYSCALL) += btf_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += btf_relocate.o
 obj-$(CONFIG_BPF_SYSCALL) += kmem_cache_iter.o
+obj-$(CONFIG_BPF_SYSCALL) += crib/
diff --git a/kernel/bpf/crib/Makefile b/kernel/bpf/crib/Makefile
new file mode 100644
index 000000000000..4e1bae1972dd
--- /dev/null
+++ b/kernel/bpf/crib/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_BPF_SYSCALL) += crib.o files.o
diff --git a/kernel/bpf/crib/crib.c b/kernel/bpf/crib/crib.c
new file mode 100644
index 000000000000..e00f4a4f0d42
--- /dev/null
+++ b/kernel/bpf/crib/crib.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Checkpoint/Restore In eBPF (CRIB)
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/btf_ids.h>
+
+BTF_KFUNCS_START(bpf_crib_kfuncs)
+
+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 = {
+	.owner = THIS_MODULE,
+	.set   = &bpf_crib_kfuncs,
+};
+
+static int __init bpf_crib_init(void)
+{
+	return register_btf_kfunc_id_set(BPF_PROG_TYPE_SYSCALL, &bpf_crib_kfunc_set);
+}
+
+late_initcall(bpf_crib_init);
diff --git a/kernel/bpf/crib/files.c b/kernel/bpf/crib/files.c
new file mode 100644
index 000000000000..61201923a35f
--- /dev/null
+++ b/kernel/bpf/crib/files.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/btf.h>
+#include <linux/file.h>
+#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
+};
+
+__bpf_kfunc_start_defs();
+
+/**
+ * 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