1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (c) 2025 Google LLC */
3#include <linux/bpf.h>
4#include <linux/btf_ids.h>
5#include <linux/dma-buf.h>
6#include <linux/kernel.h>
7#include <linux/seq_file.h>
8
9struct dmabuf_iter_priv {
10 /*
11 * If this pointer is non-NULL, the buffer's refcount is elevated to
12 * prevent destruction between stop/start. If reading is not resumed and
13 * start is never called again, then dmabuf_iter_seq_fini drops the
14 * reference when the iterator is released.
15 */
16 struct dma_buf *dmabuf;
17};
18
19static void *dmabuf_iter_seq_start(struct seq_file *seq, loff_t *pos)
20{
21 struct dmabuf_iter_priv *p = seq->private;
22
23 if (*pos) {
24 struct dma_buf *dmabuf = p->dmabuf;
25
26 if (!dmabuf)
27 return NULL;
28
29 /*
30 * Always resume from where we stopped, regardless of the value
31 * of pos.
32 */
33 p->dmabuf = NULL;
34 return dmabuf;
35 }
36
37 return dma_buf_iter_begin();
38}
39
40static void *dmabuf_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos)
41{
42 struct dma_buf *dmabuf = v;
43
44 ++*pos;
45
46 return dma_buf_iter_next(dmbuf: dmabuf);
47}
48
49struct bpf_iter__dmabuf {
50 __bpf_md_ptr(struct bpf_iter_meta *, meta);
51 __bpf_md_ptr(struct dma_buf *, dmabuf);
52};
53
54static int __dmabuf_seq_show(struct seq_file *seq, void *v, bool in_stop)
55{
56 struct bpf_iter_meta meta = {
57 .seq = seq,
58 };
59 struct bpf_iter__dmabuf ctx = {
60 .meta = &meta,
61 .dmabuf = v,
62 };
63 struct bpf_prog *prog = bpf_iter_get_info(meta: &meta, in_stop);
64
65 if (prog)
66 return bpf_iter_run_prog(prog, ctx: &ctx);
67
68 return 0;
69}
70
71static int dmabuf_iter_seq_show(struct seq_file *seq, void *v)
72{
73 return __dmabuf_seq_show(seq, v, in_stop: false);
74}
75
76static void dmabuf_iter_seq_stop(struct seq_file *seq, void *v)
77{
78 struct dma_buf *dmabuf = v;
79
80 if (dmabuf) {
81 struct dmabuf_iter_priv *p = seq->private;
82
83 p->dmabuf = dmabuf;
84 }
85}
86
87static const struct seq_operations dmabuf_iter_seq_ops = {
88 .start = dmabuf_iter_seq_start,
89 .next = dmabuf_iter_seq_next,
90 .stop = dmabuf_iter_seq_stop,
91 .show = dmabuf_iter_seq_show,
92};
93
94static void bpf_iter_dmabuf_show_fdinfo(const struct bpf_iter_aux_info *aux,
95 struct seq_file *seq)
96{
97 seq_puts(m: seq, s: "dmabuf iter\n");
98}
99
100static int dmabuf_iter_seq_init(void *priv, struct bpf_iter_aux_info *aux)
101{
102 struct dmabuf_iter_priv *p = (struct dmabuf_iter_priv *)priv;
103
104 p->dmabuf = NULL;
105 return 0;
106}
107
108static void dmabuf_iter_seq_fini(void *priv)
109{
110 struct dmabuf_iter_priv *p = (struct dmabuf_iter_priv *)priv;
111
112 if (p->dmabuf)
113 dma_buf_put(dmabuf: p->dmabuf);
114}
115
116static const struct bpf_iter_seq_info dmabuf_iter_seq_info = {
117 .seq_ops = &dmabuf_iter_seq_ops,
118 .init_seq_private = dmabuf_iter_seq_init,
119 .fini_seq_private = dmabuf_iter_seq_fini,
120 .seq_priv_size = sizeof(struct dmabuf_iter_priv),
121};
122
123static struct bpf_iter_reg bpf_dmabuf_reg_info = {
124 .target = "dmabuf",
125 .feature = BPF_ITER_RESCHED,
126 .show_fdinfo = bpf_iter_dmabuf_show_fdinfo,
127 .ctx_arg_info_size = 1,
128 .ctx_arg_info = {
129 { offsetof(struct bpf_iter__dmabuf, dmabuf),
130 PTR_TO_BTF_ID_OR_NULL },
131 },
132 .seq_info = &dmabuf_iter_seq_info,
133};
134
135DEFINE_BPF_ITER_FUNC(dmabuf, struct bpf_iter_meta *meta, struct dma_buf *dmabuf)
136BTF_ID_LIST_SINGLE(bpf_dmabuf_btf_id, struct, dma_buf)
137
138static int __init dmabuf_iter_init(void)
139{
140 bpf_dmabuf_reg_info.ctx_arg_info[0].btf_id = bpf_dmabuf_btf_id[0];
141 return bpf_iter_reg_target(reg_info: &bpf_dmabuf_reg_info);
142}
143
144late_initcall(dmabuf_iter_init);
145
146struct bpf_iter_dmabuf {
147 /*
148 * opaque iterator state; having __u64 here allows to preserve correct
149 * alignment requirements in vmlinux.h, generated from BTF
150 */
151 __u64 __opaque[1];
152} __aligned(8);
153
154/* Non-opaque version of bpf_iter_dmabuf */
155struct bpf_iter_dmabuf_kern {
156 struct dma_buf *dmabuf;
157} __aligned(8);
158
159__bpf_kfunc_start_defs();
160
161__bpf_kfunc int bpf_iter_dmabuf_new(struct bpf_iter_dmabuf *it)
162{
163 struct bpf_iter_dmabuf_kern *kit = (void *)it;
164
165 BUILD_BUG_ON(sizeof(*kit) > sizeof(*it));
166 BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it));
167
168 kit->dmabuf = NULL;
169 return 0;
170}
171
172__bpf_kfunc struct dma_buf *bpf_iter_dmabuf_next(struct bpf_iter_dmabuf *it)
173{
174 struct bpf_iter_dmabuf_kern *kit = (void *)it;
175
176 if (kit->dmabuf)
177 kit->dmabuf = dma_buf_iter_next(dmbuf: kit->dmabuf);
178 else
179 kit->dmabuf = dma_buf_iter_begin();
180
181 return kit->dmabuf;
182}
183
184__bpf_kfunc void bpf_iter_dmabuf_destroy(struct bpf_iter_dmabuf *it)
185{
186 struct bpf_iter_dmabuf_kern *kit = (void *)it;
187
188 if (kit->dmabuf)
189 dma_buf_put(dmabuf: kit->dmabuf);
190}
191
192__bpf_kfunc_end_defs();
193

source code of linux/kernel/bpf/dmabuf_iter.c