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 
9 static void *dmabuf_iter_seq_start(struct seq_file *seq, loff_t *pos)
10 {
11 	if (*pos)
12 		return NULL;
13 
14 	return dma_buf_iter_begin();
15 }
16 
17 static void *dmabuf_iter_seq_next(struct seq_file *seq, void *v, loff_t *pos)
18 {
19 	struct dma_buf *dmabuf = v;
20 
21 	++*pos;
22 
23 	return dma_buf_iter_next(dmabuf);
24 }
25 
26 struct bpf_iter__dmabuf {
27 	__bpf_md_ptr(struct bpf_iter_meta *, meta);
28 	__bpf_md_ptr(struct dma_buf *, dmabuf);
29 };
30 
31 static int __dmabuf_seq_show(struct seq_file *seq, void *v, bool in_stop)
32 {
33 	struct bpf_iter_meta meta = {
34 		.seq = seq,
35 	};
36 	struct bpf_iter__dmabuf ctx = {
37 		.meta = &meta,
38 		.dmabuf = v,
39 	};
40 	struct bpf_prog *prog = bpf_iter_get_info(&meta, in_stop);
41 
42 	if (prog)
43 		return bpf_iter_run_prog(prog, &ctx);
44 
45 	return 0;
46 }
47 
48 static int dmabuf_iter_seq_show(struct seq_file *seq, void *v)
49 {
50 	return __dmabuf_seq_show(seq, v, false);
51 }
52 
53 static void dmabuf_iter_seq_stop(struct seq_file *seq, void *v)
54 {
55 	struct dma_buf *dmabuf = v;
56 
57 	if (dmabuf)
58 		dma_buf_put(dmabuf);
59 }
60 
61 static const struct seq_operations dmabuf_iter_seq_ops = {
62 	.start	= dmabuf_iter_seq_start,
63 	.next	= dmabuf_iter_seq_next,
64 	.stop	= dmabuf_iter_seq_stop,
65 	.show	= dmabuf_iter_seq_show,
66 };
67 
68 static void bpf_iter_dmabuf_show_fdinfo(const struct bpf_iter_aux_info *aux,
69 					struct seq_file *seq)
70 {
71 	seq_puts(seq, "dmabuf iter\n");
72 }
73 
74 static const struct bpf_iter_seq_info dmabuf_iter_seq_info = {
75 	.seq_ops		= &dmabuf_iter_seq_ops,
76 	.init_seq_private	= NULL,
77 	.fini_seq_private	= NULL,
78 	.seq_priv_size		= 0,
79 };
80 
81 static struct bpf_iter_reg bpf_dmabuf_reg_info = {
82 	.target			= "dmabuf",
83 	.feature                = BPF_ITER_RESCHED,
84 	.show_fdinfo		= bpf_iter_dmabuf_show_fdinfo,
85 	.ctx_arg_info_size	= 1,
86 	.ctx_arg_info		= {
87 		{ offsetof(struct bpf_iter__dmabuf, dmabuf),
88 		  PTR_TO_BTF_ID_OR_NULL },
89 	},
90 	.seq_info		= &dmabuf_iter_seq_info,
91 };
92 
93 DEFINE_BPF_ITER_FUNC(dmabuf, struct bpf_iter_meta *meta, struct dma_buf *dmabuf)
94 BTF_ID_LIST_SINGLE(bpf_dmabuf_btf_id, struct, dma_buf)
95 
96 static int __init dmabuf_iter_init(void)
97 {
98 	bpf_dmabuf_reg_info.ctx_arg_info[0].btf_id = bpf_dmabuf_btf_id[0];
99 	return bpf_iter_reg_target(&bpf_dmabuf_reg_info);
100 }
101 
102 late_initcall(dmabuf_iter_init);
103 
104 struct bpf_iter_dmabuf {
105 	/*
106 	 * opaque iterator state; having __u64 here allows to preserve correct
107 	 * alignment requirements in vmlinux.h, generated from BTF
108 	 */
109 	__u64 __opaque[1];
110 } __aligned(8);
111 
112 /* Non-opaque version of bpf_iter_dmabuf */
113 struct bpf_iter_dmabuf_kern {
114 	struct dma_buf *dmabuf;
115 } __aligned(8);
116 
117 __bpf_kfunc_start_defs();
118 
119 __bpf_kfunc int bpf_iter_dmabuf_new(struct bpf_iter_dmabuf *it)
120 {
121 	struct bpf_iter_dmabuf_kern *kit = (void *)it;
122 
123 	BUILD_BUG_ON(sizeof(*kit) > sizeof(*it));
124 	BUILD_BUG_ON(__alignof__(*kit) != __alignof__(*it));
125 
126 	kit->dmabuf = NULL;
127 	return 0;
128 }
129 
130 __bpf_kfunc struct dma_buf *bpf_iter_dmabuf_next(struct bpf_iter_dmabuf *it)
131 {
132 	struct bpf_iter_dmabuf_kern *kit = (void *)it;
133 
134 	if (kit->dmabuf)
135 		kit->dmabuf = dma_buf_iter_next(kit->dmabuf);
136 	else
137 		kit->dmabuf = dma_buf_iter_begin();
138 
139 	return kit->dmabuf;
140 }
141 
142 __bpf_kfunc void bpf_iter_dmabuf_destroy(struct bpf_iter_dmabuf *it)
143 {
144 	struct bpf_iter_dmabuf_kern *kit = (void *)it;
145 
146 	if (kit->dmabuf)
147 		dma_buf_put(kit->dmabuf);
148 }
149 
150 __bpf_kfunc_end_defs();
151