1 | // SPDX-License-Identifier: GPL-2.0 |
2 | |
3 | #include <linux/ptrace.h> |
4 | #include <stddef.h> |
5 | #include <linux/bpf.h> |
6 | #include <bpf/bpf_helpers.h> |
7 | #include <bpf/bpf_tracing.h> |
8 | #include "bpf_misc.h" |
9 | |
10 | char _license[] SEC("license" ) = "GPL" ; |
11 | |
12 | /* typically virtio scsi has max SGs of 6 */ |
13 | #define VIRTIO_MAX_SGS 6 |
14 | |
15 | /* Verifier will fail with SG_MAX = 128. The failure can be |
16 | * workarounded with a smaller SG_MAX, e.g. 10. |
17 | */ |
18 | #define WORKAROUND |
19 | #ifdef WORKAROUND |
20 | #define SG_MAX 10 |
21 | #else |
22 | /* typically virtio blk has max SEG of 128 */ |
23 | #define SG_MAX 128 |
24 | #endif |
25 | |
26 | #define SG_CHAIN 0x01UL |
27 | #define SG_END 0x02UL |
28 | |
29 | struct scatterlist { |
30 | unsigned long page_link; |
31 | unsigned int offset; |
32 | unsigned int length; |
33 | }; |
34 | |
35 | #define sg_is_chain(sg) ((sg)->page_link & SG_CHAIN) |
36 | #define sg_is_last(sg) ((sg)->page_link & SG_END) |
37 | #define sg_chain_ptr(sg) \ |
38 | ((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_END))) |
39 | |
40 | static inline struct scatterlist *__sg_next(struct scatterlist *sgp) |
41 | { |
42 | struct scatterlist sg; |
43 | |
44 | bpf_probe_read_kernel(&sg, sizeof(sg), sgp); |
45 | if (sg_is_last(&sg)) |
46 | return NULL; |
47 | |
48 | sgp++; |
49 | |
50 | bpf_probe_read_kernel(&sg, sizeof(sg), sgp); |
51 | if (sg_is_chain(&sg)) |
52 | sgp = sg_chain_ptr(&sg); |
53 | |
54 | return sgp; |
55 | } |
56 | |
57 | static inline struct scatterlist *get_sgp(struct scatterlist **sgs, int i) |
58 | { |
59 | struct scatterlist *sgp; |
60 | |
61 | bpf_probe_read_kernel(&sgp, sizeof(sgp), sgs + i); |
62 | return sgp; |
63 | } |
64 | |
65 | int config = 0; |
66 | int result = 0; |
67 | |
68 | SEC("kprobe/virtqueue_add_sgs" ) |
69 | int BPF_KPROBE(trace_virtqueue_add_sgs, void *unused, struct scatterlist **sgs, |
70 | unsigned int out_sgs, unsigned int in_sgs) |
71 | { |
72 | struct scatterlist *sgp = NULL; |
73 | __u64 length1 = 0, length2 = 0; |
74 | unsigned int i, n, len; |
75 | |
76 | if (config != 0) |
77 | return 0; |
78 | |
79 | for (i = 0; (i < VIRTIO_MAX_SGS) && (i < out_sgs); i++) { |
80 | __sink(out_sgs); |
81 | for (n = 0, sgp = get_sgp(sgs: sgs, i); sgp && (n < SG_MAX); |
82 | sgp = __sg_next(sgp)) { |
83 | bpf_probe_read_kernel(&len, sizeof(len), &sgp->length); |
84 | length1 += len; |
85 | n++; |
86 | } |
87 | } |
88 | |
89 | for (i = 0; (i < VIRTIO_MAX_SGS) && (i < in_sgs); i++) { |
90 | __sink(in_sgs); |
91 | for (n = 0, sgp = get_sgp(sgs, i); sgp && (n < SG_MAX); |
92 | sgp = __sg_next(sgp)) { |
93 | bpf_probe_read_kernel(&len, sizeof(len), &sgp->length); |
94 | length2 += len; |
95 | n++; |
96 | } |
97 | } |
98 | |
99 | config = 1; |
100 | result = length2 - length1; |
101 | return 0; |
102 | } |
103 | |