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, 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