100 lines
2.2 KiB
C
100 lines
2.2 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/ptrace.h>
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#include <stddef.h>
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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char _license[] SEC("license") = "GPL";
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/* typically virtio scsi has max SGs of 6 */
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#define VIRTIO_MAX_SGS 6
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/* Verifier will fail with SG_MAX = 128. The failure can be
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* workarounded with a smaller SG_MAX, e.g. 10.
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*/
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#define WORKAROUND
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#ifdef WORKAROUND
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#define SG_MAX 10
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#else
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/* typically virtio blk has max SEG of 128 */
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#define SG_MAX 128
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#endif
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#define SG_CHAIN 0x01UL
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#define SG_END 0x02UL
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struct scatterlist {
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unsigned long page_link;
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unsigned int offset;
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unsigned int length;
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};
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#define sg_is_chain(sg) ((sg)->page_link & SG_CHAIN)
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#define sg_is_last(sg) ((sg)->page_link & SG_END)
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#define sg_chain_ptr(sg) \
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((struct scatterlist *) ((sg)->page_link & ~(SG_CHAIN | SG_END)))
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static inline struct scatterlist *__sg_next(struct scatterlist *sgp)
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{
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struct scatterlist sg;
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bpf_probe_read_kernel(&sg, sizeof(sg), sgp);
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if (sg_is_last(&sg))
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return NULL;
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sgp++;
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bpf_probe_read_kernel(&sg, sizeof(sg), sgp);
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if (sg_is_chain(&sg))
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sgp = sg_chain_ptr(&sg);
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return sgp;
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}
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static inline struct scatterlist *get_sgp(struct scatterlist **sgs, int i)
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{
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struct scatterlist *sgp;
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bpf_probe_read_kernel(&sgp, sizeof(sgp), sgs + i);
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return sgp;
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}
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int config = 0;
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int result = 0;
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SEC("kprobe/virtqueue_add_sgs")
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int BPF_KPROBE(trace_virtqueue_add_sgs, void *unused, struct scatterlist **sgs,
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unsigned int out_sgs, unsigned int in_sgs)
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{
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struct scatterlist *sgp = NULL;
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__u64 length1 = 0, length2 = 0;
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unsigned int i, n, len;
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if (config != 0)
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return 0;
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for (i = 0; (i < VIRTIO_MAX_SGS) && (i < out_sgs); i++) {
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for (n = 0, sgp = get_sgp(sgs, i); sgp && (n < SG_MAX);
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sgp = __sg_next(sgp)) {
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bpf_probe_read_kernel(&len, sizeof(len), &sgp->length);
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length1 += len;
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n++;
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}
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}
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for (i = 0; (i < VIRTIO_MAX_SGS) && (i < in_sgs); i++) {
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for (n = 0, sgp = get_sgp(sgs, i); sgp && (n < SG_MAX);
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sgp = __sg_next(sgp)) {
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bpf_probe_read_kernel(&len, sizeof(len), &sgp->length);
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length2 += len;
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n++;
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}
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}
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config = 1;
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result = length2 - length1;
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return 0;
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}
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