cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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loop6.c (2209B)

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