selftests/bpf: Add selftests for bpf_perf_event_output

Software event output is only enabled by a few prog types.
This test is to ensure that all supported types are enabled for
bpf_perf_event_output successfully.

Signed-off-by: Allan Zhang <allanzhang@google.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/verifier/event_output.c

@@ -0,0 +1,94 @@
+/* instructions used to output a skb based software event, produced
+ * from code snippet:
+ * struct TMP {
+ *  uint64_t tmp;
+ * } tt;
+ * tt.tmp = 5;
+ * bpf_perf_event_output(skb, &connection_tracking_event_map, 0,
+ *			 &tt, sizeof(tt));
+ * return 1;
+ *
+ * the bpf assembly from llvm is:
+ *        0:       b7 02 00 00 05 00 00 00         r2 = 5
+ *        1:       7b 2a f8 ff 00 00 00 00         *(u64 *)(r10 - 8) = r2
+ *        2:       bf a4 00 00 00 00 00 00         r4 = r10
+ *        3:       07 04 00 00 f8 ff ff ff         r4 += -8
+ *        4:       18 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00    r2 = 0ll
+ *        6:       b7 03 00 00 00 00 00 00         r3 = 0
+ *        7:       b7 05 00 00 08 00 00 00         r5 = 8
+ *        8:       85 00 00 00 19 00 00 00         call 25
+ *        9:       b7 00 00 00 01 00 00 00         r0 = 1
+ *       10:       95 00 00 00 00 00 00 00         exit
+ *
+ *     The reason I put the code here instead of fill_helpers is that map fixup
+ *     is against the insns, instead of filled prog.
+ */
+
+#define __PERF_EVENT_INSNS__					\
+	BPF_MOV64_IMM(BPF_REG_2, 5),				\
+	BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_2, -8),		\
+	BPF_MOV64_REG(BPF_REG_4, BPF_REG_10),			\
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, -8),			\
+	BPF_LD_MAP_FD(BPF_REG_2, 0),				\
+	BPF_MOV64_IMM(BPF_REG_3, 0),				\
+	BPF_MOV64_IMM(BPF_REG_5, 8),				\
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,		\
+		     BPF_FUNC_perf_event_output),		\
+	BPF_MOV64_IMM(BPF_REG_0, 1),				\
+	BPF_EXIT_INSN(),
+{
+	"perfevent for sockops",
+	.insns = { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_SOCK_OPS,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},
+{
+	"perfevent for tc",
+	.insns =  { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},
+{
+	"perfevent for lwt out",
+	.insns =  { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_LWT_OUT,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},
+{
+	"perfevent for xdp",
+	.insns =  { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_XDP,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},
+{
+	"perfevent for socket filter",
+	.insns =  { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_SOCKET_FILTER,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},
+{
+	"perfevent for sk_skb",
+	.insns =  { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_SK_SKB,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},
+{
+	"perfevent for cgroup skb",
+	.insns =  { __PERF_EVENT_INSNS__ },
+	.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
+	.fixup_map_event_output = { 4 },
+	.result = ACCEPT,
+	.retval = 1,
+},