[RFC PATCH bpf-next 3/3] selftests/bpf: call bpf_prog_test_run with trace enabled for XDP test

[Eelco Chaudron <echaudro@redhat.com>]

This adds a quick and dirty version of bpf_prog_test_run_trace() right
in the xdp.c selftest to demonstrate the new trace functionality.

This is a (too long) example output of the trace functionality:

STACK(32 bytes):
  ffffb82b4081faa8: 0x0000000000000000 0000000000000000 0000000000000000 0000000000000000

REGISTERS:
  r00-03: 0x0000000000000000 ffffb82b4081fde8 0000000000000000 0000000000000000
  r04-07: 0x0000000000000000 0000000000000000 0000000000000000 0000000000000000
  r08-11: 0x0000000000000000 0000000000000000 ffffb82b4081fac8 0000000000000000

1[0x0]: (bf) r6 = r1
  r6: 0x0000000000000000 -> 0xffffb82b4081fde8
2[0x1]: (b4) w8 = 1
  r8: 0x0000000000000000 -> 0x0000000000000001
3[0x2]: (b7) r11 = -439116112
  r11: 0x0000000000000000 -> 0xffffffffe5d39eb0
4[0x3]: (67) r11 <<= 32
  r11: 0xffffffffe5d39eb0 -> 0xe5d39eb000000000
5[0x4]: (4f) r8 |= r11
  r8: 0x0000000000000001 -> 0xe5d39eb000000001
6[0x5]: (79) r2 = *(u64 *)(r6 +8)
  r2: 0x0000000000000000 -> 0xffff8fbaec6d3b36
7[0x6]: (79) r1 = *(u64 *)(r6 +0)
  r1: 0xffffb82b4081fde8 -> 0xffff8fbaec6d3b00
8[0x7]: (bf) r3 = r1
  r3: 0x0000000000000000 -> 0xffff8fbaec6d3b00
9[0x8]: (07) r3 += 14
  r3: 0xffff8fbaec6d3b00 -> 0xffff8fbaec6d3b0e
10[0x9]: (2d) if r3 > r2 goto pc+76
  r3: 0xffff8fbaec6d3b0e <==> r2: 0xffff8fbaec6d3b36
  branch was NOT taken
...
...
300[0x152]: (a4) w2 ^= -1
  r2: 0x6ec5cf350000934d -> 0x00000000ffff6cb2
301[0x153]: (b7) r11 = -412759113
  r11: 0x6ec5cf3500000000 -> 0xffffffffe765cbb7
302[0x154]: (67) r11 <<= 32
  r11: 0xffffffffe765cbb7 -> 0xe765cbb700000000
303[0x155]: (4f) r2 |= r11
  r2: 0x00000000ffff6cb2 -> 0xe765cbb7ffff6cb2
304[0x156]: (6b) *(u16 *)(r1 +24) = r2
  MEM[ffff8fbaec6d3b04]: 0x00 -> 0xb2
305[0x157]: (71) r1 = *(u8 *)(r10 -12)
  r1: 0xffff8fbaec6d3aec -> 0x0000000000000006
306[0x158]: (b7) r11 = -1438054225
  r11: 0xe765cbb700000000 -> 0xffffffffaa4908af
307[0x159]: (67) r11 <<= 32
  r11: 0xffffffffaa4908af -> 0xaa4908af00000000
308[0x15a]: (4f) r1 |= r11
  r1: 0x0000000000000006 -> 0xaa4908af00000006
309[0x15b]: (63) *(u32 *)(r10 -4) = r1
  MEM[ffffb82b4081fac4]: 0x0000000000000000 -> 0x0000000000000006
310[0x15c]: (bf) r2 = r10
  r2: 0xe765cbb7ffff6cb2 -> 0xffffb82b4081fac8
311[0x15d]: (07) r2 += -4
  r2: 0xffffb82b4081fac8 -> 0xffffb82b4081fac4
312[0x15e]: (18) r1 = 0xffff8fbaeef8c000
  r1: 0xaa4908af00000006 -> 0xffff8fbaeef8c000
313[0x160]: (85) call percpu_array_map_lookup_elem#164336
  r0: 0x7af818e200000000 -> 0xffffd82b3fbb4048
314[0x161]: (15) if r0 == 0x0 goto pc+229
  r0: 0xffffd82b3fbb4048 <==> 0x000000
  branch was NOT taken
315[0x162]: (05) goto pc+225
  pc: 0x0000000000000162 -> 0x0000000000000244
  branch was taken
316[0x244]: (79) r1 = *(u64 *)(r0 +0)
  r1: 0xffff8fbaeef8c000 -> 0x0000000000000000
317[0x245]: (07) r1 += 1
  r1: 0x0000000000000000 -> 0x0000000000000001
318[0x246]: (7b) *(u64 *)(r0 +0) = r1
  MEM[ffffd82b3fbb4048]: 0x00 -> 0x01
319[0x247]: (b4) w8 = 3
  r8: 0x14d492f700000045 -> 0x0000000000000003
320[0x248]: (b7) r11 = -1474974291
  r11: 0xaa4908af00000000 -> 0xffffffffa815adad
321[0x249]: (67) r11 <<= 32
  r11: 0xffffffffa815adad -> 0xa815adad00000000
322[0x24a]: (4f) r8 |= r11
  r8: 0x0000000000000003 -> 0xa815adad00000003
323[0x24b]: (05) goto pc-502
  pc: 0x000000000000024b -> 0x0000000000000056
  branch was taken
324[0x56]: (bc) w0 = w8
  r0: 0xffffd82b3fbb4048 -> 0x0000000000000003
325[0x57]: (95) exit

STACK(32 bytes):
  ffffb82b4081faa8: 0x0000000000000000 0000000000000000 0000000600020000 0000000600000000

REGISTERS:
  r00-03: 0x0000000000000003 0000000000000001 ffffb82b4081fac4 9b5fd9b800000000
  r04-07: 0x03f00a9d00000000 2c071e5a00000000 7437bef800000000 ffff8fbaf4b5b6f8
  r08-11: 0xa815adad00000003 be1b210e0000934d ffffb82b4081fac8 a815adad00000000

RESULT:
  return = 0x0000000000000003


Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
---
 tools/testing/selftests/bpf/prog_tests/xdp.c |   36 +++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp.c b/tools/testing/selftests/bpf/prog_tests/xdp.c
index dcb5ecac778e..8f7a70d39dbf 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp.c
@@ -1,6 +1,38 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <test_progs.h>
 
+
+static inline int sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
+			  unsigned int size)
+{
+	return syscall(__NR_bpf, cmd, attr, size);
+}
+
+int bpf_prog_test_run_trace(int prog_fd, int repeat, void *data, __u32 size,
+			    void *data_out, __u32 *size_out, __u32 *retval,
+			    __u32 *duration)
+{
+	union bpf_attr attr;
+	int ret;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.test.prog_fd = prog_fd;
+	attr.test.data_in = ptr_to_u64(data);
+	attr.test.data_out = ptr_to_u64(data_out);
+	attr.test.data_size_in = size;
+	attr.test.repeat = repeat;
+	attr.test.flags = BPF_F_TEST_ENABLE_TRACE;
+
+	ret = sys_bpf(BPF_PROG_TEST_RUN, &attr, sizeof(attr));
+	if (size_out)
+		*size_out = attr.test.data_size_out;
+	if (retval)
+		*retval = attr.test.retval;
+	if (duration)
+		*duration = attr.test.duration;
+	return ret;
+}
+
 void test_xdp(void)
 {
 	struct vip key4 = {.protocol = 6, .family = AF_INET};
@@ -25,7 +57,7 @@ void test_xdp(void)
 	bpf_map_update_elem(map_fd, &key4, &value4, 0);
 	bpf_map_update_elem(map_fd, &key6, &value6, 0);
 
-	err = bpf_prog_test_run(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
+	err = bpf_prog_test_run_trace(prog_fd, 1, &pkt_v4, sizeof(pkt_v4),
 				buf, &size, &retval, &duration);
 
 	CHECK(err || retval != XDP_TX || size != 74 ||
@@ -33,7 +65,7 @@ void test_xdp(void)
 	      "err %d errno %d retval %d size %d\n",
 	      err, errno, retval, size);
 
-	err = bpf_prog_test_run(prog_fd, 1, &pkt_v6, sizeof(pkt_v6),
+	err = bpf_prog_test_run_trace(prog_fd, 1, &pkt_v6, sizeof(pkt_v6),
 				buf, &size, &retval, &duration);
 	CHECK(err || retval != XDP_TX || size != 114 ||
 	      iph6->nexthdr != IPPROTO_IPV6, "ipv6",