[PATCH bpf v1 1/3] selftests/bpf: Test correctness of narrow 32bit read on 64bit field

[Krzesimir Nowak]

Test the correctness of the 32bit narrow reads by reading both halves
of the 64 bit field and doing a binary or on them to see if we get the
original value.

This isn't really tested - the program is not being run, because
BPF_PROG_TYPE_PERF_EVENT is not supported by bpf_test_run_prog.

Signed-off-by: Krzesimir Nowak <krzesimir@xxxxxxxxxx>
---
 tools/testing/selftests/bpf/verifier/var_off.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/testing/selftests/bpf/verifier/var_off.c b/tools/testing/selftests/bpf/verifier/var_off.c
index 8504ac937809..2668819dcc85 100644
--- a/tools/testing/selftests/bpf/verifier/var_off.c
+++ b/tools/testing/selftests/bpf/verifier/var_off.c
@@ -246,3 +246,18 @@
 	.result = ACCEPT,
 	.prog_type = BPF_PROG_TYPE_LWT_IN,
 },
+{
+	"32bit loads of a 64bit field (both least and most significant words)",
+	.insns = {
+	BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1, offsetof(struct bpf_perf_event_data, sample_period)),
+	BPF_LDX_MEM(BPF_W, BPF_REG_5, BPF_REG_1, offsetof(struct bpf_perf_event_data, sample_period) + 4),
+	BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct bpf_perf_event_data, sample_period)),
+	BPF_ALU64_IMM(BPF_LSH, BPF_REG_4, 32),
+	BPF_ALU64_REG(BPF_OR, BPF_REG_4, BPF_REG_5),
+	BPF_ALU64_REG(BPF_XOR, BPF_REG_4, BPF_REG_6),
+	BPF_MOV64_REG(BPF_REG_0, BPF_REG_4),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.prog_type = BPF_PROG_TYPE_PERF_EVENT,
+},
-- 
2.20.1