selftests/bpf: Add a testcase for 64-bit bounds propagation issue.

./test_progs-no_alu32 -vv -t twfw

Before the 64-bit_into_32-bit fix:
19: (25) if r1 > 0x3f goto pc+6
 R1_w=inv(id=0,umax_value=63,var_off=(0x0; 0xff),s32_max_value=255,u32_max_value=255)

and eventually:

invalid access to map value, value_size=8 off=7 size=8
R6 max value is outside of the allowed memory range
libbpf: failed to load object 'no_alu32/twfw.o'

After the fix:
19: (25) if r1 > 0x3f goto pc+6
 R1_w=inv(id=0,umax_value=63,var_off=(0x0; 0x3f))

verif_twfw:OK

Signed-off-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: Alexei Starovoitov

tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c

@@ -202,3 +202,8 @@ void test_verif_scale_seg6_loop()
 {
 	scale_test("test_seg6_loop.o", BPF_PROG_TYPE_LWT_SEG6LOCAL, false);
 }
+
+void test_verif_twfw()
+{
+	scale_test("twfw.o", BPF_PROG_TYPE_CGROUP_SKB, false);
+}

tools/testing/selftests/bpf/progs/twfw.c

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Facebook */
+#include <linux/types.h>
+#include <bpf/bpf_helpers.h>
+#include <linux/bpf.h>
+#include <stdint.h>
+
+#define TWFW_MAX_TIERS (64)
+/*
+ * load is successful
+ * #define TWFW_MAX_TIERS (64u)$
+ */
+
+struct twfw_tier_value {
+	unsigned long mask[1];
+};
+
+struct rule {
+	uint8_t seqnum;
+};
+
+struct rules_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, __u32);
+	__type(value, struct rule);
+	__uint(max_entries, 1);
+};
+
+struct tiers_map {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, __u32);
+	__type(value, struct twfw_tier_value);
+	__uint(max_entries, 1);
+};
+
+struct rules_map rules SEC(".maps");
+struct tiers_map tiers SEC(".maps");
+
+SEC("cgroup_skb/ingress")
+int twfw_verifier(struct __sk_buff* skb)
+{
+	const uint32_t key = 0;
+	const struct twfw_tier_value* tier = bpf_map_lookup_elem(&tiers, &key);
+	if (!tier)
+		return 1;
+
+	struct rule* rule = bpf_map_lookup_elem(&rules, &key);
+	if (!rule)
+		return 1;
+
+	if (rule && rule->seqnum < TWFW_MAX_TIERS) {
+		/* rule->seqnum / 64 should always be 0 */
+		unsigned long mask = tier->mask[rule->seqnum / 64];
+		if (mask)
+			return 0;
+	}
+	return 1;
+}