selftests/bpf: test cases for pkt/null checks in subprogs

The first test case, for pointer null checks, is equivalent to the
following pseudo-code.  It checks that the verifier does not complain on
line 6 and recognizes that ptr isn't null.

1: ptr = bpf_map_lookup_elem(map, &key);
2: ret = subprog(ptr) {
3:   return ptr != NULL;
4: }
5: if (ret)
6:   value = *ptr;

The second test case, for packet bound checks, is equivalent to the
following pseudo-code.  It checks that the verifier does not complain on
line 7 and recognizes that the packet is at least 1 byte long.

1: pkt_end = ctx.pkt_end;
2: ptr = ctx.pkt + 8;
3: ret = subprog(ptr, pkt_end) {
4:   return ptr <= pkt_end;
5: }
6: if (ret)
7:   value = *(u8 *)ctx.pkt;
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -374,6 +374,31 @@
 	.prog_type = BPF_PROG_TYPE_XDP,
 	.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
 },
+{
+	"calls: ptr null check in subprog",
+	.insns = {
+	BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+	BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_0),
+	BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 3),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+	BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_6, 0),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 1),
+	BPF_MOV64_IMM(BPF_REG_0, 1),
+	BPF_EXIT_INSN(),
+	},
+	.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+	.fixup_map_hash_48b = { 3 },
+	.result_unpriv = REJECT,
+	.result = ACCEPT,
+	.retval = 0,
+},
 {
 	"calls: two calls with args",
 	.insns = {

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

@@ -631,3 +631,25 @@
 	.errstr = "invalid access to packet",
 	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
 },
+{
+	"direct packet access: test29 (reg > pkt_end in subprog)",
+	.insns = {
+	BPF_LDX_MEM(BPF_W, BPF_REG_6, BPF_REG_1,
+		    offsetof(struct __sk_buff, data)),
+	BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
+		    offsetof(struct __sk_buff, data_end)),
+	BPF_MOV64_REG(BPF_REG_3, BPF_REG_6),
+	BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, 8),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 4),
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
+	BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_6, 0),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_JMP_REG(BPF_JGT, BPF_REG_3, BPF_REG_2, 1),
+	BPF_MOV64_IMM(BPF_REG_0, 1),
+	BPF_EXIT_INSN(),
+	},
+	.result = ACCEPT,
+	.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+},