selftests: bpf: add tests for dead code removal

Add tests for newly added dead code elimination.  Both verifier
and BTF tests are added.  BTF test infrastructure has to be
extended to be able to account for line info which is eliminated
during dead code removal.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/test_verifier.c

@@ -15599,6 +15599,166 @@ static struct bpf_test tests[] = {
 		.result_unpriv = ACCEPT,
 		.result = ACCEPT,
 	},
+	{
+		"dead code: start",
+		.insns = {
+			BPF_JMP_IMM(BPF_JA, 0, 0, 2),
+			BPF_LDX_MEM(BPF_B, BPF_REG_8, BPF_REG_9, 0),
+			BPF_JMP_IMM(BPF_JA, 0, 0, 2),
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 10, -4),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: mid 1",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 1),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 10, 0),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: mid 2",
+		.insns = {
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
+				     BPF_FUNC_get_prandom_u32),
+			BPF_JMP_IMM(BPF_JSET, BPF_REG_0, 1, 4),
+			BPF_JMP_IMM(BPF_JSET, BPF_REG_0, 1, 1),
+			BPF_JMP_IMM(BPF_JA, 0, 0, 2),
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.retval = 1,
+	},
+	{
+		"dead code: end 1",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 10, 1),
+			BPF_EXIT_INSN(),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: end 2",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 10, 1),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 12),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: end 3",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 8, 1),
+			BPF_EXIT_INSN(),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 10, 1),
+			BPF_JMP_IMM(BPF_JA, 0, 0, 1),
+			BPF_MOV64_IMM(BPF_REG_0, 12),
+			BPF_JMP_IMM(BPF_JA, 0, 0, -5),
+		},
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: tail of main + func",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 8, 1),
+			BPF_EXIT_INSN(),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 12),
+			BPF_EXIT_INSN(),
+		},
+		.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+		.result_unpriv = REJECT,
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: tail of main + two functions",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 8, 1),
+			BPF_EXIT_INSN(),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 12),
+			BPF_EXIT_INSN(),
+		},
+		.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+		.result_unpriv = REJECT,
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: function in the middle and mid of another func",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_1, 7),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 3),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 12),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 7),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_1, 7, 1),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, -5),
+			BPF_EXIT_INSN(),
+		},
+		.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+		.result_unpriv = REJECT,
+		.result = ACCEPT,
+		.retval = 7,
+	},
+	{
+		"dead code: middle of main before call",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_1, 2),
+			BPF_JMP_IMM(BPF_JGE, BPF_REG_1, 2, 1),
+			BPF_MOV64_IMM(BPF_REG_1, 5),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+		.result_unpriv = REJECT,
+		.result = ACCEPT,
+		.retval = 2,
+	},
+	{
+		"dead code: start of a function",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_1, 2),
+			BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 1, 0, 1),
+			BPF_EXIT_INSN(),
+			BPF_JMP_IMM(BPF_JA, 0, 0, 0),
+			BPF_MOV64_REG(BPF_REG_0, BPF_REG_1),
+			BPF_EXIT_INSN(),
+		},
+		.errstr_unpriv = "function calls to other bpf functions are allowed for root only",
+		.result_unpriv = REJECT,
+		.result = ACCEPT,
+		.retval = 2,
+	},
 };
 
 static int probe_filter_length(const struct bpf_insn *fp)