linux-kernel - [PATCH AUTOSEL 5.2 024/249] selftests/bpf: adjust verifier scale test

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Date:   Mon, 15 Jul 2019 09:43:09 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andriin@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sasha Levin <sashal@...nel.org>,
        linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 5.2 024/249] selftests/bpf: adjust verifier scale test

From: Alexei Starovoitov <ast@...nel.org>

[ Upstream commit 7c0c6095d48dcd0e67c917aa73cdbb2715aafc36 ]

Adjust scale tests to check for new jmp sequence limit.

BPF_JGT had to be changed to BPF_JEQ because the verifier was
too smart. It tracked the known safe range of R0 values
and pruned the search earlier before hitting exact 8192 limit.
bpf_semi_rand_get() was too (un)?lucky.

k = 0; was missing in bpf_fill_scale2.
It was testing a bit shorter sequence of jumps than intended.

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Andrii Nakryiko <andriin@...com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/testing/selftests/bpf/test_verifier.c | 31 +++++++++++----------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 288cb740e005..6438d4dc8ae1 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -207,33 +207,35 @@ static void bpf_fill_rand_ld_dw(struct bpf_test *self)
 	self->retval = (uint32_t)res;
 }
 
-/* test the sequence of 1k jumps */
+#define MAX_JMP_SEQ 8192
+
+/* test the sequence of 8k jumps */
 static void bpf_fill_scale1(struct bpf_test *self)
 {
 	struct bpf_insn *insn = self->fill_insns;
 	int i = 0, k = 0;
 
 	insn[i++] = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1);
-	/* test to check that the sequence of 1024 jumps is acceptable */
-	while (k++ < 1024) {
+	/* test to check that the long sequence of jumps is acceptable */
+	while (k++ < MAX_JMP_SEQ) {
 		insn[i++] = BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
 					 BPF_FUNC_get_prandom_u32);
-		insn[i++] = BPF_JMP_IMM(BPF_JGT, BPF_REG_0, bpf_semi_rand_get(), 2);
+		insn[i++] = BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, bpf_semi_rand_get(), 2);
 		insn[i++] = BPF_MOV64_REG(BPF_REG_1, BPF_REG_10);
 		insn[i++] = BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_6,
 					-8 * (k % 64 + 1));
 	}
-	/* every jump adds 1024 steps to insn_processed, so to stay exactly
-	 * within 1m limit add MAX_TEST_INSNS - 1025 MOVs and 1 EXIT
+	/* every jump adds 1 step to insn_processed, so to stay exactly
+	 * within 1m limit add MAX_TEST_INSNS - MAX_JMP_SEQ - 1 MOVs and 1 EXIT
 	 */
-	while (i < MAX_TEST_INSNS - 1025)
+	while (i < MAX_TEST_INSNS - MAX_JMP_SEQ - 1)
 		insn[i++] = BPF_ALU32_IMM(BPF_MOV, BPF_REG_0, 42);
 	insn[i] = BPF_EXIT_INSN();
 	self->prog_len = i + 1;
 	self->retval = 42;
 }
 
-/* test the sequence of 1k jumps in inner most function (function depth 8)*/
+/* test the sequence of 8k jumps in inner most function (function depth 8)*/
 static void bpf_fill_scale2(struct bpf_test *self)
 {
 	struct bpf_insn *insn = self->fill_insns;
@@ -245,19 +247,20 @@ static void bpf_fill_scale2(struct bpf_test *self)
 		insn[i++] = BPF_EXIT_INSN();
 	}
 	insn[i++] = BPF_MOV64_REG(BPF_REG_6, BPF_REG_1);
-	/* test to check that the sequence of 1024 jumps is acceptable */
-	while (k++ < 1024) {
+	/* test to check that the long sequence of jumps is acceptable */
+	k = 0;
+	while (k++ < MAX_JMP_SEQ) {
 		insn[i++] = BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
 					 BPF_FUNC_get_prandom_u32);
-		insn[i++] = BPF_JMP_IMM(BPF_JGT, BPF_REG_0, bpf_semi_rand_get(), 2);
+		insn[i++] = BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, bpf_semi_rand_get(), 2);
 		insn[i++] = BPF_MOV64_REG(BPF_REG_1, BPF_REG_10);
 		insn[i++] = BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_6,
 					-8 * (k % (64 - 4 * FUNC_NEST) + 1));
 	}
-	/* every jump adds 1024 steps to insn_processed, so to stay exactly
-	 * within 1m limit add MAX_TEST_INSNS - 1025 MOVs and 1 EXIT
+	/* every jump adds 1 step to insn_processed, so to stay exactly
+	 * within 1m limit add MAX_TEST_INSNS - MAX_JMP_SEQ - 1 MOVs and 1 EXIT
 	 */
-	while (i < MAX_TEST_INSNS - 1025)
+	while (i < MAX_TEST_INSNS - MAX_JMP_SEQ - 1)
 		insn[i++] = BPF_ALU32_IMM(BPF_MOV, BPF_REG_0, 42);
 	insn[i] = BPF_EXIT_INSN();
 	self->prog_len = i + 1;
-- 
2.20.1