Subject: [PATCH bpf-next 2/2] selftests/bpf: additional stack depth tests

From: Alexei Starovoitov <[email-masked]>
Date: Fri, 22 Dec 2017 13:33:28 -0800

to test inner logic of stack depth tracking

Signed-off-by: Alexei Starovoitov <[email-masked]>
---
 tools/testing/selftests/bpf/test_verifier.c | 50 +++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 71fb0be81b78..e0b21c95c3bc 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -8764,6 +8764,56 @@ static struct bpf_test tests[] = {
 		.result = REJECT,
 	},
 	{
+		"calls: stack depth check using three frames. test1",
+		.insns = {
+			/* main */
+			BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, 4), /* call A */
+			BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, 5), /* call B */
+			BPF_ST_MEM(BPF_B, BPF_REG_10, -32, 0),
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+			/* A */
+			BPF_ST_MEM(BPF_B, BPF_REG_10, -256, 0),
+			BPF_EXIT_INSN(),
+			/* B */
+			BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, -3), /* call A */
+			BPF_ST_MEM(BPF_B, BPF_REG_10, -64, 0),
+			BPF_EXIT_INSN(),
+		},
+		.prog_type = BPF_PROG_TYPE_XDP,
+		/* though stack_main=32, stack_A=256, stack_B=64
+		 * and max(main+A, main+A+B) < 512 the program is rejected
+		 * since stack tracking is conservative
+		 * frame[0]=32, frame[1]=256, frame[2]=256
+		 */
+		.errstr = "combined stack size",
+		.result = REJECT,
+	},
+	{
+		"calls: stack depth check using three frames. test2",
+		.insns = {
+			/* main */
+			BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, 4), /* call A */
+			BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, 5), /* call B */
+			BPF_ST_MEM(BPF_B, BPF_REG_10, -32, 0),
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_EXIT_INSN(),
+			/* A */
+			BPF_ST_MEM(BPF_B, BPF_REG_10, -64, 0),
+			BPF_EXIT_INSN(),
+			/* B */
+			BPF_RAW_INSN(BPF_JMP|BPF_CALL, 0, 1, 0, -3), /* call A */
+			BPF_ST_MEM(BPF_B, BPF_REG_10, -256, 0),
+			BPF_EXIT_INSN(),
+		},
+		.prog_type = BPF_PROG_TYPE_XDP,
+		/* though stack_main=32, stack_A=64, stack_B=256
+		 * and max(main+A, main+A+B) < 512 the program is accepted
+		 * since frame[0]=32, frame[1]=256, frame[2]=64
+		 */
+		.result = ACCEPT,
+	},
+	{
 		"calls: spill into caller stack frame",
 		.insns = {
 			BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
-- 
2.9.5