netdev - [PATCH bpf 2/2] bpf: test case to check whether src/dst regs got mangled by xadd

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Date:   Thu, 19 Jul 2018 18:18:36 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     alexei.starovoitov@...il.com
Cc:     naveen.n.rao@...ux.vnet.ibm.com, sandipan@...ux.ibm.com,
        netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH bpf 2/2] bpf: test case to check whether src/dst regs got mangled by xadd

We currently do not have such a test case in test_verifier selftests
but it's important to test under bpf_jit_enable=1 to make sure JIT
implementations do not mistakenly mess with src/dst reg for xadd/{w,dw}.

Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
 tools/testing/selftests/bpf/test_verifier.c | 40 +++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index f5f7bcc..41106d9 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -12005,6 +12005,46 @@ static struct bpf_test tests[] = {
 		.prog_type = BPF_PROG_TYPE_XDP,
 	},
 	{
+		"xadd/w check whether src/dst got mangled, 1",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
+			BPF_STX_XADD(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
+			BPF_STX_XADD(BPF_DW, BPF_REG_10, BPF_REG_0, -8),
+			BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_0, 3),
+			BPF_JMP_REG(BPF_JNE, BPF_REG_7, BPF_REG_10, 2),
+			BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_10, -8),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 42),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+		.retval = 3,
+	},
+	{
+		"xadd/w check whether src/dst got mangled, 2",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+			BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+			BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -8),
+			BPF_STX_XADD(BPF_W, BPF_REG_10, BPF_REG_0, -8),
+			BPF_STX_XADD(BPF_W, BPF_REG_10, BPF_REG_0, -8),
+			BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_0, 3),
+			BPF_JMP_REG(BPF_JNE, BPF_REG_7, BPF_REG_10, 2),
+			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_10, -8),
+			BPF_EXIT_INSN(),
+			BPF_MOV64_IMM(BPF_REG_0, 42),
+			BPF_EXIT_INSN(),
+		},
+		.result = ACCEPT,
+		.prog_type = BPF_PROG_TYPE_SCHED_CLS,
+		.retval = 3,
+	},
+	{
 		"bpf_get_stack return R0 within range",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
-- 
2.9.5