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@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index f5f7bcc96046..41106d9d5cc7 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),