From f9b16ec0eeb75337aef38954a4066e6eecd7cfe5 Mon Sep 17 00:00:00 2001
From: John Fastabend <john.fastabend@gmail.com>
Date: Thu, 21 May 2020 13:08:06 -0700
Subject: [PATCH] bpf: Selftests, verifier case for non null pointer map value
branch
When we have pointer type that is known to be non-null we only follow
the non-null branch. This adds tests to cover the map_value pointer
returned from a map lookup. To force an error if both branches are
followed we do an ALU op on R10.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/159009168650.6313.7434084136067263554.stgit@john-Precision-5820-Tower
---
.../selftests/bpf/verifier/value_or_null.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/tools/testing/selftests/bpf/verifier/value_or_null.c b/tools/testing/selftests/bpf/verifier/value_or_null.c
index 860d4a71cd83..3ecb70a3d939 100644
--- a/tools/testing/selftests/bpf/verifier/value_or_null.c
+++ b/tools/testing/selftests/bpf/verifier/value_or_null.c
@@ -150,3 +150,22 @@
.result_unpriv = REJECT,
.flags = F_NEEDS_EFFICIENT_UNALIGNED_ACCESS,
},
+{
+ "map lookup and null branch prediction",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_1, 10),
+ BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_1, -8),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
+ BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 2),
+ BPF_JMP_IMM(BPF_JNE, BPF_REG_6, 0, 1),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_10, 10),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map_hash_8b = { 4 },
+ .prog_type = BPF_PROG_TYPE_SCHED_CLS,
+ .result = ACCEPT,
+},