diff mbox series

[bpf-next,v2,3/4] bpf: selftests, verifier case for non null pointer map value branch

Message ID 159009168650.6313.7434084136067263554.stgit@john-Precision-5820-Tower
State Accepted
Delegated to: BPF Maintainers
Headers show
Series ] verifier, improve ptr is_branch_taken logic | expand

Commit Message

John Fastabend May 21, 2020, 8:08 p.m. UTC 
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.

Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
 .../testing/selftests/bpf/verifier/value_or_null.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
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Patch

diff --git a/tools/testing/selftests/bpf/verifier/value_or_null.c b/tools/testing/selftests/bpf/verifier/value_or_null.c
index 860d4a7..3ecb70a 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,
+},