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bpf: Selftests, verifier case for non null pointer map value branch

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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
This commit is contained in:
John Fastabend 2020-05-21 13:08:06 -07:00 committed by Alexei Starovoitov
parent c72b5cbb09
commit f9b16ec0ee
1 changed files with 19 additions and 0 deletions
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19
tools/testing/selftests/bpf/verifier/value_or_null.c
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@ -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,
},