selftests/bpf: check nullness propagation for reg to reg comparisons
Verify that nullness information is porpagated in the branches of register to register JEQ and JNE operations. Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/r/20221115224859.2452988-3-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman
Alexei Starovoitov
parent
befae75856
commit
4741c371aa
174
tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
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174
tools/testing/selftests/bpf/verifier/jeq_infer_not_null.c
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@ -0,0 +1,174 @@
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{
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/* This is equivalent to the following program:
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*
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* r6 = skb->sk;
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* r7 = sk_fullsock(r6);
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* r0 = sk_fullsock(r6);
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* if (r0 == 0) return 0; (a)
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* if (r0 != r7) return 0; (b)
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* *r7->type; (c)
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* return 0;
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*
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* It is safe to dereference r7 at point (c), because of (a) and (b).
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* The test verifies that relation r0 == r7 is propagated from (b) to (c).
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*/
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"jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JNE false branch",
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.insns = {
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/* r6 = skb->sk; */
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BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
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/* if (r6 == 0) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 8),
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/* r7 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
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/* r0 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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/* if (r0 == null) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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/* if (r0 == r7) r0 = *(r7->type); */
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BPF_JMP_REG(BPF_JNE, BPF_REG_0, BPF_REG_7, 1), /* Use ! JNE ! */
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BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
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/* return 0 */
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BPF_MOV64_IMM(BPF_REG_0, 0),
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BPF_EXIT_INSN(),
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},
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.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
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.result = ACCEPT,
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.result_unpriv = REJECT,
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.errstr_unpriv = "R7 pointer comparison",
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},
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{
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/* Same as above, but verify that another branch of JNE still
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* prohibits access to PTR_MAYBE_NULL.
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*/
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"jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JNE true branch",
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.insns = {
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/* r6 = skb->sk */
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BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
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/* if (r6 == 0) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 9),
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/* r7 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
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/* r0 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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/* if (r0 == null) return 0; */
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BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 3),
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/* if (r0 == r7) return 0; */
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BPF_JMP_REG(BPF_JNE, BPF_REG_0, BPF_REG_7, 1), /* Use ! JNE ! */
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BPF_JMP_IMM(BPF_JA, 0, 0, 1),
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/* r0 = *(r7->type); */
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BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
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/* return 0 */
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BPF_MOV64_IMM(BPF_REG_0, 0),
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BPF_EXIT_INSN(),
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},
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.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
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.result = REJECT,
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.errstr = "R7 invalid mem access 'sock_or_null'",
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.result_unpriv = REJECT,
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.errstr_unpriv = "R7 pointer comparison",
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},
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{
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/* Same as a first test, but not null should be inferred for JEQ branch */
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"jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL -> PTR_TO_SOCKET for JEQ true branch",
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.insns = {
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/* r6 = skb->sk; */
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BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
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/* if (r6 == null) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 9),
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/* r7 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
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/* r0 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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/* if (r0 == null) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3),
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/* if (r0 != r7) return 0; */
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BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_7, 1), /* Use ! JEQ ! */
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BPF_JMP_IMM(BPF_JA, 0, 0, 1),
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/* r0 = *(r7->type); */
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BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
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/* return 0; */
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BPF_MOV64_IMM(BPF_REG_0, 0),
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BPF_EXIT_INSN(),
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},
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.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
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.result = ACCEPT,
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.result_unpriv = REJECT,
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.errstr_unpriv = "R7 pointer comparison",
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},
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{
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/* Same as above, but verify that another branch of JNE still
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* prohibits access to PTR_MAYBE_NULL.
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*/
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"jne/jeq infer not null, PTR_TO_SOCKET_OR_NULL unchanged for JEQ false branch",
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.insns = {
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/* r6 = skb->sk; */
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BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct __sk_buff, sk)),
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/* if (r6 == null) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 8),
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/* r7 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
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/* r0 = sk_fullsock(skb); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_EMIT_CALL(BPF_FUNC_sk_fullsock),
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/* if (r0 == null) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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/* if (r0 != r7) r0 = *(r7->type); */
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BPF_JMP_REG(BPF_JEQ, BPF_REG_0, BPF_REG_7, 1), /* Use ! JEQ ! */
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BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_sock, type)),
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/* return 0; */
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BPF_MOV64_IMM(BPF_REG_0, 0),
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BPF_EXIT_INSN(),
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},
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.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
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.result = REJECT,
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.errstr = "R7 invalid mem access 'sock_or_null'",
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.result_unpriv = REJECT,
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.errstr_unpriv = "R7 pointer comparison",
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},
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{
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/* Maps are treated in a different branch of `mark_ptr_not_null_reg`,
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* so separate test for maps case.
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*/
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"jne/jeq infer not null, PTR_TO_MAP_VALUE_OR_NULL -> PTR_TO_MAP_VALUE",
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.insns = {
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/* r9 = &some stack to use as key */
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BPF_ST_MEM(BPF_W, BPF_REG_10, -8, 0),
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BPF_MOV64_REG(BPF_REG_9, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_9, -8),
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/* r8 = process local map */
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BPF_LD_MAP_FD(BPF_REG_8, 0),
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/* r6 = map_lookup_elem(r8, r9); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_9),
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BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
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BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
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/* r7 = map_lookup_elem(r8, r9); */
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_8),
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_9),
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BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
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BPF_MOV64_REG(BPF_REG_7, BPF_REG_0),
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/* if (r6 == 0) return 0; */
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_6, 0, 2),
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/* if (r6 != r7) return 0; */
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BPF_JMP_REG(BPF_JNE, BPF_REG_6, BPF_REG_7, 1),
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/* read *r7; */
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BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_7, offsetof(struct bpf_xdp_sock, queue_id)),
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/* return 0; */
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BPF_MOV64_IMM(BPF_REG_0, 0),
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BPF_EXIT_INSN(),
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},
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.fixup_map_xskmap = { 3 },
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.prog_type = BPF_PROG_TYPE_XDP,
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.result = ACCEPT,
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},
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