1*37086bfdSBrendan Jackman { 2*37086bfdSBrendan Jackman "BPF_ATOMIC bounds propagation, mem->reg", 3*37086bfdSBrendan Jackman .insns = { 4*37086bfdSBrendan Jackman /* a = 0; */ 5*37086bfdSBrendan Jackman /* 6*37086bfdSBrendan Jackman * Note this is implemented with two separate instructions, 7*37086bfdSBrendan Jackman * where you might think one would suffice: 8*37086bfdSBrendan Jackman * 9*37086bfdSBrendan Jackman * BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), 10*37086bfdSBrendan Jackman * 11*37086bfdSBrendan Jackman * This is because BPF_ST_MEM doesn't seem to set the stack slot 12*37086bfdSBrendan Jackman * type to 0 when storing an immediate. 13*37086bfdSBrendan Jackman */ 14*37086bfdSBrendan Jackman BPF_MOV64_IMM(BPF_REG_0, 0), 15*37086bfdSBrendan Jackman BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_0, -8), 16*37086bfdSBrendan Jackman /* b = atomic_fetch_add(&a, 1); */ 17*37086bfdSBrendan Jackman BPF_MOV64_IMM(BPF_REG_1, 1), 18*37086bfdSBrendan Jackman BPF_ATOMIC_OP(BPF_DW, BPF_ADD | BPF_FETCH, BPF_REG_10, BPF_REG_1, -8), 19*37086bfdSBrendan Jackman /* Verifier should be able to tell that this infinite loop isn't reachable. */ 20*37086bfdSBrendan Jackman /* if (b) while (true) continue; */ 21*37086bfdSBrendan Jackman BPF_JMP_IMM(BPF_JNE, BPF_REG_1, 0, -1), 22*37086bfdSBrendan Jackman BPF_EXIT_INSN(), 23*37086bfdSBrendan Jackman }, 24*37086bfdSBrendan Jackman .result = ACCEPT, 25*37086bfdSBrendan Jackman .result_unpriv = REJECT, 26*37086bfdSBrendan Jackman .errstr_unpriv = "back-edge", 27*37086bfdSBrendan Jackman }, 28