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[BPF] Emit fatal error if out of range for FK_PCRel_2 branch target
Currently for the branch insn like "if $dst "#OpcodeStr#" $imm goto $BrDst" The $BrDst range needs to be in the range of [INT16_MIN, INT16_MAX]. When running bpf selftest with latest llvm, I found pyperf600.o generated insn with range outside of [INT16_MIN, INT16_MAX], which caused verifier failure. See below insn #12. 0000000000000000 <on_event>: ; { 0: 7b 1a 00 ff 00 00 00 00 *(u64 *)(r10 - 256) = r1 ; uint64_t pid_tgid = bpf_get_current_pid_tgid(); 1: 85 00 00 00 0e 00 00 00 call 14 2: bf 06 00 00 00 00 00 00 r6 = r0 ; pid_t pid = (pid_t)(pid_tgid >> 32); 3: bf 61 00 00 00 00 00 00 r1 = r6 4: 77 01 00 00 20 00 00 00 r1 >>= 32 5: 63 1a fc ff 00 00 00 00 *(u32 *)(r10 - 4) = r1 6: bf a2 00 00 00 00 00 00 r2 = r10 7: 07 02 00 00 fc ff ff ff r2 += -4 ; PidData* pidData = bpf_map_lookup_elem(&pidmap, &pid); 8: 18 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 r1 = 0 ll 10: 85 00 00 00 01 00 00 00 call 1 11: bf 08 00 00 00 00 00 00 r8 = r0 ; if (!pidData) 12: 15 08 15 e8 00 00 00 00 if r8 == 0 goto -6123 <LBB0_27588+0xffffffffffdae100> 13: b4 01 00 00 00 00 00 00 w1 = 0 We may need to add new insn to extend the range of $BrDst. This patch added a fatal error if out of range so compiler can warn the otherwise incorrect code generation. Differential Revision: https://reviews.llvm.org/D123877
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