Commit 170dfab4 authored by Yonghong Song's avatar Yonghong Song
Browse files

bpf: fix bug on silently truncating 64-bit immediate 

We came across an llvm bug when compiling some testcases that 64-bit
immediates are silently truncated into 32-bit and then packed into
BPF_JMP | BPF_K encoding.  This caused comparison with wrong value.

This bug looks to be introduced by r308080 (llvm 5.0). The Select_Ri pattern is
supposed to be lowered into J*_Ri while the latter only support 32-bit
immediate encoding, therefore Select_Ri should have similar immediate
predicate check as what J*_Ri are doing.

The bug is fixed by
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@315889

 91177308-0d34-0410-b5e6-96231b3b80d8
in llvm 6.0.

This patch is largely the same as the fix in llvm 6.0 except
one minor adjustment for the test case.

Reported-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Reported-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarJiong Wang <jiong.wang@netronome.com>
Reviewed-by: default avatarYonghong Song <yhs@fb.com>
llvm-svn: 319633
parent 1254c70d

llvm/lib/Target/BPF/BPFISelLowering.cpp

+6 −2
Original line number Diff line number Diff line
@@ -578,11 +578,15 @@ BPFTargetLowering::EmitInstrWithCustomInserter(MachineInstr &MI, 
        .addReg(LHS)

        .addReg(MI.getOperand(2).getReg())

        .addMBB(Copy1MBB);

  else

  else {

    int64_t imm32 = MI.getOperand(2).getImm();

    // sanity check before we build J*_ri instruction.

    assert (isInt<32>(imm32));

    BuildMI(BB, DL, TII.get(NewCC))

        .addReg(LHS)

        .addImm(MI.getOperand(2).getImm())

        .addImm(imm32)

        .addMBB(Copy1MBB);

  }



  // Copy0MBB:

  //  %FalseValue = ...

llvm/lib/Target/BPF/BPFInstrInfo.td

+1 −1
Original line number Diff line number Diff line
@@ -464,7 +464,7 @@ let usesCustomInserter = 1 in { 
                      (ins GPR:$lhs, i64imm:$rhs, i64imm:$imm, GPR:$src, GPR:$src2),

                      "# Select PSEUDO $dst = $lhs $imm $rhs ? $src : $src2",

                      [(set i64:$dst,

                       (BPFselectcc i64:$lhs, (i64 imm:$rhs), (i64 imm:$imm), i64:$src, i64:$src2))]>;

                       (BPFselectcc i64:$lhs, (i64 i64immSExt32:$rhs), (i64 imm:$imm), i64:$src, i64:$src2))]>;

}



// load 64-bit global addr into register

llvm/test/CodeGen/BPF/select_ri.ll

+35 −0
Original line number Diff line number Diff line
@@ -25,3 +25,38 @@ entry: 
}



attributes #0 = { norecurse nounwind readonly }



; test immediate out of 32-bit range

; Source file:



; unsigned long long

; load_word(void *buf, unsigned long long off)

; asm("llvm.bpf.load.word");

;

; int

; foo(void *buf)

; {

;  unsigned long long sum = 0;

;

;  sum += load_word(buf, 100);

;  sum += load_word(buf, 104);

;

;  if (sum != 0x1ffffffffULL)

;    return ~0U;

;

;  return 0;

;}



; Function Attrs: nounwind readonly

define i32 @foo(i8*) local_unnamed_addr #0 {

  %2 = tail call i64 @llvm.bpf.load.word(i8* %0, i64 100)

  %3 = tail call i64 @llvm.bpf.load.word(i8* %0, i64 104)

  %4 = add i64 %3, %2

  %5 = icmp ne i64 %4, 8589934591

; CHECK:  r{{[0-9]+}} = 8589934591ll

  %6 = sext i1 %5 to i32

  ret i32 %6

}



; Function Attrs: nounwind readonly

declare i64 @llvm.bpf.load.word(i8*, i64) #1