On Fri, Feb 5, 2021 at 9:03 PM Yonghong Song <yhs@xxxxxx> wrote:
>
>
>
> On 2/5/21 11:24 AM, Arnaldo Carvalho de Melo wrote:
> > Em Fri, Feb 05, 2021 at 11:10:08AM -0800, Yonghong Song escreveu:
> >> On 2/5/21 11:06 AM, Sedat Dilek wrote:
> >>> On Fri, Feb 5, 2021 at 7:53 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >>> Grepping through linux.git/tools I guess some BTF tools/libs need to
> >>> know what BTF_INT_UNSIGNED is?
> >
> >> BTF_INT_UNSIGNED needs kernel support. Maybe to teach pahole to
> >> ignore this for now until kernel infrastructure is ready.
> >
> > Yeah, I thought about doing that.
> >
> >> Not sure whether this information will be useful or not
> >> for BTF. This needs to be discussed separately.
> >
> > Maybe search for the rationale for its introduction in DWARF.
>
> In LLVM, we have:
> uint8_t BTFEncoding;
> switch (Encoding) {
> case dwarf::DW_ATE_boolean:
> BTFEncoding = BTF::INT_BOOL;
> break;
> case dwarf::DW_ATE_signed:
> case dwarf::DW_ATE_signed_char:
> BTFEncoding = BTF::INT_SIGNED;
> break;
> case dwarf::DW_ATE_unsigned:
> case dwarf::DW_ATE_unsigned_char:
> BTFEncoding = 0;
> break;
>
> I think DW_ATE_unsigned can be ignored in pahole since
> the default encoding = 0. A simple comment is enough.
>
For the followers (here: LLVM v12.0.0-rc1):
[ llvm/lib/Target/BPF/BTFDebug.cpp ]
BTFTypeInt::BTFTypeInt(uint32_t Encoding, uint32_t SizeInBits,
uint32_t OffsetInBits, StringRef TypeName)
: Name(TypeName) {
// Translate IR int encoding to BTF int encoding.
uint8_t BTFEncoding;
switch (Encoding) {
case dwarf::DW_ATE_boolean:
BTFEncoding = BTF::INT_BOOL;
break;
case dwarf::DW_ATE_signed:
case dwarf::DW_ATE_signed_char:
BTFEncoding = BTF::INT_SIGNED;
break;
case dwarf::DW_ATE_unsigned:
case dwarf::DW_ATE_unsigned_char:
BTFEncoding = 0;
break;
default:
llvm_unreachable("Unknown BTFTypeInt Encoding");
}
- Sedat -
