Re: ERROR: INT DW_ATE_unsigned_1 Error emitting BTF type

From: Sedat Dilek
Date: Fri Feb 05 2021 - 14:20:45 EST

On Fri, Feb 5, 2021 at 8:10 PM Yonghong Song <yhs@xxxxxx> wrote:
>
>
>
> 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:
> >>
> >> On Fri, Feb 5, 2021 at 6:48 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >>>
> >>> On Fri, Feb 5, 2021 at 4:28 PM Arnaldo Carvalho de Melo
> >>> <arnaldo.melo@xxxxxxxxx> wrote:
> >>>>
> >>>> Em Fri, Feb 05, 2021 at 04:23:59PM +0100, Sedat Dilek escreveu:
> >>>>> On Fri, Feb 5, 2021 at 3:41 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >>>>>>
> >>>>>> On Fri, Feb 5, 2021 at 3:37 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >>>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> when building with pahole v1.20 and binutils v2.35.2 plus Clang
> >>>>>>> v12.0.0-rc1 and DWARF-v5 I see:
> >>>>>>> ...
> >>>>>>> + info BTF .btf.vmlinux.bin.o
> >>>>>>> + [ != silent_ ]
> >>>>>>> + printf %-7s %s\n BTF .btf.vmlinux.bin.o
> >>>>>>> BTF .btf.vmlinux.bin.o
> >>>>>>> + LLVM_OBJCOPY=/opt/binutils/bin/objcopy /opt/pahole/bin/pahole -J
> >>>>>>> .tmp_vmlinux.btf
> >>>>>>> [115] INT DW_ATE_unsigned_1 Error emitting BTF type
> >>>>>>> Encountered error while encoding BTF.
> >>>>>>
> >>>>>> Grepping the pahole sources:
> >>>>>>
> >>>>>> $ git grep DW_ATE
> >>>>>> dwarf_loader.c: bt->is_bool = encoding == DW_ATE_boolean;
> >>>>>> dwarf_loader.c: bt->is_signed = encoding == DW_ATE_signed;
> >>>>>>
> >>>>>> Missing DW_ATE_unsigned encoding?
> >>>>>>
> >>>>>
> >>>>> Checked the LLVM sources:
> >>>>>
> >>>>> clang/lib/CodeGen/CGDebugInfo.cpp: Encoding =
> >>>>> llvm::dwarf::DW_ATE_unsigned_char;
> >>>>> clang/lib/CodeGen/CGDebugInfo.cpp: Encoding = llvm::dwarf::DW_ATE_unsigned;
> >>>>> clang/lib/CodeGen/CGDebugInfo.cpp: Encoding =
> >>>>> llvm::dwarf::DW_ATE_unsigned_fixed;
> >>>>> clang/lib/CodeGen/CGDebugInfo.cpp:
> >>>>> ? llvm::dwarf::DW_ATE_unsigned
> >>>>> ...
> >>>>> lld/test/wasm/debuginfo.test:CHECK-NEXT: DW_AT_encoding
> >>>>> (DW_ATE_unsigned)
> >>>>>
> >>>>> So, I will switch from GNU ld.bfd v2.35.2 to LLD-12.
> >>>>
> >>>> Thanks for the research, probably your conclusion is correct, can you go
> >>>> the next step and add that part and check if the end result is the
> >>>> expected one?
> >>>>
> >>>
> >>> Still building...
> >>>
> >>> Can you give me a hand on what has to be changed in dwarves/pahole?
> >>>
> >>> I guess switching from ld.bfd to ld.lld will show the same ERROR.
> >>>
> >>
> >> This builds successfully - untested:
> >>
> >> $ git diff
> >> diff --git a/btf_loader.c b/btf_loader.c
> >> index ec286f413f36..a39edd3362db 100644
> >> --- a/btf_loader.c
> >> +++ b/btf_loader.c
> >> @@ -107,6 +107,7 @@ static struct base_type *base_type__new(strings_t
> >> name, uint32_t attrs,
> >> bt->bit_size = size;
> >> bt->is_signed = attrs & BTF_INT_SIGNED;
> >> bt->is_bool = attrs & BTF_INT_BOOL;
> >> + bt->is_unsigned = attrs & BTF_INT_UNSIGNED;
> >> bt->name_has_encoding = false;
> >> bt->float_type = float_type;
> >> }
> >> diff --git a/ctf.h b/ctf.h
> >> index 25b79892bde3..9e47c3c74677 100644
> >> --- a/ctf.h
> >> +++ b/ctf.h
> >> @@ -100,6 +100,7 @@ struct ctf_full_type {
> >> #define CTF_TYPE_INT_CHAR 0x2
> >> #define CTF_TYPE_INT_BOOL 0x4
> >> #define CTF_TYPE_INT_VARARGS 0x8
> >> +#define CTF_TYPE_INT_UNSIGNED 0x16
> >>
> >> #define CTF_TYPE_FP_ATTRS(VAL) ((VAL) >> 24)
> >> #define CTF_TYPE_FP_OFFSET(VAL) (((VAL) >> 16) & 0xff)
> >> diff --git a/dwarf_loader.c b/dwarf_loader.c
> >> index b73d7867e1e6..79d40f183c24 100644
> >> --- a/dwarf_loader.c
> >> +++ b/dwarf_loader.c
> >> @@ -473,6 +473,7 @@ static struct base_type *base_type__new(Dwarf_Die
> >> *die, struct cu *cu)
> >> bt->is_bool = encoding == DW_ATE_boolean;
> >> bt->is_signed = encoding == DW_ATE_signed;
> >> bt->is_varargs = false;
> >> + bt->is_unsigned = encoding == DW_ATE_unsigned;
> >> bt->name_has_encoding = true;
> >> }
> >>
> >> diff --git a/dwarves.h b/dwarves.h
> >> index 98caf1abc54d..edf32d2e6f80 100644
> >> --- a/dwarves.h
> >> +++ b/dwarves.h
> >> @@ -1261,6 +1261,7 @@ struct base_type {
> >> uint8_t is_signed:1;
> >> uint8_t is_bool:1;
> >> uint8_t is_varargs:1;
> >> + uint8_t is_unsigned:1;
> >> uint8_t float_type:4;
> >> };
> >>
> >> diff --git a/lib/bpf b/lib/bpf
> >> --- a/lib/bpf
> >> +++ b/lib/bpf
> >> @@ -1 +1 @@
> >> -Subproject commit 5af3d86b5a2c5fecdc3ab83822d083edd32b4396
> >> +Subproject commit 5af3d86b5a2c5fecdc3ab83822d083edd32b4396-dirty
> >> diff --git a/libbtf.c b/libbtf.c
> >> index 9f7628304495..a0661a7bbed9 100644
> >> --- a/libbtf.c
> >> +++ b/libbtf.c
> >> @@ -247,6 +247,8 @@ static const char *
> >> btf_elf__int_encoding_str(uint8_t encoding)
> >> return "CHAR";
> >> else if (encoding == BTF_INT_BOOL)
> >> return "BOOL";
> >> + else if (encoding == BTF_INT_UNSIGNED)
> >> + return "UNSIGNED";
> >> else
> >> return "UNKN";
> >> }
> >> @@ -379,6 +381,8 @@ int32_t btf_elf__add_base_type(struct btf_elf
> >> *btfe, const struct base_type *bt,
> >> encoding = BTF_INT_SIGNED;
> >> } else if (bt->is_bool) {
> >> encoding = BTF_INT_BOOL;
> >> + } else if (bt->is_unsigned) {
> >> + encoding = BTF_INT_UNSIGNED;
> >> } else if (bt->float_type) {
> >> fprintf(stderr, "float_type is not supported\n");
> >> return -1;
> >>
> >> Additionally - I cannot see it with `git diff`:
> >>
> >> [ lib/bpf/include/uapi/linux/btf.h ]
> >>
> >> /* Attributes stored in the BTF_INT_ENCODING */
> >> #define BTF_INT_SIGNED (1 << 0)
> >> #define BTF_INT_CHAR (1 << 1)
> >> #define BTF_INT_BOOL (1 << 2)
> >> #define BTF_INT_UNSIGNED (1 << 3)
> >>
> >> Comments?
> >>
> >
> > Hmmm...
> >
> > + info BTF .btf.vmlinux.bin.o
> > + [ != silent_ ]
> > + printf %-7s %s\n BTF .btf.vmlinux.bin.o
> > BTF .btf.vmlinux.bin.o
> > + LLVM_OBJCOPY=llvm-objcopy /opt/pahole/bin/pahole -J .tmp_vmlinux.btf
> > [2] INT long unsigned int Error emitting BTF type
> > Encountered error while encoding BTF.
> > + llvm-objcopy --only-section=.BTF --set-section-flags
> > .BTF=alloc,readonly --strip-all .tmp_vmlinux.btf .btf.vmlinux.bin.o
> > ...
> > + info BTFIDS vmlinux
> > + [ != silent_ ]
> > + printf %-7s %s\n BTFIDS vmlinux
> > BTFIDS vmlinux
> > + ./tools/bpf/resolve_btfids/resolve_btfids vmlinux
> > FAILED: load BTF from vmlinux: Invalid argument
> > + on_exit
> > + [ 255 -ne 0 ]
> > + cleanup
> > + rm -f .btf.vmlinux.bin.o
> > + rm -f .tmp_System.map
> > + rm -f .tmp_vmlinux.btf .tmp_vmlinux.kallsyms1
> > .tmp_vmlinux.kallsyms1.S .tmp_vmlinux.kallsyms1.o
> > .tmp_vmlinux.kallsyms2 .tmp_vmlinux.kallsyms2.S .tmp_vmlinux.kallsyms
> > 2.o
> > + rm -f System.map
> > + rm -f vmlinux
> > + rm -f vmlinux.o
> > make[3]: *** [Makefile:1166: vmlinux] Error 255
> >
> > 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.
> Not sure whether this information will be useful or not
> for BTF. This needs to be discussed separately.
>

[ CC Fangrui ]

How can I teach pahole to ignore BTF_INT_UNSIGNED?

Another tryout might be to use "-fbinutils-version=..." which is
available for LLVM-12 according to Fangrui?
Fangrui, which binutils versions can I pass and how?

Thanks.

- Sedat -