On Fri, Feb 5, 2021 at 11:21 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
>
> On Fri, Feb 5, 2021 at 8:15 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote:
> >
> > 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?
> >
>
> OK, I checked LLVM-12 sources:
>
> clang/docs/ReleaseNotes.rst:101:- New option ``-fbinutils-version=``
> specifies the targeted binutils version.
> clang/docs/ReleaseNotes.rst:102: For example,
> ``-fbinutils-version=2.35`` means compatibility with GNU as/ld
> clang/docs/ReleaseNotes.rst-103- before 2.35 is not needed: new
> features can be used and there is no need to
> clang/docs/ReleaseNotes.rst-104- work around old GNU as/ld bugs.
>
> Can I pass (also patchlevel) like 2.35.2?
> Here I have Debian's v2.35.1 and a selfmade v2.35.2?
>
> - Sedat -
>
> - Sedat -
Answering specifically this question:
clang -help displays:
...
-fbinutils-version=<major.minor>
Produced object files can use all ELF
features supported by this binutils version and newer. If
-fno-integrated-as is specified, the generated assembly will consider
GNU as support. 'none' means that all ELF features can be used,
regardless of binutils support. Defaults to 2.26.
The option was introduced in https://reviews.llvm.org/D85474
major.minor.patch is not supported. In reality, very few features are
gated by this option, currently just SHF_MERGE and a pending
SHF_LINK_ORDER PGO patch.
I think we will be conservative. If a 2.37 fix is back ported to
2.35.2 and 2.36.1, we will ignore that and will use the feature only
if -fbinutils-version=2.37 or above is specified.
--
宋方睿
