| Message ID | 20210922021321.2286360-1-yhs@fb.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | generate BTF_KIND_TAG types from DW_TAG_LLVM_annotation dwarf tags | expand |
Em Tue, Sep 21, 2021 at 07:13:21PM -0700, Yonghong Song escreveu: > LLVM has implemented btf_tag attribute ([1]) which intended > to provide a "string" tag for struct/union or its member, var, > a func or its parameter. Such a "string" tag will be encoded > in dwarf. For non-BPF target like x86_64, pahole needs to > convert those dwarf btf_tag annotations to BTF so kernel > can utilize these "string" tags for bpf program verification, etc. > > Patch 1 enhanced dwarf_loader to encode DW_TAG_LLVM_annotation > tags into internal data structure and Patch 2 will encode > such information to BTF with BTF_KIND_TAGs. > > [1] https://reviews.llvm.org/D106614 Applied both locally, now building HEAD llvm/clang to test everything, - Arnaldo > Changelog: > v1 -> v2: > - handle returning error cases for btf_encoder__add_tag(). > > Yonghong Song (2): > dwarf_loader: parse dwarf tag DW_TAG_LLVM_annotation > btf_encoder: generate BTF_KIND_TAG from llvm annotations > > btf_encoder.c | 63 ++++++++++++++++++++++++++++++++++++- > dwarf_loader.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++---- > dwarves.h | 10 ++++++ > pahole.c | 8 +++++ > 4 files changed, 159 insertions(+), 7 deletions(-) > > -- > 2.30.2
Em Mon, Sep 27, 2021 at 05:40:09PM -0300, Arnaldo Carvalho de Melo escreveu: > Em Tue, Sep 21, 2021 at 07:13:21PM -0700, Yonghong Song escreveu: > > LLVM has implemented btf_tag attribute ([1]) which intended > > to provide a "string" tag for struct/union or its member, var, > > a func or its parameter. Such a "string" tag will be encoded > > in dwarf. For non-BPF target like x86_64, pahole needs to > > convert those dwarf btf_tag annotations to BTF so kernel > > can utilize these "string" tags for bpf program verification, etc. > > > > Patch 1 enhanced dwarf_loader to encode DW_TAG_LLVM_annotation > > tags into internal data structure and Patch 2 will encode > > such information to BTF with BTF_KIND_TAGs. > > > > [1] https://reviews.llvm.org/D106614 > > Applied both locally, now building HEAD llvm/clang to test everything, ⬢[acme@toolbox pahole]$ pahole -JV t.o Found per-CPU symbol 'g' at address 0x0 Found 1 per-CPU variables! Found 1 functions! File t.o: [1] INT int size=4 nr_bits=32 encoding=SIGNED [2] PTR (anon) type_id=3 [3] STRUCT t size=8 a type_id=1 bitfield_size=1 bits_offset=0 b type_id=1 bitfield_size=0 bits_offset=32 [4] TAG tag1 type_id=3 component_idx=0 [5] TAG tag2 type_id=3 component_idx=1 [6] TAG tag1 type_id=3 component_idx=-1 [7] TAG tag2 type_id=3 component_idx=-1 [8] FUNC_PROTO (anon) return=1 args=(2 a1, 1 a2) [9] FUNC foo type_id=8 [10] TAG tag2 type_id=9 component_idx=1 [11] TAG tag1 type_id=9 component_idx=-1 search cu 't.c' for percpu global variables. Variable 'g' from CU 't.c' at address 0x0 encoded [12] VAR g type=1 linkage=1 [13] TAG tag1 type_id=12 component_idx=-1 [14] DATASEC .data..percpu size=4 vlen=1 type=12 offset=0 size=4 ⬢[acme@toolbox pahole]$ pahole -JV --skip_encoding_btf_tag t.o Found per-CPU symbol 'g' at address 0x0 Found 1 per-CPU variables! Found 1 functions! File t.o: [1] INT int size=4 nr_bits=32 encoding=SIGNED [2] PTR (anon) type_id=3 [3] STRUCT t size=8 a type_id=1 bitfield_size=1 bits_offset=0 b type_id=1 bitfield_size=0 bits_offset=32 [4] FUNC_PROTO (anon) return=1 args=(2 a1, 1 a2) [5] FUNC foo type_id=4 search cu 't.c' for percpu global variables. Variable 'g' from CU 't.c' at address 0x0 encoded [6] VAR g type=1 linkage=1 [7] DATASEC .data..percpu size=4 vlen=1 type=6 offset=0 size=4 ⬢[acme@toolbox pahole]$ clang -v clang version 14.0.0 (https://github.com/llvm/llvm-project f7e82e4fa849376ea9226220847a098dc92d74a0) Target: x86_64-unknown-linux-gnu Thread model: posix InstalledDir: /usr/local/bin Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/11 Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/11 Candidate multilib: .;@m64 Candidate multilib: 32;@m32 Selected multilib: .;@m64 ⬢[acme@toolbox pahole]$ And the usual: ⬢[acme@toolbox pahole]$ pahole -J vmlinux ⬢[acme@toolbox pahole]$ btfdiff vmlinux ⬢[acme@toolbox pahole]$ So applied, pushing out to the tmp.master branch so that libbpf's CI can have a go at it, then after the next run I'll push to master, thanks! - Arnaldo
LLVM has implemented btf_tag attribute ([1]) which intended to provide a "string" tag for struct/union or its member, var, a func or its parameter. Such a "string" tag will be encoded in dwarf. For non-BPF target like x86_64, pahole needs to convert those dwarf btf_tag annotations to BTF so kernel can utilize these "string" tags for bpf program verification, etc. Patch 1 enhanced dwarf_loader to encode DW_TAG_LLVM_annotation tags into internal data structure and Patch 2 will encode such information to BTF with BTF_KIND_TAGs. [1] https://reviews.llvm.org/D106614 Changelog: v1 -> v2: - handle returning error cases for btf_encoder__add_tag(). Yonghong Song (2): dwarf_loader: parse dwarf tag DW_TAG_LLVM_annotation btf_encoder: generate BTF_KIND_TAG from llvm annotations btf_encoder.c | 63 ++++++++++++++++++++++++++++++++++++- dwarf_loader.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++---- dwarves.h | 10 ++++++ pahole.c | 8 +++++ 4 files changed, 159 insertions(+), 7 deletions(-)