On Wed, May 11, 2022 at 3:02 PM Yonghong Song <yhs@xxxxxx> wrote: > > With latest llvm15 built kernel (make -j LLVM=1), I hit the following > error when build selftests (make -C tools/testing/selftests/bpf -j LLVM=1): > In file included from skeleton/pid_iter.bpf.c:3: > .../selftests/bpf/tools/build/bpftool/vmlinux.h:84050:9: error: unknown type name > '__builtin_va_list___2'; did you mean '__builtin_va_list'? > typedef __builtin_va_list___2 va_list___2; > ^~~~~~~~~~~~~~~~~~~~~ > __builtin_va_list > note: '__builtin_va_list' declared here > In file included from skeleton/profiler.bpf.c:3: > .../selftests/bpf/tools/build/bpftool/vmlinux.h:84050:9: error: unknown type name > '__builtin_va_list__ _2'; did you mean '__builtin_va_list'? > typedef __builtin_va_list___2 va_list___2; > ^~~~~~~~~~~~~~~~~~~~~ > __builtin_va_list > note: '__builtin_va_list' declared here > > The error can be easily explained with after-dedup vmlinux btf: > [21] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED > [2300] STRUCT '__va_list_tag' size=24 vlen=4 > 'gp_offset' type_id=2 bits_offset=0 > 'fp_offset' type_id=2 bits_offset=32 > 'overflow_arg_area' type_id=32 bits_offset=64 > 'reg_save_area' type_id=32 bits_offset=128 > [2308] TYPEDEF 'va_list' type_id=2309 > [2309] TYPEDEF '__builtin_va_list' type_id=2310 > [2310] ARRAY '(anon)' type_id=2300 index_type_id=21 nr_elems=1 > > [5289] PTR '(anon)' type_id=2308 > [158520] STRUCT 'warn_args' size=32 vlen=2 > 'fmt' type_id=14 bits_offset=0 > 'args' type_id=2308 bits_offset=64 > [27299] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none) > [34590] TYPEDEF '__builtin_va_list' type_id=34591 > [34591] ARRAY '(anon)' type_id=2300 index_type_id=27299 nr_elems=1 > > The typedef __builtin_va_list is a builtin type for the compiler. > In the above case, two typedef __builtin_va_list are generated. > The reason is due to different array index_type_id. This happened > when pahole is running with more than one jobs when parsing dwarf > and generating btfs. > > Function btf_encoder__encode_cu() is used to do btf encoding for > each cu. The function will try to find an "int" type for the cu > if it is available, otherwise, it will create a special type > with name __ARRAY_SIZE_TYPE__. For example, > file1: yes 'int' type > file2: no 'int' type > > In serial mode, file1 is processed first, followed by file2. > both will have 'int' type as the array index type since file2 > will inherit the index type from file1. > > In parallel mode though, arrays in file1 will have index type 'int', > and arrays in file2 wil have index type '__ARRAY_SIZE_TYPE__'. > This will prevent some legitimate dedup and may have generated > vmlinux.h having compilation error. > I think it is two separate problems. 1. Maybe instead of this generating __ARRAY_SIZE_TYPE__ we should generate proper 'int' type? 2. __builtin_va_list___2 shouldn't have happened, it's libbpf bug. Libbpf handles __builtin_va_list specially (see btf_dump_is_blacklisted()), so we need to fix libbpf to not get confused if there are two __builtin_va_list copies in BTF. > This patch fixed the issue by normalizing all array_index types > to be the first array_index type in the whole btf. > > Signed-off-by: Yonghong Song <yhs@xxxxxx> > --- > btf_encoder.c | 24 +++++++++++++++++++++--- > btf_encoder.h | 2 +- > pahole.c | 2 +- > 3 files changed, 23 insertions(+), 5 deletions(-) > [...]
