btf_encoder: Encode DW_TAG_unspecified_type returning routines as void
Since we don´t have how to encode this info in BTF, and from what we
saw, at least in this case:
Built binutils from git://sourceware.org/git/binutils-gdb.git, then used
gcc's -B option to point to the directory with the new as, that is built
as as-new, so make a symlink, ending up with:
15e20ce2324a:~/git/linux # readelf -wi ./arch/x86/entry/entry.o
Contents of the .debug_info section:
Compilation Unit @ offset 0:
Length: 0x35 (32-bit)
Version: 5
Unit Type: DW_UT_compile (1)
Abbrev Offset: 0
Pointer Size: 8
<0><c>: Abbrev Number: 1 (DW_TAG_compile_unit)
<d> DW_AT_stmt_list : 0
<11> DW_AT_low_pc : 0
<19> DW_AT_high_pc : 19
<1a> DW_AT_name : (indirect string, offset: 0): arch/x86/entry/entry.S
<1e> DW_AT_comp_dir : (indirect string, offset: 0x17): /root/git/linux
<22> DW_AT_producer : (indirect string, offset: 0x27): GNU AS 2.39.50
<26> DW_AT_language : 32769 (MIPS assembler)
<1><28>: Abbrev Number: 2 (DW_TAG_subprogram)
<29> DW_AT_name : (indirect string, offset: 0x36): entry_ibpb
<2d> DW_AT_external : 1
<2d> DW_AT_type : <0x37>
<2e> DW_AT_low_pc : 0
<36> DW_AT_high_pc : 19
<1><37>: Abbrev Number: 3 (DW_TAG_unspecified_type)
<1><38>: Abbrev Number: 0
So we have that asm label encoded by GNU AS 2.39.50 as a
DW_TAG_subprogram that has as its DW_AT_type the DW_TAG_unspecified_type
0x37 that we convert to 0 (void):
15e20ce2324a:~/git/linux # pahole -J ./arch/x86/entry/entry.o
15e20ce2324a:~/git/linux # pahole -JV ./arch/x86/entry/entry.o
btf_encoder__new: 'entry.o' doesn't have '.data..percpu' section
Found 0 per-CPU variables!
Found 1 functions!
File entry.o:
[1] FUNC_PROTO (anon) return=0 args=(void)
[2] FUNC entry_ibpb type_id=1
15e20ce2324a:~/git/linux # pfunct -F btf ./arch/x86/entry/entry.o
entry_ibpb
15e20ce2324a:~/git/linux # pfunct --proto -F btf ./arch/x86/entry/entry.o
void entry_ibpb(void);
15e20ce2324a:~/git/linux #
15e20ce2324a:~/git/linux # tools/bpf/bpftool/bpftool btf dump file ./arch/x86/entry/entry.o format raw
[1] FUNC_PROTO '(anon)' ret_type_id=0 vlen=0
[2] FUNC 'entry_ibpb' type_id=1 linkage=static
15e20ce2324a:~/git/linux #
I think this is what can be done to avoid having to skip ASM DWARF when
gets widely used, i.e. binutils gets updated.
Acked-by: Yonghong Song <yhs@fb.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Cc: Martin Liška <mliska@suse.cz>
Link: https://lore.kernel.org/all/Y0R7uu3s%2FimnvPzM@kernel.org/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
1 file changed
