Encountered error while encoding BTF due to Unsupported DW_TAG_unspecified_type(0x3b)

[Martin Liška <mliska@xxxxxxx>]

I noticed one can't build 5.19 with latest binutils master.

One see the following error:
[ 1413s]   BTF     .btf.vmlinux.bin.o
[ 1413s] Unsupported DW_TAG_unspecified_type(0x3b)
[ 1413s] Encountered error while encoding BTF.

It's caused by DWARF coming from .S files and the change is introduced since
the following binutils revision:

commit 5578fbf672ee497ea19826edeb509f4cc3e825a8
Author: Nick Clifton <nickc@xxxxxxxxxx>
Date:   Thu Aug 25 11:48:00 2022 +0100

    GAS: Add a return type tag to DWARF DIEs generated for function symbols.

for entry.S the output changes to:

$ as-new --gdwarf-5 --64 -o entry.o entry.S && readelf -wi entry.o
Contents of the .debug_info section:

  Compilation Unit @ offset 0x0:
   Length:        0x35 (32-bit)
   Version:       5
   Unit Type:     DW_UT_compile (1)
   Abbrev Offset: 0x0
   Pointer Size:  8
 <0><c>: Abbrev Number: 3 (DW_TAG_unspecified_type) <--- the problematic TAG
 <0><d>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <e>   DW_AT_stmt_list   : 0x0
    <12>   DW_AT_low_pc      : 0x0
    <1a>   DW_AT_high_pc     : 19
    <1b>   DW_AT_name        : (indirect string, offset: 0x0): ../arch/x86/entry/entry.S
    <1f>   DW_AT_comp_dir    : (indirect string, offset: 0x1a): /tmp
    <23>   DW_AT_producer    : (indirect string, offset: 0x1f): GNU AS 2.39.50
    <27>   DW_AT_language    : 32769	(MIPS assembler)
 <1><29>: Abbrev Number: 2 (DW_TAG_subprogram)
    <2a>   DW_AT_name        : (indirect string, offset: 0x2e): entry_ibpb
    <2e>   DW_AT_external    : 1
    <2e>   DW_AT_type        : <0xc>
    <2f>   DW_AT_low_pc      : 0x0
    <37>   DW_AT_high_pc     : 19
 <1><38>: Abbrev Number: 0

Is it something pahole should handle?

Thanks,
Martin