netdev - Re: [PATCH v3 binutils] Add BPF support to binutils...

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Message-ID: <b96ef138-9862-5091-9041-76516f852e48@fb.com>
Date:   Mon, 1 May 2017 19:49:21 -0700
From:   Alexei Starovoitov <ast@...com>
To:     David Miller <davem@...emloft.net>
CC:     <daniel@...earbox.net>, <aconole@...heb.org>,
        <netdev@...r.kernel.org>, <xdp-newbies@...r.kernel.org>
Subject: Re: [PATCH v3 binutils] Add BPF support to binutils...

On 4/30/17 11:21 AM, David Miller wrote:
> built with:
>
> 	clang -O2 -target bpfel -g -c x.c -o x.o
>
> readelf can see it just fine:
>
> [davem@...alhost binutils]$ ./readelf --debug-dump=loc ./xel.o
> Contents of the .debug_loc section:
>
>     Offset   Begin            End              Expression
>     00000000 0000000000000000 0000000000000010 (DW_OP_reg1 (r1))
>     00000013 <End of list>
>     00000023 0000000000000010 0000000000000020 (DW_OP_constu: 590618314553; DW_OP_stack_value)
>     0000003d 0000000000000020 0000000000000030 (DW_OP_reg1 (r1))
>     00000050 <End of list>
>
> But with big-endian:
>
> [davem@...alhost binutils]$ ./readelf --debug-dump=loc ./xeb.o
> readelf: Warning: Invalid pointer size (0) in compunit header, using 4 instead
> readelf: Warning: Bogus end-of-siblings marker detected at offset 27 in .debug_info section
> readelf: Warning: Bogus end-of-siblings marker detected at offset 28 in .debug_info section
> readelf: Warning: DIE at offset 0x29 refers to abbreviation number 48 which does not exist
> readelf: Warning: Unable to load/parse the .debug_info section, so cannot interpret the .debug_loc section.

yeah. clang emitted dwarf for big-endian is broken.
This dwarf stuff is too complicated for normal human beings.
The tight packing making debugging it quite painful.