Re: [PATCH] btf_encoder: Check var type after checking var addr.

[Jiri Olsa <jolsa@redhat.com>]

On Mon, Oct 26, 2020 at 03:18:22PM -0700, Hao Luo wrote:
> Commit 2e719cc ("btf_encoder: revamp how per-CPU variables are
> encoded") adds percpu_var_exists() to filter out the symbols that
> are not percpu var. However, the check comes after checking the
> var's type. There can be symbols that are of zero type. If we hit
> that, btf_encoder will not work without '--btf_encode_force'.
> So we should check percpu_var_exists before checking var's type.
> 
> Tested:
>  haoluo@haoluo:~/kernel/tip$ gcc --version
>  gcc (GCC) 10.2.0
>  Copyright (C) 2020 Free Software Foundation, Inc.
>  This is free software; see the source for copying conditions.  There is NO
>  warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
>  Before:
> 
>  haoluo@haoluo:~/kernel/tip$ make clean -s
>  haoluo@haoluo:~/kernel/tip$ make -j 32 -s
>    LINK     resolve_btfids
>  error: found variable in CU 'kernel/bpf/btf.c' that has void type
>  Encountered error while encoding BTF.
>  FAILED: load BTF from vmlinux: Unknown error -2make: *** [Makefile:1164: vmlinux] Error 255
> 
>  After:
> 
>  haoluo@haoluo:~/kernel/tip$ make clean -s
>  haoluo@haoluo:~/kernel/tip$ make -j 32 -s
>    LINK     resolve_btfids
>  haoluo@haoluo:~/kernel/tip$
> 
> Fixes: 2e719cc ("btf_encoder: revamp how per-CPU variables are encoded")
> Signed-off-by: Hao Luo <haoluo@google.com>

it fixes the build issue for me

Tested-by: Jiri Olsa <jolsa@redhat.com>

thanks,
jirka