kernel-hardening - Re: [PATCH v5 bpf] kbuild: fix dependencies for DEBUG_INFO

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Message-ID: <CAEf4BzZxWTDCtcov5_TvGLR0Qp4p-JANh29WoZKEQ6FvmWrr9A@mail.gmail.com>
Date: Thu, 2 Apr 2020 14:02:57 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Slava Bacherikov <slava@...her09.org>
Cc: Andrii Nakryiko <andriin@...com>, Kees Cook <keescook@...omium.org>, bpf <bpf@...r.kernel.org>, 
	open list <linux-kernel@...r.kernel.org>, Jann Horn <jannh@...gle.com>, 
	Alexei Starovoitov <alexei.starovoitov@...il.com>, Daniel Borkmann <daniel@...earbox.net>, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>, 
	Liu Yiding <liuyd.fnst@...fujitsu.com>, KP Singh <kpsingh@...gle.com>
Subject: Re: [PATCH v5 bpf] kbuild: fix dependencies for DEBUG_INFO_BTF

On Thu, Apr 2, 2020 at 1:44 PM Slava Bacherikov <slava@...her09.org> wrote:
>
> Currently turning on DEBUG_INFO_SPLIT when DEBUG_INFO_BTF is also
> enabled will produce invalid btf file, since gen_btf function in
> link-vmlinux.sh script doesn't handle *.dwo files.
>
> Enabling DEBUG_INFO_REDUCED will also produce invalid btf file, and
> using GCC_PLUGIN_RANDSTRUCT with BTF makes no sense.
>
> Signed-off-by: Slava Bacherikov <slava@...her09.org>
> Reported-by: Jann Horn <jannh@...gle.com>
> Reported-by: Liu Yiding <liuyd.fnst@...fujitsu.com>
> Acked-by: KP Singh <kpsingh@...gle.com>
> Acked-by: Andrii Nakryiko <andriin@...com>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Fixes: e83b9f55448a ("kbuild: add ability to generate BTF type info for vmlinux")
> ---
>  lib/Kconfig.debug | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index f61d834e02fe..6118d99117da 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -223,6 +223,8 @@ config DEBUG_INFO_DWARF4
>  config DEBUG_INFO_BTF
>         bool "Generate BTF typeinfo"
>         depends on DEBUG_INFO
> +       depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
> +       depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST

Given what Kees explained, I think this looks good. Thanks!

>         help
>           Generate deduplicated BTF type information from DWARF debug info.
>           Turning this on expects presence of pahole tool, which will convert

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