From: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
To: Yonghong Song <yhs@fb.com>
Cc: Sami Tolvanen <samitolvanen@google.com>,
Kees Cook <keescook@chromium.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
<linux-kernel@vger.kernel.org>, <bpf@vger.kernel.org>
Subject: Re: CLANG LTO compatibility issue with DEBUG_INFO_BTF
Date: Mon, 22 Mar 2021 09:48:43 +0800 [thread overview]
Message-ID: <20210322094843.752254b3@xhacker.debian> (raw)
In-Reply-To: <4e1d1504-55e5-db8b-112b-921d86ef7d5b@fb.com>
On Thu, 18 Mar 2021 20:56:46 -0700 Yonghong Song wrote:
>
> On 3/18/21 8:45 PM, Jisheng Zhang wrote:
> > Hi,
> >
> > When trying the latest 5.12-rc3 with both LTO_CLANG_THIN and DEBUG_INFO_BTF
> > enabled, I met lots of warnings such as:
> >
> > ...
> > tag__recode_dwarf_type: couldn't find 0x4a7ade5 type for 0x4ab9f88 (subroutine_type)!
> > ftype__recode_dwarf_types: couldn't find 0x4a7ade5 type for 0x4ab9fa4 (formal_parameter)!
> > ...
> > namespace__recode_dwarf_types: couldn't find 0x4a8ff4a type for 0x4aba05c (member)!
> > namespace__recode_dwarf_types: couldn't find 0x4a7ae9b type for 0x4aba084 (member)!
> > ...
> > WARN: multiple IDs found for 'path': 281, 729994 - using 281
> > WARN: multiple IDs found for 'task_struct': 421, 730101 - using 421
> > ...
> >
> >
> > then finally get build error:
> > FAILED unresolved symbol vfs_truncate
> >
> >
> > Is this a known issue? Do we need to make DEBUG_INFO_BTF depend on !LTO?
>
> This is a known issue for pahole. pahole does not handle dwarf well
> generated with LTO. Bill Wendling from google is looking at the issue
> and I will help look at the issue as well. Since bpf heavily depends
> on BTF, at this point, I suggest if you are using bpf, please do not
> turn on LTO. Or if you build with LTO, just turn off DEBUG_INFO_BTF
> in your config. Thanks!
>
Got it. Thanks for the information
prev parent reply other threads:[~2021-03-22 1:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 3:45 CLANG LTO compatibility issue with DEBUG_INFO_BTF Jisheng Zhang
2021-03-19 3:56 ` Yonghong Song
2021-03-22 1:48 ` Jisheng Zhang [this message]
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