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From: Jakub Kicinski <kuba@kernel.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: "Allan, Bruce W" <bruce.w.allan@intel.com>,
	Song Liu <songliubraving@fb.com>,
	Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	"Starovoitov, Alexei" <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Kernel Team <Kernel-team@fb.com>,
	open list <linux-kernel@vger.kernel.org>,
	"rafael@kernel.org" <rafael@kernel.org>,
	"jeyu@kernel.org" <jeyu@kernel.org>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>
Subject: Re: [PATCH v4 bpf-next 3/5] kbuild: build kernel module BTFs if BTF is enabled and pahole supports it
Date: Mon, 16 Nov 2020 13:24:15 -0800	[thread overview]
Message-ID: <20201116132409.4a5b8e0b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <CAEf4BzYSN+XnaA4V3jTLEmoUZO=Yxwp7OAwAY+HOvVEKT5kRFA@mail.gmail.com>

On Mon, 16 Nov 2020 12:34:17 -0800 Andrii Nakryiko wrote:
> > This change, commit 5f9ae91f7c0d ("kbuild: Build kernel module BTFs if BTF is enabled and pahole
> > supports it") currently in net-next, linux-next, etc. breaks the use-case of compiling only a specific
> > kernel module (both in-tree and out-of-tree, e.g. 'make M=drivers/net/ethernet/intel/ice') after
> > first doing a 'make modules_prepare'.  Previously, that use-case would result in a warning noting
> > "Symbol info of vmlinux is missing. Unresolved symbol check will be entirely skipped" but now it
> > errors out after noting "No rule to make target 'vmlinux', needed by '<...>.ko'.  Stop."
> >
> > Is that intentional?  
> 
> I wasn't aware of such a use pattern, so definitely not intentional.
> But vmlinux is absolutely necessary to generate the module BTF. So I'm
> wondering what's the proper fix here? Leave it as is (that error
> message is actually surprisingly descriptive, btw)? Force vmlinux
> build? Or skip BTF generation for that module?

For an external out-of-tree module there is no guarantee that vmlinux
will even be on the system, no? So only the last option can work in
that case.

  reply	other threads:[~2020-11-16 21:24 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-10  1:19 [PATCH v4 bpf-next 0/5] Integrate kernel module BTF support Andrii Nakryiko
2020-11-10  1:19 ` [PATCH v4 bpf-next 1/5] bpf: add in-kernel split " Andrii Nakryiko
2020-11-10 17:49   ` Song Liu
2020-11-10 18:31     ` Andrii Nakryiko
2020-11-10 20:14       ` Song Liu
2020-11-10  1:19 ` [PATCH v4 bpf-next 2/5] bpf: assign ID to vmlinux BTF and return extra info for BTF in GET_OBJ_INFO Andrii Nakryiko
2020-11-10 20:24   ` Song Liu
2020-11-10  1:19 ` [PATCH v4 bpf-next 3/5] kbuild: build kernel module BTFs if BTF is enabled and pahole supports it Andrii Nakryiko
2020-11-11  1:04   ` Song Liu
2020-11-16 19:55     ` Allan, Bruce W
2020-11-16 20:34       ` Andrii Nakryiko
2020-11-16 21:24         ` Jakub Kicinski [this message]
2020-11-16 22:35           ` Andrii Nakryiko
2021-11-26 15:16           ` Fabian Grünbichler
2021-12-08  0:08             ` Andrii Nakryiko
2020-11-17  3:44   ` David Ahern
2020-11-10  1:19 ` [PATCH v4 bpf-next 4/5] bpf: load and verify kernel module BTFs Andrii Nakryiko
2020-11-11  7:11   ` kernel test robot
2020-11-11  7:11     ` kernel test robot
2020-11-11 10:13   ` Jessica Yu
2020-11-11 20:11     ` Andrii Nakryiko
2020-11-13 10:31       ` Jessica Yu
2020-11-13 18:54         ` Andrii Nakryiko
2020-11-10  1:19 ` [PATCH v4 bpf-next 5/5] tools/bpftool: add support for in-kernel and named BTF in `btf show` Andrii Nakryiko
2020-11-11  1:15   ` Song Liu
2020-11-11  4:19     ` Andrii Nakryiko
2020-11-11  7:44       ` Song Liu

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