On Thu, Feb 11, 2021 at 9:17 PM Jiri Olsa [off-list ref] wrote:

On Wed, Feb 10, 2021 at 11:26:28AM -0800, Andrii Nakryiko wrote:

SNIP

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Can't reproduce it. It works in all kinds of variants (relative and
absolute O=, clean and not clean trees, etc). Jiri, please check as
well.

Odd, this reproduces for me on a completely clean checkout of bpf-next:

$ git clone --depth=1 https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/

$ cd bpf-next

$ make -s O=build distclean
../../scripts/Makefile.include:4: *** O=/tmp/bpf-next/build/tools/bpf/resolve_btfids does not exist.  Stop.

I do not really see how this could be environment related. It seems like
this comes from tools/scripts/Makefile.include, where there is no
guarantee that $(O) is created before being used like in the main
Makefile?

right, we need to handle the case where tools/bpf/resolve_btfids
does not exist, patch below fixes it for me

jirka

Looks good to me, please send it as a proper patch to bpf-next.

But I'm curious, why is objtool not doing something like that? Is it
not doing clean at all? Or does it do it in some different way?

yes, it's not connected to global make clean

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---

diff --git a/Makefile b/Makefile
index 159d9592b587..ce9685961abe 100644
--- a/Makefile
+++ b/Makefile

@@ -1088,8 +1088,14 @@ endif

 PHONY += resolve_btfids_clean

+resolve_btfids_O = $(abspath $(objtree))/tools/bpf/resolve_btfids
+
+# tools/bpf/resolve_btfids directory might not exist
+# in output directory, skip its clean in that case
 resolve_btfids_clean:
-       $(Q)$(MAKE) -sC $(srctree)/tools/bpf/resolve_btfids O=$(abspath $(objtree))/tools/bpf/resolve_btfids clean
+ifneq (,$(wildcard $(resolve_btfids_O)))

nit: kind of backwards, usually it's in a `ifneq($var,)` form

ok

thanks,
jirka

I expected this kind of mess
when I saw 33a57ce0a54d498275f432db04850001175dfdfa


The tools/ directory is a completely different world
governed by a different build system
(no, not a build system, but a collection of adhoc makefile code)


All the other programs used during the kernel build
are located under scripts/, and can be built with
a simple syntax, and cleaned up correctly.
It is simple, clean and robust.

objtool is the first alien that opt out Kbuild,
and this is the second one.


It is scary to mix up two different things,
which run in different working directories.

See, this is wired up in the top Makefile
in an ugly way, and you are struggling
in suppressing issues, where you can never
do it in the right way.



-- 
Best Regards
Masahiro Yamada