netdev - Re: [PATCH 1/5] samples/bpf: fix test_lru

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Date:   Tue, 21 May 2019 10:06:48 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Matteo Croce <mcroce@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        xdp-newbies@...r.kernel.org, bpf@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH 1/5] samples/bpf: fix test_lru_dist build

On Tue, 21 May 2019 17:36:17 +0200, Matteo Croce wrote:
> On Tue, May 21, 2019 at 5:21 PM Daniel Borkmann <daniel@...earbox.net> wrote:
> >
> > On 05/20/2019 10:38 PM, Jakub Kicinski wrote:  
> > > On Mon, 20 May 2019 19:46:27 +0200, Matteo Croce wrote:  
> > >> On Sat, May 18, 2019 at 2:46 AM Matteo Croce <mcroce@...hat.com> wrote:  
> > >>>
> > >>> Fix the following error by removing a duplicate struct definition:  
> > >>
> > >> Hi all,
> > >>
> > >> I forget to send a cover letter for this series, but basically what I
> > >> wanted to say is that while patches 1-3 are very straightforward,
> > >> patches 4-5 are a bit rough and I accept suggstions to make a cleaner
> > >> work.  
> > >
> > > samples depend on headers being locally installed:
> > >
> > > make headers_install
> > >
> > > Are you intending to change that?  
> >
> > +1, Matteo, could you elaborate?
> >
> > On latest bpf tree, everything compiles just fine:
> >
> > [root@...ux bpf]# make headers_install
> > [root@...ux bpf]# make -C samples/bpf/
> > make: Entering directory '/home/darkstar/trees/bpf/samples/bpf'
> > make -C ../../ /home/darkstar/trees/bpf/samples/bpf/ BPF_SAMPLES_PATH=/home/darkstar/trees/bpf/samples/bpf
> > make[1]: Entering directory '/home/darkstar/trees/bpf'
> >   CALL    scripts/checksyscalls.sh
> >   CALL    scripts/atomic/check-atomics.sh
> >   DESCEND  objtool
> > make -C /home/darkstar/trees/bpf/samples/bpf/../../tools/lib/bpf/ RM='rm -rf' LDFLAGS= srctree=/home/darkstar/trees/bpf/samples/bpf/../../ O=
> >   HOSTCC  /home/darkstar/trees/bpf/samples/bpf/test_lru_dist
> >   HOSTCC  /home/darkstar/trees/bpf/samples/bpf/sock_example
> >  
> 
> Hi all,
> 
> I have kernel-headers installed from master, but yet the samples fail to build:
> 
> matteo@...bo:~/src/linux/samples/bpf$ rpm -q kernel-headers
> kernel-headers-5.2.0_rc1-38.x86_64
> 
> matteo@...bo:~/src/linux/samples/bpf$ git describe HEAD
> v5.2-rc1-97-g5bdd9ad875b6
> 
> matteo@...bo:~/src/linux/samples/bpf$ make
> make -C ../../ /home/matteo/src/linux/samples/bpf/
> BPF_SAMPLES_PATH=/home/matteo/src/linux/samples/bpf
> make[1]: Entering directory '/home/matteo/src/linux'
>   CALL    scripts/checksyscalls.sh
>   CALL    scripts/atomic/check-atomics.sh
>   DESCEND  objtool
> make -C /home/matteo/src/linux/samples/bpf/../../tools/lib/bpf/ RM='rm
> -rf' LDFLAGS= srctree=/home/matteo/src/linux/samples/bpf/../../ O=
>   HOSTCC  /home/matteo/src/linux/samples/bpf/test_lru_dist
> /home/matteo/src/linux/samples/bpf/test_lru_dist.c:39:8: error:
> redefinition of ‘struct list_head’
>    39 | struct list_head {
>       |        ^~~~~~~~~
> In file included from /home/matteo/src/linux/samples/bpf/test_lru_dist.c:9:
> ./tools/include/linux/types.h:69:8: note: originally defined here
>    69 | struct list_head {
>       |        ^~~~~~~~~
> make[2]: *** [scripts/Makefile.host:90:
> /home/matteo/src/linux/samples/bpf/test_lru_dist] Error 1
> make[1]: *** [Makefile:1762: /home/matteo/src/linux/samples/bpf/] Error 2
> make[1]: Leaving directory '/home/matteo/src/linux'
> make: *** [Makefile:231: all] Error 2
> 
> Am I missing something obvious?

Yes ;)  Samples use a local installation of headers in $objtree/usr (I
think, maybe $srctree/usr).  So you need to do make headers_install in
your kernel source tree, otherwise the include path from tools/ takes
priority over your global /usr/include and causes these issues.  I had
this path in my tree for some time, but I don't like enough to post it:

commit 35fb614049e93d46af708c0eaae6601df54017b3
Author: Jakub Kicinski <jakub.kicinski@...ronome.com>
Date:   Mon Dec 3 15:00:24 2018 -0800

    bpf: maybe warn ppl about hrds_install
    
    Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4f0a1cdbfe7c..f79a4ed2f9f7 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -208,6 +208,15 @@ HOSTCC = $(CROSS_COMPILE)gcc
 CLANG_ARCH_ARGS = -target $(ARCH)
 endif
 
+HDR_PROBE := $(shell echo "\#include <linux/types.h>\n struct list_head { int a; }; int main() { return 0; }" | \
+       gcc $(KBUILD_HOSTCFLAGS) -x c - -o /dev/null 2>/dev/null && \
+       echo okay)
+
+ifeq ($(HDR_PROBE),)
+$(warning Detected possible issues with include path.)
+$(warning Please install kernel headers locally (make headers_install))
+endif
+
 BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
 BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
 BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')