Re: [PATCH] perf build: fix in-tree build

[Charlie Jenkins <charlie@rivosinc.com>]

On Tue, Jan 28, 2025 at 10:31:14AM -0800, Namhyung Kim wrote:
> On Mon, Jan 27, 2025 at 02:48:49PM +0100, Luca Ceresoli wrote:
> > Hello Namhyung Kim, 
> > 
> > thanks for having a look!
> > 
> > On Sun, 26 Jan 2025 13:00:10 -0800
> > Namhyung Kim <namhyung@kernel.org> wrote:
> > 
> > > Hello,
> > > 
> > > On Fri, Jan 24, 2025 at 02:06:08PM +0100, Luca Ceresoli wrote:
> > > > Building perf in-tree is broken after commit 890a1961c812 ("perf tools:
> > > > Create source symlink in perf object dir") which added a 'source' symlink
> > > > in the output dir pointing to the source dir.  
> > > 
> > > I cannot reproduce it - both `make -C tools/perf` and `cd tools/perf; make`
> > > work well for me.  What do you mean by in-tree build exactly?  Can you
> > > please share your command line and the error messages?
> > 
> > I have narrowed down my reproducer script from the initial report to a
> > fairly minimal one, and here it is:
> > 
> > ------------------------8<------------------------
> > #!/bin/sh
> > 
> > set -eu
> > 
> > OUT_DIR=${1:-$(pwd)/tools/perf}
> > DESTDIR=/tmp/aaa
> > 
> > RET=0
> > 
> > echo "Kernel version: $(git describe)"
> > echo "OUT_DIR = ${OUT_DIR}"
> > echo "DESTDIR = ${DESTDIR}"
> > echo
> > 
> > git clean -xdfq
> > rm -fr ${DESTDIR}/
> > 
> > # Only for out of tree builds: clear the build dir
> > if ! echo ${OUT_DIR} | grep -q "tools/perf"; then
> >     rm -fr ${OUT_DIR}
> >     mkdir -p ${OUT_DIR}
> > fi
> > 
> > LINUX_MAKE_FLAGS="\
> >     -C tools/perf \
> >     O=${OUT_DIR} \
> >     DESTDIR=${DESTDIR} \
> > "
> > 
> > make ${LINUX_MAKE_FLAGS}
> > make ${LINUX_MAKE_FLAGS} install
> > 
> > echo
> >     
> > if [ -h ${OUT_DIR}/perf ]; then
> >     echo "*** ERROR: ${OUT_DIR}/perf is a symlink, should be an exectuable file: ***" >&2
> >     ls -l ${OUT_DIR}/perf
> >     RET=255
> > fi
> > 
> > if ! find ${DESTDIR}/ -name perf -not -type d | xargs file | grep 'ELF.*executable'; then
> >     echo "*** ERROR: perf executable not preseint in install dir ${DESTDIR} ***" >&2
> >     RET=255
> > fi
> > 
> > exit $RET
> > ------------------------8<------------------------
> > 
> > Just put it outside of your kernel dir (or it will be removed by the
> > 'git clean' command) and run it in your kernel source dir. E.g. right
> > now I'm doing:
> > 
> > cd <kernel dir>
> > git checkout v6.13
> > ../build-perf
> > 
> > You should see it failing as:
> > 
> > *** ERROR: /.../linux/tools/perf/perf is a symlink, should be an exectuable file: ***
> > lrwxrwxrwx 1 user user 39 Jan 27 14:10 /.../linux/tools/perf/perf -> /.../linux/tools/perf
> > *** ERROR: perf executable not preseint in install dir /tmp/aaa ***
> > 
> > Note that in the broken case the kernel build continues and returns 0,
> > but there is no perf exectuable.
> 
> Thanks for sharing this.  I've reproduced it and found it had a
> symlink to a directory rather than an executable.
> 
> > 
> > PS:
> > 
> > And after having come up with the above script, I also found that the
> > build succeeds with the following change:
> > 
> > ------------------------8<------------------------
> > @@ -24,11 +24,10 @@
> >  LINUX_MAKE_FLAGS="\
> >      -C tools/perf \
> >      O=${OUT_DIR} \
> > -    DESTDIR=${DESTDIR} \
> >  "
> >  
> >  make ${LINUX_MAKE_FLAGS}
> > -make ${LINUX_MAKE_FLAGS} install
> > +make ${LINUX_MAKE_FLAGS} DESTDIR=${DESTDIR} install
> > ------------------------8<------------------------
> > 
> > In other words:
> > 
> >  * This fails:
> >      make ${LINUX_MAKE_FLAGS} DESTDIR=${DESTDIR}
> >      make ${LINUX_MAKE_FLAGS} DESTDIR=${DESTDIR} install
> >  * This succeeds:
> >      make ${LINUX_MAKE_FLAGS}
> >      make ${LINUX_MAKE_FLAGS} DESTDIR=${DESTDIR} install
> > 
> > The only difference is the presence of 'DESTDIR' in the compile command.
> > 
> > My understanding and expectation is that DESTDIR has no effect on the
> > make process except in the 'install' target. This is clearly not
> > happening here.
> > 
> > I have not yet found an obvious reason why 'DESTDIR' is special in the
> > compilation stage, after a quick look.
> 
> Interesting, maybe some install commands were called internally.  I'll
> take a look.
> 
> Thanks,
> Namhyung
> 

I just stumbled across this as well. It is breaking Buildroot. Buildroot
has this in the Makefile that triggers this bug:

	$(TARGET_MAKE_ENV) $(MAKE1) $(PERF_MAKE_FLAGS) \
		-C $(LINUX_DIR)/tools/perf O=$(LINUX_DIR)/tools/perf/ install

Having the output equal the srcdir causes this overwritting. I sent
pretty much the same patch here [1] before double-checking that somebody
hadn't posted this fix already.

- Charlie

[1] https://lore.kernel.org/lkml/Z8Ixn3J2hw8TLdRj@ghost/