linux-kernel - Re: [PATCH] perf build: build BPF skeletons with fPIC

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Message-ID: <aTBopdY6tmmxbDuu@x1>
Date: Wed, 3 Dec 2025 13:43:17 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Jon Kohler <jon@...anix.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	Tomas Glozar <tglozar@...hat.com>, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] perf build: build BPF skeletons with fPIC

On Tue, Dec 02, 2025 at 08:55:26PM -0700, Jon Kohler wrote:
> Fix Makefile.perf to ensure that bpf skeletons are built with fPIC.
> 
> When building with BUILD_BPF_SKEL=1, bpf_skel's was not getting built
> with fPIC, seeing compilation failures like:
> 
> /usr/bin/ld: /builddir/.../tools/perf/util/bpf_skel/.tmp/bootstrap/main.o:
>   relocation R_X86_64_32 against `.rodata.str1.8' can not be used when
>   making a PIE object; recompile with -fPIE
> 
> Bisected down to 6.18 commit a39516805992 ("tools build: Don't assume
> libtracefs-devel is always available").
> 
> Fixes: a39516805992 ("tools build: Don't assume libtracefs-devel is always available")

How come, this patch is just:

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 9c1a69d26f5121fd..531f8fc4f7df9943 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -83,7 +83,6 @@ FEATURE_TESTS_BASIC :=                  \
         libpython                       \
         libslang                        \
         libtraceevent                   \
-        libtracefs                      \
         libcpupower                     \
         pthread-attr-setaffinity-np     \
         pthread-barrier                \
diff --git a/tools/build/feature/test-all.c b/tools/build/feature/test-all.c
index e1847db6f8e63750..2df593593b6ec15e 100644
--- a/tools/build/feature/test-all.c
+++ b/tools/build/feature/test-all.c
@@ -150,10 +150,6 @@
 # include "test-libtraceevent.c"
 #undef main

-#define main main_test_libtracefs
-# include "test-libtracefs.c"
-#undef main
-
 int main(int argc, char *argv[])
 {
        main_test_libpython();
@@ -187,7 +183,6 @@ int main(int argc, char *argv[])
        main_test_reallocarray();
        main_test_libzstd();
        main_test_libtraceevent();
-       main_test_libtracefs();

        return 0;
}


----

And your patch is touching building bpftool? Seems very unrelated :-\

- Arnaldo

> Cc: stable@...r.kernel.org
> Signed-off-by: Jon Kohler <jon@...anix.com>
> ---
>  tools/perf/Makefile.perf | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 02f87c49801f..4557c2e89e88 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -1211,7 +1211,7 @@ endif
>  
>  $(BPFTOOL): | $(SKEL_TMP_OUT)
>  	$(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
> -		OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
> +		EXTRA_CFLAGS="-fPIC" OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
>  
>  # Paths to search for a kernel to generate vmlinux.h from.
>  VMLINUX_BTF_ELF_PATHS ?= $(if $(O),$(O)/vmlinux)			\
> -- 
> 2.43.0