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perf build: build BPF skeletons with fPIC

PATCH In review Jon Kohler 2 participants 3 messages Dec 3, 2025

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Stable branch BPF perf events
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Jon Kohler

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#0 lore raw

PATCH 1/1 perf build: build BPF skeletons with fPIC

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")
Cc [email protected]
Signed-off-by Jon Kohler <[email protected]>
---
 tools/perf/Makefile.perf | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/Makefile.perf +1 -1
index 02f87c49801f..4557c2e89e88 100644
@@ -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)			\
Signature · 1 line
2.43.0
maintainer
#1 lore raw
Quoted 5 lines · Jon Kohler

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:

Quoted 8 lines

/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:

tools/build/Makefile.feature +0 -1
index 9c1a69d26f5121fd..531f8fc4f7df9943 100644
@@ -83,7 +83,6 @@ FEATURE_TESTS_BASIC :=                  \
         libpython                       \
         libslang                        \
         libtraceevent                   \
-        libtracefs                      \
         libcpupower                     \
         pthread-attr-setaffinity-np     \
         pthread-barrier                \
tools/build/feature/test-all.c +0 -5
index e1847db6f8e63750..2df593593b6ec15e 100644
@@ -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

Quoted 21 lines
Cc [email protected]
Signed-off-by Jon Kohler <[email protected]>
---
 tools/perf/Makefile.perf | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/Makefile.perf +1 -1
index 02f87c49801f..4557c2e89e88 100644
@@ -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)			\
Signature · 1 line
2.43.0
author
#2 lore raw
Quoted 14 lines · Arnaldo Carvalho de Melo
Quoted 9 lines · Jon Kohler

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

Quoted 6 lines
Quoted 4 lines

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:

It doesn’t make sense to me, but I checked the results of the bisection by hand and, hand-to-god, reverting commit a39516805992 unbreaks our build every single time. Putting a39516805992 back breaks our build 100% of the time.

Quoted 65 lines
tools/build/Makefile.feature +0 -1
index 9c1a69d26f5121fd..531f8fc4f7df9943 100644
@@ -83,7 +83,6 @@ FEATURE_TESTS_BASIC :=                  \
        libpython                       \
        libslang                        \
        libtraceevent                   \
-        libtracefs                      \
        libcpupower                     \
        pthread-attr-setaffinity-np     \
        pthread-barrier                \
tools/build/feature/test-all.c +0 -6
index e1847db6f8e63750..2df593593b6ec15e 100644
@@ -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

Quoted 21 lines
Cc [email protected]
Signed-off-by Jon Kohler <[email protected]>

---
tools/perf/Makefile.perf | 2 +-

1 file changed, 1 insertion(+), 1 deletion(-)
tools/perf/Makefile.perf +1 -1
index 02f87c49801f..4557c2e89e88 100644
@@ -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) \
Signature · 1 line
2.43.0