[PATCH v3 0/3] Makefile fixes for samples/{bpf,hid}

[PATCH v3 0/3] Makefile fixes for samples/{bpf,hid}

[Jinghao Jia]

Hi everyone,

Following commit 13b25489b6f8 ("kbuild: change working directory to
external module directory with M="), the Makefiles for both bpf and hid
samples are broken due to the use of the relative vmlinux path (i.e.,
./vmlinux) when generating vmlinux.h. Additionally, samples/hid experience
the same problem that was fixed for samples/bpf in commit 5a6ea7022ff4
("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS").

This patchset makes the following changes to fix these two problems:
 - The first patch applies the same fix from commit 5a6ea7022ff4
   ("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS") to
   samples/hid.
 - The second and third patch replace the relative vmlinux paths in
   samples/{bpf,hid}/Makefile with $(objtree)/vmlinux to correctly refer to
   the vmlinux in kernel output directory, following the recent working
   directory change in kbuild.

Changelog:
v2 -> v3:
 - v2: https://lore.kernel.org/all/20250123081950.173588-1-jinghao7@illinois.edu/
 - Address feedback from Andrii
  - Split the vmlinux path fixes for bpf and hid
v1 -> v2:
 - v1: https://lore.kernel.org/all/20250120023027.160448-1-jinghao7@illinois.edu/
 - Address feedback from Daniel
  - Apply vmlinux path fix to samples/hid
  - Add a second patch that fixes the include path issue in samples/hid,
    i.e., the same issue fixed fpr samples/bpf in commit 5a6ea7022ff4
    ("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS")
 - Address feedback from Masahiro and Nicolas
   - Use $(objtree) instead of $(srctree) in the path when referring to
     vmlinux, as it is an artifact of kbuild

Jinghao Jia (3):
  samples/hid: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
  samples/bpf: fix broken vmlinux path for VMLINUX_BTF
  samples/hid: fix broken vmlinux path for VMLINUX_BTF

 samples/bpf/Makefile |  2 +-
 samples/hid/Makefile | 13 +++++++------
 2 files changed, 8 insertions(+), 7 deletions(-)

-- 
2.48.1

[PATCH v3 1/3] samples/hid: remove unnecessary -I flags from libbpf EXTRA_CFLAGS

[Jinghao Jia]

Commit 5a6ea7022ff4 ("samples/bpf: Remove unnecessary -I flags from
libbpf EXTRA_CFLAGS") fixed the build error caused by redundant include
path for samples/bpf, but not samples/hid.

Apply the same fix on samples/hid as well.

Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Tested-by: Ruowen Qin <ruqin@redhat.com>
Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
---
 samples/hid/Makefile | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/samples/hid/Makefile b/samples/hid/Makefile
index 8ea59e9631a3..69159c81d045 100644
--- a/samples/hid/Makefile
+++ b/samples/hid/Makefile
@@ -40,16 +40,17 @@ BPF_EXTRA_CFLAGS += -I$(srctree)/arch/mips/include/asm/mach-generic
 endif
 endif
 
-TPROGS_CFLAGS += -Wall -O2
-TPROGS_CFLAGS += -Wmissing-prototypes
-TPROGS_CFLAGS += -Wstrict-prototypes
+COMMON_CFLAGS += -Wall -O2
+COMMON_CFLAGS += -Wmissing-prototypes
+COMMON_CFLAGS += -Wstrict-prototypes
 
+TPROGS_CFLAGS += $(COMMON_CFLAGS)
 TPROGS_CFLAGS += -I$(objtree)/usr/include
 TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
 TPROGS_CFLAGS += -I$(srctree)/tools/include
 
 ifdef SYSROOT
-TPROGS_CFLAGS += --sysroot=$(SYSROOT)
+COMMON_CFLAGS += --sysroot=$(SYSROOT)
 TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
 endif
 
@@ -112,7 +113,7 @@ clean:
 
 $(LIBBPF): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OUTPUT)
 # Fix up variables inherited from Kbuild that tools/ build system won't like
-	$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)" \
+	$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(COMMON_CFLAGS)" \
 		LDFLAGS=$(TPROGS_LDFLAGS) srctree=$(HID_SAMPLES_PATH)/../../ \
 		O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
 		$@ install_headers
-- 
2.48.1

[PATCH v3 2/3] samples/bpf: fix broken vmlinux path for VMLINUX_BTF

[Jinghao Jia]

Commit 13b25489b6f8 ("kbuild: change working directory to external
module directory with M=") changed kbuild working directory of bpf
sample programs to samples/bpf, which broke the vmlinux path for
VMLINUX_BTF, as the Makefiles assume the current work directory to be
the kernel output directory and use a relative path (i.e., ./vmlinux):

  Makefile:316: *** Cannot find a vmlinux for VMLINUX_BTF at any of "  /path/to/linux/samples/bpf/vmlinux", build the kernel or set VMLINUX_BTF like "VMLINUX_BTF=/sys/kernel/btf/vmlinux" or VMLINUX_H variable.  Stop.

Correctly refer to the kernel output directory using $(objtree).

Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Tested-by: Ruowen Qin <ruqin@redhat.com>
Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
---
 samples/bpf/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index dd9944a97b7e..5b632635e00d 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -307,7 +307,7 @@ $(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check=
 
 VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))				\
 		     $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux))	\
-		     $(abspath ./vmlinux)
+		     $(abspath $(objtree)/vmlinux)
 VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
 
 $(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
-- 
2.48.1

[PATCH v3 3/3] samples/hid: fix broken vmlinux path for VMLINUX_BTF

[Jinghao Jia]

Commit 13b25489b6f8 ("kbuild: change working directory to external
module directory with M=") changed kbuild working directory of hid-bpf
sample programs to samples/hid, which broke the vmlinux path for
VMLINUX_BTF, as the Makefiles assume the current work directory to be
the kernel output directory and use a relative path (i.e., ./vmlinux):

  Makefile:173: *** Cannot find a vmlinux for VMLINUX_BTF at any of "  /path/to/linux/samples/hid/vmlinux", build the kernel or set VMLINUX_BTF or VMLINUX_H variable.  Stop.

Correctly refer to the kernel output directory using $(objtree).

Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Tested-by: Ruowen Qin <ruqin@redhat.com>
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
---
 samples/hid/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/hid/Makefile b/samples/hid/Makefile
index 69159c81d045..db5a077c77fc 100644
--- a/samples/hid/Makefile
+++ b/samples/hid/Makefile
@@ -164,7 +164,7 @@ $(obj)/hid_surface_dial.o: $(obj)/hid_surface_dial.skel.h
 
 VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))				\
 		     $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux))	\
-		     $(abspath ./vmlinux)
+		     $(abspath $(objtree)/vmlinux)
 VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
 
 $(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
-- 
2.48.1

Re: (subset) [PATCH v3 0/3] Makefile fixes for samples/{bpf,hid}

[Benjamin Tissoires]

On Mon, 03 Feb 2025 02:55:03 -0600, Jinghao Jia wrote:
> Following commit 13b25489b6f8 ("kbuild: change working directory to
> external module directory with M="), the Makefiles for both bpf and hid
> samples are broken due to the use of the relative vmlinux path (i.e.,
> ./vmlinux) when generating vmlinux.h. Additionally, samples/hid experience
> the same problem that was fixed for samples/bpf in commit 5a6ea7022ff4
> ("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS").
> 
> [...]

Applied to hid/hid.git (for-6.14/upstream-fixes), thanks!

[1/3] samples/hid: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
      https://git.kernel.org/hid/hid/c/1739cafdb8de
[3/3] samples/hid: fix broken vmlinux path for VMLINUX_BTF
      https://git.kernel.org/hid/hid/c/8b125949df58

Cheers,
-- 
Benjamin Tissoires <bentiss@kernel.org>

Re: [PATCH v3 2/3] samples/bpf: fix broken vmlinux path for VMLINUX_BTF

[Andrii Nakryiko]

On Mon, Feb 3, 2025 at 12:55 AM Jinghao Jia <jinghao7@illinois.edu> wrote:
>
> Commit 13b25489b6f8 ("kbuild: change working directory to external
> module directory with M=") changed kbuild working directory of bpf
> sample programs to samples/bpf, which broke the vmlinux path for
> VMLINUX_BTF, as the Makefiles assume the current work directory to be
> the kernel output directory and use a relative path (i.e., ./vmlinux):
>
>   Makefile:316: *** Cannot find a vmlinux for VMLINUX_BTF at any of "  /path/to/linux/samples/bpf/vmlinux", build the kernel or set VMLINUX_BTF like "VMLINUX_BTF=/sys/kernel/btf/vmlinux" or VMLINUX_H variable.  Stop.
>
> Correctly refer to the kernel output directory using $(objtree).
>
> Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
> Tested-by: Ruowen Qin <ruqin@redhat.com>
> Signed-off-by: Jinghao Jia <jinghao7@illinois.edu>
> ---
>  samples/bpf/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

Applied this patch to bpf-next. I presume HID ones will go through the
respective tree. Thanks!

> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index dd9944a97b7e..5b632635e00d 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -307,7 +307,7 @@ $(obj)/$(TRACE_HELPERS): TPROGS_CFLAGS := $(TPROGS_CFLAGS) -D__must_check=
>
>  VMLINUX_BTF_PATHS ?= $(abspath $(if $(O),$(O)/vmlinux))                                \
>                      $(abspath $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)) \
> -                    $(abspath ./vmlinux)
> +                    $(abspath $(objtree)/vmlinux)
>  VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
>
>  $(obj)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
> --
> 2.48.1
>

Re: [PATCH v3 0/3] Makefile fixes for samples/{bpf,hid}

[patchwork-bot+netdevbpf]

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Mon,  3 Feb 2025 02:55:03 -0600 you wrote:
> Hi everyone,
> 
> Following commit 13b25489b6f8 ("kbuild: change working directory to
> external module directory with M="), the Makefiles for both bpf and hid
> samples are broken due to the use of the relative vmlinux path (i.e.,
> ./vmlinux) when generating vmlinux.h. Additionally, samples/hid experience
> the same problem that was fixed for samples/bpf in commit 5a6ea7022ff4
> ("samples/bpf: Remove unnecessary -I flags from libbpf EXTRA_CFLAGS").
> 
> [...]

Here is the summary with links:
  - [v3,1/3] samples/hid: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
    (no matching commit)
  - [v3,2/3] samples/bpf: fix broken vmlinux path for VMLINUX_BTF
    https://git.kernel.org/bpf/bpf-next/c/94f53edc64e1
  - [v3,3/3] samples/hid: fix broken vmlinux path for VMLINUX_BTF
    (no matching commit)

You are awesome, thank you!
-- 
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