* [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
@ 2024-12-02 23:47 Eduard Zingerman
2024-12-03 0:23 ` Stanislav Fomichev
0 siblings, 1 reply; 6+ messages in thread
From: Eduard Zingerman @ 2024-12-02 23:47 UTC (permalink / raw)
To: bpf, ast
Cc: andrii, daniel, martin.lau, kernel-team, yonghong.song, masahiroy,
Eduard Zingerman
Commit [0] breaks samples/bpf build:
$ make M=samples/bpf
...
make -C /path/to/kernel/samples/bpf/../../tools/lib/bpf \
...
EXTRA_CFLAGS=" \
...
-fsanitize=bounds \
-I/path/to/kernel/usr/include \
...
/path/to/kernel/samples/bpf/libbpf/libbpf.a install_headers
CC /path/to/kernel/samples/bpf/libbpf/staticobjs/libbpf.o
In file included from libbpf.c:29:
/path/to/kernel/tools/include/linux/err.h:35:8: error: 'inline' can only appear on functions
35 | static inline void * __must_check ERR_PTR(long error_)
| ^
The error is caused by `objtree` variable changing definition from `.`
(dot) to an absolute path:
- The variable TPROGS_CFLAGS is constructed as follows:
...
TPROGS_CFLAGS += -I$(objtree)/usr/include
- It is passed as EXTRA_CFLAGS for libbpf compilation:
$(LIBBPF): ...
...
$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)"
- Before commit [0], the line passed to libbpf makefile was
'-I./usr/include', where '.' referred to LIBBPF_SRC due to -C flag.
The directory $(LIBBPF_SRC)/usr/include does not exist and thus
was never resolved by C compiler.
- After commit [0], the line passed to libbpf makefile became:
'<output-dir>/usr/include', this directory exists and is resolved by
C compiler.
- Both 'tools/include' and 'usr/include' define files err.h and types.h.
- libbpf expects headers like 'linux/err.h' and 'linux/types.h'
defined in 'tools/include', not 'usr/include', hence the compilation
error.
This commit removes unnecessary -I flags from libbpf compilation.
(libbpf sets up the necessary includes at lib/bpf/Makefile:63).
Changes v1 [1] -> v2:
- dropped unnecessary replacement of KBUILD_OUTPUT with $(objtree)
[0] commit 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
[1] https://lore.kernel.org/bpf/20241202212154.3174402-1-eddyz87@gmail.com/
Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
samples/bpf/Makefile | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index bcf103a4c14f..44f7e05973de 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -146,13 +146,14 @@ ifeq ($(ARCH), x86)
BPF_EXTRA_CFLAGS += -fcf-protection
endif
-TPROGS_CFLAGS += -Wall -O2
-TPROGS_CFLAGS += -Wmissing-prototypes
-TPROGS_CFLAGS += -Wstrict-prototypes
-TPROGS_CFLAGS += $(call try-run,\
+COMMON_CFLAGS += -Wall -O2
+COMMON_CFLAGS += -Wmissing-prototypes
+COMMON_CFLAGS += -Wstrict-prototypes
+COMMON_CFLAGS += $(call try-run,\
printf "int main() { return 0; }" |\
$(CC) -Werror -fsanitize=bounds -x c - -o "$$TMP",-fsanitize=bounds,)
+TPROGS_CFLAGS += $(COMMON_CFLAGS)
TPROGS_CFLAGS += -I$(objtree)/usr/include
TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
@@ -229,7 +230,7 @@ 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=$(BPF_SAMPLES_PATH)/../../ \
O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
$@ install_headers
--
2.47.0
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
2024-12-02 23:47 [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS Eduard Zingerman
@ 2024-12-03 0:23 ` Stanislav Fomichev
2024-12-03 0:52 ` Eduard Zingerman
0 siblings, 1 reply; 6+ messages in thread
From: Stanislav Fomichev @ 2024-12-03 0:23 UTC (permalink / raw)
To: Eduard Zingerman
Cc: bpf, ast, andrii, daniel, martin.lau, kernel-team, yonghong.song,
masahiroy
On 12/02, Eduard Zingerman wrote:
> Commit [0] breaks samples/bpf build:
>
> $ make M=samples/bpf
> ...
> make -C /path/to/kernel/samples/bpf/../../tools/lib/bpf \
> ...
> EXTRA_CFLAGS=" \
> ...
> -fsanitize=bounds \
> -I/path/to/kernel/usr/include \
> ...
> /path/to/kernel/samples/bpf/libbpf/libbpf.a install_headers
> CC /path/to/kernel/samples/bpf/libbpf/staticobjs/libbpf.o
> In file included from libbpf.c:29:
> /path/to/kernel/tools/include/linux/err.h:35:8: error: 'inline' can only appear on functions
> 35 | static inline void * __must_check ERR_PTR(long error_)
> | ^
>
> The error is caused by `objtree` variable changing definition from `.`
> (dot) to an absolute path:
> - The variable TPROGS_CFLAGS is constructed as follows:
> ...
> TPROGS_CFLAGS += -I$(objtree)/usr/include
> - It is passed as EXTRA_CFLAGS for libbpf compilation:
> $(LIBBPF): ...
> ...
> $(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)"
> - Before commit [0], the line passed to libbpf makefile was
> '-I./usr/include', where '.' referred to LIBBPF_SRC due to -C flag.
> The directory $(LIBBPF_SRC)/usr/include does not exist and thus
> was never resolved by C compiler.
> - After commit [0], the line passed to libbpf makefile became:
> '<output-dir>/usr/include', this directory exists and is resolved by
> C compiler.
> - Both 'tools/include' and 'usr/include' define files err.h and types.h.
> - libbpf expects headers like 'linux/err.h' and 'linux/types.h'
> defined in 'tools/include', not 'usr/include', hence the compilation
> error.
>
> This commit removes unnecessary -I flags from libbpf compilation.
> (libbpf sets up the necessary includes at lib/bpf/Makefile:63).
>
> Changes v1 [1] -> v2:
> - dropped unnecessary replacement of KBUILD_OUTPUT with $(objtree)
>
> [0] commit 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
> [1] https://lore.kernel.org/bpf/20241202212154.3174402-1-eddyz87@gmail.com/
>
> Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
>
> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
> ---
> samples/bpf/Makefile | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index bcf103a4c14f..44f7e05973de 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -146,13 +146,14 @@ ifeq ($(ARCH), x86)
> BPF_EXTRA_CFLAGS += -fcf-protection
> endif
>
> -TPROGS_CFLAGS += -Wall -O2
> -TPROGS_CFLAGS += -Wmissing-prototypes
> -TPROGS_CFLAGS += -Wstrict-prototypes
> -TPROGS_CFLAGS += $(call try-run,\
> +COMMON_CFLAGS += -Wall -O2
> +COMMON_CFLAGS += -Wmissing-prototypes
> +COMMON_CFLAGS += -Wstrict-prototypes
> +COMMON_CFLAGS += $(call try-run,\
> printf "int main() { return 0; }" |\
> $(CC) -Werror -fsanitize=bounds -x c - -o "$$TMP",-fsanitize=bounds,)
>
> +TPROGS_CFLAGS += $(COMMON_CFLAGS)
> TPROGS_CFLAGS += -I$(objtree)/usr/include
> TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
> TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
> @@ -229,7 +230,7 @@ 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="$(TPROGS_LDFLAGS)" srctree=$(BPF_SAMPLES_PATH)/../../ \
> O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
> $@ install_headers
> --
> 2.47.0
>
Naive question: why pass EXTRA_CFLAGS to libbpf at all? Can we drop it?
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
2024-12-03 0:23 ` Stanislav Fomichev
@ 2024-12-03 0:52 ` Eduard Zingerman
2024-12-03 1:44 ` Eduard Zingerman
0 siblings, 1 reply; 6+ messages in thread
From: Eduard Zingerman @ 2024-12-03 0:52 UTC (permalink / raw)
To: Stanislav Fomichev
Cc: bpf, ast, andrii, daniel, martin.lau, kernel-team, yonghong.song,
masahiroy
On Mon, 2024-12-02 at 16:23 -0800, Stanislav Fomichev wrote:
[...[
> > diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> > index bcf103a4c14f..44f7e05973de 100644
> > --- a/samples/bpf/Makefile
> > +++ b/samples/bpf/Makefile
> > @@ -146,13 +146,14 @@ ifeq ($(ARCH), x86)
> > BPF_EXTRA_CFLAGS += -fcf-protection
> > endif
> >
> > -TPROGS_CFLAGS += -Wall -O2
> > -TPROGS_CFLAGS += -Wmissing-prototypes
> > -TPROGS_CFLAGS += -Wstrict-prototypes
> > -TPROGS_CFLAGS += $(call try-run,\
> > +COMMON_CFLAGS += -Wall -O2
> > +COMMON_CFLAGS += -Wmissing-prototypes
> > +COMMON_CFLAGS += -Wstrict-prototypes
> > +COMMON_CFLAGS += $(call try-run,\
> > printf "int main() { return 0; }" |\
> > $(CC) -Werror -fsanitize=bounds -x c - -o "$$TMP",-fsanitize=bounds,)
> >
> > +TPROGS_CFLAGS += $(COMMON_CFLAGS)
> > TPROGS_CFLAGS += -I$(objtree)/usr/include
> > TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
> > TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
> > @@ -229,7 +230,7 @@ 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=$(BPF_SAMPLES_PATH)/../../ \
> > O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
> > $@ install_headers
> > --
> > 2.47.0
> >
>
> Naive question: why pass EXTRA_CFLAGS to libbpf at all? Can we drop it?
This was added by the commit [0].
As far as I understand, the idea is to pass the following flags:
ifeq ($(ARCH), arm)
# Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
# headers when arm instruction set identification is requested.
ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS))
...
TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
endif
ifeq ($(ARCH), mips)
TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
...
endif
Not sure if these are still necessary.
[0] commit d8ceae91e9f0 ("samples/bpf: Provide C/LDFLAGS to libbpf")
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
2024-12-03 0:52 ` Eduard Zingerman
@ 2024-12-03 1:44 ` Eduard Zingerman
2024-12-03 4:50 ` Eduard Zingerman
0 siblings, 1 reply; 6+ messages in thread
From: Eduard Zingerman @ 2024-12-03 1:44 UTC (permalink / raw)
To: Stanislav Fomichev
Cc: bpf, ast, andrii, daniel, martin.lau, kernel-team, yonghong.song,
masahiroy
On Mon, 2024-12-02 at 16:52 -0800, Eduard Zingerman wrote:
[...]
> > Naive question: why pass EXTRA_CFLAGS to libbpf at all? Can we drop it?
>
> This was added by the commit [0].
> As far as I understand, the idea is to pass the following flags:
>
> ifeq ($(ARCH), arm)
> # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
> # headers when arm instruction set identification is requested.
> ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS))
> ...
> TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
> endif
>
> ifeq ($(ARCH), mips)
> TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
> ...
> endif
>
> Not sure if these are still necessary.
>
> [0] commit d8ceae91e9f0 ("samples/bpf: Provide C/LDFLAGS to libbpf")
>
But this means that I should include sysroot part in the COMMON_CFLAGS.
I'll get the arm cross-compilation environment and double check.
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
2024-12-03 1:44 ` Eduard Zingerman
@ 2024-12-03 4:50 ` Eduard Zingerman
2024-12-03 5:00 ` Stanislav Fomichev
0 siblings, 1 reply; 6+ messages in thread
From: Eduard Zingerman @ 2024-12-03 4:50 UTC (permalink / raw)
To: Stanislav Fomichev
Cc: bpf, ast, andrii, daniel, martin.lau, kernel-team, yonghong.song,
masahiroy
On Mon, 2024-12-02 at 17:44 -0800, Eduard Zingerman wrote:
> On Mon, 2024-12-02 at 16:52 -0800, Eduard Zingerman wrote:
>
> [...]
>
> > > Naive question: why pass EXTRA_CFLAGS to libbpf at all? Can we drop it?
> >
> > This was added by the commit [0].
> > As far as I understand, the idea is to pass the following flags:
> >
> > ifeq ($(ARCH), arm)
> > # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
> > # headers when arm instruction set identification is requested.
> > ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS))
> > ...
> > TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
> > endif
> >
> > ifeq ($(ARCH), mips)
> > TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
> > ...
> > endif
> >
> > Not sure if these are still necessary.
> >
> > [0] commit d8ceae91e9f0 ("samples/bpf: Provide C/LDFLAGS to libbpf")
> >
>
> But this means that I should include sysroot part in the COMMON_CFLAGS.
> I'll get the arm cross-compilation environment and double check.
>
So, I tested build as follows:
- setup a debian chroot for 'testing';
- added gcc-arm-linux-gnueabihf toolchain and dependencies necessary
for kernel build (as in [0]) + clang-18 + qemu-system-arm + qemu-user-static;
- cross-compiled kernel for ARM inside that chroot:
$ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make olddefconfig
$ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make -j
- prepared an ARM sysroot (again, debian 'testing'):
$ debootstrap --arch armhf --variant=buildd testing \
/some/dir/trixie-armhf http://deb.debian.org/debian
(and installed libelf-dev inside chroot)
- compiled samples with the following command:
$ CLANG=clang-18 LLC=llc-18 OPT=opt-18 LLVM_DIS=llvm-dis-18 \
LLVM_OBJCOPY=llvm-objcopy-18 LLVM_READELF=llvm-readelf-18 \
ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- \
SYSROOT=/some/dir/trixie-armhf/ \
make M=samples/bpf
[0] https://docs.kernel.org/bpf/s390.html
The compilation finishes successfully with and without EXTRA_CFLAGS
passed to libbpf build. When EXTRA_CFLAGS are passed, I don't see any
-D__LINUX_ARM_ARCH__% flags passed to libbpf build.
Still, I'm hesitant to remove this flag, I'd prefer to post a v3
covering sysroot flag and be done with this. E.g. as below:
--- 8< ----------------------------------------------------
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index bcf103a4c14f..96a05e70ace3 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -146,13 +146,14 @@ ifeq ($(ARCH), x86)
BPF_EXTRA_CFLAGS += -fcf-protection
endif
-TPROGS_CFLAGS += -Wall -O2
-TPROGS_CFLAGS += -Wmissing-prototypes
-TPROGS_CFLAGS += -Wstrict-prototypes
-TPROGS_CFLAGS += $(call try-run,\
+COMMON_CFLAGS += -Wall -O2
+COMMON_CFLAGS += -Wmissing-prototypes
+COMMON_CFLAGS += -Wstrict-prototypes
+COMMON_CFLAGS += $(call try-run,\
printf "int main() { return 0; }" |\
$(CC) -Werror -fsanitize=bounds -x c - -o "$$TMP",-fsanitize=bounds,)
+TPROGS_CFLAGS += $(COMMON_CFLAGS)
TPROGS_CFLAGS += -I$(objtree)/usr/include
TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
@@ -162,7 +163,7 @@ TPROGS_CFLAGS += -I$(srctree)/tools/lib
TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0
ifdef SYSROOT
-TPROGS_CFLAGS += --sysroot=$(SYSROOT)
+COMMON_CFLAGS += --sysroot=$(SYSROOT)
TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
endif
@@ -229,7 +230,7 @@ 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="$(TPROGS_LDFLAGS)" srctree=$(BPF_SAMPLES_PATH)/../../ \
O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
$@ install_headers
---------------------------------------------------- >8 ---
(and maybe peek a better name for COMMON_CFLAGS).
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS
2024-12-03 4:50 ` Eduard Zingerman
@ 2024-12-03 5:00 ` Stanislav Fomichev
0 siblings, 0 replies; 6+ messages in thread
From: Stanislav Fomichev @ 2024-12-03 5:00 UTC (permalink / raw)
To: Eduard Zingerman
Cc: bpf, ast, andrii, daniel, martin.lau, kernel-team, yonghong.song,
masahiroy
On 12/02, Eduard Zingerman wrote:
> On Mon, 2024-12-02 at 17:44 -0800, Eduard Zingerman wrote:
> > On Mon, 2024-12-02 at 16:52 -0800, Eduard Zingerman wrote:
> >
> > [...]
> >
> > > > Naive question: why pass EXTRA_CFLAGS to libbpf at all? Can we drop it?
> > >
> > > This was added by the commit [0].
> > > As far as I understand, the idea is to pass the following flags:
> > >
> > > ifeq ($(ARCH), arm)
> > > # Strip all except -D__LINUX_ARM_ARCH__ option needed to handle linux
> > > # headers when arm instruction set identification is requested.
> > > ARM_ARCH_SELECTOR := $(filter -D__LINUX_ARM_ARCH__%, $(KBUILD_CFLAGS))
> > > ...
> > > TPROGS_CFLAGS += $(ARM_ARCH_SELECTOR)
> > > endif
> > >
> > > ifeq ($(ARCH), mips)
> > > TPROGS_CFLAGS += -D__SANE_USERSPACE_TYPES__
> > > ...
> > > endif
> > >
> > > Not sure if these are still necessary.
> > >
> > > [0] commit d8ceae91e9f0 ("samples/bpf: Provide C/LDFLAGS to libbpf")
> > >
> >
> > But this means that I should include sysroot part in the COMMON_CFLAGS.
> > I'll get the arm cross-compilation environment and double check.
> >
>
> So, I tested build as follows:
> - setup a debian chroot for 'testing';
> - added gcc-arm-linux-gnueabihf toolchain and dependencies necessary
> for kernel build (as in [0]) + clang-18 + qemu-system-arm + qemu-user-static;
> - cross-compiled kernel for ARM inside that chroot:
> $ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make olddefconfig
> $ ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- make -j
> - prepared an ARM sysroot (again, debian 'testing'):
> $ debootstrap --arch armhf --variant=buildd testing \
> /some/dir/trixie-armhf http://deb.debian.org/debian
> (and installed libelf-dev inside chroot)
> - compiled samples with the following command:
> $ CLANG=clang-18 LLC=llc-18 OPT=opt-18 LLVM_DIS=llvm-dis-18 \
> LLVM_OBJCOPY=llvm-objcopy-18 LLVM_READELF=llvm-readelf-18 \
> ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- \
> SYSROOT=/some/dir/trixie-armhf/ \
> make M=samples/bpf
>
> [0] https://docs.kernel.org/bpf/s390.html
>
> The compilation finishes successfully with and without EXTRA_CFLAGS
> passed to libbpf build. When EXTRA_CFLAGS are passed, I don't see any
> -D__LINUX_ARM_ARCH__% flags passed to libbpf build.
>
> Still, I'm hesitant to remove this flag, I'd prefer to post a v3
> covering sysroot flag and be done with this. E.g. as below:
>
> --- 8< ----------------------------------------------------
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index bcf103a4c14f..96a05e70ace3 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -146,13 +146,14 @@ ifeq ($(ARCH), x86)
> BPF_EXTRA_CFLAGS += -fcf-protection
> endif
>
> -TPROGS_CFLAGS += -Wall -O2
> -TPROGS_CFLAGS += -Wmissing-prototypes
> -TPROGS_CFLAGS += -Wstrict-prototypes
> -TPROGS_CFLAGS += $(call try-run,\
> +COMMON_CFLAGS += -Wall -O2
> +COMMON_CFLAGS += -Wmissing-prototypes
> +COMMON_CFLAGS += -Wstrict-prototypes
> +COMMON_CFLAGS += $(call try-run,\
> printf "int main() { return 0; }" |\
> $(CC) -Werror -fsanitize=bounds -x c - -o "$$TMP",-fsanitize=bounds,)
>
> +TPROGS_CFLAGS += $(COMMON_CFLAGS)
> TPROGS_CFLAGS += -I$(objtree)/usr/include
> TPROGS_CFLAGS += -I$(srctree)/tools/testing/selftests/bpf/
> TPROGS_CFLAGS += -I$(LIBBPF_INCLUDE)
> @@ -162,7 +163,7 @@ TPROGS_CFLAGS += -I$(srctree)/tools/lib
> TPROGS_CFLAGS += -DHAVE_ATTR_TEST=0
>
> ifdef SYSROOT
> -TPROGS_CFLAGS += --sysroot=$(SYSROOT)
> +COMMON_CFLAGS += --sysroot=$(SYSROOT)
> TPROGS_LDFLAGS := -L$(SYSROOT)/usr/lib
> endif
>
> @@ -229,7 +230,7 @@ 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="$(TPROGS_LDFLAGS)" srctree=$(BPF_SAMPLES_PATH)/../../ \
> O= OUTPUT=$(LIBBPF_OUTPUT)/ DESTDIR=$(LIBBPF_DESTDIR) prefix= \
> $@ install_headers
> ---------------------------------------------------- >8 ---
>
> (and maybe peek a better name for COMMON_CFLAGS).
>
Agreed, let's go with what you have (especially since you've tested it).
The samples are mostly deprecated / in maintenance mode anyway.
Feel free to slap:
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2024-12-03 5:00 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2024-12-02 23:47 [PATCH bpf v2] samples/bpf: remove unnecessary -I flags from libbpf EXTRA_CFLAGS Eduard Zingerman
2024-12-03 0:23 ` Stanislav Fomichev
2024-12-03 0:52 ` Eduard Zingerman
2024-12-03 1:44 ` Eduard Zingerman
2024-12-03 4:50 ` Eduard Zingerman
2024-12-03 5:00 ` Stanislav Fomichev
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