[Buildroot] [RFC PATCH v1 0/2] Use host-libbpf for host-pahole.

[Buildroot] [RFC PATCH v1 0/2] Use host-libbpf for host-pahole.

[Francis Laniel]

Hi.


Following a failed build involving libbpf, Thomas Pettazzoni suggested me to
remove git submodule from host-pahole to build it the "buildroot way".

So, in this contribution, I first added host recipe to libbpf.
Then, I removed git submobule used by host-pahole to get libbpf to instead use
host-libbpf.

I was able to build and run a qemu image:
Welcome to Buildroot
buildroot login: root
# zcat /proc/config.gz | grep BTF
CONFIG_DEBUG_INFO_BTF=y
CONFIG_PAHOLE_HAS_SPLIT_BTF=y
CONFIG_DEBUG_INFO_BTF_MODULES=y

Nonetheless, I am not really happy with this contribution as I had to add a bad
tweak removing a header file installed by host-libbpf to avoid a kernel build
error:

So, I marked this contribution as RFC to get your opinions about it.

Francis Laniel (2):
  package/libbpf: build for host
  package/pahole: use commit 73383b3a39af

 linux/linux.mk             | 11 +++++++++++
 package/libbpf/libbpf.mk   |  7 +++++++
 package/pahole/pahole.hash |  2 +-
 package/pahole/pahole.mk   | 14 +++++++-------
 4 files changed, 26 insertions(+), 8 deletions(-)


Best regards and thank you in advance.
-- 
2.25.1

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[Buildroot] [RFC PATCH v1 1/2] package/libbpf: build for host

[Francis Laniel]

Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
---
 package/libbpf/libbpf.mk | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/package/libbpf/libbpf.mk b/package/libbpf/libbpf.mk
index d6914757d7..709277fac4 100644
--- a/package/libbpf/libbpf.mk
+++ b/package/libbpf/libbpf.mk
@@ -10,6 +10,7 @@ LIBBPF_LICENSE = GPL-2.0, LGPL-2.1, BSD-2-Clause
 LIBBPF_LICENSE_FILES = LICENSE LICENSE.BSD-2-Clause LICENSE.LGPL-2.1
 LIBBPF_CPE_ID_VENDOR = libbpf_project
 LIBBPF_DEPENDENCIES = host-bison host-flex host-pkgconf elfutils zlib
+HOST_LIBBPF_DEPENDENCIES = host-bison host-flex host-pkgconf host-elfutils host-zlib
 LIBBPF_INSTALL_STAGING = YES
 
 define LIBBPF_BUILD_CMDS
@@ -38,4 +39,28 @@ define LIBBPF_INSTALL_TARGET_CMDS
 		-C $(@D)/src install DESTDIR=$(TARGET_DIR)
 endef
 
+define HOST_LIBBPF_INSTALL_CMDS
+	$(HOST_MAKE_ENV) $(HOST_CONFIGURE_OPTS) $(MAKE) \
+		-C $(@D)/src install install_uapi_headers DESTDIR=$(HOST_DIR)
+
+	# We need to install_uapi_headers so we have btf.h to compile
+	# host-pahole.
+	# Nonetheless, this target adds bpf.h which generates a conflict when
+	# building the kernel:
+	# In file included from libbpf_internal.h:17:0, from strset.c:9:
+	# relo_core.h:10:6: error: nested redefinition of ‘enum bpf_core_relo_kind’
+	# enum bpf_core_relo_kind {
+	# ^~~~~~~~~~~~~~~~~~
+	# relo_core.h:10:6: error: redeclaration of ‘enum bpf_core_relo_kind’
+	# In file included from libbpf_legacy.h:13:0,
+	# 		from libbpf_internal.h:16,
+	# 		from strset.c:9:
+	# /home/francis/buildroot/output/host/include/linux/bpf.h:6497:6: note: originally defined here
+	# enum bpf_core_relo_kind {
+	# So, better to remove remove it now since we do not need it to build
+	# host-pahole.
+	rm $(HOST_DIR)/include/linux/bpf.h
+endef
+
 $(eval $(generic-package))
+$(eval $(host-generic-package))
-- 
2.25.1

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[Buildroot] [RFC PATCH v1 2/2] package/pahole: use commit 73383b3a39af

[Francis Laniel]

This modification uses buildroot host-libbpf instead of pahole libbpf git
submodule.
Also, it nows uses commit:
73383b3a39af ("libbpf: Update libbpf to the latest git HEAD")
To avoid compile errors due to use of depecrated APIs (like btf__get_nr_types).

A build pre hook was also added to Linux to avoid conflicts regarding bpf.h
which added to HOST_DIR by host-libbpf.

Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
---
 package/pahole/pahole.hash |  2 +-
 package/pahole/pahole.mk   | 14 +++++++-------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/package/pahole/pahole.hash b/package/pahole/pahole.hash
index 420db15e75..8e5560b5e7 100644
--- a/package/pahole/pahole.hash
+++ b/package/pahole/pahole.hash
@@ -1,3 +1,3 @@
 # Locally computed
-sha256  cde85af68b368f50a913be387f94f6b43612a04af6c92387b4dcabb712a668fe  pahole-v1.23-br1.tar.gz
+sha256  3531396c0568793ef8ca1a2fbb44ef2e1e81bdd55496a4487b83ba4d95df9d99  pahole-73383b3a39afe86b22e098773e47b8546c48a649.tar.gz
 sha256  ab15fd526bd8dd18a9e77ebc139656bf4d33e97fc7238cd11bf60e2b9b8666c6  COPYING
diff --git a/package/pahole/pahole.mk b/package/pahole/pahole.mk
index da6d67e6a2..199fa8cc11 100644
--- a/package/pahole/pahole.mk
+++ b/package/pahole/pahole.mk
@@ -4,14 +4,14 @@
 #
 ################################################################################
 
-PAHOLE_VERSION = v1.23
-PAHOLE_SITE = https://git.kernel.org/pub/scm/devel/pahole/pahole.git
-PAHOLE_SITE_METHOD = git
-# pahole contains git submodule and relies on them to be built.
-PAHOLE_GIT_SUBMODULES = YES
-HOST_PAHOLE_DEPENDENCIES = host-elfutils
+PAHOLE_VERSION = 73383b3a39afe86b22e098773e47b8546c48a649
+PAHOLE_SITE = https://git.kernel.org/pub/scm/devel/pahole/pahole.git/snapshot
+HOST_PAHOLE_DEPENDENCIES = \
+	host-elfutils \
+	host-libbpf
 # Defining __LIB is needed to build pahole.
-HOST_PAHOLE_CONF_OPTS = -D__LIB=lib
+# Set LIBBPF_EMBEDDED to OFF to use host-libbpf.
+HOST_PAHOLE_CONF_OPTS = -D__LIB=lib -DLIBBPF_EMBEDDED=OFF
 PAHOLE_LICENSE = GPL-2.0
 PAHOLE_LICENSE_FILES = COPYING
 
-- 
2.25.1

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Re: [Buildroot] [RFC PATCH v1 1/2] package/libbpf: build for host

[Arnout Vandecappelle]

On 22/04/2022 20:16, Francis Laniel wrote:
> Signed-off-by: Francis Laniel <flaniel@linux.microsoft.com>
> ---
>   package/libbpf/libbpf.mk | 25 +++++++++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 
> diff --git a/package/libbpf/libbpf.mk b/package/libbpf/libbpf.mk
> index d6914757d7..709277fac4 100644
> --- a/package/libbpf/libbpf.mk
> +++ b/package/libbpf/libbpf.mk
> @@ -10,6 +10,7 @@ LIBBPF_LICENSE = GPL-2.0, LGPL-2.1, BSD-2-Clause
>   LIBBPF_LICENSE_FILES = LICENSE LICENSE.BSD-2-Clause LICENSE.LGPL-2.1
>   LIBBPF_CPE_ID_VENDOR = libbpf_project
>   LIBBPF_DEPENDENCIES = host-bison host-flex host-pkgconf elfutils zlib
> +HOST_LIBBPF_DEPENDENCIES = host-bison host-flex host-pkgconf host-elfutils host-zlib
>   LIBBPF_INSTALL_STAGING = YES
>   
>   define LIBBPF_BUILD_CMDS
> @@ -38,4 +39,28 @@ define LIBBPF_INSTALL_TARGET_CMDS
>   		-C $(@D)/src install DESTDIR=$(TARGET_DIR)
>   endef
>   
> +define HOST_LIBBPF_INSTALL_CMDS
> +	$(HOST_MAKE_ENV) $(HOST_CONFIGURE_OPTS) $(MAKE) \
> +		-C $(@D)/src install install_uapi_headers DESTDIR=$(HOST_DIR)
> +
> +	# We need to install_uapi_headers so we have btf.h to compile
> +	# host-pahole.
> +	# Nonetheless, this target adds bpf.h which generates a conflict when
> +	# building the kernel:
> +	# In file included from libbpf_internal.h:17:0, from strset.c:9:
> +	# relo_core.h:10:6: error: nested redefinition of ‘enum bpf_core_relo_kind’
> +	# enum bpf_core_relo_kind {
> +	# ^~~~~~~~~~~~~~~~~~
> +	# relo_core.h:10:6: error: redeclaration of ‘enum bpf_core_relo_kind’
> +	# In file included from libbpf_legacy.h:13:0,
> +	# 		from libbpf_internal.h:16,
> +	# 		from strset.c:9:
> +	# /home/francis/buildroot/output/host/include/linux/bpf.h:6497:6: note: originally defined here
> +	# enum bpf_core_relo_kind {
> +	# So, better to remove remove it now since we do not need it to build
> +	# host-pahole.

  This entire comment shows up in the build log because make echoes commands and 
these are commands. So I moved it outside of the define.


  Applied both to master, thanks. In the second commit, I also reworded the 
commit message a bit.

  Regards,
  Arnout


> +	rm $(HOST_DIR)/include/linux/bpf.h
> +endef
> +
>   $(eval $(generic-package))
> +$(eval $(host-generic-package))
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