[PATCH] net/tap: fix BPF build failure in cross-compilation environment

[PATCH] net/tap: fix BPF build failure in cross-compilation environment

[Ashok Kaladi]

During cross-compilation, BPF build incorrectly includes header files
from the host system instead of the target sysroot. This leads to
build failures due to incompatible headers or unavailability of header
files in the host.

Fix by using the Meson sysroot property to correctly locate and include
BPF-related headers from the cross-compilation environment.

Fixes: d8d065045c4a ("net/tap: rewrite RSS BPF program")
Cc: stephen@networkplumber.org

Signed-off-by: Ashok Kaladi <ashok.k.kaladi@intel.com>
---
 drivers/net/tap/bpf/meson.build | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/tap/bpf/meson.build b/drivers/net/tap/bpf/meson.build
index 35d7438c74..1b87d5018e 100644
--- a/drivers/net/tap/bpf/meson.build
+++ b/drivers/net/tap/bpf/meson.build
@@ -39,13 +39,14 @@ endif
 
 enable_tap_rss = true
 
-libbpf_include_dir = libbpf.get_variable(pkgconfig : 'includedir')
+# Determine sysroot if cross-compiling and the property exists in the
+# init files. Note that this environment variable will have to be passed
+# in as a property during meson setup.
+sysroot = meson.get_external_property('sysroot', '')
+libbpf_include_dir = sysroot + libbpf.get_variable(pkgconfig : 'includedir')
 
-# The include files <linux/bpf.h> and others include <asm/types.h>
-# but <asm/types.h> is not defined for multi-lib environment target.
-# Workaround by using include directoriy from the host build environment.
 machine_name = run_command('uname', '-m', check: true).stdout().strip()
-march_include_dir = '/usr/include/' + machine_name + '-linux-gnu'
+march_include_dir = sysroot + '/usr/include/' + machine_name + '-linux-gnu'
 
 clang_flags = [
         # these are flags used to build the BPF code
-- 
2.43.0

Re: [PATCH] net/tap: fix BPF build failure in cross-compilation environment

[Stephen Hemminger]

On Wed, 23 Jul 2025 07:57:02 -0500
Ashok Kaladi <ashok.k.kaladi@intel.com> wrote:

> During cross-compilation, BPF build incorrectly includes header files
> from the host system instead of the target sysroot. This leads to
> build failures due to incompatible headers or unavailability of header
> files in the host.
> 
> Fix by using the Meson sysroot property to correctly locate and include
> BPF-related headers from the cross-compilation environment.
> 
> Fixes: d8d065045c4a ("net/tap: rewrite RSS BPF program")
> Cc: stephen@networkplumber.org
> 
> Signed-off-by: Ashok Kaladi <ashok.k.kaladi@intel.com>
> ---
>  drivers/net/tap/bpf/meson.build | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/tap/bpf/meson.build b/drivers/net/tap/bpf/meson.build
> index 35d7438c74..1b87d5018e 100644
> --- a/drivers/net/tap/bpf/meson.build
> +++ b/drivers/net/tap/bpf/meson.build
> @@ -39,13 +39,14 @@ endif
>  
>  enable_tap_rss = true
>  
> -libbpf_include_dir = libbpf.get_variable(pkgconfig : 'includedir')
> +# Determine sysroot if cross-compiling and the property exists in the
> +# init files. Note that this environment variable will have to be passed
> +# in as a property during meson setup.
> +sysroot = meson.get_external_property('sysroot', '')
> +libbpf_include_dir = sysroot + libbpf.get_variable(pkgconfig : 'includedir')
>  
> -# The include files <linux/bpf.h> and others include <asm/types.h>
> -# but <asm/types.h> is not defined for multi-lib environment target.
> -# Workaround by using include directoriy from the host build environment.
>  machine_name = run_command('uname', '-m', check: true).stdout().strip()
> -march_include_dir = '/usr/include/' + machine_name + '-linux-gnu'
> +march_include_dir = sysroot + '/usr/include/' + machine_name + '-linux-gnu'

Keep the comment about why uname -m is used.