[PATCH] build: try to get kernel version from kernel source

[Bruce Richardson]

On Sat, Feb 26, 2022 at 10:40:45PM +0100, Ferdinand Thiessen wrote:
> When building the kernel modules, try to get the kernel
> version from the kernel sources first. This fixes the
> kernel modules installation directory if the target kernel
> version differs from the host kernel version, like for
> CI build or when packaging for linux distributions.
> 
> Signed-off-by: Ferdinand Thiessen <rpm at fthiessen.de>
> ---

On initial review I don't see any problems with the overall approach taken
by this patch, but I think others more familiar with kernel build paths
could do with reviewing it too. One small comment inline below.

/Bruce

>  kernel/linux/meson.build | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/linux/meson.build b/kernel/linux/meson.build
> index d8fb20c1c3..78f28ffb0c 100644
> --- a/kernel/linux/meson.build
> +++ b/kernel/linux/meson.build
> @@ -10,17 +10,23 @@ install = not meson.is_cross_build()
>  cross_args = []
>  
>  if not meson.is_cross_build()
> -    # native build
> -    kernel_version = run_command('uname', '-r', check: true).stdout().strip()
> +    # native target build
> +    kernel_version = run_command('uname', '-r').stdout().strip()

These two lines can be dropped from the patch, I think. The comment change
doesn't appear significant, and we definitely want to keep the "check:
true" in the run_command call to avoid meson warnings.

> +    if kernel_source_dir != ''
> +        # Try kernel release from sources first
> +        r = run_command('make', '-s', '-C', kernel_source_dir, 'kernelrelease', check: false)
> +        if r.returncode() == 0
> +            kernel_version = r.stdout().strip()
> +        endif
> +    else
> +        # use default path for native builds
> +        kernel_source_dir = '/lib/modules/' + kernel_version + '/source'
> +    endif
>      kernel_install_dir = '/lib/modules/' + kernel_version + '/extra/dpdk'
>      if kernel_build_dir == ''
>          # use default path for native builds
>          kernel_build_dir = '/lib/modules/' + kernel_version + '/build'
>      endif
> -    if kernel_source_dir == ''
> -        # use default path for native builds
> -        kernel_source_dir = '/lib/modules/' + kernel_version + '/source'
> -    endif
>  
>      # test running make in kernel directory, using "make kernelversion"
>      make_returncode = run_command('make', '-sC', kernel_build_dir,
> -- 
> 2.35.1
>