Re: [Buildroot] [PATCH 2/3] utils/docker-run: also mount externals

[Brandon Maier via buildroot <buildroot@buildroot.org>]

Hi Arnout,

On Sat Jul 13, 2024 at 2:43 PM UTC, Arnout Vandecappelle via buildroot wrote:
> When building in docker, we may want to include BR2_EXTERNALs that are
> not in the current directory. These need to be mounted into the
> container as well.
>
> There is unfortunately no easy, generic way to find the list of
> externals, except by running `make printvars`, but we'd need to run that
> inside the container with all the command-line overrides set in order to
> be fully correct. That is pretty hopeless, so as an approximation we
> look for `.br2-external.mk` in the current directory.

I have a maybe bad idea. But Buildroot does have a feature where it will
call `make` inside of `make` to set umask and other args, the '_all'
target in '$(TOPDIR)/Makefile'. Could we support all of these features
like this?

    ifeq ($(BR2_ENABLE_DOCKER),y)
    ifeq ($(BR2_SOME_VARIABLE_SET_INSIDE_DOCKER),)
    _all:
        $(TOPDIR)/utils/docker-run umask $(REQ_UMASK) && $(MAKE) ...
    else
    _all:
        ...
    endif

Buildroot has access to the actual BR2_EXTERNAL, OUTPUT_DIR, etc. So it
would be able to call docker-run with the correct arguments. And then it
would work when calling make from $(TOPDIR), or from inside custom
scripts like `brmake`.

Thanks,
Brandon

>
> Clearly this is quite limited because it doesn't support O= or
> BR2_EXTERNAL= passed on the command line. This also means that the first
> time, it doesn't work at all, because .br2-external.mk doesn't exist
> yet. The EXTRA_MOUNTPOINTS feature can be used for that.
>
> Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
> ---
> Since this feature is not bulletproof, and EXTRA_MOUNTPOINTS already
> covers the use case, it's perhaps not necessary to include this patch.
> ---
>  utils/docker-run | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/utils/docker-run b/utils/docker-run
> index 3bb7b6a41b..76fb81b074 100755
> --- a/utils/docker-run
> +++ b/utils/docker-run
> @@ -29,6 +29,19 @@ declare -a mountpoints=(
>      "$(pwd)"
>  )
>
> +# If any externals are defined, mount them as well. We assume that the current
> +# directory is OUTPUT_DIR - ideally we'd parse O= and BR2_EXTERNAL= from the
> +# command line but that's not really feasible in practice.
> +if [ -e '.br2-external.mk' ]; then
> +    mapfile -t mountpoints_external < <(
> +        # We obviously want to quote the make syntax here
> +        # shellcheck disable=SC2016
> +        make -f .br2-external.mk -E \
> +            'default:; @:$(foreach external,$(BR2_EXTERNAL_DIRS),$(info $(external)))'
> +    )
> +    mountpoints+=("${mountpoints_external[@]}")
> +fi
> +
>  # We use the PODMAN_USERNS environment variable rather than using the
>  # --userns command line argument because Fedora system may have the
>  # podman-docker package installed, providing the "docker"
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