netdev - Re: [PATCH bpf-next] scripts/bpf: Print an error when known types list needs updating

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Date:   Thu, 17 Oct 2019 17:11:55 +0000
From:   Andrii Nakryiko <andriin@...com>
To:     Jakub Sitnicki <jakub@...udflare.com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kernel-team@...udflare.com" <kernel-team@...udflare.com>
Subject: Re: [PATCH bpf-next] scripts/bpf: Print an error when known types
 list needs updating

On 10/17/19 2:44 AM, Jakub Sitnicki wrote:
> Don't generate a broken bpf_helper_defs.h header if the helper script needs
> updating because it doesn't recognize a newly added type. Instead print an
> error that explains why the build is failing and stop.
> 
> Fixes: 456a513bb5d4 ("scripts/bpf: Emit an #error directive known types list needs updating")
> Suggested-by: Andrii Nakryiko <andriin@...com>
> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
> ---
>   scripts/bpf_helpers_doc.py | 4 ++--
>   tools/lib/bpf/Makefile     | 3 ++-
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
> index 08300bc024da..7548569e8076 100755
> --- a/scripts/bpf_helpers_doc.py
> +++ b/scripts/bpf_helpers_doc.py
> @@ -488,8 +488,8 @@ class PrinterHelpers(Printer):
>               return t
>           if t in self.mapped_types:
>               return self.mapped_types[t]
> -        print("")
> -        print("#error \"Unrecognized type '%s', please add it to known types!\"" % t)
> +        print("Unrecognized type '%s', please add it to known types!" % t,
> +              file=sys.stderr)

This looks good, thanks!

>           sys.exit(1)
>   
>       seen_helpers = set()
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index 75b538577c17..26c202261c5f 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -169,7 +169,8 @@ $(BPF_IN): force elfdep bpfdep bpf_helper_defs.h
>   
>   bpf_helper_defs.h: $(srctree)/include/uapi/linux/bpf.h
>   	$(Q)$(srctree)/scripts/bpf_helpers_doc.py --header 		\
> -		--file $(srctree)/include/uapi/linux/bpf.h > bpf_helper_defs.h
> +		--file $(srctree)/include/uapi/linux/bpf.h > $@...p
> +	@mv $@...p $@

This is unnecessary. Let's add ".DELETE_ON_ERROR:" at the end Makefile 
instead to trigger this auto-deletion of failed targets automatically.

>   
>   $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
>   
>