netdev - RE: [PATCH bpf v1 2/3] bpf: prevent .BTF section elimination

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Message-ID: <5f68ca9c9302a_17370208f9@john-XPS-13-9370.notmuch>
Date:   Mon, 21 Sep 2020 08:45:32 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Tony Ambardar <tony.ambardar@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     Tony Ambardar <Tony.Ambardar@...il.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-arch@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>
Subject: RE: [PATCH bpf v1 2/3] bpf: prevent .BTF section elimination

Tony Ambardar wrote:
> Systems with memory or disk constraints often reduce the kernel footprint
> by configuring LD_DEAD_CODE_DATA_ELIMINATION. However, this can result in
> removal of any BTF information.
> 
> Use the KEEP() macro to preserve the BTF data as done with other important
> sections, while still allowing for smaller kernels.
> 
> Fixes: 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF")
> 
> Signed-off-by: Tony Ambardar <Tony.Ambardar@...il.com>
> ---
>  include/asm-generic/vmlinux.lds.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 5430febd34be..7636bc71c71f 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -661,7 +661,7 @@
>  #define BTF								\
>  	.BTF : AT(ADDR(.BTF) - LOAD_OFFSET) {				\
>  		__start_BTF = .;					\
> -		*(.BTF)							\
> +		KEEP(*(.BTF))						\
>  		__stop_BTF = .;						\
>  	}								\
>  	. = ALIGN(4);							\
> -- 
> 2.25.1
> 

Acked-by: John Fastabend <john.fastabend@...il.com>