Message-ID: <555A30C3.6000907@plumgrid.com>
Date: Mon, 18 May 2015 11:34:43 -0700
From: Alexei Starovoitov <ast@plumgrid.com>
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To: Wang Nan <wangnan0@huawei.com>, paulus@samba.org, a.p.zijlstra@chello.nl,
        mingo@redhat.com, acme@kernel.org, namhyung@kernel.org,
        jolsa@kernel.org, dsahern@gmail.com, daniel@iogearbox.net,
        brendan.d.gregg@gmail.com, masami.hiramatsu.pt@hitachi.com
CC: lizefan@huawei.com, linux-kernel@vger.kernel.org, pi3orama@163.com
Subject: Re: [RFC PATCH v3 18/37] bpf tools: Record map accessing instructions
 for each program
References: <1431860222-61636-1-git-send-email-wangnan0@huawei.com> <1431860222-61636-19-git-send-email-wangnan0@huawei.com>
In-Reply-To: <1431860222-61636-19-git-send-email-wangnan0@huawei.com>
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On 5/17/15 3:56 AM, Wang Nan wrote:
> This patch records the indics of instructions which are needed to be
> relocated. Those information are saved in 'reloc_desc' field in
> 'struct bpf_program'. In loading phase (this patch takes effect in
> opening phase), the collected instructions will be replaced by
> map loading instructions.
>
> Since we are going to close the ELF file and clear all data at the end
> of 'opening' phase, ELF information will no longer be valid in
> 'loading' phase. We have to locate the instructions before maps are
> loaded, instead of directly modifying the instruction.
>
> 'struct bpf_map_def' is introduce in this patch to let us know how many
> maps defined in the object.
>
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
...
> +/*
> + * packed attribute is unnecessary for 'bpf_map_def'.
> + */
> +struct bpf_map_def {
> +	unsigned int type;
> +	unsigned int key_size;
> +	unsigned int value_size;
> +	unsigned int max_entries;
> +};

the comment looks out of place. 'packed' is necessary somewhere else?
What were you concerned about here?

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