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References: <20210927145941.1383001-1-memxor@gmail.com> <20210927145941.1383001-9-memxor@gmail.com>
In-Reply-To: <20210927145941.1383001-9-memxor@gmail.com>
From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Wed, 29 Sep 2021 13:50:54 -0700
Message-ID: <CAADnVQKnoFc=_jKNH=8-HWYuEw=FP941igh5Y1OgtQjdnoFLTw@mail.gmail.com>
Subject: Re: [PATCH bpf-next v5 08/12] libbpf: Make gen_loader data aligned.
To:     Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc:     bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= <toke@redhat.com>,
        Network Development <netdev@vger.kernel.org>
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On Mon, Sep 27, 2021 at 8:00 AM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.org>
>
> Align gen_loader data to 8 byte boundary to make sure union bpf_attr,
> bpf_insns and other structs are aligned.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>  tools/lib/bpf/gen_loader.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
> index 8df718a6b142..80087b13877f 100644
> --- a/tools/lib/bpf/gen_loader.c
> +++ b/tools/lib/bpf/gen_loader.c
> @@ -5,6 +5,7 @@
>  #include <string.h>
>  #include <errno.h>
>  #include <linux/filter.h>
> +#include <sys/param.h>
>  #include "btf.h"
>  #include "bpf.h"
>  #include "libbpf.h"
> @@ -135,13 +136,17 @@ void bpf_gen__init(struct bpf_gen *gen, int log_level)
>
>  static int add_data(struct bpf_gen *gen, const void *data, __u32 size)
>  {
> +       __u32 size8 = roundup(size, 8);
> +       __u64 zero = 0;
>         void *prev;
>
> -       if (realloc_data_buf(gen, size))
> +       if (realloc_data_buf(gen, size8))
>                 return 0;
>         prev = gen->data_cur;
>         memcpy(gen->data_cur, data, size);
>         gen->data_cur += size;
> +       memcpy(gen->data_cur, &zero, size8 - size);
> +       gen->data_cur += size8 - size;

Since we both need this patch, I pushed it to bpf-next to
simplify rebasing.