From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Giuliano Procida <gprocida@google.com>
Cc: dwarves@vger.kernel.org,
"Arnaldo Carvalho de Melo" <acme@kernel.org>,
"Andrii Nakryiko" <andrii@kernel.org>,
"Alexei Starovoitov" <ast@kernel.org>,
"Matthias Männich" <maennich@google.com>,
kernel-team@android.com, "Kernel Team" <kernel-team@fb.com>,
bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH dwarves v3 5/5] btf_encoder: Align .BTF section to 8 bytes
Date: Mon, 8 Feb 2021 14:29:58 -0800 [thread overview]
Message-ID: <CAEf4Bza+mCKjva7BnChhFugjnE0mHzmfB4XErnmoZtkh6+jBpw@mail.gmail.com> (raw)
In-Reply-To: <20210205134221.2953163-6-gprocida@google.com>
On Fri, Feb 5, 2021 at 5:42 AM Giuliano Procida <gprocida@google.com> wrote:
>
> This is to avoid misaligned access to BTF type structs when
> memory-mapping ELF objects.
>
> Signed-off-by: Giuliano Procida <gprocida@google.com>
> ---
I trust you did verify that it actually works in cases where
previously .BTF was mis-aligned?
Acked-by: Andrii Nakryiko <andrii@kernel.org>
> libbtf.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/libbtf.c b/libbtf.c
> index 9f4abb3..6754a17 100644
> --- a/libbtf.c
> +++ b/libbtf.c
> @@ -744,6 +744,14 @@ static int btf_elf__write(const char *filename, struct btf *btf)
> goto out;
> }
>
> + /*
> + * We'll align .BTF to 8 bytes to cater for all architectures. It'd be
> + * nice if we could fetch this value from somewhere. The BTF
> + * specification does not discuss alignment and its trailing string
> + * table is not currently padded to any particular alignment.
> + */
> + const size_t btf_alignment = 8;
> +
> /*
> * First we check if there is already a .BTF section present.
> */
> @@ -821,6 +829,7 @@ static int btf_elf__write(const char *filename, struct btf *btf)
> elf_error("elf_getshdr(btf_scn) failed");
> goto out;
> }
> + btf_shdr.sh_addralign = btf_alignment;
> btf_shdr.sh_entsize = 0;
> btf_shdr.sh_flags = 0;
> if (dot_btf_offset)
> --
> 2.30.0.478.g8a0d178c01-goog
>
next prev parent reply other threads:[~2021-02-08 22:31 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87a83353155506cc02141e6e4108d89aa4e7d284>
2021-02-01 17:25 ` [PATCH dwarves v2 0/4] BTF ELF writing changes Giuliano Procida
2021-02-01 17:25 ` [PATCH dwarves v2 1/4] btf_encoder: Add .BTF section using libelf Giuliano Procida
2021-02-04 4:10 ` Andrii Nakryiko
2021-02-04 18:29 ` Giuliano Procida
2021-02-01 17:25 ` [PATCH dwarves v2 2/4] btf_encoder: Manually lay out updated ELF sections Giuliano Procida
2021-02-04 4:13 ` Andrii Nakryiko
2021-02-04 18:34 ` Giuliano Procida
2021-02-04 23:06 ` Andrii Nakryiko
2021-02-01 17:25 ` [PATCH dwarves v2 3/4] btf_encoder: Add .BTF as a loadable segment Giuliano Procida
2021-02-02 10:54 ` Giuliano Procida
2021-02-01 17:25 ` [PATCH dwarves v2 4/4] btf_encoder: Align .BTF section/segment to 8 bytes Giuliano Procida
2021-02-04 4:10 ` Andrii Nakryiko
2021-02-04 15:11 ` Giuliano Procida
2021-02-04 15:11 ` [PATCH] btf_encoder: Align .BTF section " Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 0/5] ELF writing changes Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 1/5] btf_encoder: Funnel ELF error reporting through a macro Giuliano Procida
2021-02-08 22:20 ` Andrii Nakryiko
2021-02-05 13:42 ` [PATCH dwarves v3 2/5] btf_encoder: Do not use both structs and pointers for the same data Giuliano Procida
2021-02-08 22:23 ` Andrii Nakryiko
2021-02-09 14:52 ` Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 3/5] btf_encoder: Traverse sections using a for-loop Giuliano Procida
2021-02-08 22:24 ` Andrii Nakryiko
2021-02-09 14:59 ` Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 4/5] btf_encoder: Add .BTF section using libelf Giuliano Procida
2021-02-08 22:29 ` Andrii Nakryiko
2021-02-09 15:04 ` Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 5/5] btf_encoder: Align .BTF section to 8 bytes Giuliano Procida
2021-02-08 22:29 ` Andrii Nakryiko [this message]
2021-02-09 15:05 ` Giuliano Procida
2021-02-17 11:07 ` [PATCH dwarves v4 0/5] ELF writing changes Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 1/5] btf_encoder: Funnel ELF error reporting through a macro Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 2/5] btf_encoder: Do not use both structs and pointers for the same data Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 3/5] btf_encoder: Traverse sections using a for-loop Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 4/5] btf_encoder: Add .BTF section using libelf Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 5/5] btf_encoder: Align .BTF section to 8 bytes Giuliano Procida
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