From: Masahiro Yamada <masahiroy@kernel.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: nicolas@fjasle.eu, ndesaulniers@google.com, morbo@google.com,
justinstitt@google.com, keescook@chromium.org,
maskray@google.com, linux-kbuild@vger.kernel.org,
bpf@vger.kernel.org, llvm@lists.linux.dev,
patches@lists.linux.dev, stable@vger.kernel.org
Subject: Re: [PATCH v2] kbuild: Fix changing ELF file type for output of gen_btf for big endian
Date: Thu, 15 Feb 2024 06:37:31 +0900 [thread overview]
Message-ID: <CAK7LNATZAh9fa8rd6jLwdEGUBHkAs9e4hZh=WvKeNLkGs2=8Aw@mail.gmail.com> (raw)
In-Reply-To: <20240212-fix-elf-type-btf-vmlinux-bin-o-big-endian-v2-1-22c0a6352069@kernel.org>
On Tue, Feb 13, 2024 at 11:06 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> Commit 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF")
> changed the ELF type of .btf.vmlinux.bin.o to ET_REL via dd, which works
> fine for little endian platforms:
>
> 00000000 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 |.ELF............|
> -00000010 03 00 b7 00 01 00 00 00 00 00 00 80 00 80 ff ff |................|
> +00000010 01 00 b7 00 01 00 00 00 00 00 00 80 00 80 ff ff |................|
>
> However, for big endian platforms, it changes the wrong byte, resulting
> in an invalid ELF file type, which ld.lld rejects:
>
> 00000000 7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00 |.ELF............|
> -00000010 00 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................|
> +00000010 01 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................|
>
> Type: <unknown>: 103
>
> ld.lld: error: .btf.vmlinux.bin.o: unknown file type
>
> Fix this by updating the entire 16-bit e_type field rather than just a
> single byte, so that everything works correctly for all platforms and
> linkers.
>
> 00000000 7f 45 4c 46 02 02 01 00 00 00 00 00 00 00 00 00 |.ELF............|
> -00000010 00 03 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................|
> +00000010 00 01 00 16 00 00 00 01 00 00 00 00 00 10 00 00 |................|
>
> Type: REL (Relocatable file)
>
> While in the area, update the comment to mention that binutils 2.35+
> matches LLD's behavior of rejecting an ET_EXEC input, which occurred
> after the comment was added.
>
> Cc: stable@vger.kernel.org
> Fixes: 90ceddcb4950 ("bpf: Support llvm-objcopy for vmlinux BTF")
> Link: https://github.com/llvm/llvm-project/pull/75643
> Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
Applied to linux-kbuild/fixes.
Thanks.
--
Best Regards
Masahiro Yamada
prev parent reply other threads:[~2024-02-14 21:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-13 2:05 [PATCH v2] kbuild: Fix changing ELF file type for output of gen_btf for big endian Nathan Chancellor
2024-02-13 2:15 ` Masahiro Yamada
2024-02-13 2:47 ` Fangrui Song
2024-02-13 20:52 ` Nicolas Schier
2024-02-13 22:19 ` Kees Cook
2024-02-13 23:56 ` Justin Stitt
2024-02-14 21:37 ` Masahiro Yamada [this message]
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