From: Daniel Borkmann <daniel@iogearbox.net>
To: Yonghong Song <yhs@fb.com>, bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
kernel-team@fb.com, Ian Rogers <irogers@google.com>
Subject: Re: [PATCH bpf] libbpf: do not use __builtin_offsetof for offsetof
Date: Tue, 11 Aug 2020 15:19:24 +0200 [thread overview]
Message-ID: <b868a00c-c1c0-3309-78bd-1a0f54e2fa7d@iogearbox.net> (raw)
In-Reply-To: <20200811030852.3396929-1-yhs@fb.com>
On 8/11/20 5:08 AM, Yonghong Song wrote:
> Commit 5fbc220862fc ("tools/libpf: Add offsetof/container_of macro
> in bpf_helpers.h") added a macro offsetof() to get the offset of a
> structure member:
> #define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER)
>
> In certain use cases, size_t type may not be available so
> Commit da7a35062bcc ("libbpf bpf_helpers: Use __builtin_offsetof
> for offsetof") changed to use __builtin_offsetof which removed
> the dependency on type size_t, which I suggested.
>
> But using __builtin_offsetof will prevent CO-RE relocation
> generation in case that, e.g., TYPE is annotated with "preserve_access_info"
> where a relocation is desirable in case the member offset is changed
> in a different kernel version. So this patch reverted back to
> the original macro but using "unsigned long" instead of "site_t".
>
> Cc: Ian Rogers <irogers@google.com>
> Fixes: da7a35062bcc ("libbpf bpf_helpers: Use __builtin_offsetof for offsetof")
> Signed-off-by: Yonghong Song <yhs@fb.com>
Applied, thanks!
prev parent reply other threads:[~2020-08-11 13:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-11 3:08 [PATCH bpf] libbpf: do not use __builtin_offsetof for offsetof Yonghong Song
2020-08-11 4:32 ` Andrii Nakryiko
2020-08-11 4:34 ` Ian Rogers
2020-08-11 13:19 ` Daniel Borkmann [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=b868a00c-c1c0-3309-78bd-1a0f54e2fa7d@iogearbox.net \
--to=daniel@iogearbox.net \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=irogers@google.com \
--cc=kernel-team@fb.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.