From: Jiri Olsa <olsajiri@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, Martin KaFai Lau <kafai@fb.com>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
"Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Subject: Re: [PATCHv2 bpf-next 3/6] bpf: Use given function address for trampoline ip arg
Date: Mon, 15 Aug 2022 12:57:39 +0200 [thread overview]
Message-ID: <YvomoyS/3Op8FAMa@krava> (raw)
In-Reply-To: <Yvodfh6OJhSIq8X9@worktop.programming.kicks-ass.net>
On Mon, Aug 15, 2022 at 12:18:38PM +0200, Peter Zijlstra wrote:
> On Thu, Aug 11, 2022 at 11:15:23AM +0200, Jiri Olsa wrote:
> > Using function address given at the generation time as the trampoline
> > ip argument. This way we get directly the function address that we
> > need, so we don't need to:
> > - read the ip from the stack
> > - subtract X86_PATCH_SIZE
> > - subtract ENDBR_INSN_SIZE if CONFIG_X86_KERNEL_IBT is enabled
> > which is not even implemented yet ;-)
>
> Can you please tell me what all this does and why?
>
arch_prepare_bpf_trampoline prepares bpf trampoline for given function
specified by 'func_addr' argument
the changed code is storing/preparing caller's 'ip' address on the
trampoline's stack so the get_func_ip helper can use it
currently the trampoline code gets the caller's ip address by reading
caller's return address from stack and subtracting X86_PATCH_SIZE from
it
the change uses 'func_addr' as caller's 'ip' address when trampoline is
generated .. this way we don't need to retrieve the return address from
stack and care about endbr instruction if IBT is enabled
jirka
next prev parent reply other threads:[~2022-08-15 10:57 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-11 9:15 [PATCHv2 bpf-next 0/6] bpf: Fixes for CONFIG_X86_KERNEL_IBT Jiri Olsa
2022-08-11 9:15 ` [PATCHv2 bpf-next 1/6] kprobes: Add new KPROBE_FLAG_ON_FUNC_ENTRY kprobe flag Jiri Olsa
2022-08-15 9:57 ` Peter Zijlstra
2022-08-15 10:10 ` Jiri Olsa
2022-08-15 12:40 ` Peter Zijlstra
2022-08-16 7:01 ` Jiri Olsa
2022-08-30 15:08 ` Jiri Olsa
2022-09-08 8:26 ` Jiri Olsa
2022-09-08 12:01 ` Masami Hiramatsu
2022-08-11 9:15 ` [PATCHv2 bpf-next 2/6] ftrace: Keep the resolved addr in kallsyms_callback Jiri Olsa
2022-08-15 10:13 ` Peter Zijlstra
2022-08-15 10:30 ` Jiri Olsa
2022-08-15 12:45 ` Peter Zijlstra
2022-08-16 7:06 ` Jiri Olsa
2022-09-08 12:35 ` Masami Hiramatsu
2022-09-08 19:41 ` Jiri Olsa
2022-08-11 9:15 ` [PATCHv2 bpf-next 3/6] bpf: Use given function address for trampoline ip arg Jiri Olsa
2022-08-15 10:18 ` Peter Zijlstra
2022-08-15 10:57 ` Jiri Olsa [this message]
2022-08-15 12:51 ` Peter Zijlstra
2022-08-17 13:40 ` Jiri Olsa
2022-08-11 9:15 ` [PATCHv2 bpf-next 4/6] bpf: Adjust kprobe_multi entry_ip for CONFIG_X86_KERNEL_IBT Jiri Olsa
2022-08-11 9:15 ` [PATCHv2 bpf-next 5/6] bpf: Return value in kprobe get_func_ip only for entry address Jiri Olsa
2022-08-11 9:15 ` [PATCHv2 bpf-next 6/6] selftests/bpf: Fix get_func_ip offset test for CONFIG_X86_KERNEL_IBT Jiri Olsa
2022-08-16 3:25 ` Andrii Nakryiko
2022-08-16 7:00 ` Jiri Olsa
2022-08-16 10:18 ` Jiri Olsa
2022-08-16 17:28 ` Andrii Nakryiko
2022-08-16 17:19 ` Andrii Nakryiko
2022-08-16 3:27 ` [PATCHv2 bpf-next 0/6] bpf: Fixes " Andrii Nakryiko
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=YvomoyS/3Op8FAMa@krava \
--to=olsajiri@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=haoluo@google.com \
--cc=john.fastabend@gmail.com \
--cc=kafai@fb.com \
--cc=kpsingh@chromium.org \
--cc=mhiramat@kernel.org \
--cc=peterz@infradead.org \
--cc=sdf@google.com \
--cc=songliubraving@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.