Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230403112059.2749695-1-revest@chromium.org>
In-Reply-To: <20230403112059.2749695-1-revest@chromium.org>
From:   Florent Revest <revest@chromium.org>
Date:   Mon, 3 Apr 2023 13:25:56 +0200
Message-ID: <CABRcYm+p-_z0i7TyyA16NPY3GkR37mFxN1SKiV6RBS1pGEoa1Q@mail.gmail.com>
Subject: Re: [PATCH v4 0/4] Add ftrace direct call for arm64
To:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org
Cc:     catalin.marinas@arm.com, will@kernel.org, rostedt@goodmis.org,
        mhiramat@kernel.org, mark.rutland@arm.com, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, kpsingh@kernel.org,
        jolsa@kernel.org, xukuohai@huaweicloud.com, lihuafei1@huawei.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Mon, Apr 3, 2023 at 1:21=E2=80=AFPM Florent Revest <revest@chromium.org>=
 wrote:
>
> This series adds ftrace direct call support to arm64.
> This makes BPF tracing programs (fentry/fexit/fmod_ret/lsm) work on arm64=
.
>
> It is meant to be taken by the arm64 tree but it depends on the
> trace-direct-v6.3-rc3 tag of the linux-trace tree:
>   git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
> That tag was created by Steven Rostedt so the arm64 tree can pull the pri=
or work
> this depends on. [1]
>
> Thanks to the ftrace refactoring under that tag, an ftrace_ops backing a =
ftrace
> direct call will only ever point to *one* direct call. This means we can =
look up
> the direct called trampoline address stored in the ops from the ftrace_ca=
ller
> trampoline in the case when the destination would be out of reach of a BL
> instruction at the ftrace callsite. This fixes limitations of previous at=
tempts
> such as [2].
>
> This series has been tested on arm64 with:
> 1- CONFIG_FTRACE_SELFTEST
> 2- samples/ftrace/*.ko (cf: patch 3)
> 3- tools/testing/selftests/bpf/test_progs (cf: patch 4)
>
> Changes since v3 [3]:
> - Added "BTI C" instructions at the beginning of each ftrace direct call =
sample

Ugh, I am an idiot (let's just blame Mondays!) and didn't actually
amend this change, I'm sending the series again as a v5 and this time
with the change actually folded in... Please ignore this v4, sorry for
the noise! :|