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Date:   Wed, 30 Sep 2020 14:10:33 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>
Cc:     Sami Tolvanen <samitolvanen@google.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Will Deacon <will@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        clang-built-linux@googlegroups.com,
        kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
        x86@kernel.org
Subject: Re: [PATCH v4 00/29] Add support for Clang LTO
Message-ID: <202009301402.27A40DD1@keescook>
References: <20200929214631.3516445-1-samitolvanen@google.com>
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On Tue, Sep 29, 2020 at 02:46:02PM -0700, Sami Tolvanen wrote:
> Furthermore, patches 4-8 include Peter's patch for generating
> __mcount_loc with objtool, and build system changes to enable it on
> x86. With these patches, we no longer need to annotate functions
> that have non-call references to __fentry__ with LTO, which makes
> supporting dynamic ftrace much simpler.

Peter, can you take patches 4-8 into -tip? I think it'd make sense
to keep them together. Steven, it sounds like you're okay with the
changes (i.e. Sami showed the one concern you had was already handled)?
Getting these into v5.10 would be really really nice.

I'd really like to get the tree-spanning prerequisites nailed down
for this series. It's been difficult to coordinate given the multiple
maintainers. :)

Specifically these patches:

Peter Zijlstra (1):
  objtool: Add a pass for generating __mcount_loc

Sami Tolvanen (4):
  objtool: Don't autodetect vmlinux.o
  tracing: move function tracer options to Kconfig
  tracing: add support for objtool mcount
  x86, build: use objtool mcount

https://lore.kernel.org/lkml/20200929214631.3516445-5-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-6-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-7-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-8-samitolvanen@google.com/
https://lore.kernel.org/lkml/20200929214631.3516445-9-samitolvanen@google.com/

Thanks!

-- 
Kees Cook