Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sun, 11 Apr 2021 14:27:32 -0700 (PDT)
Subject:     Re: [PATCH 0/3] Fix CONFIG_FUNCTION_TRACER with clang
In-Reply-To: <20210325223807.2423265-1-nathan@kernel.org>
CC:     Paul Walmsley <paul.walmsley@sifive.com>, aou@eecs.berkeley.edu,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        clang-built-linux@googlegroups.com, nathan@kernel.org
From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     nathan@kernel.org
Message-ID: <mhng-fbfe4121-4626-4641-b596-d027d6cfc50c@palmerdabbelt-glaptop>
Mime-Version: 1.0 (MHng)
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk

On Thu, 25 Mar 2021 15:38:04 PDT (-0700), nathan@kernel.org wrote:
> Hi all,
>
> This series fixes function tracing with clang.
>
> Patch 1 adjusts the mcount regex in scripts/recordmcount.pl to handle
> the presence of PLT relocations, which happen with clang. Without this,
> the mcount_loc section will not be created properly.
>
> Patch 2 adds a workaround for clang less than 13.0.0 in relation to the
> mcount symbol name, which was "mcount" rather than "_mcount". This was
> written as a separate patch so that it can be reverted when the minimum
> clang version is bumped to clang 13.0.0.
>
> Patch 3 avoids a build error when -fpatchable-function-entry is not
> available, which is the case with clang less than 13.0.0. This will make
> dynamic ftrace unavailable but all of the other function tracing should
> work due to the prescence of the previous patch.
>
> I am hoping this series can go in as fixes for 5.12, due to patch 3, but
> if not, they can always be backported (patches 1 and 2 are already
> marked for stable).
>
> This series has been build tested with gcc-8 through gcc-10 and clang-11
> through clang-13 with defconfig and nommu_virt_defconfig plus
> CONFIG_FTRACE=y and CONFIG_FUNCTION_TRACER=y then boot tested under
> QEMU.
>
> Cheers,
> Nathan
>
> Nathan Chancellor (3):
>   scripts/recordmcount.pl: Fix RISC-V regex for clang
>   riscv: Workaround mcount name prior to clang-13
>   riscv: Select HAVE_DYNAMIC_FTRACE when -fpatchable-function-entry is
>     available
>
>  arch/riscv/Kconfig              |  2 +-
>  arch/riscv/include/asm/ftrace.h | 14 ++++++++++++--
>  arch/riscv/kernel/mcount.S      | 10 +++++-----
>  scripts/recordmcount.pl         |  2 +-
>  4 files changed, 19 insertions(+), 9 deletions(-)

Thanks, these are on for-next.