Re: [PATCH 0/3] Fix CONFIG_FUNCTION_TRACER with clang
From: Sedat Dilek
Date: Fri Mar 26 2021 - 04:39:32 EST
On Thu, Mar 25, 2021 at 11:38 PM Nathan Chancellor <nathan@xxxxxxxxxx> 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
>
Does this only fixes stuff for clang + riscv?
If so, please put a label "riscv" also in the cover-letter.
- Sedat -
> 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(-)
>
> --
> 2.31.0
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210325223807.2423265-1-nathan%40kernel.org.