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From:   Song Shuai <suagrfillet@gmail.com>
Date:   Wed, 17 May 2023 11:09:52 +0000
Message-ID: <CAAYs2=gS+fX0v8n3GhQrb82nRNMnYqrEL7MSrLh-CgOZRLu2jg@mail.gmail.com>
Subject: Re: [PATCH V10 0/4] riscv: Optimize function trace
To:     palmer@dabbelt.com
Cc:     mark.rutland@arm.com, bjorn@rivosinc.com, e.shatokhin@yadro.com,
        jszhang@kernel.org, guoren@kernel.org, mhiramat@kernel.org,
        rostedt@goodmis.org, aou@eecs.berkeley.edu,
        paul.walmsley@sifive.com, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org
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Song Shuai <suagrfillet@gmail.com> =E4=BA=8E2023=E5=B9=B45=E6=9C=8816=E6=97=
=A5=E5=91=A8=E4=BA=8C 09:50=E5=86=99=E9=81=93=EF=BC=9A
>
> Song Shuai <suagrfillet@gmail.com> =E4=BA=8E2023=E5=B9=B45=E6=9C=8811=E6=
=97=A5=E5=91=A8=E5=9B=9B 09:32=E5=86=99=E9=81=93=EF=BC=9A
>
> >
> > Changes in v10:
> >
> > - add Acked-by from Bj=C3=B6rn T=C3=B6pel in patch 2 and patch 4
> > - replace `move` with `mv` in patch3
> > - prettify patch 2/4 with proper tabs
> >
> > You can directly try it with:
> >
> > https://github.com/sugarfillet/linux/tree/6.4-rc1-rv-ftrace-v10
> >
> >
> Hi, plamer:
> This series is ready for its acceptance, you can pick it up.
>
Apologize for the typo in your name, Palmer.

> > This series optimizes function trace. The first 3 independent
> > patches has been picked in the V7 version of this series, the
> > subsequent version continues the following 4 patches:
> >
> > select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY [1] (patch 1)
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > In RISC-V, -fpatchable-function-entry option is used to support
> > dynamic ftrace in this commit afc76b8b8011 ("riscv: Using
> > PATCHABLE_FUNCTION_ENTRY instead of MCOUNT"). So recordmcount
> > don't have to be called to create the __mcount_loc section before
> > the vmlinux linking.
> >
> > Here selects FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY to tell
> > Makefile not to run recordmcount.
> >
> > Make function graph use ftrace directly [2] (patch 2)
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > In RISC-V architecture, when we enable the ftrace_graph tracer on some
> > functions, the function tracings on other functions will suffer extra
> > graph tracing work. In essence, graph_ops isn't limited by its func_has=
h
> > due to the global ftrace_graph_[regs]_call label. That should be
> > corrected.
> >
> > What inspires me is the commit 0c0593b45c9b ("x86/ftrace: Make function
> > graph use ftrace directly") that uses graph_ops::func function to
> > install return_hooker and makes the function called against its
> > func_hash.
> >
> > Add WITH_DIRECT_CALLS support [3] (patch 3, 4)
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > This series adds DYNAMIC_FTRACE_WITH_DIRECT_CALLS support for RISC-V.
> > SAMPLE_FTRACE_DIRECT and SAMPLE_FTRACE_DIRECT_MULTI are also included
> > here as the samples for testing DIRECT_CALLS related interface.
> >
> > First, select the DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide
> > register_ftrace_direct[_multi] interfaces allowing user to register
> > the customed trampoline (direct_caller) as the mcount for one or
> > more target functions. And modify_ftrace_direct[_multi] are also
> > provided for modify direct_caller.
> >
> > At the same time, the samples in ./samples/ftrace/ can be built
> > as kerenl module for testing these interfaces with SAMPLE_FTRACE_DIRECT
> > and SAMPLE_FTRACE_DIRECT_MULTI selected.
> >
> > Second, to make the direct_caller and the other ftrace hooks
> > (eg. function/fgraph tracer, k[ret]probes) co-exist, a temporary
> > register
> > are nominated to store the address of direct_caller in
> > ftrace_regs_caller.
> > After the setting of the address direct_caller by direct_ops->func and
> > the RESTORE_REGS in ftrace_regs_caller, direct_caller will be jumped to
> > by the `jr` inst.
> >
> > The series's old changes related these patches
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> >
> > Changes in v9:
> > https://lore.kernel.org/linux-riscv/20230510101857.2953955-1-suagrfille=
t@gmail.com/
> >
> > 1. add Acked-by from Bj=C3=B6rn T=C3=B6pel in patch 1
> >
> > 2. rebase patch2/patch3 on Linux v6.4-rc1
> >
> >   - patch 2: to make the `SAVE_ABI_REGS` configurable, revert the
> >     modification of mcount-dyn.S from commit (45b32b946a97 "riscv:
> > entry: Consolidate general regs saving/restoring")
> >
> >   - patch 3: to pass the trace_selftest, add the implement of
> >     `ftrace_stub_direct_tramp` from commit (fee86a4ed536 "ftrace:
> > selftest: remove broken trace_direct_tramp") ; and fixup the context
> > conflict in Kconfig
> >
> > Changes in v8:
> > https://lore.kernel.org/linux-riscv/20230324033342.3177979-1-suagrfille=
t@gmail.com/
> >  - Fix incorrect address values in the 4nd patch
> >  - Rebased on v6.3-rc2
> >
> > Changes in v7:
> > https://lore.kernel.org/linux-riscv/20230112090603.1295340-1-guoren@ker=
nel.org/
> >  - Fixup RESTORE_ABI_REGS by remove PT_T0(sp) overwrite.
> >  - Add FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY [1]
> >  - Fixup kconfig with HAVE_SAMPLE_FTRACE_DIRECT &
> >    HAVE_SAMPLE_FTRACE_DIRECT_MULTI
> >
> > Changes in v6:
> > https://lore.kernel.org/linux-riscv/20230107133549.4192639-1-guoren@ker=
nel.org/
> >  - Replace 8 with MCOUNT_INSN_SIZE
> >  - Replace "REG_L a1, PT_RA(sp)" with "mv a1, ra"
> >  - Add Evgenii Shatokhin comment
> >
> > Changes in v5:
> > https://lore.kernel.org/linux-riscv/20221208091244.203407-1-guoren@kern=
el.org/
> >  - Sort Kconfig entries in alphabetical order.
> >
> > Changes in v4:
> > https://lore.kernel.org/linux-riscv/20221129033230.255947-1-guoren@kern=
el.org/
> >  - Include [3] for maintenance. [Song Shuai]
> >
> > Changes in V3:
> > https://lore.kernel.org/linux-riscv/20221123153950.2911981-1-guoren@ker=
nel.org/
> >  - Include [2] for maintenance. [Song Shuai]
> >
> > [1]: https://lore.kernel.org/linux-riscv/CAAYs2=3Dj3Eak9vU6xbAw0zPuoh00=
rh8v5C2U3fePkokZFibWs2g@mail.gmail.com/T/#t
> > [2]: https://lore.kernel.org/lkml/20221120084230.910152-1-suagrfillet@g=
mail.com/
> > [3]: https://lore.kernel.org/linux-riscv/20221123142025.1504030-1-suagr=
fillet@gmail.com/
> >
> > Song Shuai (4):
> >   riscv: select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
> >   riscv: ftrace: Add ftrace_graph_func
> >   riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support
> >   samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI]
> >
> >  arch/riscv/Kconfig                          |   4 +
> >  arch/riscv/include/asm/ftrace.h             |  19 +-
> >  arch/riscv/kernel/ftrace.c                  |  30 ++-
> >  arch/riscv/kernel/mcount-dyn.S              | 200 ++++++++++++++++----
> >  samples/ftrace/ftrace-direct-modify.c       |  34 ++++
> >  samples/ftrace/ftrace-direct-multi-modify.c |  40 ++++
> >  samples/ftrace/ftrace-direct-multi.c        |  24 +++
> >  samples/ftrace/ftrace-direct-too.c          |  27 +++
> >  samples/ftrace/ftrace-direct.c              |  23 +++
> >  9 files changed, 345 insertions(+), 56 deletions(-)
> >
> > --
> > 2.20.1
> >
>
>
> --
> Thanks,
> Song


--=20
Thanks,
Song