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From:   Song Shuai <suagrfillet@gmail.com>
Date:   Sun, 20 Nov 2022 09:12:06 +0000
Message-ID: <CAAYs2=hvw0eKDpZtxmQzqXrgvfoj+XD9qCjcAmddZLQvOEqtHQ@mail.gmail.com>
Subject: Re: [PATCH v3 0/2] riscv/ftrace: make function graph use ftrace directly
To:     Guo Ren <guoren@kernel.org>
Cc:     rostedt@goodmis.org, mhiramat@kernel.org, mark.rutland@arm.com,
        paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, linux-riscv@lists.infradead.org,
        linux-kernel@vger.kernel.org
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Guo Ren <guoren@kernel.org> =E4=BA=8E2022=E5=B9=B411=E6=9C=8820=E6=97=A5=E5=
=91=A8=E6=97=A5 04:26=E5=86=99=E9=81=93=EF=BC=9A
>
> On Sat, Nov 19, 2022 at 1:32 AM Song Shuai <suagrfillet@gmail.com> wrote:
> >
> > 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 correc=
ted.
> >
> > What inspires me is the commit 0c0593b45c9b ("x86/ftrace: Make function
> > graph use ftrace directly") that uses graph_ops::func function to insta=
ll
> > return_hooker and makes the function called against its func_hash.
> >
> > This series of patches makes function graph use ftrace directly for ris=
cv.
> >
> > If FTRACE_WITH_REGS isn't defined, ftrace_caller keeps ftrace_graph_cal=
l
> > so that it can be replaced with the calling of prepare_ftrace_return by
> > the enable/disable helper.
> >
> > As for defining FTRACE_WITH_REGS, ftrace_caller is adjusted to save the
> > necessary regs against the pt_regs layout, so it can reasonably call th=
e
> > graph_ops::func function - ftrace_graph_func. And ftrace_graph_[regs]_c=
all
> > and its enable/disable helper aren't needed.
> >
> > The tests generated by CONFIG_FTRACE_STARTUP_TEST have passed in the lo=
cal
> > qemu-system-riscv64 virt machine. The following is the log during start=
up.
> >
> > ```
> > Nov 15 03:07:13 stage4 kernel: Testing tracer function: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace ops #1:
> > Nov 15 03:07:13 stage4 kernel: (1 0 1 0 0)
> > Nov 15 03:07:13 stage4 kernel: (1 1 2 0 0)
> > Nov 15 03:07:13 stage4 kernel: (2 1 3 0 365)
> > Nov 15 03:07:13 stage4 kernel: (2 2 4 0 399)
> > Nov 15 03:07:13 stage4 kernel: (3 2 4 0 146071)
> > Nov 15 03:07:13 stage4 kernel: (3 3 5 0 146105) PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing dynamic ftrace ops #2:
> > Nov 15 03:07:13 stage4 kernel: (1 0 1 589 0)
> > Nov 15 03:07:13 stage4 kernel: (1 1 2 635 0)
> > Nov 15 03:07:13 stage4 kernel: (2 1 3 1 2)
> > Nov 15 03:07:13 stage4 kernel: (2 2 4 125 126)
> > Nov 15 03:07:13 stage4 kernel: (3 2 4 146001 146078)
> > Nov 15 03:07:13 stage4 kernel: (3 3 5 146035 146112) PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing ftrace recursion: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing ftrace recursion safe: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing ftrace regs: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing tracer nop: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing tracer irqsoff: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup:
> > Nov 15 03:07:13 stage4 kernel: sched: DL replenish lagged too much
> > Nov 15 03:07:13 stage4 kernel: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup_rt: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing tracer wakeup_dl: PASSED
> > Nov 15 03:07:13 stage4 kernel: Testing tracer function_graph: PASSED
> > ```
> >
> > Note that the changes of mcount-dyn.S conflicts with this unmerged
> > commit (riscv: entry: consolidate general regs saving/restoring).
> > https://lore.kernel.org/linux-riscv/20221103075047.1634923-15-guoren@ke=
rnel.org
> >
> > Changes since v2:
> > - line up the comments [Andrew]
> > - rename SAVE_ALL as SAVE_ABI_REGS [Guo Ren]
> > - consolidate the modifications of mcount-dyn.S into one patch [Guo Ren=
]
> > - adapt this series based on [riscv: ftrace: Fixup ftrace detour code][=
1] [Guo Ren]
> Tested-by: Guo Ren <guoren@kernel.org>
>
> https://github.com/guoren83/linux/tree/ftrace_fixup_v3
>
Thanks for your tests.

And the PREPARE_ARGS you suggested has been added in the v4 thread.
Here is the link for your convenience.
https://lore.kernel.org/linux-riscv/20221120084230.910152-1-suagrfillet@gma=
il.com/

> >
> > [1]: https://lore.kernel.org/linux-riscv/20220921034910.3142465-1-guore=
n@kernel.org/
> > v2 Link: https://lore.kernel.org/linux-riscv/20221116031305.286634-1-su=
agrfillet@gmail.com/
> >
> > Changes since v1:
> > - fix the checkpatch warnings in patch 1
> > v1 Link: https://lore.kernel.org/linux-riscv/20221115061525.112757-1-su=
agrfillet@gmail.com
> >
> > Song Shuai (2):
> >   riscv/ftrace: add ftrace_graph_func
> >   riscv/ftrace: make ftrace_caller call ftrace_graph_func
> >
> >  arch/riscv/include/asm/ftrace.h |  13 ++-
> >  arch/riscv/kernel/ftrace.c      |  30 +++----
> >  arch/riscv/kernel/mcount-dyn.S  | 143 +++++++++++++++++++++++---------
> >  3 files changed, 129 insertions(+), 57 deletions(-)
> >
> > --
> > 2.20.1
> >
>
>
> --
> Best Regards
>  Guo Ren
Thanks,
Song