linux-kernel - Re: [PATCH v3 0/2] riscv/ftrace: make function graph use ftrace directly

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Date:   Sun, 20 Nov 2022 12:26:28 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Song Shuai <suagrfillet@...il.com>
Cc:     rostedt@...dmis.org, mhiramat@...nel.org, mark.rutland@....com,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/2] riscv/ftrace: make function graph use ftrace directly

On Sat, Nov 19, 2022 at 1:32 AM Song Shuai <suagrfillet@...il.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_hash
> 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.
>
> This series of patches makes function graph use ftrace directly for riscv.
>
> If FTRACE_WITH_REGS isn't defined, ftrace_caller keeps ftrace_graph_call
> 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 the
> graph_ops::func function - ftrace_graph_func. And ftrace_graph_[regs]_call
> and its enable/disable helper aren't needed.
>
> The tests generated by CONFIG_FTRACE_STARTUP_TEST have passed in the local
> qemu-system-riscv64 virt machine. The following is the log during startup.
>
> ```
> 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@kernel.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@...nel.org>

https://github.com/guoren83/linux/tree/ftrace_fixup_v3

>
> [1]: https://lore.kernel.org/linux-riscv/20220921034910.3142465-1-guoren@kernel.org/
> v2 Link: https://lore.kernel.org/linux-riscv/20221116031305.286634-1-suagrfillet@gmail.com/
>
> Changes since v1:
> - fix the checkpatch warnings in patch 1
> v1 Link: https://lore.kernel.org/linux-riscv/20221115061525.112757-1-suagrfillet@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