linux-kernel - Re: [PATCH RESEND v8 0/9] LoongArch: Add ftrace support

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Date:   Sat, 19 Nov 2022 12:55:07 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Qing Zhang <zhangqing@...ngson.cn>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v8 0/9] LoongArch: Add ftrace support

Hi, Qing,

I have applied this series to
https://github.com/loongson/linux/commits/loongarch-next with some
slight modifications, please test that branch to see if everything is
correct.

Huacai

On Wed, Nov 16, 2022 at 4:23 PM Qing Zhang <zhangqing@...ngson.cn> wrote:
>
> This patch series to support basic and dynamic ftrace.
>
> 1) -pg
> Use `-pg` makes stub like a child function `void _mcount(void *ra)`.
> Thus, it can be seen store RA and open stack before `call _mcount`.
> Find `open stack` at first, and then find `store RA`.
>
> 2) -fpatchable-function-entry=2
> The compiler has inserted 2 NOPs before the regular function prologue.
> T series registers are available and safe because of LoongArch psABI.
>
> At runtime, replace nop with bl to enable ftrace call and replace bl with
> nop to disable ftrace call. The bl requires us to save the original RA value,
> so here it saves RA at t0.
> details are:
>
> | Compiled   |       Disabled         |        Enabled         |
> +------------+------------------------+------------------------+
> | nop        | move     t0, ra        | move     t0, ra        |
> | nop        | nop                    | bl      ftrace_caller  |
> | func_body  | func_body              | func_body              |
>
> The RA value will be recovered by ftrace_regs_entry, and restored into RA
> before returning to the regular function prologue. When a function is not
> being traced, the move t0, ra is not harmful.
>
> performs a series of startup tests on ftrace and The test cases in selftests
> has passed on LoongArch.
>
> Changes in v2:
>  - Remove patch "LoongArch: ftrace: Add CALLER_ADDRx macros" there are other
>    better ways
>  Suggested by Steve:
>  - Add HAVE_DYNAMIC_FTRACE_WITH_ARGS support (6/10)
>  Suggested by Jinyang:
>  - Change addu16id to lu12iw and Adjust module_finalize return value (7/10)
>  - Use the "jr" pseudo-instruction where applicable (1/10)
>  - Use the "la.pcrel" instead of "la" (3/10)
>
> Changes in v3:
>  Reported by Jeff:
>  - Fix unwind state when option func_stack_trace (10/10)
>
> Changes in v4:
>  - No comments. Just resend the series.
>  - Rebased onto v6.0.0-rc4.
>
> Changes in v5:
>  - Modify the indentation of Kconfig and small changes
>
> Changes in v6:
>  Suggested by Huacai:
>  - Adjusting the patch Sequence
>  - renamed mcount-dyn.S for consistency
>
> Changes in v7:
>  - delete redefinition
>
> Changes in v8:
>  - remove useless macro judgment and modify the return location
>  - move some code to Patch-3
>
> Qing Zhang (9):
>   LoongArch/ftrace: Add basic support
>   LoongArch/ftrace: Add recordmcount support
>   LoongArch/ftrace: Add dynamic function tracer support
>   LoongArch/ftrace: Add dynamic function graph tracer support
>   LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_REGS support
>   LoongArch/ftrace: Add HAVE_DYNAMIC_FTRACE_WITH_ARGS support
>   LoongArch/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support
>   LoongArch: modules/ftrace: Initialize PLT at load time
>   LoongArch: Enable CONFIG_KALLSYMS_ALL and CONFIG_DEBUG_FS
>
>  arch/loongarch/Kconfig                     |   7 +
>  arch/loongarch/Makefile                    |   5 +
>  arch/loongarch/configs/loongson3_defconfig |   2 +
>  arch/loongarch/include/asm/ftrace.h        |  59 +++++
>  arch/loongarch/include/asm/inst.h          |  15 ++
>  arch/loongarch/include/asm/module.h        |   5 +-
>  arch/loongarch/include/asm/module.lds.h    |   1 +
>  arch/loongarch/include/asm/unwind.h        |   3 +-
>  arch/loongarch/kernel/Makefile             |  13 +
>  arch/loongarch/kernel/ftrace.c             |  74 ++++++
>  arch/loongarch/kernel/ftrace_dyn.c         | 264 +++++++++++++++++++++
>  arch/loongarch/kernel/inst.c               | 127 ++++++++++
>  arch/loongarch/kernel/mcount.S             |  94 ++++++++
>  arch/loongarch/kernel/mcount_dyn.S         | 154 ++++++++++++
>  arch/loongarch/kernel/module-sections.c    |  11 +
>  arch/loongarch/kernel/module.c             |  21 ++
>  arch/loongarch/kernel/unwind_guess.c       |   4 +-
>  arch/loongarch/kernel/unwind_prologue.c    |  46 +++-
>  scripts/recordmcount.c                     |  23 ++
>  19 files changed, 918 insertions(+), 10 deletions(-)
>  create mode 100644 arch/loongarch/include/asm/ftrace.h
>  create mode 100644 arch/loongarch/kernel/ftrace.c
>  create mode 100644 arch/loongarch/kernel/ftrace_dyn.c
>  create mode 100644 arch/loongarch/kernel/mcount.S
>  create mode 100644 arch/loongarch/kernel/mcount_dyn.S
>
> --
> 2.36.0
>
>