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From:   Huacai Chen <chenhuacai@kernel.org>
Date:   Tue, 15 Nov 2022 18:55:44 +0800
Message-ID: <CAAhV-H4tj-fr=QOXoSCiaYJhJjn7y-rVECnbOZrParypMAXq5Q@mail.gmail.com>
Subject: Re: [PATCH v6 5/9] LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_REGS support
To:     Qing Zhang <zhangqing@loongson.cn>
Cc:     Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org, Jinyang He <hejinyang@loongson.cn>
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On Tue, Nov 15, 2022 at 6:44 PM Qing Zhang <zhangqing@loongson.cn> wrote:
>
>
> Hi, huacai
> On 2022/11/15 =E4=B8=8B=E5=8D=885:24, Huacai Chen wrote:
> > On Tue, Nov 15, 2022 at 5:22 PM Qing Zhang <zhangqing@loongson.cn> wrot=
e:
> >>
> >> Hi, Huacai
> >>
> >> On 2022/11/15 =E4=B8=8B=E5=8D=884:41, Huacai Chen wrote:
> >>> Hi, Qing,
> >>>
> >>> Patch5 and Patch6 are small and related, maybe they can be combined
> >>> with a name "LoongArch/ftrace: Add DYNAMIC_FTRACE_WITH_{ARGS,REGS}
> >>> support"
> >> I think they should be independent due to different use scenarios.
> >  From the commit message it seems  DYNAMIC_FTRACE_WITH_ARGS depend on
> > DYNAMIC_FTRACE_WITH_REGS.
>
> DYNAMIC_FTRACE_WITH_REGS : which allows trace function saved registers,
> It means that these registers can be modified, eg: Kprobe=E3=80=81Livepat=
ch.
>
> DYNAMIC_FTRACE_WITH_ARGS: uses pt_regs as a parameter for get sp,
> which means it can be used to access registers on the stack, and
> use graph_ops::func to install return_hooker to replace the special
> hook, eg: Livepatch.
>
>  From the following Kconfig, they are reasonable as separate patches.
> config LIVEPATCH
>          bool "Kernel Live Patching"
>          depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
>
OK, then keeping them separately is reasonable.

Huacai
> Thanks
> - Qing
> >
> > Huacai
> >>
> >> Thanks,
> >> -Qing
> >>>
> >>> Huacai
> >>>
> >>> On Tue, Nov 15, 2022 at 10:55 AM Qing Zhang <zhangqing@loongson.cn> w=
rote:
> >>>>
> >>>> This patch implements DYNAMIC_FTRACE_WITH_REGS on LoongArch, which a=
llows
> >>>> a traced function's arguments (and some other registers) to be captu=
red
> >>>> into a struct pt_regs, allowing these to be inspected and modified.
> >>>>
> >>>> Co-developed-by: Jinyang He <hejinyang@loongson.cn>
> >>>> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
> >>>> Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
> >>>> ---
> >>>>    arch/loongarch/Kconfig              |  1 +
> >>>>    arch/loongarch/include/asm/ftrace.h |  3 +++
> >>>>    arch/loongarch/kernel/ftrace_dyn.c  | 17 ++++++++++++++
> >>>>    arch/loongarch/kernel/mcount-dyn.S  | 36 ++++++++++++++++++++++++=
+++--
> >>>>    4 files changed, 55 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> >>>> index 615ce62422b8..12e3e91a68ae 100644
> >>>> --- a/arch/loongarch/Kconfig
> >>>> +++ b/arch/loongarch/Kconfig
> >>>> @@ -90,6 +90,7 @@ config LOONGARCH
> >>>>           select HAVE_DEBUG_STACKOVERFLOW
> >>>>           select HAVE_DMA_CONTIGUOUS
> >>>>           select HAVE_DYNAMIC_FTRACE
> >>>> +       select HAVE_DYNAMIC_FTRACE_WITH_REGS
> >>>>           select HAVE_EBPF_JIT
> >>>>           select HAVE_EXIT_THREAD
> >>>>           select HAVE_FAST_GUP
> >>>> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/in=
clude/asm/ftrace.h
> >>>> index 76ca58767f4d..a3f974a7a5ce 100644
> >>>> --- a/arch/loongarch/include/asm/ftrace.h
> >>>> +++ b/arch/loongarch/include/asm/ftrace.h
> >>>> @@ -28,6 +28,9 @@ struct dyn_ftrace;
> >>>>    int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> >>>>    #define ftrace_init_nop ftrace_init_nop
> >>>>
> >>>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> >>>> +#define ARCH_SUPPORTS_FTRACE_OPS 1
> >>>> +#endif
> >>>>    #endif /* CONFIG_DYNAMIC_FTRACE */
> >>>>    #endif /* __ASSEMBLY__ */
> >>>>    #endif /* CONFIG_FUNCTION_TRACER */
> >>>> diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/ker=
nel/ftrace_dyn.c
> >>>> index 3fe791b6783e..ec3d951be50c 100644
> >>>> --- a/arch/loongarch/kernel/ftrace_dyn.c
> >>>> +++ b/arch/loongarch/kernel/ftrace_dyn.c
> >>>> @@ -99,6 +99,23 @@ int ftrace_make_nop(struct module *mod, struct dy=
n_ftrace *rec,
> >>>>           return ftrace_modify_code(pc, old, new, true);
> >>>>    }
> >>>>
> >>>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> >>>> +int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_ad=
dr,
> >>>> +                       unsigned long addr)
> >>>> +{
> >>>> +       unsigned long pc;
> >>>> +       long offset;
> >>>> +       u32 old, new;
> >>>> +
> >>>> +       pc =3D rec->ip + LOONGARCH_INSN_SIZE;
> >>>> +
> >>>> +       old =3D larch_insn_gen_bl(pc, old_addr);
> >>>> +       new =3D larch_insn_gen_bl(pc, addr);
> >>>> +
> >>>> +       return ftrace_modify_code(pc, old, new, true);
> >>>> +}
> >>>> +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> >>>> +
> >>>>    void arch_ftrace_update_code(int command)
> >>>>    {
> >>>>           command |=3D FTRACE_MAY_SLEEP;
> >>>> diff --git a/arch/loongarch/kernel/mcount-dyn.S b/arch/loongarch/ker=
nel/mcount-dyn.S
> >>>> index 0c12cc108e6f..02835186b463 100644
> >>>> --- a/arch/loongarch/kernel/mcount-dyn.S
> >>>> +++ b/arch/loongarch/kernel/mcount-dyn.S
> >>>> @@ -27,7 +27,7 @@
> >>>>     * follows the LoongArch psABI well.
> >>>>     */
> >>>>
> >>>> -       .macro  ftrace_regs_entry
> >>>> +       .macro  ftrace_regs_entry allregs=3D0
> >>>>           PTR_ADDI sp, sp, -PT_SIZE
> >>>>           /* Save trace function ra at PT_ERA */
> >>>>           PTR_S   ra, sp, PT_ERA
> >>>> @@ -43,16 +43,48 @@
> >>>>           PTR_S   a7, sp, PT_R11
> >>>>           PTR_S   fp, sp, PT_R22
> >>>>
> >>>> +       .if \allregs
> >>>> +       PTR_S   t0, sp, PT_R12
> >>>> +       PTR_S   t1, sp, PT_R13
> >>>> +       PTR_S   t2, sp, PT_R14
> >>>> +       PTR_S   t3, sp, PT_R15
> >>>> +       PTR_S   t4, sp, PT_R16
> >>>> +       PTR_S   t5, sp, PT_R17
> >>>> +       PTR_S   t6, sp, PT_R18
> >>>> +       PTR_S   t7, sp, PT_R19
> >>>> +       PTR_S   t8, sp, PT_R20
> >>>> +       PTR_S   s0, sp, PT_R23
> >>>> +       PTR_S   s1, sp, PT_R24
> >>>> +       PTR_S   s2, sp, PT_R25
> >>>> +       PTR_S   s3, sp, PT_R26
> >>>> +       PTR_S   s4, sp, PT_R27
> >>>> +       PTR_S   s5, sp, PT_R28
> >>>> +       PTR_S   s6, sp, PT_R29
> >>>> +       PTR_S   s7, sp, PT_R30
> >>>> +       PTR_S   s8, sp, PT_R31
> >>>> +       PTR_S   tp, sp, PT_R2
> >>>> +       /* Clear it for later use as a flag sometimes. */
> >>>> +       PTR_S   zero, sp, PT_R0
> >>>> +       PTR_S   $r21, sp, PT_R21
> >>>> +       .endif
> >>>> +
> >>>>           PTR_ADDI t8, sp, PT_SIZE
> >>>>           PTR_S   t8, sp, PT_R3
> >>>>
> >>>>           .endm
> >>>>
> >>>>    SYM_CODE_START(ftrace_caller)
> >>>> -       ftrace_regs_entry
> >>>> +       ftrace_regs_entry allregs=3D0
> >>>>           b       ftrace_common
> >>>>    SYM_CODE_END(ftrace_caller)
> >>>>
> >>>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> >>>> +SYM_CODE_START(ftrace_regs_caller)
> >>>> +       ftrace_regs_entry allregs=3D1
> >>>> +       b       ftrace_common
> >>>> +SYM_CODE_END(ftrace_regs_caller)
> >>>> +#endif
> >>>> +
> >>>>    SYM_CODE_START(ftrace_common)
> >>>>           PTR_ADDI        a0, ra, -8      /* arg0: ip */
> >>>>           move            a1, t0          /* arg1: parent_ip */
> >>>> --
> >>>> 2.36.0
> >>>>
> >>>>
> >>
> >>
>
>