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In-Reply-To: <926b0971-5c0c-2d12-5366-8a0e2aa7ae0f@yadro.com>
From:   Guo Ren <guoren@kernel.org>
Date:   Thu, 19 Jan 2023 14:05:04 +0800
Message-ID: <CAJF2gTR5QFGseLOJqBbi9mMAVE5jXyva7o3--mV2j=OkGtp5GQ@mail.gmail.com>
Subject: Re: [PATCH -next V7 6/7] samples: ftrace: Add riscv support for SAMPLE_FTRACE_DIRECT[_MULTI]
To:     Evgenii Shatokhin <e.shatokhin@yadro.com>
Cc:     Song Shuai <suagrfillet@gmail.com>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com,
        conor.dooley@microchip.com, heiko@sntech.de, rostedt@goodmis.org,
        mhiramat@kernel.org, jolsa@redhat.com, bp@suse.de,
        jpoimboe@kernel.org, andy.chiu@sifive.com, linux@yadro.com
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Thx Evgenii & Song,

I got it; it would be put into v8.

On Wed, Jan 18, 2023 at 11:19 PM Evgenii Shatokhin
<e.shatokhin@yadro.com> wrote:
>
> On 18.01.2023 05:37, Song Shuai wrote:
> > Evgenii Shatokhin <e.shatokhin@yadro.com> =E4=BA=8E2023=E5=B9=B41=E6=9C=
=8817=E6=97=A5=E5=91=A8=E4=BA=8C 16:22=E5=86=99=E9=81=93=EF=BC=9A
> >>
> >> On 17.01.2023 16:16, Evgenii Shatokhin wrote:
> >>> Hi, Song,
> >>>
> >>> On 17.01.2023 12:32, Song Shuai wrote:
> >>>>
> >>>> Hi, Evgenii:
> >>>>
> >>>> Evgenii Shatokhin <e.shatokhin@yadro.com> =E4=BA=8E2023=E5=B9=B41=E6=
=9C=8816=E6=97=A5=E5=91=A8=E4=B8=80 14:30=E5=86=99=E9=81=93=EF=BC=9A
> >>>>
> >>>>>
> >>>>> Hi,
> >>>>>
> >>>>> On 12.01.2023 12:06, guoren@kernel.org wrote:
> >>>>>> From: Song Shuai <suagrfillet@gmail.com>
> >>>>>>
> >>>>>> select HAVE_SAMPLE_FTRACE_DIRECT and HAVE_SAMPLE_FTRACE_DIRECT_MUL=
TI
> >>>>>> for ARCH_RV64I in arch/riscv/Kconfig. And add riscv asm code for
> >>>>>> the ftrace-direct*.c files in samples/ftrace/.
> >>>>>>
> >>>>>> Signed-off-by: Song Shuai <suagrfillet@gmail.com>
> >>>>>> Tested-by: Guo Ren <guoren@kernel.org>
> >>>>>> Signed-off-by: Guo Ren <guoren@kernel.org>
> >>>>>> ---
> >>>>>>     arch/riscv/Kconfig                          |  2 ++
> >>>>>>     samples/ftrace/ftrace-direct-modify.c       | 33 +++++++++++++=
+++++
> >>>>>>     samples/ftrace/ftrace-direct-multi-modify.c | 37
> >>>>>> +++++++++++++++++++++
> >>>>>>     samples/ftrace/ftrace-direct-multi.c        | 22 ++++++++++++
> >>>>>>     samples/ftrace/ftrace-direct-too.c          | 26 +++++++++++++=
++
> >>>>>>     samples/ftrace/ftrace-direct.c              | 22 ++++++++++++
> >>>>>>     6 files changed, 142 insertions(+)
> >>>>>
> >>>>> The samples were built OK now, but ftrace-direct-multi and
> >>>>> ftrace-direct-multi-modify report incorrect values of ip/pc it seem=
s.
> >>>>>
> >>>>> I ran 'insmod ftrace-direct-multi.ko', waited a little and then che=
cked
> >>>>> the messages in the trace:
> >>>>>
> >>>>> #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
> >>>>> #              | |         |   |||||     |         |
> >>>>>         migration/1-19      [001] .....  3858.532131: my_direct_fun=
c1: my
> >>>>> direct func1 ip 0
> >>>>>         migration/0-15      [000] d.s2.  3858.532136: my_direct_fun=
c1: my
> >>>>> direct func1 ip ff60000001ba9600
> >>>>>         migration/0-15      [000] d..2.  3858.532204: my_direct_fun=
c1: my
> >>>>> direct func1 ip ff60000003334d00
> >>>>>         migration/0-15      [000] .....  3858.532232: my_direct_fun=
c1: my
> >>>>> direct func1 ip 0
> >>>>>           rcu_sched-14      [001] .....  3858.532257: my_direct_fun=
c1: my
> >>>>> direct func1 ip 0
> >>>>>              insmod-415     [000] .....  3858.532270: my_direct_fun=
c1: my
> >>>>> direct func1 ip 7fffffffffffffff
> >>>>>              <idle>-0       [001] ..s1.  3858.539051: my_direct_fun=
c1: my
> >>>>> direct func1 ip ff60000001ba9600
> >>>>>              <idle>-0       [001] dns2.  3858.539124: my_direct_fun=
c1: my
> >>>>> direct func1 ip ff60000001ba9600
> >>>>>           rcu_sched-14      [001] .....  3858.539208: my_direct_fun=
c1: my
> >>>>> direct func1 ip 0
> >>>>> [...]
> >>>>>
> >>>>> If I understand it right, my_direct_func1() should print the addres=
s of
> >>>>> some location in the code, probably - at the beginning of the trace=
d
> >>>>> functions.
> >>>>>
> >>>>> The printed values (0x0, 0x7fffffffffffffff, ...) are not valid cod=
e
> >>>>> addresses.
> >>>>>
> >>>> The invalid code address is only printed by accessing the schedule()
> >>>> function's first argument whose address stores in a0 register.
> >>>> While schedule() actually has no parameter declared, so my_direct_fu=
nc
> >>>> just prints the a0 in the context of the schedule()'s caller and
> >>>> the address maybe varies depending on the caller.
> >>>>
> >>>> I can't really understand why tracing the first argument of the
> >>>> schedule() function, but it seems nonsense at this point.
> >>>
> >>> The question is, what should be passed as the argument(s) of
> >>> my_direct_func() in this particular sample module. The kernel docs an=
d
> >>> commit logs seem to contain no info on that.
> >>>
> >>> With direct functions, I suppose, the trampoline can pass anything it
> >>> wants to my_direct_func(), not just the arguments of the traced funct=
ion.
> >>>
> >>> I'd check what these sample modules do on x86 and would try to match
> >>> that behaviour on RISC-V.
> >>
> >> I have checked ftrace-direct-multi.ko and ftrace-direct-multi-modify.k=
o
> >> on 6.2-rc4 built for x86-64 - yes, ip/pc in the traced function should
> >> be passed to my_direct_func().
> >>
> >> ftrace-direct-multi.ko:
> >> #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
> >> #              | |         |   |||||     |         |
> >>             insmod-10829   [000] d.h1.  1719.518535: my_direct_func: i=
p
> >> ffffffff87332f45 // wake_up_process+0x5
> >>    rcu_tasks_kthre-11      [000] .....  1719.518696: my_direct_func: i=
p
> >> ffffffff8828d935 // schedule+0x5
> >>             insmod-10829   [000] .....  1719.518708: my_direct_func: i=
p
> >> ffffffff8828d935
> >>    systemd-journal-293     [001] .....  1719.518823: my_direct_func: i=
p
> >> ffffffff8828d935
> >>            systemd-1       [000] .....  1719.519141: my_direct_func: i=
p
> >> ffffffff8828d935
> >>             <idle>-0       [001] ..s1.  1719.521889: my_direct_func: i=
p
> >> ffffffff87332f45
> >>             <idle>-0       [000] d.s2.  1719.521901: my_direct_func: i=
p
> >> ffffffff87332f45
> >>        rcu_preempt-15      [001] .....  1719.521917: my_direct_func: i=
p
> >> ffffffff8828d935
> >> [...]
> >>
> >> The ip values are wake_up_process+0x5 and schedule+0x5, the locations
> >> where the execution of the traced functions resumes after the Ftrace
> >> trampoline has finished.
> >>
> >> The results with ftrace-direct-multi-modify.ko are similar to that.
> >>
> >> The samples look like a demonstration, that one can pass anything
> >> necessary to the handler in case of "direct" functions.
> >>
> >> I suppose, the RISC-V-specific asm code in these two sample modules
> >> could be updated to pass the saved pc value to my_direct_func() in a0.
> >
> > Yes, you're right.
> >
> > I added 'mv a0,t0' in front of `call my_direct_func` to pass the addres=
s of
> > traced function with mcount offset.
> >
> > Here is the updated patch for your reference.
> > https://github.com/sugarfillet/linux/commit/95b174fb104dd970b982ee6fa19=
879393e229318
>
> Thank you for the quick fix. This one looks good to me.
>
> ftrace-direct-multi*.ko now report the ip values corresponding to
> schedule+0x8 and wake_up_process+0x8, which is what was expected here.
>
> One more thing: please change my "Co-developed-by:" into "Tested-by:" in
> your patch, becase this is what I actually did: tested it and reported
> the results. I cannot take your credit for development of this patch ;-)
>
> Looking forward for v8 of the series.
> >
> >
> >>
> >>>
> >>>>
> >>>> As for this patch, it just impls a simple mcount (direct_caller) to
> >>>> trace kernel functions, and basically saves the necessary ABI,
> >>>> call the tracing function, and restores the ABI, just like other
> >>>> arches do.
> >>>> so It shouldn't be blamed.
> >>>>
> >>>> I started an independent patch to replace schedule with kick_process
> >>>> to make these samples more reasonable. And It has no conflict with t=
he
> >>>> current patch, so we can go on.
> >>>>
> >>>> Link:
> >>>> https://lore.kernel.org/linux-kernel/20230117091101.3669996-1-suagrf=
illet@gmail.com/T/#u
> >>>>
> >>>>> The same issue is with ftrace-direct-multi-modify.ko.
> >>>>>
> >>>>> Is anything missing here?
> >>>>>
> >>>>>>
> >>>>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> >>>>>> index 307a9f413edd..e944af44f681 100644
> >>>>>> --- a/arch/riscv/Kconfig
> >>>>>> +++ b/arch/riscv/Kconfig
> >>>>>> @@ -112,6 +112,8 @@ config RISCV
> >>>>>>            select HAVE_POSIX_CPU_TIMERS_TASK_WORK
> >>>>>>            select HAVE_REGS_AND_STACK_ACCESS_API
> >>>>>>            select HAVE_FUNCTION_ARG_ACCESS_API
> >>>>>> +       select HAVE_SAMPLE_FTRACE_DIRECT
> >>>>>> +       select HAVE_SAMPLE_FTRACE_DIRECT_MULTI
> >>>>>>            select HAVE_STACKPROTECTOR
> >>>>>>            select HAVE_SYSCALL_TRACEPOINTS
> >>>>>>            select HAVE_RSEQ
> >>>>>> diff --git a/samples/ftrace/ftrace-direct-modify.c
> >>>>>> b/samples/ftrace/ftrace-direct-modify.c
> >>>>>> index de5a0f67f320..be7bf472c3c7 100644
> >>>>>> --- a/samples/ftrace/ftrace-direct-modify.c
> >>>>>> +++ b/samples/ftrace/ftrace-direct-modify.c
> >>>>>> @@ -23,6 +23,39 @@ extern void my_tramp2(void *);
> >>>>>>
> >>>>>>     static unsigned long my_ip =3D (unsigned long)schedule;
> >>>>>>
> >>>>>> +#ifdef CONFIG_RISCV
> >>>>>> +
> >>>>>> +asm (" .pushsection    .text, \"ax\", @progbits\n"
> >>>>>> +"      .type           my_tramp1, @function\n"
> >>>>>> +"      .globl          my_tramp1\n"
> >>>>>> +"   my_tramp1:\n"
> >>>>>> +"      addi sp,sp,-16\n"
> >>>>>> +"      sd   t0,0(sp)\n"
> >>>>>> +"      sd   ra,8(sp)\n"
> >>>>>> +"      call my_direct_func1\n"
> >>>>>> +"      ld   t0,0(sp)\n"
> >>>>>> +"      ld   ra,8(sp)\n"
> >>>>>> +"      addi sp,sp,16\n"
> >>>>>> +"      jr t0\n"
> >>>>>> +"      .size           my_tramp1, .-my_tramp1\n"
> >>>>>> +
> >>>>>> +"      .type           my_tramp2, @function\n"
> >>>>>> +"      .globl          my_tramp2\n"
> >>>>>> +"   my_tramp2:\n"
> >>>>>> +"      addi sp,sp,-16\n"
> >>>>>> +"      sd   t0,0(sp)\n"
> >>>>>> +"      sd   ra,8(sp)\n"
> >>>>>> +"      call my_direct_func2\n"
> >>>>>> +"      ld   t0,0(sp)\n"
> >>>>>> +"      ld   ra,8(sp)\n"
> >>>>>> +"      addi sp,sp,16\n"
> >>>>>> +"      jr t0\n"
> >>>>>> +"      .size           my_tramp2, .-my_tramp2\n"
> >>>>>> +"      .popsection\n"
> >>>>>> +);
> >>>>>> +
> >>>>>> +#endif /* CONFIG_RISCV */
> >>>>>> +
> >>>>>>     #ifdef CONFIG_X86_64
> >>>>>>
> >>>>>>     #include <asm/ibt.h>
> >>>>>> diff --git a/samples/ftrace/ftrace-direct-multi-modify.c
> >>>>>> b/samples/ftrace/ftrace-direct-multi-modify.c
> >>>>>> index d52370cad0b6..10884bf418f7 100644
> >>>>>> --- a/samples/ftrace/ftrace-direct-multi-modify.c
> >>>>>> +++ b/samples/ftrace/ftrace-direct-multi-modify.c
> >>>>>> @@ -21,6 +21,43 @@ void my_direct_func2(unsigned long ip)
> >>>>>>     extern void my_tramp1(void *);
> >>>>>>     extern void my_tramp2(void *);
> >>>>>>
> >>>>>> +#ifdef CONFIG_RISCV
> >>>>>> +
> >>>>>> +asm (" .pushsection    .text, \"ax\", @progbits\n"
> >>>>>> +"      .type           my_tramp1, @function\n"
> >>>>>> +"      .globl          my_tramp1\n"
> >>>>>> +"   my_tramp1:\n"
> >>>>>> +"       addi sp,sp,-24\n"
> >>>>>> +"       sd   a0,0(sp)\n"
> >>>>>> +"       sd   t0,8(sp)\n"
> >>>>>> +"       sd   ra,16(sp)\n"
> >>>>>> +"       call my_direct_func1\n"
> >>>>>> +"       ld   a0,0(sp)\n"
> >>>>>> +"       ld   t0,8(sp)\n"
> >>>>>> +"       ld   ra,16(sp)\n"
> >>>>>> +"       addi sp,sp,24\n"
> >>>>>> +"      jr t0\n"
> >>>>>> +"      .size           my_tramp1, .-my_tramp1\n"
> >>>>>> +
> >>>>>> +"      .type           my_tramp2, @function\n"
> >>>>>> +"      .globl          my_tramp2\n"
> >>>>>> +"   my_tramp2:\n"
> >>>>>> +"       addi sp,sp,-24\n"
> >>>>>> +"       sd   a0,0(sp)\n"
> >>>>>> +"       sd   t0,8(sp)\n"
> >>>>>> +"       sd   ra,16(sp)\n"
> >>>>>> +"       call my_direct_func2\n"
> >>>>>> +"       ld   a0,0(sp)\n"
> >>>>>> +"       ld   t0,8(sp)\n"
> >>>>>> +"       ld   ra,16(sp)\n"
> >>>>>> +"       addi sp,sp,24\n"
> >>>>>> +"      jr t0\n"
> >>>>>> +"      .size           my_tramp2, .-my_tramp2\n"
> >>>>>> +"      .popsection\n"
> >>>>>> +);
> >>>>>> +
> >>>>>> +#endif /* CONFIG_RISCV */
> >>>>>> +
> >>>>>>     #ifdef CONFIG_X86_64
> >>>>>>
> >>>>>>     #include <asm/ibt.h>
> >>>>>> diff --git a/samples/ftrace/ftrace-direct-multi.c
> >>>>>> b/samples/ftrace/ftrace-direct-multi.c
> >>>>>> index ec1088922517..a35bf43bf6d7 100644
> >>>>>> --- a/samples/ftrace/ftrace-direct-multi.c
> >>>>>> +++ b/samples/ftrace/ftrace-direct-multi.c
> >>>>>> @@ -16,6 +16,28 @@ void my_direct_func(unsigned long ip)
> >>>>>>
> >>>>>>     extern void my_tramp(void *);
> >>>>>>
> >>>>>> +#ifdef CONFIG_RISCV
> >>>>>> +
> >>>>>> +asm ("       .pushsection    .text, \"ax\", @progbits\n"
> >>>>>> +"       .type           my_tramp, @function\n"
> >>>>>> +"       .globl          my_tramp\n"
> >>>>>> +"   my_tramp:\n"
> >>>>>> +"       addi sp,sp,-24\n"
> >>>>>> +"       sd   a0,0(sp)\n"
> >>>>>> +"       sd   t0,8(sp)\n"
> >>>>>> +"       sd   ra,16(sp)\n"
> >>>>>> +"       call my_direct_func\n"
> >>>>>> +"       ld   a0,0(sp)\n"
> >>>>>> +"       ld   t0,8(sp)\n"
> >>>>>> +"       ld   ra,16(sp)\n"
> >>>>>> +"       addi sp,sp,24\n"
> >>>>>> +"       jr t0\n"
> >>>>>> +"       .size           my_tramp, .-my_tramp\n"
> >>>>>> +"       .popsection\n"
> >>>>>> +);
> >>>>>> +
> >>>>>> +#endif /* CONFIG_RISCV */
> >>>>>> +
> >>>>>>     #ifdef CONFIG_X86_64
> >>>>>>
> >>>>>>     #include <asm/ibt.h>
> >>>>>> diff --git a/samples/ftrace/ftrace-direct-too.c
> >>>>>> b/samples/ftrace/ftrace-direct-too.c
> >>>>>> index e13fb59a2b47..3b62e33c2e6d 100644
> >>>>>> --- a/samples/ftrace/ftrace-direct-too.c
> >>>>>> +++ b/samples/ftrace/ftrace-direct-too.c
> >>>>>> @@ -18,6 +18,32 @@ void my_direct_func(struct vm_area_struct *vma,
> >>>>>>
> >>>>>>     extern void my_tramp(void *);
> >>>>>>
> >>>>>> +#ifdef CONFIG_RISCV
> >>>>>> +
> >>>>>> +asm ("       .pushsection    .text, \"ax\", @progbits\n"
> >>>>>> +"       .type           my_tramp, @function\n"
> >>>>>> +"       .globl          my_tramp\n"
> >>>>>> +"   my_tramp:\n"
> >>>>>> +"       addi sp,sp,-40\n"
> >>>>>> +"       sd   a0,0(sp)\n"
> >>>>>> +"       sd   a1,8(sp)\n"
> >>>>>> +"       sd   a2,16(sp)\n"
> >>>>>> +"       sd   t0,24(sp)\n"
> >>>>>> +"       sd   ra,32(sp)\n"
> >>>>>> +"       call my_direct_func\n"
> >>>>>> +"       ld   a0,0(sp)\n"
> >>>>>> +"       ld   a1,8(sp)\n"
> >>>>>> +"       ld   a2,16(sp)\n"
> >>>>>> +"       ld   t0,24(sp)\n"
> >>>>>> +"       ld   ra,32(sp)\n"
> >>>>>> +"       addi sp,sp,40\n"
> >>>>>> +"       jr t0\n"
> >>>>>> +"       .size           my_tramp, .-my_tramp\n"
> >>>>>> +"       .popsection\n"
> >>>>>> +);
> >>>>>> +
> >>>>>> +#endif /* CONFIG_RISCV */
> >>>>>> +
> >>>>>>     #ifdef CONFIG_X86_64
> >>>>>>
> >>>>>>     #include <asm/ibt.h>
> >>>>>> diff --git a/samples/ftrace/ftrace-direct.c
> >>>>>> b/samples/ftrace/ftrace-direct.c
> >>>>>> index 1f769d0db20f..2cfe5a7d2d70 100644
> >>>>>> --- a/samples/ftrace/ftrace-direct.c
> >>>>>> +++ b/samples/ftrace/ftrace-direct.c
> >>>>>> @@ -15,6 +15,28 @@ void my_direct_func(struct task_struct *p)
> >>>>>>
> >>>>>>     extern void my_tramp(void *);
> >>>>>>
> >>>>>> +#ifdef CONFIG_RISCV
> >>>>>> +
> >>>>>> +asm ("       .pushsection    .text, \"ax\", @progbits\n"
> >>>>>> +"       .type           my_tramp, @function\n"
> >>>>>> +"       .globl          my_tramp\n"
> >>>>>> +"   my_tramp:\n"
> >>>>>> +"       addi sp,sp,-24\n"
> >>>>>> +"       sd   a0,0(sp)\n"
> >>>>>> +"       sd   t0,8(sp)\n"
> >>>>>> +"       sd   ra,16(sp)\n"
> >>>>>> +"       call my_direct_func\n"
> >>>>>> +"       ld   a0,0(sp)\n"
> >>>>>> +"       ld   t0,8(sp)\n"
> >>>>>> +"       ld   ra,16(sp)\n"
> >>>>>> +"       addi sp,sp,24\n"
> >>>>>> +"       jr t0\n"
> >>>>>> +"       .size           my_tramp, .-my_tramp\n"
> >>>>>> +"       .popsection\n"
> >>>>>> +);
> >>>>>> +
> >>>>>> +#endif /* CONFIG_RISCV */
> >>>>>> +
> >>>>>>     #ifdef CONFIG_X86_64
> >>>>>>
> >>>>>>     #include <asm/ibt.h>
> >>>>>> --
> >>>>>> 2.36.1
> >>>>
> >>>> --
> >>>> Thanks,
> >>>> Song
> >>>>
> >>>
> >>> Regards,
> >>> Evgenii
> >>
> >>
> >
> >
> > --
> > Thanks,
> > Song
> >
>
>


--=20
Best Regards
 Guo Ren