From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Jiri Kosina <jikos@kernel.org>,
Joe Lawrence <joe.lawrence@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Miroslav Benes <mbenes@suse.cz>, Ingo Molnar <mingo@redhat.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
"live-patching@vger.kernel.org" <live-patching@vger.kernel.org>
Subject: Re: [PATCH v2 09/13] powerpc/ftrace: Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS
Date: Tue, 15 Feb 2022 15:51:58 +0100 [thread overview]
Message-ID: <5c7b5334-6071-f131-a509-9a49ca3d628c@csgroup.eu> (raw)
In-Reply-To: <6dc50f09-4d14-afa2-d2a1-34b72b880edf@csgroup.eu>
+ S390 people
Le 15/02/2022 à 15:28, Christophe Leroy a écrit :
>
>
> Le 15/02/2022 à 14:36, Naveen N. Rao a écrit :
>> Michael Ellerman wrote:
>>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>>>> Le 14/02/2022 à 16:25, Naveen N. Rao a écrit :
>>>>> Christophe Leroy wrote:
>>>>>> Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS. It accelerates the call
>>>>>> of livepatching.
>>>>>>
>>>>>> Also note that powerpc being the last one to convert to
>>>>>> CONFIG_DYNAMIC_FTRACE_WITH_ARGS, it will now be possible to remove
>>>>>> klp_arch_set_pc() on all architectures.
>>>>>>
>>>>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>>>>> ---
>>>>>> arch/powerpc/Kconfig | 1 +
>>>>>> arch/powerpc/include/asm/ftrace.h | 17 +++++++++++++++++
>>>>>> arch/powerpc/include/asm/livepatch.h | 4 +---
>>>>>> 3 files changed, 19 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>>>>> index cdac2115eb00..e2b1792b2aae 100644
>>>>>> --- a/arch/powerpc/Kconfig
>>>>>> +++ b/arch/powerpc/Kconfig
>>>>>> @@ -210,6 +210,7 @@ config PPC
>>>>>> select HAVE_DEBUG_KMEMLEAK
>>>>>> select HAVE_DEBUG_STACKOVERFLOW
>>>>>> select HAVE_DYNAMIC_FTRACE
>>>>>> + select HAVE_DYNAMIC_FTRACE_WITH_ARGS if MPROFILE_KERNEL ||
>>>>>> PPC32
>>>>>> select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL ||
>>>>>> PPC32
>>>>>> select HAVE_EBPF_JIT
>>>>>> select HAVE_EFFICIENT_UNALIGNED_ACCESS if
>>>>>> !(CPU_LITTLE_ENDIAN && POWER7_CPU)
>>>>>> diff --git a/arch/powerpc/include/asm/ftrace.h
>>>>>> b/arch/powerpc/include/asm/ftrace.h
>>>>>> index b3f6184f77ea..45c3d6f11daa 100644
>>>>>> --- a/arch/powerpc/include/asm/ftrace.h
>>>>>> +++ b/arch/powerpc/include/asm/ftrace.h
>>>>>> @@ -22,6 +22,23 @@ static inline unsigned long
>>>>>> ftrace_call_adjust(unsigned long addr)
>>>>>> struct dyn_arch_ftrace {
>>>>>> struct module *mod;
>>>>>> };
>>>>>> +
>>>>>> +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
>>>>>> +struct ftrace_regs {
>>>>>> + struct pt_regs regs;
>>>>>> +};
>>>>>> +
>>>>>> +static __always_inline struct pt_regs
>>>>>> *arch_ftrace_get_regs(struct ftrace_regs *fregs)
>>>>>> +{
>>>>>> + return &fregs->regs;
>>>>>> +}
>>>>>
>>>>> I think this is wrong. We need to differentiate between
>>>>> ftrace_caller() and ftrace_regs_caller() here, and only return
>>>>> pt_regs if coming in through ftrace_regs_caller() (i.e.,
>>>>> FL_SAVE_REGS is set).
>>>>
>>>> Not sure I follow you.
>>>>
>>>> This is based on 5740a7c71ab6 ("s390/ftrace: add
>>>> HAVE_DYNAMIC_FTRACE_WITH_ARGS support")
>>>>
>>>> It's all the point of HAVE_DYNAMIC_FTRACE_WITH_ARGS, have the regs
>>>> also with ftrace_caller().
>>>>
>>>> Sure you only have the params, but that's the same on s390, so what
>>>> did I miss ?
>>
>> It looks like s390 is special since it apparently saves all registers
>> even for ftrace_caller:
>> https://lore.kernel.org/all/YbipdU5X4HNDWIni@osiris/
>
> It is not what I understand from their code, see
> https://elixir.bootlin.com/linux/v5.17-rc3/source/arch/s390/kernel/mcount.S#L37
>
>
> They have a common macro called with argument 'allregs' which is set to
> 0 for ftrace_caller() and 1 for ftrace_regs_caller().
> When allregs == 1, the macro seems to save more.
>
> But ok, I can do like x86, but I need a trick to know whether
> FL_SAVE_REGS is set or not, like they do with fregs->regs.cs
> Any idea what the condition can be for powerpc ?
>
Finally, it looks like this change is done via commit 894979689d3a
("s390/ftrace: provide separate ftrace_caller/ftrace_regs_caller
implementations") four hours the same day after the implementation of
arch_ftrace_get_regs()
They may have forgotten to change arch_ftrace_get_regs() which was added
in commit 5740a7c71ab6 ("s390/ftrace: add HAVE_DYNAMIC_FTRACE_WITH_ARGS
support") with the assumption that ftrace_caller and ftrace_regs_caller
where identical.
Christophe
next prev parent reply other threads:[~2022-02-15 15:20 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 16:37 [PATCH v2 00/13] Implement livepatch on PPC32 and more Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 01/13] livepatch: Fix build failure on 32 bits processors Christophe Leroy
2021-12-22 13:47 ` Miroslav Benes
2022-01-04 19:35 ` Joe Lawrence
2021-12-20 16:38 ` [PATCH v2 02/13] tracing: Fix selftest config check for function graph start up test Christophe Leroy
2022-02-24 13:43 ` Christophe Leroy
2022-02-24 14:53 ` Steven Rostedt
2022-02-24 15:13 ` Christophe Leroy
2022-02-24 15:17 ` Steven Rostedt
2022-02-25 2:42 ` Michael Ellerman
2021-12-20 16:38 ` [PATCH v2 03/13] powerpc/module_32: Fix livepatching for RO modules Christophe Leroy
2022-01-04 19:44 ` Joe Lawrence
2021-12-20 16:38 ` [PATCH v2 04/13] powerpc/ftrace: Add support for livepatch to PPC32 Christophe Leroy
2021-12-22 14:00 ` Miroslav Benes
2021-12-20 16:38 ` [PATCH v2 05/13] powerpc/ftrace: Don't save again LR in ftrace_regs_caller() on PPC32 Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 06/13] powerpc/ftrace: Simplify PPC32's return_to_handler() Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 07/13] powerpc/ftrace: Prepare PPC32's ftrace_caller() for CONFIG_DYNAMIC_FTRACE_WITH_ARGS Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 08/13] powerpc/ftrace: Prepare PPC64's " Christophe Leroy
2022-02-14 15:19 ` Naveen N. Rao
2021-12-20 16:38 ` [PATCH v2 09/13] powerpc/ftrace: Implement CONFIG_DYNAMIC_FTRACE_WITH_ARGS Christophe Leroy
2021-12-22 14:19 ` Miroslav Benes
2022-02-14 15:25 ` Naveen N. Rao
2022-02-15 8:00 ` Christophe Leroy
2022-02-15 11:05 ` Michael Ellerman
2022-02-15 13:36 ` Naveen N. Rao
2022-02-15 14:28 ` Christophe Leroy
2022-02-15 14:51 ` Christophe Leroy [this message]
2022-02-15 16:25 ` Naveen N. Rao
2022-02-16 13:04 ` Heiko Carstens
2022-02-16 13:27 ` Sven Schnelle
2022-02-15 14:38 ` Steven Rostedt
2022-02-15 16:26 ` Naveen N. Rao
2021-12-20 16:38 ` [PATCH v2 10/13] powerpc/ftrace: Refactor ftrace_{en/dis}able_ftrace_graph_caller Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 11/13] powerpc/ftrace: directly call of function graph tracer by ftrace caller Christophe Leroy
2022-02-14 17:24 ` Naveen N. Rao
2022-02-14 19:03 ` Steven Rostedt
2021-12-20 16:38 ` [PATCH v2 12/13] powerpc/ftrace: Prepare ftrace_64_mprofile.S for reuse by PPC32 Christophe Leroy
2022-02-14 17:51 ` Naveen N. Rao
2022-02-15 8:33 ` Christophe Leroy
2021-12-20 16:38 ` [PATCH v2 13/13] powerpc/ftrace: Remove ftrace_32.S Christophe Leroy
2022-02-11 7:41 ` [PATCH] Fixup for next-test 3a1a8f078670 ("powerpc/ftrace: Remove ftrace_32.S") Christophe Leroy
2022-02-16 12:26 ` [PATCH v2 00/13] Implement livepatch on PPC32 and more Michael Ellerman
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