From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> To: Christophe Leroy <christophe.leroy@csgroup.eu>, Vasily Gorbik <gor@linux.ibm.com>, Heiko Carstens <hca@linux.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> Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.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 21:55:52 +0530 [thread overview] Message-ID: <1644941712.lqdstzo09z.naveen@linux.ibm.com> (raw) In-Reply-To: <5c7b5334-6071-f131-a509-9a49ca3d628c@csgroup.eu> Christophe Leroy wrote: > + 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 ? Steven has explained the rationale for this in his other response: https://lore.kernel.org/all/20220215093849.556d5444@gandalf.local.home/ >>> >>> 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 ? We'll need to explicitly zero-out something in pt_regs in ftrace_caller(). We can probably use regs->msr since we don't expect it to be zero when saved from ftrace_regs_caller(). >> > > 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. Indeed, good find! Thanks, Naveen
WARNING: multiple messages have this Message-ID (diff)
From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> To: Christophe Leroy <christophe.leroy@csgroup.eu>, Vasily Gorbik <gor@linux.ibm.com>, Heiko Carstens <hca@linux.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> Cc: "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>, "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>, "linux-kernel@vger.kernel.org" <linux-kernel@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 21:55:52 +0530 [thread overview] Message-ID: <1644941712.lqdstzo09z.naveen@linux.ibm.com> (raw) In-Reply-To: <5c7b5334-6071-f131-a509-9a49ca3d628c@csgroup.eu> Christophe Leroy wrote: > + 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 ? Steven has explained the rationale for this in his other response: https://lore.kernel.org/all/20220215093849.556d5444@gandalf.local.home/ >>> >>> 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 ? We'll need to explicitly zero-out something in pt_regs in ftrace_caller(). We can probably use regs->msr since we don't expect it to be zero when saved from ftrace_regs_caller(). >> > > 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. Indeed, good find! Thanks, Naveen
next prev parent reply other threads:[~2022-02-15 16:26 UTC|newest] Thread overview: 84+ 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 16:37 ` Christophe Leroy 2021-12-20 16:38 ` [PATCH v2 01/13] livepatch: Fix build failure on 32 bits processors Christophe Leroy 2021-12-20 16:38 ` Christophe Leroy 2021-12-22 13:47 ` Miroslav Benes 2021-12-22 13:47 ` Miroslav Benes 2022-01-04 19:35 ` Joe Lawrence 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 2021-12-20 16:38 ` Christophe Leroy 2022-02-24 13:43 ` Christophe Leroy 2022-02-24 13:43 ` Christophe Leroy 2022-02-24 14:53 ` Steven Rostedt 2022-02-24 14:53 ` Steven Rostedt 2022-02-24 15:13 ` Christophe Leroy 2022-02-24 15:13 ` Christophe Leroy 2022-02-24 15:17 ` Steven Rostedt 2022-02-24 15:17 ` Steven Rostedt 2022-02-25 2:42 ` Michael Ellerman 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 2021-12-20 16:38 ` Christophe Leroy 2022-01-04 19:44 ` Joe Lawrence 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 2021-12-20 16:38 ` Christophe Leroy 2021-12-22 14:00 ` Miroslav Benes 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 ` 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 ` 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 ` Christophe Leroy 2021-12-20 16:38 ` [PATCH v2 08/13] powerpc/ftrace: Prepare PPC64's " Christophe Leroy 2021-12-20 16:38 ` Christophe Leroy 2022-02-14 15:19 ` Naveen N. Rao 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 2021-12-20 16:38 ` Christophe Leroy 2021-12-22 14:19 ` Miroslav Benes 2021-12-22 14:19 ` Miroslav Benes 2021-12-22 14:19 ` Miroslav Benes 2022-02-14 15:25 ` Naveen N. Rao 2022-02-14 15:25 ` Naveen N. Rao 2022-02-15 8:00 ` Christophe Leroy 2022-02-15 8:00 ` Christophe Leroy 2022-02-15 11:05 ` Michael Ellerman 2022-02-15 11:05 ` Michael Ellerman 2022-02-15 13:36 ` Naveen N. Rao 2022-02-15 13:36 ` Naveen N. Rao 2022-02-15 14:28 ` Christophe Leroy 2022-02-15 14:28 ` Christophe Leroy 2022-02-15 14:51 ` Christophe Leroy 2022-02-15 14:51 ` Christophe Leroy 2022-02-15 16:25 ` Naveen N. Rao [this message] 2022-02-15 16:25 ` Naveen N. Rao 2022-02-16 13:04 ` Heiko Carstens 2022-02-16 13:04 ` Heiko Carstens 2022-02-16 13:27 ` Sven Schnelle 2022-02-16 13:27 ` Sven Schnelle 2022-02-15 14:38 ` Steven Rostedt 2022-02-15 14:38 ` Steven Rostedt 2022-02-15 16:26 ` Naveen N. Rao 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 ` Christophe Leroy 2021-12-20 16:38 ` [PATCH v2 11/13] powerpc/ftrace: directly call of function graph tracer by ftrace caller Christophe Leroy 2021-12-20 16:38 ` Christophe Leroy 2022-02-14 17:24 ` Naveen N. Rao 2022-02-14 17:24 ` Naveen N. Rao 2022-02-14 19:03 ` Steven Rostedt 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 2021-12-20 16:38 ` Christophe Leroy 2022-02-14 17:51 ` Naveen N. Rao 2022-02-14 17:51 ` Naveen N. Rao 2022-02-15 8:33 ` Christophe Leroy 2022-02-15 8:33 ` Christophe Leroy 2021-12-20 16:38 ` [PATCH v2 13/13] powerpc/ftrace: Remove ftrace_32.S Christophe Leroy 2021-12-20 16:38 ` Christophe Leroy 2022-02-11 7:41 ` [PATCH] Fixup for next-test 3a1a8f078670 ("powerpc/ftrace: Remove ftrace_32.S") Christophe Leroy 2022-02-11 7:41 ` Christophe Leroy 2022-02-16 12:26 ` [PATCH v2 00/13] Implement livepatch on PPC32 and more Michael Ellerman
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=1644941712.lqdstzo09z.naveen@linux.ibm.com \ --to=naveen.n.rao@linux.vnet.ibm.com \ --cc=christophe.leroy@csgroup.eu \ --cc=gor@linux.ibm.com \ --cc=hca@linux.ibm.com \ --cc=jikos@kernel.org \ --cc=joe.lawrence@redhat.com \ --cc=jpoimboe@redhat.com \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-s390@vger.kernel.org \ --cc=linuxppc-dev@lists.ozlabs.org \ --cc=live-patching@vger.kernel.org \ --cc=mbenes@suse.cz \ --cc=mingo@redhat.com \ --cc=mpe@ellerman.id.au \ --cc=pmladek@suse.com \ --cc=rostedt@goodmis.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.