From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Torsten Duwe <duwe@lst.de>
Cc: Julien Thierry <julien.thierry@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Will Deacon <will.deacon@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Ingo Molnar <mingo@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
AKASHI Takahiro <takahiro.akashi@linaro.org>,
Amit Daniel Kachhap <amit.kachhap@arm.com>,
"Singh, Balbir" <bsingharora@gmail.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
live-patching@vger.kernel.org
Subject: Re: [PATCH v7 2/3] arm64: implement ftrace with regs
Date: Mon, 4 Feb 2019 14:43:42 +0100 [thread overview]
Message-ID: <CAKv+Gu-3vzo4YJxN=qQ5yRDJnWjCt7L96HkoG3y2AUJk_zX3ag@mail.gmail.com> (raw)
In-Reply-To: <20190204120308.GA7660@lst.de>
On Mon, 4 Feb 2019 at 13:03, Torsten Duwe <duwe@lst.de> wrote:
>
> On Tue, Jan 22, 2019 at 02:55:12PM +0100, Ard Biesheuvel wrote:
> > On Tue, 22 Jan 2019 at 14:28, Torsten Duwe <duwe@lst.de> wrote:
> > >
> > > On Tue, Jan 22, 2019 at 10:18:17AM +0000, Julien Thierry wrote:
> > > > Hi Torsten,
> > > >
> > > > A few suggestions below.
> > > >
> > > > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> > > > > +#define ARCH_SUPPORTS_FTRACE_OPS 1
> > > > > +#define REC_IP_BRANCH_OFFSET AARCH64_INSN_SIZE
> > > > > +/* All we need is some magic value. Simply use "_mCount:" */
> > > >
> > > > Nit: Should the casing be "_mcount" ?
> > >
> > > No! The string makes it clear what it's supposed to be and the peculiar
> > > casing makes it unique and leaves no doubt were it came from. So whenever
> > > you see this register value in a crash dump you don't have to wonder about
> > > weird linkage errors, as it surely did not originate from a symtab.
> > >
> >
> > In that case, do you need to deal with endianness here?
> >
> > > > > +#define MCOUNT_ADDR (0x5f6d436f756e743a)
>
> Strictly speaking, yes. OTOH "wrong-andian" machines always show a difference
> when memory is dumped in bigger units than bytes, so when you see the register
> value in hex...
>
> Since all that's needed is a somewhat unique constant, let's not over-engineer
> this ok?
>
Ah ok, if it is only for visual recognition, then I guess it doesn't matter.
> If there are no other comments I'll send out v8 with the discussed changes.
>
> Torsten
>
WARNING: multiple messages have this Message-ID (diff)
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Torsten Duwe <duwe@lst.de>
Cc: Mark Rutland <mark.rutland@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Julien Thierry <julien.thierry@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
"Singh, Balbir" <bsingharora@gmail.com>,
Will Deacon <will.deacon@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
AKASHI Takahiro <takahiro.akashi@linaro.org>,
Ingo Molnar <mingo@redhat.com>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Amit Daniel Kachhap <amit.kachhap@arm.com>,
live-patching@vger.kernel.org,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v7 2/3] arm64: implement ftrace with regs
Date: Mon, 4 Feb 2019 14:43:42 +0100 [thread overview]
Message-ID: <CAKv+Gu-3vzo4YJxN=qQ5yRDJnWjCt7L96HkoG3y2AUJk_zX3ag@mail.gmail.com> (raw)
In-Reply-To: <20190204120308.GA7660@lst.de>
On Mon, 4 Feb 2019 at 13:03, Torsten Duwe <duwe@lst.de> wrote:
>
> On Tue, Jan 22, 2019 at 02:55:12PM +0100, Ard Biesheuvel wrote:
> > On Tue, 22 Jan 2019 at 14:28, Torsten Duwe <duwe@lst.de> wrote:
> > >
> > > On Tue, Jan 22, 2019 at 10:18:17AM +0000, Julien Thierry wrote:
> > > > Hi Torsten,
> > > >
> > > > A few suggestions below.
> > > >
> > > > > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> > > > > +#define ARCH_SUPPORTS_FTRACE_OPS 1
> > > > > +#define REC_IP_BRANCH_OFFSET AARCH64_INSN_SIZE
> > > > > +/* All we need is some magic value. Simply use "_mCount:" */
> > > >
> > > > Nit: Should the casing be "_mcount" ?
> > >
> > > No! The string makes it clear what it's supposed to be and the peculiar
> > > casing makes it unique and leaves no doubt were it came from. So whenever
> > > you see this register value in a crash dump you don't have to wonder about
> > > weird linkage errors, as it surely did not originate from a symtab.
> > >
> >
> > In that case, do you need to deal with endianness here?
> >
> > > > > +#define MCOUNT_ADDR (0x5f6d436f756e743a)
>
> Strictly speaking, yes. OTOH "wrong-andian" machines always show a difference
> when memory is dumped in bigger units than bytes, so when you see the register
> value in hex...
>
> Since all that's needed is a somewhat unique constant, let's not over-engineer
> this ok?
>
Ah ok, if it is only for visual recognition, then I guess it doesn't matter.
> If there are no other comments I'll send out v8 with the discussed changes.
>
> Torsten
>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-02-04 13:43 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-18 16:37 [PATCH v7 0/3] arm64: ftrace with regs Torsten Duwe
2019-01-18 16:37 ` Torsten Duwe
2019-01-18 16:39 ` [PATCH v7 1/3] arm64: replace -pg with CC_FLAGS_FTRACE in Makefiles Torsten Duwe
2019-01-18 16:39 ` Torsten Duwe
2019-01-18 17:24 ` Mark Rutland
2019-01-18 17:24 ` Mark Rutland
2019-01-18 16:39 ` [PATCH v7 2/3] arm64: implement ftrace with regs Torsten Duwe
2019-01-18 16:39 ` Torsten Duwe
2019-01-22 1:39 ` Singh, Balbir
2019-01-22 1:39 ` Singh, Balbir
2019-01-22 13:09 ` Torsten Duwe
2019-01-22 13:09 ` Torsten Duwe
2019-01-23 20:38 ` Singh, Balbir
2019-01-23 20:38 ` Singh, Balbir
2019-01-22 10:18 ` Julien Thierry
2019-01-22 10:18 ` Julien Thierry
2019-01-22 13:28 ` Torsten Duwe
2019-01-22 13:28 ` Torsten Duwe
2019-01-22 13:49 ` Julien Thierry
2019-01-22 13:49 ` Julien Thierry
2019-01-22 13:55 ` Ard Biesheuvel
2019-01-22 13:55 ` Ard Biesheuvel
2019-02-04 12:03 ` Torsten Duwe
2019-02-04 12:03 ` Torsten Duwe
2019-02-04 13:43 ` Ard Biesheuvel [this message]
2019-02-04 13:43 ` Ard Biesheuvel
2019-02-06 8:59 ` Julien Thierry
2019-02-06 8:59 ` Julien Thierry
2019-02-06 9:30 ` Julien Thierry
2019-02-06 9:30 ` Julien Thierry
2019-02-06 14:09 ` Steven Rostedt
2019-02-06 14:09 ` Steven Rostedt
2019-02-06 15:05 ` Torsten Duwe
2019-02-06 15:05 ` Torsten Duwe
2019-02-07 10:33 ` Julien Thierry
2019-02-07 10:33 ` Julien Thierry
2019-02-07 12:51 ` Torsten Duwe
2019-02-07 12:51 ` Torsten Duwe
2019-02-07 13:47 ` Julien Thierry
2019-02-07 13:47 ` Julien Thierry
2019-02-07 14:51 ` Steven Rostedt
2019-02-07 14:51 ` Steven Rostedt
2019-02-07 14:58 ` Julien Thierry
2019-02-07 14:58 ` Julien Thierry
2019-02-07 15:00 ` Torsten Duwe
2019-02-07 15:00 ` Torsten Duwe
2019-04-03 2:48 ` Mark Rutland
2019-04-03 2:48 ` Mark Rutland
2019-04-03 12:30 ` Steven Rostedt
2019-04-03 12:30 ` Steven Rostedt
2019-04-03 13:05 ` Torsten Duwe
2019-04-03 13:05 ` Torsten Duwe
2019-01-18 16:39 ` [PATCH v7 3/3] arm64: use -fpatchable-function-entry if available Torsten Duwe
2019-01-18 16:39 ` Torsten Duwe
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