| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <20170809172848.GZ3730@linux.vnet.ibm.com>
Date: Wed, 9 Aug 2017 10:28:48 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Prarit Bhargava <prarit@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
John Stultz <john.stultz@...aro.org>,
lkml <linux-kernel@...r.kernel.org>,
Mark Salyzyn <salyzyn@...roid.com>,
Jonathan Corbet <corbet@....net>,
Petr Mladek <pmladek@...e.com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
Stephen Boyd <sboyd@...eaurora.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Christoffer Dall <cdall@...aro.org>,
Deepa Dinamani <deepa.kernel@...il.com>,
Ingo Molnar <mingo@...nel.org>,
Joel Fernandes <joelaf@...gle.com>,
Kees Cook <keescook@...omium.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
"Luis R. Rodriguez" <mcgrof@...nel.org>,
Nicholas Piggin <npiggin@...il.com>,
"Jason A. Donenfeld" <Jason@...c4.com>,
Olof Johansson <olof@...om.net>,
Josh Poimboeuf <jpoimboe@...hat.com>, linux-doc@...r.kernel.org
Subject: Re: [PATCH v4] printk: Add monotonic, boottime, and realtime
timestamps
On Tue, Aug 08, 2017 at 07:08:00PM -0400, Prarit Bhargava wrote:
>
>
> On 08/08/2017 04:28 AM, Peter Zijlstra wrote:
> > On Mon, Aug 07, 2017 at 01:36:39PM -0700, Paul E. McKenney wrote:
> >> On Mon, Aug 07, 2017 at 04:06:09PM -0400, Prarit Bhargava wrote:
> >
> >>> peterz? Want to offer a suggestion? The issue is that I'm changing a bool
> >>> config option to an int and that impacts all the arch's defconfigs. John points
> >>> out that this is a lot of churn and we're both wondering if there's a better way
> >>> to do the configs.
> >>
> >> The usual approach is to keep the old bool Kconfig option, and add another
> >> int Kconfig option that depends on the original one. The tests for
> >> the int value get a bit more complex, but one way to handle this is to
> >> define a cpp macro something like the following:
> >>
> >> #ifdef CONFIG_OLD_OPTION
> >> #define CPP_NEW_OPTION 0
> >> #else
> >> #define CPP_NEW_OPTION CONFIG_NEW_OPTION
> >> #endif
> >>
> >> Then use CPP_NEW_OPTION, where zero means disabled and other numbers
> >> select the available options.
> >>
> >> Adjust to suit depending on what values mean what.
> >>
> >> Another approach is to make the range of the new Kconfig option
> >> depend on the old option:
> >>
> >> config NEW_OPTION
> >> int "your description here"
> >> range 1 5 if OLD_OPTION
> >> range 0 0 if !OLD_OPTION
> >> default 0
> >> help
> >> your help here
> >>
> >> Again, adjust to suit depending on what values mean what.
> >
> > Right this. Except I don't see the !OLD_OPTION working as expected.
> > A 'new' config will not include the old one, so the !OLD_OPTION thing
> > will 'always' be true.
> >
> > So your:
> >
> >> @@ -1,8 +1,46 @@
> >> menu "printk and dmesg options"
> >>
> >> +choice
> >> + prompt "printk default clock"
> >> + config PRINTK_TIME_DISABLE
> >> + bool "Disabled"
> >> + help
> >> + Selecting this option disables the time stamps of printk().
> >> +
> >> + config PRINTK_TIME_LOCAL
> >> + bool "Local Clock"
> >> + help
> >> + Selecting this option causes the time stamps of printk() to be
> >> + stamped with the unadjusted hardware clock.
> >> +
> >> + config PRINTK_TIME_BOOT
> >> + bool "CLOCK_BOOTTIME"
> >> + help
> >> + Selecting this option causes the time stamps of printk() to be
> >> + stamped with the adjusted boottime clock.
> >> +
> >> + config PRINTK_TIME_MONO
> >> + bool "CLOCK_MONOTONIC"
> >> + help
> >> + Selecting this option causes the time stamps of printk() to be
> >> + stamped with the adjusted monotonic clock.
> >> +
> >> + config PRINTK_TIME_REAL
> >> + bool "CLOCK_REALTIME"
> >> + help
> >> + Selecting this option causes the time stamps of printk() to be
> >> + stamped with the adjusted realtime clock.
> >> +
> >> +endchoice
> >> +
> >> config PRINTK_TIME
> >
> > Change that into something like:
> >
> > config PRINTK_CLOCK
> >
> >
> >> - bool "Show timing information on printks"
> >> + int "Show time stamp information on printks"
> >> depends on PRINTK
> >> + default 0 if PRINTK_TIME_DISABLE
> >> + default 1 if PRINTK_TIME_LOCAL
> >
> > And that into:
> >
> > default 1 if PRINTK_TIME_LOCAL || PRINTK_TIME
> >
> >> + default 2 if PRINTK_TIME_BOOT
> >> + default 3 if PRINTK_TIME_MONO
> >> + default 4 if PRINTK_TIME_REAL
> >> help
> >> Selecting this option causes time stamps of the printk()
> >
> > Then the old PRINTK_TIME symbol will auto-convert into the new
> > equivalent.
> >
>
> I don't think there's an easy code way around this. Essentially this Kconfig
> code boils down to properly evaluating
>
> config PRINTK_CLOCK
> default 1 if PRINTK_TIME
> default 0
>
> where there is no Kconfig entry for PRINTK_TIME.
>
> If undefined CONFIG_PRINTK_TIME is used in a config, it is immediately
> scrubbed by the kconfig script so it doesn't "exist" when CONFIG_PRINTK_CLOCK
> is evaluated. The result of that is CONFIG_PRINT_CLOCK=0.
>
> I tried
>
> config PRINTK_TIME
> bool "old config option"
>
> then I end up with both a CONFIG_PRINTK_CLOCK=1 and a CONFIG_PRINTK_TIME=y in
> the resulting config which is confusing.
>
> I've debated using the other suggestion that Paul made but TBH (sorry
> Paul) it seems like I'm avoiding the real but noisy solution of
>
> s/PRINTK_TIME=y/PRINTK_TIME=1/g
>
> I'm obviously open to other suggestions...
It is someone else's turn to provide a suggestion. ;-)
Thanx, Paul
Powered by blists - more mailing lists