From: Dmitry Vyukov <dvyukov@google.com>
To: Fengguang Wu <fengguang.wu@intel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
syzkaller <syzkaller@googlegroups.com>,
Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] printk: inject caller information into the body of message
Date: Wed, 20 Jun 2018 14:45:25 +0200 [thread overview]
Message-ID: <CACT4Y+b0XGxnJtvB2T3hZHm_UvT7Mk6zT35ODWBtdtQK7KZ=JA@mail.gmail.com> (raw)
In-Reply-To: <20180620124157.gd5245o63dq6teul@wfg-t540p.sh.intel.com>
On Wed, Jun 20, 2018 at 2:41 PM, Fengguang Wu <fengguang.wu@intel.com> wrote:
> On Wed, Jun 20, 2018 at 02:31:51PM +0200, Dmitry Vyukov wrote:
>>
>> On Wed, Jun 20, 2018 at 1:37 PM, Fengguang Wu <fengguang.wu@intel.com>
>> wrote:
>>>
>>> On Wed, Jun 20, 2018 at 11:30:05AM +0200, Dmitry Vyukov wrote:
>>>>
>>>>
>>>> On Wed, Jun 20, 2018 at 11:06 AM, Sergey Senozhatsky
>>>> <sergey.senozhatsky.work@gmail.com> wrote:
>>>>>
>>>>>
>>>>> Hi Dmitry,
>>>>>
>>>>> On (06/20/18 10:45), Dmitry Vyukov wrote:
>>>>>>
>>>>>>
>>>>>> Hi Sergey,
>>>>>>
>>>>>> What are the visible differences between this patch and Tetsuo's
>>>>>> patch?
>>>>>
>>>>>
>>>>>
>>>>> I guess none, and looking at your requirements below I tend to agree
>>>>> that Tetsuo's approach is probably what you need at the end of the day.
>>>>>
>>>>>> The only thing that will matter for syzkaller parsing in the
>>>>>> end is the resulting text format as it appears on console. But you say
>>>>>> "I'm not pushing for this particular message format", so what exactly
>>>>>> do you want me to provide feedback on?
>>>>>> I guess we need to handle pr_cont properly whatever approach we take.
>>>>>
>>>>>
>>>>>
>>>>> Mostly, was wondering about if:
>>>>> a) you need pr_cont() handling
>>>>> b) you need printk_safe() handling
>>>>>
>>>>> The reasons I left those things behind:
>>>>>
>>>>> a) pr_cont() is officially hated. It was never supposed to be used
>>>>> on SMP systems. So I wasn't sure if we need all that effort and
>>>>> add tricky code to handle pr_cont(). Given that syzkaller is
>>>>> probably the only user of that functionality.
>>>>
>>>>
>>>>
>>>> Well, if I put my syzkaller hat on, then I don't care what exactly
>>>> happens in the kernel, the only thing I care is well-formed output on
>>>> console that can be parsed unambiguously in all cases.
>>>
>>>
>>>
>>> +1 for 0day kernel testing.
>>>
>>> I admit that goal may never be 100% achievable -- at least some serial
>>> console logs can sometimes become messy. So we'll have to write dmesg
>>> parsing code in defensive ways.
>>>
>>> But some unnecessary pr_cont() broken-up messages can obviously be
>>> avoided. For example,
>>>
>>> arch/x86/mm/fault.c:
>>>
>>> printk(KERN_ALERT "BUG: unable to handle kernel ");
>>> if (address < PAGE_SIZE)
>>> printk(KERN_CONT "NULL pointer dereference");
>>> else
>>> printk(KERN_CONT "paging request");
>>>
>>> I've actually proposed to remove the above KERN_CONT, unfortunately the
>>> patch was silently ignored.
>>
>>
>>
>> I've just cooked this change too, but do you mind reviving your patch?
>
>
> Yes, sure. My version is more dumb. Since I'm not sure if it's OK to
> do string formatting at this critical point. Let's see how others
> think about the 2 approaches. I'm fine as long as our problem is fixed. :)
It already does string formatting for address. And I think we also
need to get rid of KERN_CONT for address while we are here.
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index 9a84a0d08727..c7b068c6b010 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -671,11 +671,10 @@ show_fault_oops(struct pt_regs *regs, unsigned long
> error_code,
> printk(smep_warning, from_kuid(&init_user_ns,
> current_uid()));
> }
>
> - printk(KERN_ALERT "BUG: unable to handle kernel ");
> if (address < PAGE_SIZE)
> - printk(KERN_CONT "NULL pointer dereference");
> + printk(KERN_ALERT "BUG: unable to handle kernel NULL pointer
> dereference");
> else
> - printk(KERN_CONT "paging request");
> + printk(KERN_ALERT "BUG: unable to handle kernel paging
> request");
>
>
> printk(KERN_CONT " at %px\n", (void *) address);
>
>> It actually makes the code even shorter, which is nice:
>>
>> --- a/arch/x86/mm/fault.c
>> +++ b/arch/x86/mm/fault.c
>> @@ -671,13 +671,9 @@ show_fault_oops(struct pt_regs *regs, unsigned
>> long error_code,
>> printk(smep_warning, from_kuid(&init_user_ns,
>> current_uid()));
>> }
>>
>> - printk(KERN_ALERT "BUG: unable to handle kernel ");
>> - if (address < PAGE_SIZE)
>> - printk(KERN_CONT "NULL pointer dereference");
>> - else
>> - printk(KERN_CONT "paging request");
>> -
>> - printk(KERN_CONT " at %px\n", (void *) address);
>> + printk(KERN_ALERT "BUG: unable to handle kernel %s at %px\n",
>> + (address < PAGE_SIZE ? "NULL pointer dereference" :
>> + "paging request"), (void *) address);
>>
>> dump_pagetable(address);
>> }
>>
>
next prev parent reply other threads:[~2018-06-20 12:45 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <201804232233.CIC65675.OJSOMFQOFFHVtL@I-love.SAKURA.ne.jp>
[not found] ` <CACT4Y+boyw_Qy=y-iTnsKZrtTgF0Hk3nHN_xtqUdX4etgiYDQw@mail.gmail.com>
2018-04-24 1:33 ` printk feature for syzbot? Sergey Senozhatsky
2018-04-24 14:40 ` Steven Rostedt
2018-04-26 10:06 ` Petr Mladek
2018-05-10 4:22 ` Sergey Senozhatsky
2018-05-10 11:30 ` Petr Mladek
2018-05-10 12:11 ` Sergey Senozhatsky
2018-05-10 14:22 ` Steven Rostedt
2018-05-10 14:50 ` Tetsuo Handa
2018-05-11 1:45 ` Sergey Senozhatsky
[not found] ` <201805110238.w4B2cIGH079602@www262.sakura.ne.jp>
2018-05-11 6:21 ` Sergey Senozhatsky
2018-05-11 9:17 ` Dmitry Vyukov
2018-05-11 9:50 ` Sergey Senozhatsky
2018-05-11 11:58 ` [PATCH] printk: inject caller information into the body of message Tetsuo Handa
2018-05-17 11:21 ` Sergey Senozhatsky
2018-05-17 11:52 ` Sergey Senozhatsky
2018-05-18 12:15 ` Petr Mladek
2018-05-18 12:25 ` Dmitry Vyukov
2018-05-18 12:54 ` Petr Mladek
2018-05-18 13:08 ` Dmitry Vyukov
2018-05-24 2:21 ` Sergey Senozhatsky
2018-05-23 10:19 ` Tetsuo Handa
2018-05-24 2:14 ` Sergey Senozhatsky
2018-05-26 6:36 ` Dmitry Vyukov
2018-06-20 5:44 ` Dmitry Vyukov
2018-06-20 8:31 ` Sergey Senozhatsky
2018-06-20 8:45 ` Dmitry Vyukov
2018-06-20 9:06 ` Sergey Senozhatsky
2018-06-20 9:18 ` Sergey Senozhatsky
2018-06-20 9:31 ` Dmitry Vyukov
2018-06-20 11:07 ` Sergey Senozhatsky
2018-06-20 11:32 ` Dmitry Vyukov
2018-06-20 13:06 ` Sergey Senozhatsky
2018-06-22 13:06 ` Tetsuo Handa
2018-06-25 1:41 ` Sergey Senozhatsky
2018-06-25 9:36 ` Dmitry Vyukov
2018-06-27 10:29 ` Tetsuo Handa
2018-09-10 11:20 ` Alexander Potapenko
2018-09-12 6:53 ` Sergey Senozhatsky
2018-09-12 16:05 ` Steven Rostedt
2018-09-13 7:12 ` Sergey Senozhatsky
2018-09-13 12:26 ` Petr Mladek
2018-09-13 14:28 ` Sergey Senozhatsky
2018-09-14 1:22 ` Steven Rostedt
2018-09-14 2:15 ` Sergey Senozhatsky
2018-09-14 6:57 ` Sergey Senozhatsky
2018-09-14 10:37 ` Tetsuo Handa
2018-09-14 11:50 ` Sergey Senozhatsky
2018-09-14 12:03 ` Tetsuo Handa
2018-09-14 12:22 ` Sergey Senozhatsky
2018-09-19 11:02 ` Tetsuo Handa
2018-09-24 8:11 ` Tetsuo Handa
2018-09-27 16:10 ` Tetsuo Handa
2018-09-28 9:02 ` Sergey Senozhatsky
2018-09-28 9:09 ` Sergey Senozhatsky
2018-09-28 11:01 ` Tetsuo Handa
2018-09-29 10:51 ` Sergey Senozhatsky
2018-09-29 11:15 ` Tetsuo Handa
2018-10-01 2:37 ` Sergey Senozhatsky
2018-10-01 2:58 ` Sergey Senozhatsky
2018-10-01 11:21 ` Tetsuo Handa
2018-10-02 6:38 ` Sergey Senozhatsky
2018-10-08 10:31 ` Tetsuo Handa
2018-10-08 16:03 ` Petr Mladek
2018-10-08 20:48 ` Tetsuo Handa
2018-10-09 14:52 ` Petr Mladek
2018-10-09 21:19 ` Tetsuo Handa
2018-10-10 10:14 ` Tetsuo Handa
2018-10-11 10:20 ` Tetsuo Handa
2018-10-11 13:47 ` Steven Rostedt
2018-10-08 15:43 ` Petr Mladek
2018-09-28 8:56 ` Sergey Senozhatsky
2018-09-28 11:21 ` Tetsuo Handa
2018-09-29 11:13 ` Sergey Senozhatsky
2018-09-29 11:39 ` Tetsuo Handa
2018-10-01 5:52 ` Sergey Senozhatsky
2018-10-01 8:37 ` Sergey Senozhatsky
2018-10-01 18:06 ` Steven Rostedt
2018-09-14 1:12 ` Steven Rostedt
2018-09-14 1:55 ` Sergey Senozhatsky
2018-06-21 8:29 ` Sergey Senozhatsky
2018-06-20 9:30 ` Dmitry Vyukov
2018-06-20 11:19 ` Sergey Senozhatsky
2018-06-20 11:25 ` Dmitry Vyukov
2018-06-20 11:37 ` Fengguang Wu
2018-06-20 12:31 ` Dmitry Vyukov
2018-06-20 12:41 ` Fengguang Wu
2018-06-20 12:45 ` Dmitry Vyukov [this message]
2018-06-20 12:48 ` Fengguang Wu
2018-05-11 13:37 ` printk feature for syzbot? Steven Rostedt
2018-05-15 5:20 ` Sergey Senozhatsky
2018-05-15 14:39 ` Steven Rostedt
2018-05-11 11:02 ` [PATCH] printk: fix possible reuse of va_list variable Tetsuo Handa
2018-05-11 11:27 ` Sergey Senozhatsky
2018-05-17 11:57 ` Petr Mladek
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='CACT4Y+b0XGxnJtvB2T3hZHm_UvT7Mk6zT35ODWBtdtQK7KZ=JA@mail.gmail.com' \
--to=dvyukov@google.com \
--cc=akpm@linux-foundation.org \
--cc=fengguang.wu@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=penguin-kernel@i-love.sakura.ne.jp \
--cc=pmladek@suse.com \
--cc=rostedt@goodmis.org \
--cc=sergey.senozhatsky.work@gmail.com \
--cc=sergey.senozhatsky@gmail.com \
--cc=syzkaller@googlegroups.com \
--cc=torvalds@linux-foundation.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: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).