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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: sergey.senozhatsky.work@gmail.com, dvyukov@google.com,
	pmladek@suse.com, sergey.senozhatsky@gmail.com,
	syzkaller@googlegroups.com, rostedt@goodmis.org,
	fengguang.wu@intel.com, linux-kernel@vger.kernel.org,
	torvalds@linux-foundation.org, akpm@linux-foundation.org
Subject: Re: [PATCH] printk: inject caller information into the body of message
Date: Thu, 17 May 2018 20:21:35 +0900
Message-ID: <20180517112135.GB20796@jagdpanzerIV> (raw)
In-Reply-To: <201805112058.AAB05258.HJQFFOMFOVtOSL@I-love.SAKURA.ne.jp>

On (05/11/18 20:58), Tetsuo Handa wrote:
[..]
> -	if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
> +	if (nr_ext_console_drivers) {
> +		cont_flush();
> +		return false;
> +	}
> +
> +	/* Inject before memcpy() in order to avoid overflow. */
> +	if (!cont.len)
> +		text = printk_inject_caller_info(text, &len);
> +
> +	/* If the line gets too long, split it up in separate records. */
> +	if (cont.len + len > sizeof(cont.buf)) {
>  		cont_flush();
>  		return false;
>  	}
> @@ -1820,6 +1860,9 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
>  			return text_len;
>  	}
>  
> +	/* Inject caller info. */
> +	text = printk_inject_caller_info(text, &text_len);
> +
>  	/* Store it in the record log */
>  	return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
>  }

[..]

I think this is slightly intrusive. I understand that you want to avoid
struct printk_log modification, let's try to see if we have any other
options.

Dunno...
For instance, can we store context tracking info as a extended record
data? We have that dict/dict_len thing. So may we can store tracking
info there? Extended records will appear on the serial console /* if
console supports extended data */ or can be read in via devkmsg_read().
Any other options?

>  #include "internal.h"
>  
> @@ -83,6 +84,17 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s,
[..]
>  	len = atomic_read(&s->len);
> @@ -102,7 +114,15 @@ static __printf(2, 0) int printk_safe_log_store(struct printk_safe_seq_buf *s,
>  		smp_rmb();
>  
>  	va_copy(ap, args);
> -	add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len, fmt, ap);
> +	if (printk_caller_info) {
> +		struct va_format vaf = { .fmt = fmt, .va = &ap };
> +
> +		add = scnprintf(s->buffer + len, sizeof(s->buffer) - len,
> +				"(%c%u) %pV", c, v, &vaf);
> +	} else {
> +		add = vscnprintf(s->buffer + len, sizeof(s->buffer) - len,
> +				 fmt, ap);
> +	}

A bit of a silly question - do we want to modify printk_safe at this
point? With this implementation printk_safe entries will have two context
info-s attached: one from original printk_safe_log_store and another one
from printk_safe_flush->log_store. I suspect that adding context info in
printk_safe_log_store is, probably, not really needed. We flush printk_safe
from irq work on the CPU that issued unsafe printk, so part of the context
info will be valid if you append context info only in printk log_store - at
least the correct smp_processor_id.

	-ss

  reply index

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 [this message]
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
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

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