From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
zhe.he@windriver.com, rostedt@goodmis.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 4/4] printk: Give error on attempt to set log buffer length to over 4G
Date: Wed, 10 Oct 2018 17:21:29 +0900 [thread overview]
Message-ID: <20181010082129.GA631@jagdpanzerIV> (raw)
In-Reply-To: <20181010080932.h6nln2qsgg4oef4l@pathway.suse.cz>
On (10/10/18 10:09), Petr Mladek wrote:
> > > +#define LOG_BUF_LEN_MAX (u32)(1 << 31)
> > [..]
> > > + if (size > (u64)LOG_BUF_LEN_MAX) {
> > > + size = (u64)LOG_BUF_LEN_MAX;
> > > + pr_err("log_buf over 2G is not supported.\n");
> > > + }
> >
> > Why not INT_MAX?
>
> INT_MAX is 0x7fffffff but we need 0x80000000. I did not find
> any predefined macro.
Hmm, OK. I need to think about it more.
> > > + pr_info("log_buf_len: %u bytes\n", log_buf_len);
> > > + pr_info("early log buf free: %u(%u%%)\n",
> > > free, (free * 100) / __LOG_BUF_LEN);
> >
> > Can 'free * 100' overflow?
>
> Good question. It uses the size of the static buffer. If I count
> correctly then we are on the safe side because LOG_BUF_SHIFT
> is limited by
>
> range 12 25
I didn't know there was Kconfig "range" :)
$ echo $(((1<<25)*100))
3355443200
-ss
next prev parent reply other threads:[~2018-10-10 8:21 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-29 16:45 [PATCH v5 1/4] printk: Fix panic caused by passing log_buf_len to command line zhe.he
2018-09-29 16:45 ` [PATCH v5 2/4] printk: Correct wrong casting zhe.he
2018-10-02 5:50 ` Sergey Senozhatsky
2018-10-08 13:03 ` Petr Mladek
2018-09-29 16:45 ` [PATCH v5 3/4] printk: Add KBUILD_MODNAME and remove a redundant print prefix zhe.he
2018-10-02 5:52 ` Sergey Senozhatsky
2018-10-08 13:04 ` Petr Mladek
2018-09-29 16:45 ` [PATCH v5 4/4] printk: Give error on attempt to set log buffer length to over 4G zhe.he
2018-10-02 5:51 ` Sergey Senozhatsky
2018-10-08 13:59 ` Petr Mladek
2018-10-08 14:59 ` Sergey Senozhatsky
2018-10-09 13:05 ` Petr Mladek
2018-10-09 13:57 ` Sergey Senozhatsky
2018-10-10 8:09 ` Petr Mladek
2018-10-10 8:21 ` Sergey Senozhatsky [this message]
2018-10-08 16:30 ` He Zhe
2018-10-02 5:48 ` [PATCH v5 1/4] printk: Fix panic caused by passing log_buf_len to command line Sergey Senozhatsky
2018-10-08 13:01 ` Petr Mladek
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