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Date: Wed, 20 May 2020 13:41:27 +0900 From: Sergey Senozhatsky <sergey.senozhatsky@...il.com> To: Joe Perches <joe@...ches.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Chenggang Wang <wangchenggang@...o.com>, linux-kernel@...r.kernel.org, Petr Mladek <pmladek@...e.com>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Steven Rostedt <rostedt@...dmis.org> Subject: Re: [RFC PATCH 2/2] init: Allow multi-line output of kernel command line On (20/05/19 12:42), Joe Perches wrote: > +static void __init print_cmdline(char *line) > +{ > +#ifdef CONFIG_PRINTK > + const char *prefix = "Kernel command line"; > + size_t len = strlen(line); > + > + while (len > PRINTK_LOG_LINE_MAX) { > + char *pos = line; > + char *last_pos = pos + PRINTK_LOG_LINE_MAX - 1; > + char saved_char; > + /* Find last space char within the maximum line length */ > + while ((pos = memchr(pos, ' ', len - (pos - line))) && > + (pos - line) < PRINTK_LOG_LINE_MAX - 1) { Don't you need to also count in the 'prefix' length? > + last_pos = pos; > + } > + saved_char = line[last_pos - line]; > + line[last_pos - line] = 0; > + pr_notice("%s: %s\n", prefix, line); > + prefix = "Kernel command line (continued)"; > + line[last_pos - line] = saved_char; > + len -= pos - line; > + line += pos - line; > + } > + > + pr_notice("%s: %s\n", prefix, line); > +#endif > +} I like this in general. And I agree that we better handle this externally, on the printk() caller side, so that printk() will still have sane limits and won't print a 1G string for example. I wonder if we need to export PRINTK_LOG_LINE_MAX. Maybe we can use here something rather random and much shorter instead. E.g. 256 chars. Hmm. How many crash/monitoring tools can get confused by multiple "Kernel command line" prefixes? -ss
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