On 2008-02-25 23:27, linux-os (Dick Johnson) wrote: > On Mon, 25 Feb 2008, Arvid Brodin wrote: > >> I need to write messages > 1023 characters long to the console from a >> module*. printk() is limited to 1023 characters, and splitting the message >> over several printk()'s results in a line break and "Month hh:mm:ss host >> kernel:" being inserted in my text. >> >> I tried including <linux/console.h> and using the console_drivers declared >> there, but get >> "WARNING: "console_drivers" [<path>/log.ko] undefined!" when compiling and >> "insmod: error inserting 'log.ko': -1 Unknown symbol in module" when >> insmodding. >> >> I guess this is because non EXPORT_SYMBOL'd symbols are only accessible to >> statically linked code, and not to modules? I see in printk.c that >> console_drivers is set up there, and I haven't been able to find any other >> interface to console_drivers. >> >> In short: is there any way to print messages to the console from a kernel >> module, except printk()? Is opening /dev/tty and writing to it the way to go? >> >> >> * I'm writing an in-memory logger to be included in a module. The log can be >> several megabytes. The idea is to use SysRq to print the contents of the log >> to console after a kernel panic or otherwise when writing to disk might not >> work. >> > > Write the data to a kernel buffer. Impliment read() or ioctl() and > poll(). Have a user-mode task sleep in poll, waiting for data to > become available. That user-mode task can do anything it wants, > unrestricted, with the data including writing it to files or any > tty it wants to open.
Thank you for your answer. However, I don't see how a user-mode task will help me print my log after a kernel panic, through SysRq? Please clarify. What we want is essentially a replacement for printk(), where the messages are instead logged in a big ring buffer, and can be printed with Alt-SysRq-l when need be. And the problem is the actual printing of the buffer to the console, since printk() inserts its timestamp after every linebreak or 1023 characters, whichever comes first. -- Arvid Brodin Enea LCC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
