Путем этого достичь: используя текущий указатель на задачу, выполняемую в настоящее время, получить ее структуру tty. Затем мы смотрим внутри этой структура tty, чтобы найти указатель на функцию, пишущую строку на tty. Ее мы и используем для вывода.
/* printk.c - send textual output to the tty you're
* running on, regardless of whether it's passed
* through X11, telnet, etc.
*/
/* Copyright (C) 1998 by Ori Pomerantz */
/* The necessary header files */
/* Standard in kernel modules */
#include
#include
/* Deal with CONFIG_MODVERSIONS */
#if CONFIG_MODVERSIONS==1
#define MODVERSIONS
#include
#endif
/* Necessary here */
#include
#include
/* Print the string to the appropriate tty, the one
* the current task uses */
void print_string(char *str) {
struct tty_struct *my_tty;
/* The tty for the current task */
my_tty = current->tty;
/* If my_tty is NULL, it means that the current task
* has no tty you can print to (this is possible, for
* example, if it's a daemon). In this case, there's
* nothing we can do. */
if (my_tty != NULL) {
/* my_tty->driver is a struct which holds the tty's
* functions, one of which (write) is used to
* write strings to the tty. It can be used to take
* a string either from the user's memory segment
* or the kernel's memory segment.
*
* The function's first parameter is the tty to
* write to, because the same function would
* normally be used for all tty's of a certain type.
* The second parameter controls whether the
* function receives a string from kernel memory
* (false, 0) or from user memory (true, non zero).
* The third parameter is a pointer to a string,
* and the fourth parameter is the length of
* the string. */
(*(my_tty->driver).write)(
my_tty, /* The tty itself */
0, /* We don't take the string from user space */
str, /* String */
strlen(str)); /* Length */
/* ttys were originally hardware devices, which
* (usually) adhered strictly to the ASCII standard.
* According to ASCII, to move to a new line you
* need two characters, a carriage return and a
* line feed. In Unix, on the other hand, the
* ASCII line feed is used for both purposes - so
* we can't just use \n, because it wouldn't have
* a carriage return and the next line will
* start at the column right after the line feed.
*
* BTW, this is the reason why the text file
* is different between Unix and Windows.
* In CP/M and its derivatives, such as MS-DOS and
* Windows, the ASCII standard was strictly
* adhered to, and therefore a new line requires
* both a line feed and a carriage return. */
(*(my_tty->driver).write)(my_tty, 0, "\015\012", 2);
}
}
