Замена для printk

В начале ( глава1), я сказал, что X и программирование модулей ядра не совместимы. Это истинно при разработке модуля, но в фактическом использовании, Вы должны быть способны послать сообщениям любому tty 9.1. Это важно для идентификации ошибок после того, как модуль выпущен, потому что он будет использоваться через любой из терминалов.

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 <linux/kernel.h> /* We're doing kernel work */ #include <linux/module.h> /* Specifically, a module */ /* Deal with CONFIG_MODVERSIONS */ #if CONFIG_MODVERSIONS==1 #define MODVERSIONS #include <linux/modversions.h> #endif /* Necessary here */ #include <linux/sched.h> /* For current */ #include <linux/tty.h> /* For the tty declarations */ /* 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); } } /* Module initialization and cleanup ****************** */ /* Initialize the module - register the proc file */ int init_module() { print_string("Module Inserted"); return 0; } /* Cleanup - unregister our file from /proc */ void cleanup_module() { print_string("Module Removed"); }