/* * jit.c -- the just-in-time module * * Tested with 2.0 on the x86, Sparc *//* BUGS: this module is not reentrant: only one file can be read at a time *       the module usage count is not used: you could remove the module *           while reading it, thus asking for troubles */ #ifndef __KERNEL__#  define __KERNEL__#endif#ifndef MODULE#  define MODULE#endif#include <linux/module.h>#define VERSION_CODE(vers,rel,seq) ( ((vers)<<16) | ((rel)<<8) | (seq) )#if LINUX_VERSION_CODE < VERSION_CODE(1,99,4)#  error "This module needs Linux 1.99.4 or newer"#else#include <linux/sched.h>#include <linux/kernel.h> /* printk() */#include <linux/fs.h>     /* everything... */#include <linux/proc_fs.h>#include <linux/errno.h>  /* error codes */#include <linux/types.h>  /* size_t *//* * This module is a silly one: it only embeds short code fragments * that show how time delays can be handled in the kernel. */int jit_delay = 1; /* the default delay in read() */char jit_spoke[] = "This is a meaningless string, fiftysix characters long.\n";#define LIMIT (PAGE_SIZE-128) /* don't print any more after this size */static int jit_print(char *buf){    int len = 0;    while(len < LIMIT)        len += sprintf(buf+len,"%s",jit_spoke);    return len;}int jit_read_busy(char *buf, char **start, off_t offset,                   int len, int unused){    /* delay one second (or the chosen value), before printing */    unsigned long j= jiffies + jit_delay * HZ;    while (jiffies < j)	/* nothing */;    return jit_print(buf);}int jit_read_sched(char *buf, char **start, off_t offset,                   int len, int unused){    /* delay one second (or the chosen value), before printing */    unsigned long j= jiffies + jit_delay * HZ;    while (jiffies < j)	schedule();    return jit_print(buf);}int jit_read_queue(char *buf, char **start, off_t offset,                   int len, int unused){    /* delay one second (or the chosen value), before printing */    unsigned long j= jiffies + jit_delay * HZ;        struct wait_queue *wait = NULL;    current->timeout = j;    interruptible_sleep_on(&wait);    return jit_print(buf);}int jit_read_self(char *buf, char **start, off_t offset,                   int len, int unused){    /* delay one second (or the chosen value), before printing */    unsigned long j= jiffies + jit_delay * HZ;    current->timeout = j;    current->state = TASK_INTERRUPTIBLE;    schedule();    current->timeout = 0; /* reset the timeout */    return jit_print(buf);}struct proc_dir_entry jit_proc_busy = {        0,                 /* low_ino: the inode -- dynamic */        7, "jitbusy",      /* len of name and name */        S_IFREG | S_IRUGO, /* mode */        1, 0, 0,           /* nlinks, owner, group */        0, NULL,           /* size - unused; operations -- use default */        &jit_read_busy,    /* function used to read data */        /* nothing more */    };struct proc_dir_entry jit_proc_sched = {        0,                 /* low_ino: the inode -- dynamic */        8, "jitsched",     /* len of name and name */        S_IFREG | S_IRUGO, /* mode */        1, 0, 0,           /* nlinks, owner, group */        0, NULL,           /* size - unused; operations -- use default */        &jit_read_sched,   /* function used to read data */        /* nothing more */    };struct proc_dir_entry jit_proc_queue = {        0,                 /* low_ino: the inode -- dynamic */        8, "jitqueue",     /* len of name and name */        S_IFREG | S_IRUGO, /* mode */        1, 0, 0,           /* nlinks, owner, group */        0, NULL,           /* size - unused; operations -- use default */        &jit_read_queue,    /* function used to read data */        /* nothing more */    };struct proc_dir_entry jit_proc_self = {        0,                 /* low_ino: the inode -- dynamic */        7, "jitself",      /* len of name and name */        S_IFREG | S_IRUGO, /* mode */        1, 0, 0,           /* nlinks, owner, group */        0, NULL,           /* size - unused; operations -- use default */        &jit_read_self,    /* function used to read data */        /* nothing more */    };/* * There is also a silly file returning the current time. */int jit_read_current(char *buf, char **start, off_t offset,                   int len, int unused){    struct timeval tv1, tv2;    unsigned long flags;    do_gettimeofday(&tv1);    save_flags(flags);    cli();    tv2 = xtime;    restore_flags(flags);    len=0;    len += sprintf(buf,"gettime: %9i.%06i\nxtime:   %9i.%06i\njiffies: %li\n",                   tv1.tv_sec, tv1.tv_usec,                   tv2.tv_sec, tv2.tv_usec, jiffies);    return len;}struct proc_dir_entry jit_proc_current = {        0,                 /* low_ino: the inode -- dynamic */        10, "currentime",  /* len of name and name */        S_IFREG | S_IRUGO, /* mode */        1, 0, 0,           /* nlinks, owner, group */        0, NULL,           /* size - unused; operations -- use default */        &jit_read_current, /* function used to read data */        /* nothing more */    };int init_module(void){    proc_register_dynamic(&proc_root, &jit_proc_busy);    proc_register_dynamic(&proc_root, &jit_proc_sched);    proc_register_dynamic(&proc_root, &jit_proc_queue);    proc_register_dynamic(&proc_root, &jit_proc_self);    proc_register_dynamic(&proc_root, &jit_proc_current);#ifndef JIT_DEBUG    register_symtab(NULL); /* hide symbols */#endif    return 0; /* succeed */}void cleanup_module(void){    proc_unregister(&proc_root, jit_proc_busy.low_ino);    proc_unregister(&proc_root, jit_proc_sched.low_ino);    proc_unregister(&proc_root, jit_proc_queue.low_ino);    proc_unregister(&proc_root, jit_proc_self.low_ino);    proc_unregister(&proc_root, jit_proc_current.low_ino);}#endif /* version 1.99.4 or newer */