南京.旧事

[root@plato]# ls /proc

1     2040  2347  2874  474          fb           mdstat      sys

104   2061  2356  2930  9            filesystems  meminfo     sysrq-trigger

113   2073  2375  2933  acpi         fs           misc        sysvipc

1375  21    2409  2934  buddyinfo    ide          modules     tty

1395  2189  2445  2935  bus          interrupts   mounts      uptime

1706  2201  2514  2938  cmdline      iomem        mtrr        version

179   2211  2515  2947  cpuinfo      ioports      net         vmstat

180   2223  2607  3     crypto       irq          partitions

181   2278  2608  3004  devices      kallsyms     pci

182   2291  2609  3008  diskstats    kcore        self

2     2301  263   3056  dma          kmsg         slabinfo

2015  2311  2805  394   driver       loadavg      stat

2019  2337  2821  4     execdomains  locks        swaps

[root@plato 1]# ls /proc/1

auxv     cwd      exe  loginuid  mem     oom_adj    root  statm   task

cmdline  environ  fd   maps      mounts  oom_score  stat  status  wchan

[root@plato]# cat /proc/1/cmdline

init [5]

[root@plato]#

[root@plato]# cat /proc/sys/net/ipv4/ip_forward

0

[root@plato]# echo "1" > /proc/sys/net/ipv4/ip_forward

[root@plato]# cat /proc/sys/net/ipv4/ip_forward

1

[root@plato]#

#include <linux/module.h>

/* Defines the license for this LKM */

MODULE_LICENSE("GPL");

/* Init function called on module entry */

int my_module_init( void )

{

  printk(KERN_INFO "my_module_init called.  Module is now loaded.\n");

  return 0;

}

/* Cleanup function called on module exit */

void my_module_cleanup( void )

{

  printk(KERN_INFO "my_module_cleanup called.  Module is now unloaded.\n");

  return;

}

/* Declare entry and exit functions */

module_init( my_module_init );

module_exit( my_module_cleanup );

obj-m += simple-lkm.o

[root@plato]# make -C /usr/src/linux-`uname -r` SUBDIRS=$PWD modules

make: Entering directory `/usr/src/linux-2.6.11'

  CC [M]  /root/projects/misc/module2.6/simple/simple-lkm.o

  Building modules, stage 2.

  MODPOST

  CC      /root/projects/misc/module2.6/simple/simple-lkm.mod.o

  LD [M]  /root/projects/misc/module2.6/simple/simple-lkm.ko

make: Leaving directory `/usr/src/linux-2.6.11'

[root@plato]#

[root@plato]# insmod simple-lkm.ko

[root@plato]# lsmod

Module                  Size  Used by

simple_lkm              1536  0

autofs4                26244  0

video                  13956  0

button                  5264  0

battery                 7684  0

ac                      3716  0

yenta_socket           18952  3

rsrc_nonstatic          9472  1 yenta_socket

uhci_hcd               32144  0

i2c_piix4               7824  0

dm_mod                 56468  3

[root@plato]# rmmod simple-lkm

[root@plato]#

[root@plato]# dmesg | tail -5

cs: IO port probe 0xa00-0xaff: clean.

eth0: Link is down

eth0: Link is up, running at 100Mbit half-duplex

my_module_init called.  Module is now loaded.

my_module_cleanup called.  Module is now unloaded.

[root@plato]#

struct proc_dir_entry *create_proc_entry( const char *name, mode_t mode,

                                             struct proc_dir_entry *parent );

struct proc_dir_entry {

      const char *name;              // virtual file name

      mode_t mode;                   // mode permissions

      uid_t uid;                     // File's user id

      gid_t gid;                     // File's group id

      struct inode_operations *proc_iops;  // Inode operations functions

      struct file_operations *proc_fops;   // File operations functions

      struct proc_dir_entry *parent;       // Parent directory

      ...

      read_proc_t *read_proc;              // /proc read function

      write_proc_t *write_proc;            // /proc write function

      void *data;                    // Pointer to private data

      atomic_t count;                      // use count

      ...

};

void remove_proc_entry( const char *name, struct proc_dir_entry *parent );

proc_dir_entry

在文件系统中的位置

proc_root_fs

/proc

proc_net

/proc/net

proc_bus

/proc/bus

proc_root_driver

/proc/driver

int mod_write( struct file *filp, const char __user *buff,

               unsigned long len, void *data );

int mod_read( char *page, char **start, off_t off,

              int count, int *eof, void *data );

/* Create a directory in the proc filesystem */

struct proc_dir_entry *proc_mkdir( const char *name,

                                     struct proc_dir_entry *parent );

/* Create a symlink in the proc filesystem */

struct proc_dir_entry *proc_symlink( const char *name,

                                       struct proc_dir_entry *parent,

                                       const char *dest );

/* Create a proc_dir_entry with a read_proc_t in one call */

struct proc_dir_entry *create_proc_read_entry( const char *name,

                                                  mode_t mode,

                                                  struct proc_dir_entry *base,

                                                  read_proc_t *read_proc,

                                                  void *data );

/* Copy buffer to user-space from kernel-space */

unsigned long copy_to_user( void __user *to,

                              const void *from,

                              unsigned long n );

/* Copy buffer to kernel-space from user-space */

unsigned long copy_from_user( void *to,

                                const void __user *from,

                                unsigned long n );

/* Allocate a 'virtually' contiguous block of memory */

void *vmalloc( unsigned long size );

/* Free a vmalloc'd block of memory */

void vfree( void *addr );

/* Export a symbol to the kernel (make it visible to the kernel) */

EXPORT_SYMBOL( symbol );

/* Export all symbols in a file to the kernel (declare before module.h) */

EXPORT_SYMTAB

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/proc_fs.h>

#include <linux/string.h>

#include <linux/vmalloc.h>

#include <asm/uaccess.h>

MODULE_LICENSE("GPL");

MODULE_DESCRIPTION("Fortune Cookie Kernel Module");

MODULE_AUTHOR("M. Tim Jones");

#define MAX_COOKIE_LENGTH       PAGE_SIZE

static struct proc_dir_entry *proc_entry;

static char *cookie_pot;  // Space for fortune strings

static int cookie_index;  // Index to write next fortune

static int next_fortune;  // Index to read next fortune

int init_fortune_module( void )

{

  int ret = 0;

  cookie_pot = (char *)vmalloc( MAX_COOKIE_LENGTH );

  if (!cookie_pot) {

    ret = -ENOMEM;

  } else {

    memset( cookie_pot, 0, MAX_COOKIE_LENGTH );

    proc_entry = create_proc_entry( "fortune", 0644, NULL );

    if (proc_entry == NULL) {

      ret = -ENOMEM;

      vfree(cookie_pot);

      printk(KERN_INFO "fortune: Couldn't create proc entry\n");

    } else {

      cookie_index = 0;

      next_fortune = 0;

      proc_entry->read_proc = fortune_read;

      proc_entry->write_proc = fortune_write;

      proc_entry->owner = THIS_MODULE;

      printk(KERN_INFO "fortune: Module loaded.\n");

    }

  }

  return ret;

}

void cleanup_fortune_module( void )

{

  remove_proc_entry("fortune", &proc_root);

  vfree(cookie_pot);

  printk(KERN_INFO "fortune: Module unloaded.\n");

}

module_init( init_fortune_module );

module_exit( cleanup_fortune_module );

ssize_t fortune_write( struct file *filp, const char __user *buff,

                        unsigned long len, void *data )

{

  int space_available = (MAX_COOKIE_LENGTH-cookie_index)+1;

  if (len > space_available) {

    printk(KERN_INFO "fortune: cookie pot is full!\n");

    return -ENOSPC;

  }

  if (copy_from_user( &cookie_pot[cookie_index], buff, len )) {

    return -EFAULT;

  }

  cookie_index += len;

  cookie_pot[cookie_index-1] = 0;

  return len;

}

int fortune_read( char *page, char **start, off_t off,

                   int count, int *eof, void *data )

{

  int len;

  if (off > 0) {

    *eof = 1;

    return 0;

  }

  /* Wrap-around */

  if (next_fortune >= cookie_index) next_fortune = 0;

  len = sprintf(page, "%s\n", &cookie_pot[next_fortune]);

  next_fortune += len;

  return len;

}

[root@plato]# insmod fortune.ko

[root@plato]# echo "Success is an individual proposition.  Thomas Watson" > /proc/fortune

[root@plato]# echo "If a man does his best, what else is there?  Gen. Patton" > /proc/fortune

[root@plato]# echo "Cats: All your base are belong to us.  Zero Wing" > /proc/fortune

[root@plato]# cat /proc/fortune

Success is an individual proposition.  Thomas Watson

[root@plato]# cat /proc/fortune

If a man does his best, what else is there?  General Patton

[root@plato]#