Re: Kernel page table and module text

[Dave Airlie <airlied@gmail.com>]

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> I want to find where each module is loaded in memory by traversing the
> module list . Once I have the address and the size of the module, I
> want to read the bytes in memory of the module and hash it to check
> it's integrity.
> 

Heres some code I wrote for Stargames to do a CRC tracking of every
module loaded, it may have a race condition on module unload, but it
works perfectly for what they want to use it for....

It just runs a kthread doing the CRCing of the kernel test and modules
every so often...

I also have similiar code to do the same for shared objects loaded in
userspace, but it requires a daemon in userspace to the CRCing whose
license I'm not entirely sure of..

Dave.

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diff -urpN --exclude-from=/storage/devel/dontdiff clean/linux-2.6.10/arch/i386/Kconfig linux-2.6.10/arch/i386/Kconfig
--- clean/linux-2.6.10/arch/i386/Kconfig	2005-02-23 16:29:08.000000000 +1100
+++ linux-2.6.10/arch/i386/Kconfig	2005-02-23 16:38:04.000000000 +1100
@@ -876,6 +876,24 @@ config REGPARM
 
 endmenu
 
+menu "Stargames Options"
+
+config KERNEL_CRC
+	prompt "Kernel CRC Support"
+	bool
+	default y
+
+config SG_CRC_USE_KERNEL
+	prompt "Use in-kernel routines for CRC"
+	bool
+	default y
+
+endmenu
 
 menu "Power management options (ACPI, APM)"
 	depends on !X86_VOYAGER
diff -urpN --exclude-from=/storage/devel/dontdiff clean/linux-2.6.10/fs/proc/root.c linux-2.6.10/fs/proc/root.c
--- clean/linux-2.6.10/fs/proc/root.c	2005-02-23 16:30:13.000000000 +1100
+++ linux-2.6.10/fs/proc/root.c	2005-02-23 16:38:05.000000000 +1100
@@ -76,6 +76,9 @@ void __init proc_root_init(void)
 #ifdef CONFIG_PROC_DEVICETREE
 	proc_device_tree_init();
 #endif
+#if defined(CONFIG_KERNEL_CRC)
+	proc_mkdir("stargames", 0);
+#endif
 	proc_bus = proc_mkdir("bus", NULL);
 }
 
diff -urpN --exclude-from=/storage/devel/dontdiff clean/linux-2.6.10/include/linux/kern_crc.h linux-2.6.10/include/linux/kern_crc.h
--- clean/linux-2.6.10/include/linux/kern_crc.h	1970-01-01 10:00:00.000000000 +1000
+++ linux-2.6.10/include/linux/kern_crc.h	2005-02-23 16:38:05.000000000 +1100
@@ -0,0 +1,8 @@
+#ifndef LINUX_KERNEL_CRC_H
+#define LINUX_KERNEL_CRC_H
+
+int kernel_crc_init(void);
+int kernel_crc_module_init(const char *modname, const void *modstart);
+int kernel_crc_module_remove(const char *modname);
+int kernel_crc_module_enable(struct module *mod);
+#endif
diff -urpN --exclude-from=/storage/devel/dontdiff clean/linux-2.6.10/kernel/kern_crc.c linux-2.6.10/kernel/kern_crc.c
--- clean/linux-2.6.10/kernel/kern_crc.c	1970-01-01 10:00:00.000000000 +1000
+++ linux-2.6.10/kernel/kern_crc.c	2005-02-23 16:38:05.000000000 +1100
@@ -0,0 +1,419 @@
+/*****************************************************************************
+*                Copyright Stargames Ltd. 2003, 2004, 2005                   *
+*                                                                            *
+* This file is under the GNU GPL as it is part of the Linux Kernel used      *
+* in the SGP_1000 project.                                                   *
+*                                                                            *
+* File             :  kern_crc.c
+* Purpose          :  Linux Kernel CRC Check
+* Creator          :  David Airlie (davidairlie@stargames.com.au)
+* When             :  Jan 2003
+* $Log:
+* $
+* TODO:  Add handler for when a CRC error occurs
+* 
+\****************************************************************************/
+
+#include <linux/config.h>
+#include <linux/version.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/file.h>
+#include <linux/list.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/init.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+//#define KERNEL_CRC_DEBUG 
+/* Initialise the Kernel CRC Thread */
+
+struct kcrc_module_list {
+  struct list_head list;
+  struct semaphore per_module_semaphore;
+  struct module *mod;
+  __u32 crc;
+  int enabled;
+};
+
+LIST_HEAD(kcrc_modules);
+
+#ifdef CONFIG_SG_CRC_USE_KERNEL
+#include <linux/crc32.h>
+#else
+static const __u32 crc32_table[];
+#endif
+
+extern unsigned long _etext, _stext;
+
+static __u32 num_loops;
+static __u32 kernel_text_crc;
+
+static struct semaphore module_semaphore;
+
+#define INTER_CRC_SECS 30
+#define SCHEDULE_OFTEN 0x1000
+
+static inline unsigned long kcrc_do_crc(__u32 crc_start, __u32 crc_end, unsigned char allow_sched)
+{
+  unsigned long crc=0;
+  unsigned long cur_length, total_length, this_length;
+  unsigned long time_start;
+
+  cur_length = 0;
+  total_length = crc_end - crc_start;
+
+  while (cur_length < total_length)
+  {
+    this_length = total_length - cur_length;
+    if (this_length > SCHEDULE_OFTEN)
+      this_length = SCHEDULE_OFTEN;
+    
+#ifdef CONFIG_SG_CRC_USE_KERNEL
+    crc=crc32(crc, crc_start+cur_length, this_length);
+#else
+    {
+      unsigned char *curbyte;
+      
+      for (curbyte=(unsigned char *)crc_start_cur_length; curbyte<(unsigned char *)(crc_start+cur_length+this_length); curbyte++)
+	crc = crc32_table[(crc ^ *curbyte) & 0xff] ^ (crc >> 8);
+    }
+#endif
+    cur_length += this_length;
+    if (allow_sched)
+    {
+      set_current_state(TASK_INTERRUPTIBLE);
+      schedule_timeout(HZ);
+    }
+  }
+  return crc;
+}
+
+/* 
+ * this thread should also do the segments for modules loaded into the system
+ * modules however don't have segments we can see from the kernel,
+ * so the module loading system has to let us know the start, length and CRC
+ * of the text segments of the modules when loading them
+ */
+int kernel_crc(void *unused)
+{
+  /* Run for-ever */
+  /* print out kernel text segment start and end */
+  struct list_head *m;
+  unsigned long length = ((__u32)&_etext) - ((__u32)&_stext);
+  unsigned long start;
+  unsigned long checksum=0;
+  struct kcrc_module_list *mod;
+
+  sema_init(&module_semaphore, 1);
+  /* daemonizse, set name and block signals */
+  daemonize("kernel_crcd");
+
+  printk("CRC: Thread checking %p, %p size: %8lX\n", &_stext, &_etext, length);
+  kernel_text_crc = kcrc_do_crc((__u32)&_stext, (__u32)&_etext, 0);
+  printk("CRC: Initial CRC: %8lX\n", (unsigned long)kernel_text_crc);
+
+  while(!kthread_should_stop())  {
+    /* set the task to interruptible so the schedules below can switch tasks */
+    set_current_state(TASK_INTERRUPTIBLE);
+    
+    /* get a jiffies count */
+    start=jiffies;
+    num_loops++;
+    /* We need to CRC check the entire text segment */
+    checksum=kcrc_do_crc((__u32)&_stext,(__u32)&_etext, 1);
+
+    if (checksum!=kernel_text_crc)
+    {
+      printk("CRC: Checksum incorrect %8lX\n", checksum);
+      goto do_crc_error;
+    }
+#ifdef KERNEL_CRC_DEBUG
+    else
+      printk("CRC: Checksum is %8lX took %lu jiffies\n", (unsigned long)checksum, jiffies-start);
+#endif
+    start=0;
+    printk("do_check: About do Down module semaphore\n");
+    down(&module_semaphore);
+    printk("do_check Downed module semaphore\n");
+    /* Traverse the linked list of modules and check their CRCs */
+    list_for_each(m, &kcrc_modules) {
+      mod=list_entry(m, struct kcrc_module_list, list);
+      down(&(mod->per_module_semaphore));
+      up(&module_semaphore);
+#ifdef KERNEL_CRC_DEBUG
+      printk("CRC: Thread checking module %8lX, size: %8lX: crc %8lX\n", mod->mod->module_core, mod->mod->core_text_size, mod->crc);
+#endif
+      if (mod->enabled)
+      {
+	checksum=kcrc_do_crc((__u32)mod->mod->module_core, (__u32)mod->mod->module_core+mod->mod->core_text_size, 1);
+	if (checksum!=mod->crc)
+	{
+	  printk("CRC: Module Checksum incorrect %s expected: %8lX got: %8lX\n", mod->mod->name, (unsigned long)mod->crc, checksum);
+	  goto do_crc_error;
+	}
+      }
+      up(&mod->per_module_semaphore);
+      down(&module_semaphore);
+    }
+
+    /* Only run once ever INTER_CRC_SECS second */
+    printk("do_Check about to up\n");
+    up(&module_semaphore);
+    set_current_state(TASK_INTERRUPTIBLE);
+    schedule_timeout(HZ*INTER_CRC_SECS);    
+  }
+  
+ do_crc_error:
+  /* oh no bad stuff has happened.. duck and cover */
+  /* executing any code is a bad idea now do as little as possible */
+
+  /* write something to NVRAM */
+  /* hang the machine up and let the watchdog blow us away */
+  return 0;
+}
+
+// 2.6 only
+int kernel_crc_module_enable(struct module *mod)
+{
+  /* run through the list and look for the modname in it */
+  struct kcrc_module_list *new_ent;
+
+  printk("CRC: enabling module %s, %p %8lX\n", mod->name, mod->module_core, mod->core_text_size);
+
+  new_ent = kmalloc(sizeof(struct kcrc_module_list), GFP_KERNEL);
+  if (new_ent==NULL)
+    return -EFAULT;
+
+  new_ent->mod=mod;
+  new_ent->enabled=1;
+  sema_init(&new_ent->per_module_semaphore, 1);
+  new_ent->crc = kcrc_do_crc((__u32)new_ent->mod->module_core, (__u32)new_ent->mod->module_core+new_ent->mod->core_text_size, 0);
+  list_add_tail(&new_ent->list, &kcrc_modules);
+  return 0;
+}
+
+int kernel_crc_module_remove(const char *modname)
+{
+  /* run through the list and look for the modname in it */
+  struct list_head *m;
+  struct kcrc_module_list *mod;
+  int ret;
+
+  printk("CRC: removing module about to down sem %s\n", modname);
+
+  ret=down_interruptible(&module_semaphore);
+  if (ret!=0)
+    goto out;
+
+  printk("CRC: remove sema down\n");
+  list_for_each(m, &kcrc_modules) {
+    mod=list_entry(m, struct kcrc_module_list, list);
+    
+    if (strcmp(mod->mod->name, modname)==0)
+    {
+      if (down_interruptible(&mod->per_module_semaphore))
+      {
+	goto out_unlock;
+      }
+
+      /* disable and free it */
+      mod->enabled=0;
+      list_del(&mod->list);
+      kfree(mod);
+      break;
+    }
+  }
+ out_unlock:
+  up(&module_semaphore);
+ out:
+  return ret;
+}
+
+int __init kernel_crc_init(void)
+{
+  struct task_struct *p;
+  printk("CRC: Starting Thread\n");
+  
+  p=kthread_run(kernel_crc, NULL, "kernel_crcd");
+  return 0;
+}
+
+/* iterator */
+static void *kcrc_seq_start(struct seq_file *m, loff_t *pos)
+{
+  struct list_head *p = &kcrc_modules;
+  loff_t n = *pos;
+  
+  /* XXX: surely we need some locking for traversing the list? */
+  while (n--) {
+    p = p->next;
+    if (p == &kcrc_modules)
+      return NULL;
+  }
+  return p;
+}
+
+static void *kcrc_seq_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	struct list_head *p = v;
+	(*pos)++;
+	return p->next != &kcrc_modules ? p->next : NULL;
+}
+
+static void kcrc_seq_stop(struct seq_file *m, void *v)
+{
+	/* release whatever locks we need */
+}
+
+static int kcrc_seq_show_list(struct seq_file *m, void *v)
+{
+  struct list_head *p=v;
+  const struct kcrc_module_list *mod;
+
+  if (p == &kcrc_modules) {
+    seq_printf(m, "Kernel: loops %d: CRC %08lX\n", num_loops, (unsigned long)kernel_text_crc);
+    seq_puts(m, "Module Name(e)\tStart\t\tLength\t\tCRC\n");
+    return 0;
+  }
+  
+  mod=list_entry(p, struct kcrc_module_list, list);
+  
+  seq_printf(m,"%s(%d)\t\t0x%8X\t0x%08lX\t0x%08X\n", mod->mod->name, mod->enabled,(__u32)mod->mod->module_core, mod->mod->core_text_size, mod->crc);
+  return 0;
+}
+
+static struct seq_operations proc_kcrc_op = {
+	start:	kcrc_seq_start,
+	next:	kcrc_seq_next,
+	stop:	kcrc_seq_stop,
+	show:   kcrc_seq_show_list
+};
+
+static int proc_kcrc_open(struct inode *inode, struct file *file)
+{
+	return seq_open(file, &proc_kcrc_op);
+}
+
+static struct file_operations proc_kcrc_operations = {
+	open:		proc_kcrc_open,
+	read:		seq_read,
+	llseek:		seq_lseek,
+	release:	seq_release,
+};
+
+static int __init kcrc_proc_init(void)
+{
+  struct proc_dir_entry *entry;
+  
+  entry = create_proc_entry("stargames/kcrc", 0, NULL);
+  if (entry)
+    entry->proc_fops = &proc_kcrc_operations;
+  return 0;
+}
+
+__initcall(kernel_crc_init);
+__initcall(kcrc_proc_init);
+
+#ifndef CONFIG_SG_CRC_USE_KERNEL
+/*
+ *  COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or
+ *  code or tables extracted from it, as desired without restriction.
+ *
+ *  First, the polynomial itself and its table of feedback terms.  The
+ *  polynomial is
+ *  X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
+ *
+ *  Note that we take it "backwards" and put the highest-order term in
+ *  the lowest-order bit.  The X^32 term is "implied"; the LSB is the
+ *  X^31 term, etc.  The X^0 term (usually shown as "+1") results in
+ *  the MSB being 1
+ *
+ *  Note that the usual hardware shift register implementation, which
+ *  is what we're using (we're merely optimizing it by doing eight-bit
+ *  chunks at a time) shifts bits into the lowest-order term.  In our
+ *  implementation, that means shifting towards the right.  Why do we
+ *  do it this way?  Because the calculated CRC must be transmitted in
+ *  order from highest-order term to lowest-order term.  UARTs transmit
+ *  characters in order from LSB to MSB.  By storing the CRC this way
+ *  we hand it to the UART in the order low-byte to high-byte; the UART
+ *  sends each low-bit to hight-bit; and the result is transmission bit
+ *  by bit from highest- to lowest-order term without requiring any bit
+ *  shuffling on our part.  Reception works similarly
+ *
+ *  The feedback terms table consists of 256, 32-bit entries.  Notes
+ *
+ *      The table can be generated at runtime if desired; code to do so
+ *      is shown later.  It might not be obvious, but the feedback
+ *      terms simply represent the results of eight shift/xor opera
+ *      tions for all combinations of data and CRC register values
+ *
+ *      The values must be right-shifted by eight bits by the "updcrc
+ *      logic; the shift must be unsigned (bring in zeroes).  On some
+ *      hardware you could probably optimize the shift in assembler by
+ *      using byte-swap instructions
+ *      polynomial $edb88320
+ */
+
+/* $Id: kern_crc.c,v 1.6 2003/02/27 23:22:01 airlied Exp $ */
+
+static const __u32 crc32_table[256] = {
+	0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
+	0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
+	0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
+	0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
+	0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
+	0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
+	0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
+	0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
+	0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
+	0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
+	0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
+	0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
+	0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
+	0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
+	0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
+	0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
+	0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
+	0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
+	0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
+	0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
+	0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
+	0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
+	0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
+	0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
+	0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
+	0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
+	0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
+	0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
+	0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
+	0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
+	0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
+	0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
+	0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
+	0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
+	0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
+	0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
+	0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
+	0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
+	0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
+	0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
+	0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
+	0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
+	0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
+	0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
+	0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
+	0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
+	0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
+	0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
+	0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
+	0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
+	0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
+	0x2d02ef8dL
+};
+
+
+
+#endif
diff -urpN --exclude-from=/storage/devel/dontdiff clean/linux-2.6.10/kernel/Makefile linux-2.6.10/kernel/Makefile
--- clean/linux-2.6.10/kernel/Makefile	2005-02-23 16:30:28.000000000 +1100
+++ linux-2.6.10/kernel/Makefile	2005-02-23 16:38:05.000000000 +1100
@@ -27,6 +27,9 @@ obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
 
+obj-$(CONFIG_KERNEL_CRC) += kern_crc.o
+
 ifneq ($(CONFIG_IA64),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
 # needed for x86 only.  Why this used to be enabled for all architectures is beyond
diff -urpN --exclude-from=/storage/devel/dontdiff clean/linux-2.6.10/kernel/module.c linux-2.6.10/kernel/module.c
--- clean/linux-2.6.10/kernel/module.c	2005-02-23 16:30:28.000000000 +1100
+++ linux-2.6.10/kernel/module.c	2005-02-23 16:39:30.000000000 +1100
@@ -35,6 +35,7 @@
 #include <linux/notifier.h>
 #include <linux/stop_machine.h>
 #include <linux/device.h>
+#include <linux/kern_crc.h>
 #include <asm/uaccess.h>
 #include <asm/semaphore.h>
 #include <asm/cacheflush.h>
@@ -1105,6 +1106,9 @@ static void free_module(struct module *m
 	remove_sect_attrs(mod);
 	mod_kobject_remove(mod);
 
+#ifdef CONFIG_KERNEL_CRC
+	kernel_crc_module_remove(mod->name);
+#endif
 	/* Arch-specific cleanup. */
 	module_arch_cleanup(mod);
 
@@ -1775,6 +1779,10 @@ sys_init_module(void __user *umod,
 		return PTR_ERR(mod);
 	}
 
+#ifdef CONFIG_KERNEL_CRC
+	kernel_crc_module_enable(mod);
+#endif
+
 	/* Flush the instruction cache, since we've played with text */
 	if (mod->module_init)
 		flush_icache_range((unsigned long)mod->module_init,