Fwd: How to call a function in a module from the kernel code !!! (Linux kernel)

From: omkar lagu
Date: Fri Feb 10 2006 - 05:29:02 EST

hello sir,

PROBLEM::How to call a function in a module from
the kernel code ??

what we did ? ::
we wanted to call a function in our module ll from
shm.c file (which is in the kernel)

so we declared function pointer in shm.c
:: unsigned long long (*ptr1)(int)

we declared it as extern in shm.h
:: extern unsigned long long (*ptr1)(int)

then we declared also in our module (ll)
:: extern unsigned long long (*ptr1)(int)

error

but it gave an error as undefined refernce to ptr1
when we inserted our module..

as per the request i am attaching the source code
plz look into it i have put comments where i tried
to
do all this stuff ??
after doing this i was expecting ptr1 ptr2 ptr3 to
be in the file kallsyms which is in /proc after
compiling the kernel.
but it didn`t happen ??
but ptr1 ptr2 ptr3 are present in system.map file
when i compiled the kernel
i want to do all this cause i want to implement the
hook i.e the function ptr1 ptr2 ptr3 are only called

when i insmod my module
i have attached shm.c shm.h and ll.c
in ll.c you will find only ptr1 and ptr2 you won`t
find ptr3
plz cc to omkarlagu@xxxxxxxxx




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http://mail.yahoo.com /*
* linux/ipc/shm.c
* Copyright (C) 1992, 1993 Krishna Balasubramanian
* Many improvements/fixes by Bruno Haible.
* Replaced `struct shm_desc' by `struct vm_area_struct', July 1994.
* Fixed the shm swap deallocation (shm_unuse()), August 1998 Andrea Arcangeli.
*
* /proc/sysvipc/shm support (c) 1999 Dragos Acostachioaie <dragos@xxxxxxxxx>
* BIGMEM support, Andrea Arcangeli <andrea@xxxxxxx>
* SMP thread shm, Jean-Luc Boyard <jean-luc.boyard@xxxxxxxxxx>
* HIGHMEM support, Ingo Molnar <mingo@xxxxxxxxxx>
* Make shmmax, shmall, shmmni sysctl'able, Christoph Rohland <cr@xxxxxxx>
* Shared /dev/zero support, Kanoj Sarcar <kanoj@xxxxxxx>
* Move the mm functionality over to mm/shmem.c, Christoph Rohland <cr@xxxxxxx>
*
*/

#include <linux/config.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/shmem_fs.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/ptrace.h>
#include <linux/seq_file.h>
#include <asm/uaccess.h>
#include <linux/ipc.h> /* For DIPC definition */
#include "util.h"
//#include <linux/module.h>
#define shm_flags shm_perm.mode

static struct file_operations shm_file_operations;
static struct vm_operations_struct shm_vm_ops;
static struct ipc_ids shm_ids;

#define shm_lock(id) ((struct shmid_kernel*)ipc_lock(&shm_ids,id))
#define shm_unlock(shp) ipc_unlock(&(shp)->shm_perm)
#define shm_get(id) ((struct shmid_kernel*)ipc_get(&shm_ids,id))
#define shm_buildid(id, seq) \
ipc_buildid(&shm_ids, id, seq)

static int newseg (unsigned long long j, key_t key, int shmflg, size_t size);
static void shm_open (struct vm_area_struct *shmd);
static void shm_close (struct vm_area_struct *shmd);
unsigned long long concatanate(int shmid);



/* Here are the three function pointers declared */
/* you can see this 3 functions are called in sys_shmget function below */

unsigned long long (*ptr1)(int);
void (*ptr2)(int, unsigned long long);
unsigned long long (*ptr3)(int,struct buffer *,int);


/*---------------------------------------------------------*/



#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it);
#endif

size_t shm_ctlmax = SHMMAX;
size_t shm_ctlall = SHMALL;
int shm_ctlmni = SHMMNI;

static int shm_tot; /* total number of shared memory pages */

void __init shm_init (void)
{
ipc_init_ids(&shm_ids, 1);
ipc_init_proc_interface("sysvipc/shm",
" key shmid perms size cpid lpid nattch uid gid cuid cgid atime dtime ctime\n",
&shm_ids,
sysvipc_shm_proc_show);
}

static inline int shm_checkid(struct shmid_kernel *s, int id)
{
if (ipc_checkid(&shm_ids,&s->shm_perm,id))
return -EIDRM;
return 0;
}

static inline struct shmid_kernel *shm_rmid(int id)
{
return (struct shmid_kernel *)ipc_rmid(&shm_ids,id);
}

static inline int shm_addid(struct shmid_kernel *shp)
{
return ipc_addid(&shm_ids, &shp->shm_perm, shm_ctlmni);
}



static inline void shm_inc (int id) {
struct shmid_kernel *shp;

if(!(shp = shm_lock(id)))
BUG();
shp->shm_atim = get_seconds();
shp->shm_lprid = current->tgid;
shp->shm_nattch++;
shm_unlock(shp);
}

/* This is called by fork, once for every shm attach. */
static void shm_open (struct vm_area_struct *shmd)
{
shm_inc (shmd->vm_file->f_dentry->d_inode->i_ino);
}

/*
* shm_destroy - free the struct shmid_kernel
*
* @shp: struct to free
*
* It has to be called with shp and shm_ids.sem locked,
* but returns with shp unlocked and freed.
*/
static void shm_destroy (struct shmid_kernel *shp)
{
shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
shm_rmid (shp->id);
shm_unlock(shp);
if (!is_file_hugepages(shp->shm_file))
shmem_lock(shp->shm_file, 0, shp->mlock_user);
else
user_shm_unlock(shp->shm_file->f_dentry->d_inode->i_size,
shp->mlock_user);
fput (shp->shm_file);
security_shm_free(shp);
ipc_rcu_putref(shp);
}

/*
* remove the attach descriptor shmd.
* free memory for segment if it is marked destroyed.
* The descriptor has already been removed from the current->mm->mmap list
* and will later be kfree()d.
*/
static void shm_close (struct vm_area_struct *shmd)
{
struct file * file = shmd->vm_file;
int id = file->f_dentry->d_inode->i_ino;
struct shmid_kernel *shp;

down (&shm_ids.sem);
/* remove from the list of attaches of the shm segment */
if(!(shp = shm_lock(id)))
BUG();
shp->shm_lprid = current->tgid;
shp->shm_dtim = get_seconds();
shp->shm_nattch--;
if(shp->shm_nattch == 0 &&
shp->shm_flags & SHM_DEST)
shm_destroy (shp);
else
shm_unlock(shp);
up (&shm_ids.sem);
}

static int shm_mmap(struct file * file, struct vm_area_struct * vma)
{
file_accessed(file);
vma->vm_ops = &shm_vm_ops;
shm_inc(file->f_dentry->d_inode->i_ino);
return 0;
}

static struct file_operations shm_file_operations = {
.mmap = shm_mmap
};

static struct vm_operations_struct shm_vm_ops = {
.open = shm_open, /* callback for a new vm-area open */
.close = shm_close, /* callback for when the vm-area is released */
.nopage = shmem_nopage,
#if defined(CONFIG_NUMA) && defined(CONFIG_SHMEM)
.set_policy = shmem_set_policy,
.get_policy = shmem_get_policy,
#endif
};

unsigned long long concatanate(int shmid) {
unsigned long long temp1, temp2;
temp1 = shmid;
temp2 = CURR_NODE;
temp2 = temp2 << 33;
return ((temp1 | temp2));
}

static int newseg (unsigned long long j, key_t key, int shmflg, size_t size)
{
int error;
struct shmid_kernel *shp;
int numpages = (size + PAGE_SIZE -1) >> PAGE_SHIFT;
struct file * file;
char name[13];
int id;
unsigned long long temp;

if (size < SHMMIN || size > shm_ctlmax)
return -EINVAL;

if (shm_tot + numpages >= shm_ctlall)
return -ENOSPC;

shp = ipc_rcu_alloc(sizeof(*shp));
if (!shp)
return -ENOMEM;

shp->shm_perm.key = key;
shp->shm_flags = ((shmflg & S_IRWXUGO));
shp->mlock_user = NULL;

shp->shm_perm.security = NULL;
error = security_shm_alloc(shp);
if (error) {
ipc_rcu_putref(shp);
return error;
}

if (shmflg & SHM_HUGETLB) {
/* hugetlb_zero_setup takes care of mlock user accounting */
file = hugetlb_zero_setup(size);
shp->mlock_user = current->user;
} else {
sprintf (name, "SYSV%08x", key);
file = shmem_file_setup(name, size, VM_ACCOUNT);
}
error = PTR_ERR(file);
if (IS_ERR(file))
goto no_file;

error = -ENOSPC;
id = shm_addid(shp);
if(id == -1)
goto no_id;

shp->shm_cprid = current->tgid;
shp->shm_lprid = 0;
shp->shm_atim = shp->shm_dtim = 0;
shp->shm_ctim = get_seconds();
shp->shm_segsz = size;
shp->shm_nattch = 0;
shp->id = shm_buildid(id,shp->shm_perm.seq);
if (shmflg & IPC_DIPC) {
if( j == 0 || j == 1) {
temp = concatanate(shp->id);
shp->glob_info.global_id = temp;
if (j == 0)
if(ptr2)
(*ptr2)(key,shp->glob_info.global_id);
}
else
shp->glob_info.global_id = j;
}
else
shp->glob_info.global_id = 0;
shp->shm_file = file;
file->f_dentry->d_inode->i_ino = shp->id;
if (shmflg & SHM_HUGETLB)
set_file_hugepages(file);
else
file->f_op = &shm_file_operations;
shm_tot += numpages;
shm_unlock(shp);
return shp->id;

no_id:
fput(file);
no_file:
security_shm_free(shp);
ipc_rcu_putref(shp);
return error;
}

int hash(int key) { /* Hash function */
return(key % 2);

}


asmlinkage long sys_shmget (key_t key, size_t size, int shmflg)
{
struct shmid_kernel *shp;
int err, id = 0, i = 0, nodeid;
unsigned long long j = 0, temp;
struct buffer *bf;
down(&shm_ids.sem);

if (shmflg & IPC_DIPC) { /* Checking if DIPC flag is set */
if((nodeid = hash(key)) == CURR_NODE) { /* Checking if key mgr is present node */
if(ptr1)
j = (*ptr1)(key); //Function call in ll module
if(j == 0) /* Segment with given key is being created for the first time on local node*/
err = newseg(j, key, shmflg, size);
else {
if((id = ipc_findkey(&shm_ids, key)) == -1) { /*Segment with given key exists but we */
err = newseg(j, key, shmflg, size); /*have to check if it has been created */
} /*on local node.*/
else {
shp = shm_lock(id);
if(shp==NULL)
BUG();
if (shp->shm_segsz < size)
err = -EINVAL;
else if (ipcperms(&shp->shm_perm, shmflg))
err = -EACCES;
else {
int shmid = shm_buildid(id, shp->shm_perm.seq);
err = security_shm_associate(shp, shmflg);
if (!err)
err = shmid;
}
shm_unlock(shp);
}
}
}
else {
printk("Key manager not present node");
bf = (struct buffer*)kmalloc(sizeof(struct buffer),GFP_KERNEL);
bf->msgtype = 1;
bf->data.key = key;
printk(KERN_ALERT "\n First time key : %d",bf->data.key);
if(ptr3)
j=(*ptr3)(nodeid,bf,sizeof(struct buffer)); //Functioncall
if(j == 1) {
err = newseg(j, key, shmflg, size);
temp = concatanate(err);
bf = (struct buffer*)kmalloc(sizeof(struct buffer),GFP_KERNEL);
bf->msgtype = 6;
bf->data.key = key;
bf->data.global_id = temp;
printk(KERN_ALERT "\nSecond time key :%d -> %lli", bf->data.key, bf->data.global_id);
if(ptr3)
j=(*ptr3)(nodeid,bf,sizeof(struct buffer)); //Function call
}
else {
if((id = ipc_findkey(&shm_ids, key)) == -1) { /*Segment with given key exists but we */
err = newseg(j, key, shmflg, size); /*have to check if it has been created */
} /*on local node.*/
else {
shp = shm_lock(id);
if(shp==NULL)
BUG();
if (shp->shm_segsz < size)
err = -EINVAL;
else if (ipcperms(&shp->shm_perm, shmflg))
err = -EACCES;
else {
int shmid = shm_buildid(id, shp->shm_perm.seq);
err = security_shm_associate(shp, shmflg);
if (!err)
err = shmid;
}
shm_unlock(shp);
}
}
/* Code for communication with communication layer */
}
}
else {
if (key == IPC_PRIVATE) {
err = newseg(j, key, shmflg, size);
} else if ((id = ipc_findkey(&shm_ids, key)) == -1) {
if (!(shmflg & IPC_CREAT))
err = -ENOENT;
else
err = newseg(j, key, shmflg, size);
} else if ((shmflg & IPC_CREAT) && (shmflg & IPC_EXCL)) {
err = -EEXIST;
} else {
shp = shm_lock(id);
if(shp==NULL)
BUG();
if (shp->shm_segsz < size)
err = -EINVAL;
else if (ipcperms(&shp->shm_perm, shmflg))
err = -EACCES;
else {
int shmid = shm_buildid(id, shp->shm_perm.seq);
err = security_shm_associate(shp, shmflg);
if (!err)
err = shmid;
}
shm_unlock(shp);
}
}
up(&shm_ids.sem);

return err;
}



/* The 3 pointers are expoted here */
EXPORT_SYMBOL(ptr1);
EXPORT_SYMBOL(ptr2);
EXPORT_SYMBOL(ptr3);
/*------------------------------------------------------------*/



static inline unsigned long copy_shmid_to_user(void __user *buf, struct shmid64_ds *in, int version)
{
switch(version) {
case IPC_64:
return copy_to_user(buf, in, sizeof(*in));
case IPC_OLD:
{
struct shmid_ds out;

ipc64_perm_to_ipc_perm(&in->shm_perm, &out.shm_perm);
out.shm_segsz = in->shm_segsz;
out.shm_atime = in->shm_atime;
out.shm_dtime = in->shm_dtime;
out.shm_ctime = in->shm_ctime;
out.shm_cpid = in->shm_cpid;
out.shm_lpid = in->shm_lpid;
out.shm_nattch = in->shm_nattch;

return copy_to_user(buf, &out, sizeof(out));
}
default:
return -EINVAL;
}
}

struct shm_setbuf {
uid_t uid;
gid_t gid;
mode_t mode;
};

static inline unsigned long copy_shmid_from_user(struct shm_setbuf *out, void __user *buf, int version)
{
switch(version) {
case IPC_64:
{
struct shmid64_ds tbuf;

if (copy_from_user(&tbuf, buf, sizeof(tbuf)))
return -EFAULT;

out->uid = tbuf.shm_perm.uid;
out->gid = tbuf.shm_perm.gid;
out->mode = tbuf.shm_flags;

return 0;
}
case IPC_OLD:
{
struct shmid_ds tbuf_old;

if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
return -EFAULT;

out->uid = tbuf_old.shm_perm.uid;
out->gid = tbuf_old.shm_perm.gid;
out->mode = tbuf_old.shm_flags;

return 0;
}
default:
return -EINVAL;
}
}

static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminfo64 *in, int version)
{
switch(version) {
case IPC_64:
return copy_to_user(buf, in, sizeof(*in));
case IPC_OLD:
{
struct shminfo out;

if(in->shmmax > INT_MAX)
out.shmmax = INT_MAX;
else
out.shmmax = (int)in->shmmax;

out.shmmin = in->shmmin;
out.shmmni = in->shmmni;
out.shmseg = in->shmseg;
out.shmall = in->shmall;

return copy_to_user(buf, &out, sizeof(out));
}
default:
return -EINVAL;
}
}

static void shm_get_stat(unsigned long *rss, unsigned long *swp)
{
int i;

*rss = 0;
*swp = 0;

for (i = 0; i <= shm_ids.max_id; i++) {
struct shmid_kernel *shp;
struct inode *inode;

shp = shm_get(i);
if(!shp)
continue;

inode = shp->shm_file->f_dentry->d_inode;

if (is_file_hugepages(shp->shm_file)) {
struct address_space *mapping = inode->i_mapping;
*rss += (HPAGE_SIZE/PAGE_SIZE)*mapping->nrpages;
} else {
struct shmem_inode_info *info = SHMEM_I(inode);
spin_lock(&info->lock);
*rss += inode->i_mapping->nrpages;
*swp += info->swapped;
spin_unlock(&info->lock);
}
}
}

asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf)
{
struct shm_setbuf setbuf;
struct shmid_kernel *shp;
int err, version;

if (cmd < 0 || shmid < 0) {
err = -EINVAL;
goto out;
}

version = ipc_parse_version(&cmd);

switch (cmd) { /* replace with proc interface ? */
case IPC_INFO:
{
struct shminfo64 shminfo;

err = security_shm_shmctl(NULL, cmd);
if (err)
return err;

memset(&shminfo,0,sizeof(shminfo));
shminfo.shmmni = shminfo.shmseg = shm_ctlmni;
shminfo.shmmax = shm_ctlmax;
shminfo.shmall = shm_ctlall;

shminfo.shmmin = SHMMIN;
if(copy_shminfo_to_user (buf, &shminfo, version))
return -EFAULT;
/* reading a integer is always atomic */
err= shm_ids.max_id;
if(err<0)
err = 0;
goto out;
}
case SHM_INFO:
{
struct shm_info shm_info;

err = security_shm_shmctl(NULL, cmd);
if (err)
return err;

memset(&shm_info,0,sizeof(shm_info));
down(&shm_ids.sem);
shm_info.used_ids = shm_ids.in_use;
shm_get_stat (&shm_info.shm_rss, &shm_info.shm_swp);
shm_info.shm_tot = shm_tot;
shm_info.swap_attempts = 0;
shm_info.swap_successes = 0;
err = shm_ids.max_id;
up(&shm_ids.sem);
if(copy_to_user (buf, &shm_info, sizeof(shm_info))) {
err = -EFAULT;
goto out;
}

err = err < 0 ? 0 : err;
goto out;
}
case SHM_STAT:
case IPC_STAT:
{
struct shmid64_ds tbuf;
int result;
memset(&tbuf, 0, sizeof(tbuf));
shp = shm_lock(shmid);
if(shp==NULL) {
err = -EINVAL;
goto out;
} else if(cmd==SHM_STAT) {
err = -EINVAL;
if (shmid > shm_ids.max_id)
goto out_unlock;
result = shm_buildid(shmid, shp->shm_perm.seq);
} else {
err = shm_checkid(shp,shmid);
if(err)
goto out_unlock;
result = 0;
}
err=-EACCES;
if (ipcperms (&shp->shm_perm, S_IRUGO))
goto out_unlock;
err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock;
kernel_to_ipc64_perm(&shp->shm_perm, &tbuf.shm_perm);
tbuf.shm_segsz = shp->shm_segsz;
tbuf.shm_atime = shp->shm_atim;
tbuf.shm_dtime = shp->shm_dtim;
tbuf.shm_ctime = shp->shm_ctim;
tbuf.shm_cpid = shp->shm_cprid;
tbuf.shm_lpid = shp->shm_lprid;
if (!is_file_hugepages(shp->shm_file))
tbuf.shm_nattch = shp->shm_nattch;
else
tbuf.shm_nattch = file_count(shp->shm_file) - 1;
shm_unlock(shp);
if(copy_shmid_to_user (buf, &tbuf, version))
err = -EFAULT;
else
err = result;
goto out;
}
case SHM_LOCK:
case SHM_UNLOCK:
{
shp = shm_lock(shmid);
if(shp==NULL) {
err = -EINVAL;
goto out;
}
err = shm_checkid(shp,shmid);
if(err)
goto out_unlock;

if (!capable(CAP_IPC_LOCK)) {
err = -EPERM;
if (current->euid != shp->shm_perm.uid &&
current->euid != shp->shm_perm.cuid)
goto out_unlock;
if (cmd == SHM_LOCK &&
!current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur)
goto out_unlock;
}

err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock;

if(cmd==SHM_LOCK) {
struct user_struct * user = current->user;
if (!is_file_hugepages(shp->shm_file)) {
err = shmem_lock(shp->shm_file, 1, user);
if (!err) {
shp->shm_flags |= SHM_LOCKED;
shp->mlock_user = user;
}
}
} else if (!is_file_hugepages(shp->shm_file)) {
shmem_lock(shp->shm_file, 0, shp->mlock_user);
shp->shm_flags &= ~SHM_LOCKED;
shp->mlock_user = NULL;
}
shm_unlock(shp);
goto out;
}
case IPC_RMID:
{
/*
* We cannot simply remove the file. The SVID states
* that the block remains until the last person
* detaches from it, then is deleted. A shmat() on
* an RMID segment is legal in older Linux and if
* we change it apps break...
*
* Instead we set a destroyed flag, and then blow
* the name away when the usage hits zero.
*/
down(&shm_ids.sem);
shp = shm_lock(shmid);
err = -EINVAL;
if (shp == NULL)
goto out_up;
err = shm_checkid(shp, shmid);
if(err)
goto out_unlock_up;

if (current->euid != shp->shm_perm.uid &&
current->euid != shp->shm_perm.cuid &&
!capable(CAP_SYS_ADMIN)) {
err=-EPERM;
goto out_unlock_up;
}

err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock_up;

if (shp->shm_nattch){
shp->shm_flags |= SHM_DEST;
/* Do not find it any more */
shp->shm_perm.key = IPC_PRIVATE;
shm_unlock(shp);
} else
shm_destroy (shp);
up(&shm_ids.sem);
goto out;
}

case IPC_SET:
{
if (copy_shmid_from_user (&setbuf, buf, version)) {
err = -EFAULT;
goto out;
}
if ((err = audit_ipc_perms(0, setbuf.uid, setbuf.gid, setbuf.mode)))
return err;
down(&shm_ids.sem);
shp = shm_lock(shmid);
err=-EINVAL;
if(shp==NULL)
goto out_up;
err = shm_checkid(shp,shmid);
if(err)
goto out_unlock_up;
err=-EPERM;
if (current->euid != shp->shm_perm.uid &&
current->euid != shp->shm_perm.cuid &&
!capable(CAP_SYS_ADMIN)) {
goto out_unlock_up;
}

err = security_shm_shmctl(shp, cmd);
if (err)
goto out_unlock_up;

shp->shm_perm.uid = setbuf.uid;
shp->shm_perm.gid = setbuf.gid;
shp->shm_flags = (shp->shm_flags & ~S_IRWXUGO)
| (setbuf.mode & S_IRWXUGO);
shp->shm_ctim = get_seconds();
break;
}

default:
err = -EINVAL;
goto out;
}

err = 0;
out_unlock_up:
shm_unlock(shp);
out_up:
up(&shm_ids.sem);
goto out;
out_unlock:
shm_unlock(shp);
out:
return err;
}

/*
* Fix shmaddr, allocate descriptor, map shm, add attach descriptor to lists.
*
* NOTE! Despite the name, this is NOT a direct system call entrypoint. The
* "raddr" thing points to kernel space, and there has to be a wrapper around
* this.
*/
long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr)
{
struct shmid_kernel *shp;
unsigned long addr;
unsigned long size;
struct file * file;
int err;
unsigned long flags;
unsigned long prot;
unsigned long o_flags;
int acc_mode;
void *user_addr;

if (shmid < 0) {
err = -EINVAL;
goto out;
} else if ((addr = (ulong)shmaddr)) {
if (addr & (SHMLBA-1)) {
if (shmflg & SHM_RND)
addr &= ~(SHMLBA-1); /* round down */
else
#ifndef __ARCH_FORCE_SHMLBA
if (addr & ~PAGE_MASK)
#endif
return -EINVAL;
}
flags = MAP_SHARED | MAP_FIXED;
} else {
if ((shmflg & SHM_REMAP))
return -EINVAL;

flags = MAP_SHARED;
}

if (shmflg & SHM_RDONLY) {
prot = PROT_READ;
o_flags = O_RDONLY;
acc_mode = S_IRUGO;
} else {
prot = PROT_READ | PROT_WRITE;
o_flags = O_RDWR;
acc_mode = S_IRUGO | S_IWUGO;
}
if (shmflg & SHM_EXEC) {
prot |= PROT_EXEC;
acc_mode |= S_IXUGO;
}

/*
* We cannot rely on the fs check since SYSV IPC does have an
* additional creator id...
*/
shp = shm_lock(shmid);
if(shp == NULL) {
err = -EINVAL;
goto out;
}
err = shm_checkid(shp,shmid);
if (err) {
shm_unlock(shp);
goto out;
}
if (ipcperms(&shp->shm_perm, acc_mode)) {
shm_unlock(shp);
err = -EACCES;
goto out;
}

err = security_shm_shmat(shp, shmaddr, shmflg);
if (err) {
shm_unlock(shp);
return err;
}

file = shp->shm_file;
size = i_size_read(file->f_dentry->d_inode);
shp->shm_nattch++;
shm_unlock(shp);

down_write(&current->mm->mmap_sem);
if (addr && !(shmflg & SHM_REMAP)) {
user_addr = ERR_PTR(-EINVAL);
if (find_vma_intersection(current->mm, addr, addr + size))
goto invalid;
/*
* If shm segment goes below stack, make sure there is some
* space left for the stack to grow (at least 4 pages).
*/
if (addr < current->mm->start_stack &&
addr > current->mm->start_stack - size - PAGE_SIZE * 5)
goto invalid;
}

user_addr = (void*) do_mmap (file, addr, size, prot, flags, 0);

invalid:
up_write(&current->mm->mmap_sem);

down (&shm_ids.sem);
if(!(shp = shm_lock(shmid)))
BUG();
shp->shm_nattch--;
if(shp->shm_nattch == 0 &&
shp->shm_flags & SHM_DEST)
shm_destroy (shp);
else
shm_unlock(shp);
up (&shm_ids.sem);

*raddr = (unsigned long) user_addr;
err = 0;
if (IS_ERR(user_addr))
err = PTR_ERR(user_addr);
out:
return err;
}


EXPORT_SYMBOL(ptr1);
EXPORT_SYMBOL(ptr2);
EXPORT_SYMBOL(ptr3);

asmlinkage long sys_shmat(int shmid, char __user *shmaddr, int shmflg)
{
unsigned long ret;
long err;

err = do_shmat(shmid, shmaddr, shmflg, &ret);
if (err)
return err;
force_successful_syscall_return();
return (long)ret;
}

/*
* detach and kill segment if marked destroyed.
* The work is done in shm_close.
*/
asmlinkage long sys_shmdt(char __user *shmaddr)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *next;
unsigned long addr = (unsigned long)shmaddr;
loff_t size = 0;
int retval = -EINVAL;

down_write(&mm->mmap_sem);

/*
* This function tries to be smart and unmap shm segments that
* were modified by partial mlock or munmap calls:
* - It first determines the size of the shm segment that should be
* unmapped: It searches for a vma that is backed by shm and that
* started at address shmaddr. It records it's size and then unmaps
* it.
* - Then it unmaps all shm vmas that started at shmaddr and that
* are within the initially determined size.
* Errors from do_munmap are ignored: the function only fails if
* it's called with invalid parameters or if it's called to unmap
* a part of a vma. Both calls in this function are for full vmas,
* the parameters are directly copied from the vma itself and always
* valid - therefore do_munmap cannot fail. (famous last words?)
*/
/*
* If it had been mremap()'d, the starting address would not
* match the usual checks anyway. So assume all vma's are
* above the starting address given.
*/
vma = find_vma(mm, addr);

while (vma) {
next = vma->vm_next;

/*
* Check if the starting address would match, i.e. it's
* a fragment created by mprotect() and/or munmap(), or it
* otherwise it starts at this address with no hassles.
*/
if ((vma->vm_ops == &shm_vm_ops || is_vm_hugetlb_page(vma)) &&
(vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff) {


size = vma->vm_file->f_dentry->d_inode->i_size;
do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
/*
* We discovered the size of the shm segment, so
* break out of here and fall through to the next
* loop that uses the size information to stop
* searching for matching vma's.
*/
retval = 0;
vma = next;
break;
}
vma = next;
}

/*
* We need look no further than the maximum address a fragment
* could possibly have landed at. Also cast things to loff_t to
* prevent overflows and make comparisions vs. equal-width types.
*/
while (vma && (loff_t)(vma->vm_end - addr) <= size) {
next = vma->vm_next;

/* finding a matching vma now does not alter retval */
if ((vma->vm_ops == &shm_vm_ops || is_vm_hugetlb_page(vma)) &&
(vma->vm_start - addr)/PAGE_SIZE == vma->vm_pgoff)

do_munmap(mm, vma->vm_start, vma->vm_end - vma->vm_start);
vma = next;
}

up_write(&mm->mmap_sem);
return retval;
}

#ifdef CONFIG_PROC_FS
static int sysvipc_shm_proc_show(struct seq_file *s, void *it)
{
struct shmid_kernel *shp = it;
char *format;

#define SMALL_STRING "%10d %10d %4o %10u %5u %5u %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"
#define BIG_STRING "%10d %10d %4o %21u %5u %5u %5d %5u %5u %5u %5u %10lu %10lu %10lu\n"

if (sizeof(size_t) <= sizeof(int))
format = SMALL_STRING;
else
format = BIG_STRING;
return seq_printf(s, format,
shp->shm_perm.key,
shp->id,
shp->shm_flags,
shp->shm_segsz,
shp->shm_cprid,
shp->shm_lprid,
is_file_hugepages(shp->shm_file) ? (file_count(shp->shm_file) - 1) : shp->shm_nattch,
shp->shm_perm.uid,
shp->shm_perm.gid,
shp->shm_perm.cuid,
shp->shm_perm.cgid,
shp->shm_atim,
shp->shm_dtim,
shp->shm_ctim);
}
#endif

/* Implementation of Linklist in Kernel */

# include <linux/init.h>
# include <linux/module.h>
# include <linux/list.h>
# include <linux/ipc.h>
# include <linux/shm.h>

typedef struct key_map {
struct list_head list;
int key;
unsigned long long global_id;
} key_map;

int i=0;
key_map *ptr = NULL;

/** here i have declared it as extern and then assigned them in ll_init */
extern unsigned long long (*ptr1)(int);
extern void (*ptr2)(int, unsigned long long);
/*--------------------------------------------------------------------- */


void start(void)
{
ptr=(key_map *)kmalloc(sizeof(key_map),GFP_KERNEL);
ptr->key = 0;
ptr->global_id = 0;
INIT_LIST_HEAD(&ptr->list);
}


void addk(int key, unsigned long long global_id) {
key_map *temp = NULL;
temp = (key_map *)kmalloc(sizeof(key_map),GFP_KERNEL);
temp->key = key;
temp->global_id = global_id;
list_add(&temp->list,&ptr->list);
printk(KERN_ALERT "\n Inserted a value : %d -> %lli ",temp->key,temp->global_id);
}

unsigned long long findk(int key) {
key_map *temp = NULL;
int i=0;
printk(KERN_ALERT "\nwhat is the value of key(findk)::%d",key);
for (temp=(key_map *)ptr->list.next;temp!=ptr;temp=(key_map *)temp->list.next) {
printk(KERN_ALERT "\n%d -> %lli(findk)",temp->key,temp->global_id);
if(temp->key == key) {
i++;
return(temp->global_id);
}

}
printk(KERN_ALERT "\nhow many times i went in da loop %d\n",i);
return 0;

}

static int ll_init(void) {
printk(KERN_ALERT "\nLL entered !!!");
start();
ptr1 = findk;
ptr2 = addk;
return 0;
}

static void ll_exit(void) {
printk(KERN_ALERT "\nLL exited !!!");
}

module_init(ll_init);
module_exit(ll_exit);
#ifndef _LINUX_SHM_H_
#define _LINUX_SHM_H_

#include <linux/ipc.h>
#include <linux/errno.h>
#include <asm/page.h>

/*
* SHMMAX, SHMMNI and SHMALL are upper limits are defaults which can
* be increased by sysctl
*/

#define SHMMAX 0x2000000 /* max shared seg size (bytes) */
#define SHMMIN 1 /* min shared seg size (bytes) */
#define SHMMNI 4096 /* max num of segs system wide */
#define SHMALL (SHMMAX/PAGE_SIZE*(SHMMNI/16)) /* max shm system wide (pages) */
#define SHMSEG SHMMNI /* max shared segs per process */

#include <asm/shmparam.h>

/*Declared as extern over here */
extern unsigned long long (*ptr1)(int);
extern void (*ptr2)(int, unsigned long long);
extern unsigned long long (*ptr3)(int,struct buffer *,int);
/*--------------------------------------------------------------------*/


/* Obsolete, used only for backwards compatibility and libc5 compiles */
struct shmid_ds {
struct ipc_perm shm_perm; /* operation perms */
int shm_segsz; /* size of segment (bytes) */
__kernel_time_t shm_atime; /* last attach time */
__kernel_time_t shm_dtime; /* last detach time */
__kernel_time_t shm_ctime; /* last change time */
__kernel_ipc_pid_t shm_cpid; /* pid of creator */
__kernel_ipc_pid_t shm_lpid; /* pid of last operator */
unsigned short shm_nattch; /* no. of current attaches */
unsigned short shm_unused; /* compatibility */
void *shm_unused2; /* ditto - used by DIPC */
void *shm_unused3; /* unused */
};

/* Include the definition of shmid64_ds and shminfo64 */
#include <asm/shmbuf.h>

/* permission flag for shmget */
#define SHM_R 0400 /* or S_IRUGO from <linux/stat.h> */
#define SHM_W 0200 /* or S_IWUGO from <linux/stat.h> */

/* mode for attach */
#define SHM_RDONLY 010000 /* read-only access */
#define SHM_RND 020000 /* round attach address to SHMLBA boundary */
#define SHM_REMAP 040000 /* take-over region on attach */
#define SHM_EXEC 0100000 /* execution access */

/* super user shmctl commands */
#define SHM_LOCK 11
#define SHM_UNLOCK 12

/* ipcs ctl commands */
#define SHM_STAT 13
#define SHM_INFO 14


/* Obsolete, used only for backwards compatibility */
struct shminfo {
int shmmax;
int shmmin;
int shmmni;
int shmseg;
int shmall;
};

struct shm_info {
int used_ids;
unsigned long shm_tot; /* total allocated shm */
unsigned long shm_rss; /* total resident shm */
unsigned long shm_swp; /* total swapped shm */
unsigned long swap_attempts;
unsigned long swap_successes;
};



#ifdef __KERNEL__

struct dipc_info {
unsigned long long global_id;
};


struct shmid_kernel /* private to the kernel */
{
struct kern_ipc_perm shm_perm;
struct file * shm_file;
struct dipc_info glob_info;
int id;
unsigned long shm_nattch;
unsigned long shm_segsz;
time_t shm_atim;
time_t shm_dtim;
time_t shm_ctim;
pid_t shm_cprid;
pid_t shm_lprid;
struct user_struct *mlock_user;
};

/* shm_mode upper byte flags */
#define SHM_DEST 01000 /* segment will be destroyed on last detach */
#define SHM_LOCKED 02000 /* segment will not be swapped */
#define SHM_HUGETLB 04000 /* segment will use huge TLB pages */

#ifdef CONFIG_SYSVIPC
long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr);
#else
static inline long do_shmat(int shmid, char __user *shmaddr,
int shmflg, unsigned long *addr)
{
return -ENOSYS;
}
#endif

#endif /* __KERNEL__ */

#endif /* _LINUX_SHM_H_ */