shm.c

在linux下的进程间通信的源代码

/*
 * 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 <[e-mail]>
 * BIGMEM support, Andrea Arcangeli <[e-mail]>
 * SMP thread shm, Jean-Luc Boyard <[e-mail]>
 * HIGHMEM support, Ingo Molnar <[e-mail]>
 * Make shmmax, shmall, shmmni sysctl'able, Christoph Rohland <[e-mail]>
 * Shared /dev/zero support, Kanoj Sarcar <[e-mail]>
 * Move the mm functionality over to mm/shmem.c, Christoph Rohland <[e-mail]>
 *
 */

#include <linux/config.h>
#include <linux/malloc.h>
#include <linux/shm.h>
#include <linux/init.h>
#include <linux/file.h>
#include <linux/mman.h>
#include <linux/proc_fs.h>
#include <asm/uaccess.h>

#include "util.h"

struct shmid_kernel /* private to the kernel */
{	
	struct kern_ipc_perm	shm_perm;
	struct file *		shm_file;
	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;
};

#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(id)	ipc_unlock(&shm_ids,id)
#define shm_lockall()	ipc_lockall(&shm_ids)
#define shm_unlockall()	ipc_unlockall(&shm_ids)
#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 (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);
#ifdef CONFIG_PROC_FS
static int sysvipc_shm_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
#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);
	create_proc_read_entry("sysvipc/shm", 0, 0, sysvipc_shm_read_proc, NULL);
}

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+1);
}



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

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

/* 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
 */
static void shm_destroy (struct shmid_kernel *shp)
{
	shm_tot -= (shp->shm_segsz + PAGE_SIZE - 1) >> PAGE_SHIFT;
	shm_rmid (shp->id);
	fput (shp->shm_file);
	kfree (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->pid;
	shp->shm_dtim = CURRENT_TIME;
	shp->shm_nattch--;
	if(shp->shm_nattch == 0 &&
	   shp->shm_flags & SHM_DEST)
		shm_destroy (shp);

	shm_unlock(id);
	up (&shm_ids.sem);
}

static int shm_mmap(struct file * file, struct vm_area_struct * vma)
{
	UPDATE_ATIME(file->f_dentry->d_inode);
	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,
};

static int newseg (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;

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

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

	shp = (struct shmid_kernel *) kmalloc (sizeof (*shp), GFP_USER);
	if (!shp)
		return -ENOMEM;
	sprintf (name, "SYSV%08x", key);
	file = shmem_file_setup(name, size);
	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_perm.key = key;
	shp->shm_flags = (shmflg & S_IRWXUGO);
	shp->shm_cprid = current->pid;
	shp->shm_lprid = 0;
	shp->shm_atim = shp->shm_dtim = 0;
	shp->shm_ctim = CURRENT_TIME;
	shp->shm_segsz = size;
	shp->shm_nattch = 0;
	shp->id = shm_buildid(id,shp->shm_perm.seq);
	shp->shm_file = file;
	file->f_dentry->d_inode->i_ino = shp->id;
	file->f_op = &shm_file_operations;
	shm_tot += numpages;
	shm_unlock (id);
	return shp->id;

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

asmlinkage long sys_shmget (key_t key, size_t size, int shmflg)
{
	struct shmid_kernel *shp;
	int err, id = 0;

	down(&shm_ids.sem);
	if (key == IPC_PRIVATE) {
		err = newseg(key, shmflg, size);
	} else if ((id = ipc_findkey(&shm_ids, key)) == -1) {
		if (!(shmflg & IPC_CREAT))
			err = -ENOENT;
		else
			err = newseg(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
			err = shm_buildid(id, shp->shm_perm.seq);
		shm_unlock(id);
	}
	up(&shm_ids.sem);
	return err;
}

static inline unsigned long copy_shmid_to_user(void *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 *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 *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;