socket32.c

这个linux源代码是很全面的~基本完整了~使用c编译的~由于时间问题我没有亲自测试~但就算用来做参考资料也是非常好的

/* 
 * 32bit Socket syscall emulation. Based on arch/sparc64/kernel/sys_sparc32.c.
 *
 * Copyright (C) 2000		VA Linux Co
 * Copyright (C) 2000		Don Dugger <[e-mail]>
 * Copyright (C) 1999 		Arun Sharma <[e-mail]>
 * Copyright (C) 1997,1998 	Jakub Jelinek ([e-mail])
 * Copyright (C) 1997 		David S. Miller ([e-mail])
 * Copyright (C) 2000		Hewlett-Packard Co.
 * Copyright (C) 2000		David Mosberger-Tang <[e-mail]>
 * Copyright (C) 2000,2001	Andi Kleen, SuSE Labs 
 */

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/file.h>
#include <linux/icmpv6.h>
#include <linux/socket.h>
#include <linux/filter.h>

#include <net/scm.h>
#include <net/sock.h>
#include <asm/ia32.h>
#include <asm/uaccess.h>
#include <asm/socket32.h>

#define A(__x)		((unsigned long)(__x))
#define AA(__x)		((unsigned long)(__x))


static inline int iov_from_user32_to_kern(struct iovec *kiov,
					  struct iovec32 *uiov32,
					  int niov)
{
	int tot_len = 0;

	while(niov > 0) {
		u32 len, buf;

		if(get_user(len, &uiov32->iov_len) ||
		   get_user(buf, &uiov32->iov_base)) {
			tot_len = -EFAULT;
			break;
		}
		tot_len += len;
		kiov->iov_base = (void *)A(buf);
		kiov->iov_len = (__kernel_size_t) len;
		uiov32++;
		kiov++;
		niov--;
	}
	return tot_len;
}

static inline int msghdr_from_user32_to_kern(struct msghdr *kmsg,
					     struct msghdr32 *umsg)
{
	u32 tmp1, tmp2, tmp3;
	int err;

	err = get_user(tmp1, &umsg->msg_name);
	err |= __get_user(tmp2, &umsg->msg_iov);
	err |= __get_user(tmp3, &umsg->msg_control);
	if (err)
		return -EFAULT;

	kmsg->msg_name = (void *)A(tmp1);
	kmsg->msg_iov = (struct iovec *)A(tmp2);
	kmsg->msg_control = (void *)A(tmp3);

	err = get_user(kmsg->msg_namelen, &umsg->msg_namelen);
	err |= get_user(kmsg->msg_iovlen, &umsg->msg_iovlen);
	err |= get_user(kmsg->msg_controllen, &umsg->msg_controllen);
	err |= get_user(kmsg->msg_flags, &umsg->msg_flags);
	
	return err;
}

/* I've named the args so it is easy to tell whose space the pointers are in. */
static int verify_iovec32(struct msghdr *kern_msg, struct iovec *kern_iov,
			  char *kern_address, int mode)
{
	int tot_len;

	if(kern_msg->msg_namelen) {
		if(mode==VERIFY_READ) {
			int err = move_addr_to_kernel(kern_msg->msg_name,
						      kern_msg->msg_namelen,
						      kern_address);
			if(err < 0)
				return err;
		}
		kern_msg->msg_name = kern_address;
	} else
		kern_msg->msg_name = NULL;

	if(kern_msg->msg_iovlen > UIO_FASTIOV) {
		kern_iov = kmalloc(kern_msg->msg_iovlen * sizeof(struct iovec),
				   GFP_KERNEL);
		if(!kern_iov)
			return -ENOMEM;
	}

	tot_len = iov_from_user32_to_kern(kern_iov,
					  (struct iovec32 *)kern_msg->msg_iov,
					  kern_msg->msg_iovlen);
	if(tot_len >= 0)
		kern_msg->msg_iov = kern_iov;
	else if(kern_msg->msg_iovlen > UIO_FASTIOV)
		kfree(kern_iov);

	return tot_len;
}

/* There is a lot of hair here because the alignment rules (and
 * thus placement) of cmsg headers and length are different for
 * 32-bit apps.  -DaveM
 */
static int cmsghdr_from_user32_to_kern(struct msghdr *kmsg,
				       unsigned char *stackbuf, int stackbuf_size)
{
	struct cmsghdr32 *ucmsg;
	struct cmsghdr *kcmsg, *kcmsg_base;
	__kernel_size_t32 ucmlen;
	__kernel_size_t kcmlen, tmp;

	kcmlen = 0;
	kcmsg_base = kcmsg = (struct cmsghdr *)stackbuf;
	ucmsg = CMSG32_FIRSTHDR(kmsg);
	while(ucmsg != NULL) {
		if(get_user(ucmlen, &ucmsg->cmsg_len))
			return -EFAULT;

		/* Catch bogons. */
		if(CMSG32_ALIGN(ucmlen) <
		   CMSG32_ALIGN(sizeof(struct cmsghdr32)))
			return -EINVAL;
		if((unsigned long)(((char *)ucmsg - (char *)kmsg->msg_control)
				   + ucmlen) > kmsg->msg_controllen)
			return -EINVAL;

		tmp = ((ucmlen - CMSG32_ALIGN(sizeof(*ucmsg))) +
		       CMSG_ALIGN(sizeof(struct cmsghdr)));
		kcmlen += tmp;
		ucmsg = CMSG32_NXTHDR(kmsg, ucmsg, ucmlen);
	}
	if(kcmlen == 0)
		return -EINVAL;

	/* The kcmlen holds the 64-bit version of the control length.
	 * It may not be modified as we do not stick it into the kmsg
	 * until we have successfully copied over all of the data
	 * from the user.
	 */
	if(kcmlen > stackbuf_size)
		kcmsg_base = kcmsg = kmalloc(kcmlen, GFP_KERNEL);
	if(kcmsg == NULL)
		return -ENOBUFS;

	/* Now copy them over neatly. */
	memset(kcmsg, 0, kcmlen);
	ucmsg = CMSG32_FIRSTHDR(kmsg);
	while(ucmsg != NULL) {
		__get_user(ucmlen, &ucmsg->cmsg_len);
		tmp = ((ucmlen - CMSG32_ALIGN(sizeof(*ucmsg))) +
		       CMSG_ALIGN(sizeof(struct cmsghdr)));
		kcmsg->cmsg_len = tmp;
		__get_user(kcmsg->cmsg_level, &ucmsg->cmsg_level);
		__get_user(kcmsg->cmsg_type, &ucmsg->cmsg_type);

		/* Copy over the data. */
		if(copy_from_user(CMSG_DATA(kcmsg),
				  CMSG32_DATA(ucmsg),
				  (ucmlen - CMSG32_ALIGN(sizeof(*ucmsg)))))
			goto out_free_efault;

		/* Advance. */
		kcmsg = (struct cmsghdr *)((char *)kcmsg + CMSG_ALIGN(tmp));
		ucmsg = CMSG32_NXTHDR(kmsg, ucmsg, ucmlen);
	}

	/* Ok, looks like we made it.  Hook it up and return success. */
	kmsg->msg_control = kcmsg_base;
	kmsg->msg_controllen = kcmlen;
	return 0;

out_free_efault:
	if(kcmsg_base != (struct cmsghdr *)stackbuf)
		kfree(kcmsg_base);
	return -EFAULT;
}

static void put_cmsg32(struct msghdr *kmsg, int level, int type,
		       int len, void *data)
{
	struct cmsghdr32 *cm = (struct cmsghdr32 *) kmsg->msg_control;
	struct cmsghdr32 cmhdr;
	int cmlen = CMSG32_LEN(len);

	if(cm == NULL || kmsg->msg_controllen < sizeof(*cm)) {
		kmsg->msg_flags |= MSG_CTRUNC;
		return;
	}

	if(kmsg->msg_controllen < cmlen) {
		kmsg->msg_flags |= MSG_CTRUNC;
		cmlen = kmsg->msg_controllen;
	}
	cmhdr.cmsg_level = level;
	cmhdr.cmsg_type = type;
	cmhdr.cmsg_len = cmlen;

	if(copy_to_user(cm, &cmhdr, sizeof cmhdr))
		return;
	if(copy_to_user(CMSG32_DATA(cm), data, cmlen - sizeof(struct cmsghdr32)))
		return;
	cmlen = CMSG32_SPACE(len);
	kmsg->msg_control += cmlen;
	kmsg->msg_controllen -= cmlen;
}

static void scm_detach_fds32(struct msghdr *kmsg, struct scm_cookie *scm)
{
	struct cmsghdr32 *cm = (struct cmsghdr32 *) kmsg->msg_control;
	int fdmax = (kmsg->msg_controllen - sizeof(struct cmsghdr32)) / sizeof(int);
	int fdnum = scm->fp->count;
	struct file **fp = scm->fp->fp;
	int *cmfptr;
	int err = 0, i;

	if (fdnum < fdmax)
		fdmax = fdnum;

	for (i = 0, cmfptr = (int *) CMSG32_DATA(cm); i < fdmax; i++, cmfptr++) {
		int new_fd;
		err = get_unused_fd();
		if (err < 0)
			break;
		new_fd = err;
		err = put_user(new_fd, cmfptr);
		if (err) {
			put_unused_fd(new_fd);
			break;
		}
		/* Bump the usage count and install the file. */
		get_file(fp[i]);
		fd_install(new_fd, fp[i]);
	}

	if (i > 0) {
		int cmlen = CMSG32_LEN(i * sizeof(int));
		if (!err)
			err = put_user(SOL_SOCKET, &cm->cmsg_level);
		if (!err)
			err = put_user(SCM_RIGHTS, &cm->cmsg_type);
		if (!err)
			err = put_user(cmlen, &cm->cmsg_len);
		if (!err) {
			cmlen = CMSG32_SPACE(i * sizeof(int));
			kmsg->msg_control += cmlen;
			kmsg->msg_controllen -= cmlen;
		}
	}
	if (i < fdnum)
		kmsg->msg_flags |= MSG_CTRUNC;

	/*
	 * All of the files that fit in the message have had their
	 * usage counts incremented, so we just free the list.
	 */
	__scm_destroy(scm);
}

/* In these cases we (currently) can just copy to data over verbatim
 * because all CMSGs created by the kernel have well defined types which
 * have the same layout in both the 32-bit and 64-bit API.  One must add
 * some special cased conversions here if we start sending control messages
 * with incompatible types.
 *
 * SCM_RIGHTS and SCM_CREDENTIALS are done by hand in recvmsg32 right after
 * we do our work.  The remaining cases are:
 *
 * SOL_IP	IP_PKTINFO	struct in_pktinfo	32-bit clean
 *		IP_TTL		int			32-bit clean
 *		IP_TOS		__u8			32-bit clean
 *		IP_RECVOPTS	variable length		32-bit clean
 *		IP_RETOPTS	variable length		32-bit clean
 *		(these last two are clean because the types are defined
 *		 by the IPv4 protocol)
 *		IP_RECVERR	struct sock_extended_err +
 *				struct sockaddr_in	32-bit clean
 * SOL_IPV6	IPV6_RECVERR	struct sock_extended_err +
 *				struct sockaddr_in6	32-bit clean
 *		IPV6_PKTINFO	struct in6_pktinfo	32-bit clean
 *		IPV6_HOPLIMIT	int			32-bit clean
 *		IPV6_FLOWINFO	u32			32-bit clean
 *		IPV6_HOPOPTS	ipv6 hop exthdr		32-bit clean
 *		IPV6_DSTOPTS	ipv6 dst exthdr(s)	32-bit clean
 *		IPV6_RTHDR	ipv6 routing exthdr	32-bit clean
 *		IPV6_AUTHHDR	ipv6 auth exthdr	32-bit clean
 */
static void cmsg32_recvmsg_fixup(struct msghdr *kmsg, unsigned long orig_cmsg_uptr)
{
	unsigned char *workbuf, *wp;
	unsigned long bufsz, space_avail;
	struct cmsghdr *ucmsg;

	bufsz = ((unsigned long)kmsg->msg_control) - orig_cmsg_uptr;
	space_avail = kmsg->msg_controllen + bufsz;
	wp = workbuf = kmalloc(bufsz, GFP_KERNEL);
	if(workbuf == NULL)
		goto fail;

	/* To make this more sane we assume the kernel sends back properly
	 * formatted control messages.  Because of how the kernel will truncate
	 * the cmsg_len for MSG_TRUNC cases, we need not check that case either.
	 */
	ucmsg = (struct cmsghdr *) orig_cmsg_uptr;
	while(((unsigned long)ucmsg) <=
	      (((unsigned long)kmsg->msg_control) - sizeof(struct cmsghdr))) {
		struct cmsghdr32 *kcmsg32 = (struct cmsghdr32 *) wp;
		int clen64, clen32;

		/* UCMSG is the 64-bit format CMSG entry in user-space.
		 * KCMSG32 is within the kernel space temporary buffer
		 * we use to convert into a 32-bit style CMSG.
		 */
		__get_user(kcmsg32->cmsg_len, &ucmsg->cmsg_len);
		__get_user(kcmsg32->cmsg_level, &ucmsg->cmsg_level);
		__get_user(kcmsg32->cmsg_type, &ucmsg->cmsg_type);

		clen64 = kcmsg32->cmsg_len;
		copy_from_user(CMSG32_DATA(kcmsg32), CMSG_DATA(ucmsg),
			       clen64 - CMSG_ALIGN(sizeof(*ucmsg)));
		clen32 = ((clen64 - CMSG_ALIGN(sizeof(*ucmsg))) +
			  CMSG32_ALIGN(sizeof(struct cmsghdr32)));
		kcmsg32->cmsg_len = clen32;

		ucmsg = (struct cmsghdr *) (((char *)ucmsg) + CMSG_ALIGN(clen64));
		wp = (((char *)kcmsg32) + CMSG32_ALIGN(clen32));
	}