sys_oabi-compat.c

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/*
 *  arch/arm/kernel/sys_oabi-compat.c
 *
 *  Compatibility wrappers for syscalls that are used from
 *  old ABI user space binaries with an EABI kernel.
 *
 *  Author: Nicolas Pitre
 *  Created:    Oct 7, 2005
 *  Copyright:  MontaVista Software, Inc.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 */

/*
 * The legacy ABI and the new ARM EABI have different rules making some
 * syscalls incompatible especially with structure arguments.
 * Most notably, Eabi says 64-bit members should be 64-bit aligned instead of
 * simply word aligned.  EABI also pads structures to the size of the largest
 * member it contains instead of the invariant 32-bit.
 *
 * The following syscalls are affected:
 *
 * sys_stat64:
 * sys_lstat64:
 * sys_fstat64:
 * sys_fstatat64:
 *
 *   struct stat64 has different sizes and some members are shifted
 *   Compatibility wrappers are needed for them and provided below.
 *
 * sys_fcntl64:
 *
 *   struct flock64 has different sizes and some members are shifted
 *   A compatibility wrapper is needed and provided below.
 *
 * sys_statfs64:
 * sys_fstatfs64:
 *
 *   struct statfs64 has extra padding with EABI growing its size from
 *   84 to 88.  This struct is now __attribute__((packed,aligned(4)))
 *   with a small assembly wrapper to force the sz argument to 84 if it is 88
 *   to avoid copying the extra padding over user space unexpecting it.
 *
 * sys_newuname:
 *
 *   struct new_utsname has no padding with EABI.  No problem there.
 *
 * sys_epoll_ctl:
 * sys_epoll_wait:
 *
 *   struct epoll_event has its second member shifted also affecting the
 *   structure size. Compatibility wrappers are needed and provided below.
 *
 * sys_ipc:
 * sys_semop:
 * sys_semtimedop:
 *
 *   struct sembuf loses its padding with EABI.  Since arrays of them are
 *   used they have to be copyed to remove the padding. Compatibility wrappers
 *   provided below.
 *
 * sys_bind:
 * sys_connect:
 * sys_sendmsg:
 * sys_sendto:
 * sys_socketcall:
 *
 *   struct sockaddr_un loses its padding with EABI.  Since the size of the
 *   structure is used as a validation test in unix_mkname(), we need to
 *   change the length argument to 110 whenever it is 112.  Compatibility
 *   wrappers provided below.
 */

#include <linux/syscalls.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/fcntl.h>
#include <linux/eventpoll.h>
#include <linux/sem.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/ipc.h>
#include <linux/uaccess.h>
#include <linux/slab.h>

struct oldabi_stat64 {
    unsigned long long st_dev;
    unsigned int    __pad1;
    unsigned long   __st_ino;
    unsigned int    st_mode;
    unsigned int    st_nlink;

    unsigned long   st_uid;
    unsigned long   st_gid;

    unsigned long long st_rdev;
    unsigned int    __pad2;

    long long   st_size;
    unsigned long   st_blksize;
    unsigned long long st_blocks;

    unsigned long   st_atime;
    unsigned long   st_atime_nsec;

    unsigned long   st_mtime;
    unsigned long   st_mtime_nsec;

    unsigned long   st_ctime;
    unsigned long   st_ctime_nsec;

    unsigned long long st_ino;
} __attribute__ ((packed,aligned(4)));

static long cp_oldabi_stat64(struct kstat *stat,
                 struct oldabi_stat64 __user *statbuf)
{
    struct oldabi_stat64 tmp;

    tmp.st_dev = huge_encode_dev(stat->dev);
    tmp.__pad1 = 0;
    tmp.__st_ino = stat->ino;
    tmp.st_mode = stat->mode;
    tmp.st_nlink = stat->nlink;
    tmp.st_uid = from_kuid_munged(current_user_ns(), stat->uid);
    tmp.st_gid = from_kgid_munged(current_user_ns(), stat->gid);
    tmp.st_rdev = huge_encode_dev(stat->rdev);
    tmp.st_size = stat->size;
    tmp.st_blocks = stat->blocks;
    tmp.__pad2 = 0;
    tmp.st_blksize = stat->blksize;
    tmp.st_atime = stat->atime.tv_sec;
    tmp.st_atime_nsec = stat->atime.tv_nsec;
    tmp.st_mtime = stat->mtime.tv_sec;
    tmp.st_mtime_nsec = stat->mtime.tv_nsec;
    tmp.st_ctime = stat->ctime.tv_sec;
    tmp.st_ctime_nsec = stat->ctime.tv_nsec;
    tmp.st_ino = stat->ino;
    return copy_to_user(statbuf,&tmp,sizeof(tmp)) ? -EFAULT : 0;
}

asmlinkage long sys_oabi_stat64(const char __user * filename,
                struct oldabi_stat64 __user * statbuf)
{
    struct kstat stat;
    int error = vfs_stat(filename, &stat);
    if (!error)
        error = cp_oldabi_stat64(&stat, statbuf);
    return error;
}

asmlinkage long sys_oabi_lstat64(const char __user * filename,
                 struct oldabi_stat64 __user * statbuf)
{
    struct kstat stat;
    int error = vfs_lstat(filename, &stat);
    if (!error)
        error = cp_oldabi_stat64(&stat, statbuf);
    return error;
}

asmlinkage long sys_oabi_fstat64(unsigned long fd,
                 struct oldabi_stat64 __user * statbuf)
{
    struct kstat stat;
    int error = vfs_fstat(fd, &stat);
    if (!error)
        error = cp_oldabi_stat64(&stat, statbuf);
    return error;
}

asmlinkage long sys_oabi_fstatat64(int dfd,
                   const char __user *filename,
                   struct oldabi_stat64  __user *statbuf,
                   int flag)
{
    struct kstat stat;
    int error;

    error = vfs_fstatat(dfd, filename, &stat, flag);
    if (error)
        return error;
    return cp_oldabi_stat64(&stat, statbuf);
}

struct oabi_flock64 {
    short   l_type;
    short   l_whence;
    loff_t  l_start;
    loff_t  l_len;
    pid_t   l_pid;
} __attribute__ ((packed,aligned(4)));

asmlinkage long sys_oabi_fcntl64(unsigned int fd, unsigned int cmd,
                 unsigned long arg)
{
    struct oabi_flock64 user;
    struct flock64 kernel;
    mm_segment_t fs = USER_DS; /* initialized to kill a warning */
    unsigned long local_arg = arg;
    int ret;

    switch (cmd) {
    case F_GETLK64:
    case F_SETLK64:
    case F_SETLKW64:
        if (copy_from_user(&user, (struct oabi_flock64 __user *)arg,
                   sizeof(user)))
            return -EFAULT;
        kernel.l_type   = user.l_type;
        kernel.l_whence = user.l_whence;
        kernel.l_start  = user.l_start;
        kernel.l_len    = user.l_len;
        kernel.l_pid    = user.l_pid;
        local_arg = (unsigned long)&kernel;
        fs = get_fs();
        set_fs(KERNEL_DS);
    }

    ret = sys_fcntl64(fd, cmd, local_arg);

    switch (cmd) {
    case F_GETLK64:
        if (!ret) {
            user.l_type = kernel.l_type;
            user.l_whence   = kernel.l_whence;
            user.l_start    = kernel.l_start;
            user.l_len  = kernel.l_len;
            user.l_pid  = kernel.l_pid;
            if (copy_to_user((struct oabi_flock64 __user *)arg,
                     &user, sizeof(user)))
                ret = -EFAULT;
        }
    case F_SETLK64:
    case F_SETLKW64:
        set_fs(fs);
    }

    return ret;
}

struct oabi_epoll_event {
    __u32 events;
    __u64 data;
} __attribute__ ((packed,aligned(4)));

asmlinkage long sys_oabi_epoll_ctl(int epfd, int op, int fd,
                   struct oabi_epoll_event __user *event)
{
    struct oabi_epoll_event user;
    struct epoll_event kernel;
    mm_segment_t fs;
    long ret;

    if (op == EPOLL_CTL_DEL)
        return sys_epoll_ctl(epfd, op, fd, NULL);
    if (copy_from_user(&user, event, sizeof(user)))
        return -EFAULT;
    kernel.events = user.events;
    kernel.data   = user.data;
    fs = get_fs();
    set_fs(KERNEL_DS);
    ret = sys_epoll_ctl(epfd, op, fd, &kernel);
    set_fs(fs);
    return ret;
}

asmlinkage long sys_oabi_epoll_wait(int epfd,
                    struct oabi_epoll_event __user *events,
                    int maxevents, int timeout)
{
    struct epoll_event *kbuf;
    mm_segment_t fs;
    long ret, err, i;

    if (maxevents <= 0 || maxevents > (INT_MAX/sizeof(struct epoll_event)))
        return -EINVAL;
    kbuf = kmalloc(sizeof(*kbuf) * maxevents, GFP_KERNEL);
    if (!kbuf)
        return -ENOMEM;
    fs = get_fs();
    set_fs(KERNEL_DS);
    ret = sys_epoll_wait(epfd, kbuf, maxevents, timeout);
    set_fs(fs);
    err = 0;
    for (i = 0; i < ret; i++) {
        __put_user_error(kbuf[i].events, &events->events, err);
        __put_user_error(kbuf[i].data,   &events->data,   err);
        events++;
    }
    kfree(kbuf);
    return err ? -EFAULT : ret;
}

struct oabi_sembuf {
    unsigned short  sem_num;
    short       sem_op;
    short       sem_flg;
    unsigned short  __pad;
};

asmlinkage long sys_oabi_semtimedop(int semid,
                    struct oabi_sembuf __user *tsops,
                    unsigned nsops,
                    const struct timespec __user *timeout)
{
    struct sembuf *sops;
    struct timespec local_timeout;
    long err;
    int i;

    if (nsops < 1 || nsops > SEMOPM)
        return -EINVAL;
    sops = kmalloc(sizeof(*sops) * nsops, GFP_KERNEL);
    if (!sops)
        return -ENOMEM;
    err = 0;
    for (i = 0; i < nsops; i++) {
        __get_user_error(sops[i].sem_num, &tsops->sem_num, err);
        __get_user_error(sops[i].sem_op,  &tsops->sem_op,  err);
        __get_user_error(sops[i].sem_flg, &tsops->sem_flg, err);
        tsops++;
    }
    if (timeout) {
        /* copy this as well before changing domain protection */
        err |= copy_from_user(&local_timeout, timeout, sizeof(*timeout));
        timeout = &local_timeout;
    }
    if (err) {
        err = -EFAULT;
    } else {
        mm_segment_t fs = get_fs();
        set_fs(KERNEL_DS);
        err = sys_semtimedop(semid, sops, nsops, timeout);
        set_fs(fs);
    }
    kfree(sops);
    return err;
}

asmlinkage long sys_oabi_semop(int semid, struct oabi_sembuf __user *tsops,
                   unsigned nsops)
{
    return sys_oabi_semtimedop(semid, tsops, nsops, NULL);
}

asmlinkage int sys_oabi_ipc(uint call, int first, int second, int third,
                void __user *ptr, long fifth)
{
    switch (call & 0xffff) {
    case SEMOP:
        return  sys_oabi_semtimedop(first,
                        (struct oabi_sembuf __user *)ptr,
                        second, NULL);
    case SEMTIMEDOP:
        return  sys_oabi_semtimedop(first,
                        (struct oabi_sembuf __user *)ptr,
                        second,
                        (const struct timespec __user *)fifth);
    default:
        return sys_ipc(call, first, second, third, ptr, fifth);
    }
}

asmlinkage long sys_oabi_bind(int fd, struct sockaddr __user *addr, int addrlen)
{
    sa_family_t sa_family;
    if (addrlen == 112 &&
        get_user(sa_family, &addr->sa_family) == 0 &&
        sa_family == AF_UNIX)
            addrlen = 110;
    return sys_bind(fd, addr, addrlen);
}

asmlinkage long sys_oabi_connect(int fd, struct sockaddr __user *addr, int addrlen)
{
    sa_family_t sa_family;
    if (addrlen == 112 &&
        get_user(sa_family, &addr->sa_family) == 0 &&
        sa_family == AF_UNIX)
            addrlen = 110;
    return sys_connect(fd, addr, addrlen);
}

asmlinkage long sys_oabi_sendto(int fd, void __user *buff,
                size_t len, unsigned flags,
                struct sockaddr __user *addr,
                int addrlen)
{
    sa_family_t sa_family;
    if (addrlen == 112 &&
        get_user(sa_family, &addr->sa_family) == 0 &&
        sa_family == AF_UNIX)
            addrlen = 110;
    return sys_sendto(fd, buff, len, flags, addr, addrlen);
}

asmlinkage long sys_oabi_sendmsg(int fd, struct msghdr __user *msg, unsigned flags)
{
    struct sockaddr __user *addr;
    int msg_namelen;
    sa_family_t sa_family;
    if (msg &&
        get_user(msg_namelen, &msg->msg_namelen) == 0 &&
        msg_namelen == 112 &&
        get_user(addr, &msg->msg_name) == 0 &&
        get_user(sa_family, &addr->sa_family) == 0 &&
        sa_family == AF_UNIX)
    {
        /*
         * HACK ALERT: there is a limit to how much backward bending
         * we should do for what is actually a transitional
         * compatibility layer.  This already has known flaws with
         * a few ioctls that we don't intend to fix.  Therefore
         * consider this blatent hack as another one... and take care
         * to run for cover.  In most cases it will "just work fine".
         * If it doesn't, well, tough.
         */
        put_user(110, &msg->msg_namelen);
    }
    return sys_sendmsg(fd, msg, flags);
}

asmlinkage long sys_oabi_socketcall(int call, unsigned long __user *args)
{
    unsigned long r = -EFAULT, a[6];

    switch (call) {
    case SYS_BIND:
        if (copy_from_user(a, args, 3 * sizeof(long)) == 0)
            r = sys_oabi_bind(a[0], (struct sockaddr __user *)a[1], a[2]);
        break;
    case SYS_CONNECT:
        if (copy_from_user(a, args, 3 * sizeof(long)) == 0)
            r = sys_oabi_connect(a[0], (struct sockaddr __user *)a[1], a[2]);
        break;
    case SYS_SENDTO:
        if (copy_from_user(a, args, 6 * sizeof(long)) == 0)
            r = sys_oabi_sendto(a[0], (void __user *)a[1], a[2], a[3],
                        (struct sockaddr __user *)a[4], a[5]);
        break;
    case SYS_SENDMSG:
        if (copy_from_user(a, args, 3 * sizeof(long)) == 0)
            r = sys_oabi_sendmsg(a[0], (struct msghdr __user *)a[1], a[2]);
        break;
    default:
        r = sys_socketcall(call, args);
    }

    return r;
}