fs: add ksys_ioctl() helper; remove in-kernel calls to sys_ioctl()

Using this helper allows us to avoid the in-kernel calls to the
sys_ioctl() syscall. The ksys_ prefix denotes that this function
is meant as a drop-in replacement for the syscall. In particular, it
uses the same calling convention as sys_ioctl().

After careful review, at least some of these calls could be converted
to do_vfs_ioctl() in future.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

6 files changed, 22 insertions, 15 deletions

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 5ace7efb0d04..4823431d1c9d 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -689,7 +689,7 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
         return error;
 }
 
-SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
+int ksys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)
 {
         int error;
         struct fd f = fdget(fd);
@@ -702,3 +702,8 @@ SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
         fdput(f);
         return error;
 }
+
+SYSCALL_DEFINE3(ioctl, unsigned int, fd, unsigned int, cmd, unsigned long, arg)
+{
+        return ksys_ioctl(fd, cmd, arg);
+}
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index c056aff6d7ad..5a959efd8fb7 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -957,6 +957,7 @@ int ksys_fchmod(unsigned int fd, umode_t mode);
 int ksys_fchown(unsigned int fd, uid_t user, gid_t group);
 int ksys_getdents64(unsigned int fd, struct linux_dirent64 __user *dirent,
                     unsigned int count);
+int ksys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg);
 
 /*
  * The following kernel syscall equivalents are just wrappers to fs-internal
diff --git a/init/do_mounts.c b/init/do_mounts.c
index cc1103477071..b17e0095eb4e 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -491,18 +491,18 @@ void __init change_floppy(char *fmt, ...)
         va_end(args);
         fd = ksys_open("/dev/root", O_RDWR | O_NDELAY, 0);
         if (fd >= 0) {
-                sys_ioctl(fd, FDEJECT, 0);
+                ksys_ioctl(fd, FDEJECT, 0);
                 ksys_close(fd);
         }
         printk(KERN_NOTICE "VFS: Insert %s and press ENTER\n", buf);
         fd = ksys_open("/dev/console", O_RDWR, 0);
         if (fd >= 0) {
-                sys_ioctl(fd, TCGETS, (long)&termios);
+                ksys_ioctl(fd, TCGETS, (long)&termios);
                 termios.c_lflag &= ~ICANON;
-                sys_ioctl(fd, TCSETSF, (long)&termios);
+                ksys_ioctl(fd, TCSETSF, (long)&termios);
                 sys_read(fd, &c, 1);
                 termios.c_lflag |= ICANON;
-                sys_ioctl(fd, TCSETSF, (long)&termios);
+                ksys_ioctl(fd, TCSETSF, (long)&termios);
                 ksys_close(fd);
         }
 }
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index cedca8fd2590..03ec0c1b7553 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -110,7 +110,7 @@ static void __init handle_initrd(void)
                 if (fd < 0) {
                         error = fd;
                 } else {
-                        error = sys_ioctl(fd, BLKFLSBUF, 0);
+                        error = ksys_ioctl(fd, BLKFLSBUF, 0);
                         ksys_close(fd);
                 }
                 printk(!error ? "okay\n" : "failed\n");
diff --git a/init/do_mounts_md.c b/init/do_mounts_md.c
index 76dcfaada3ed..7d85d172bc7e 100644
--- a/init/do_mounts_md.c
+++ b/init/do_mounts_md.c
@@ -187,7 +187,7 @@ static void __init md_setup_drive(void)
                                         "array %s\n", name);
                         continue;
                 }
-                if (sys_ioctl(fd, SET_ARRAY_INFO, 0) == -EBUSY) {
+                if (ksys_ioctl(fd, SET_ARRAY_INFO, 0) == -EBUSY) {
                         printk(KERN_WARNING
                                "md: Ignoring md=%d, already autodetected. (Use raid=noautodetect)\n",
                                minor);
@@ -210,7 +210,7 @@ static void __init md_setup_drive(void)
                         ainfo.state = (1 << MD_SB_CLEAN);
                         ainfo.layout = 0;
                         ainfo.chunk_size = md_setup_args[ent].chunk;
-                        err = sys_ioctl(fd, SET_ARRAY_INFO, (long)&ainfo);
+                        err = ksys_ioctl(fd, SET_ARRAY_INFO, (long)&ainfo);
                         for (i = 0; !err && i <= MD_SB_DISKS; i++) {
                                 dev = devices[i];
                                 if (!dev)
@@ -220,7 +220,8 @@ static void __init md_setup_drive(void)
                                 dinfo.state = (1<<MD_DISK_ACTIVE)|(1<<MD_DISK_SYNC);
                                 dinfo.major = MAJOR(dev);
                                 dinfo.minor = MINOR(dev);
-                                err = sys_ioctl(fd, ADD_NEW_DISK, (long)&dinfo);
+                                err = ksys_ioctl(fd, ADD_NEW_DISK,
+                                                 (long)&dinfo);
                         }
                 } else {
                         /* persistent */
@@ -230,11 +231,11 @@ static void __init md_setup_drive(void)
                                         break;
                                 dinfo.major = MAJOR(dev);
                                 dinfo.minor = MINOR(dev);
-                                sys_ioctl(fd, ADD_NEW_DISK, (long)&dinfo);
+                                ksys_ioctl(fd, ADD_NEW_DISK, (long)&dinfo);
                         }
                 }
                 if (!err)
-                        err = sys_ioctl(fd, RUN_ARRAY, 0);
+                        err = ksys_ioctl(fd, RUN_ARRAY, 0);
                 if (err)
                         printk(KERN_WARNING "md: starting md%d failed\n", minor);
                 else {
@@ -245,7 +246,7 @@ static void __init md_setup_drive(void)
                          */
                         ksys_close(fd);
                         fd = ksys_open(name, 0, 0);
-                        sys_ioctl(fd, BLKRRPART, 0);
+                        ksys_ioctl(fd, BLKRRPART, 0);
                 }
                 ksys_close(fd);
         }
@@ -296,7 +297,7 @@ static void __init autodetect_raid(void)
 
         fd = ksys_open("/dev/md0", 0, 0);
         if (fd >= 0) {
-                sys_ioctl(fd, RAID_AUTORUN, raid_autopart);
+                ksys_ioctl(fd, RAID_AUTORUN, raid_autopart);
                 ksys_close(fd);
         }
 }
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index a6706314baa7..4dafaed5736f 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -218,7 +218,7 @@ int __init rd_load_image(char *from)
          * NOTE NOTE: nblocks is not actually blocks but
          * the number of kibibytes of data to load into a ramdisk.
          */
-        if (sys_ioctl(out_fd, BLKGETSIZE, (unsigned long)&rd_blocks) < 0)
+        if (ksys_ioctl(out_fd, BLKGETSIZE, (unsigned long)&rd_blocks) < 0)
                 rd_blocks = 0;
         else
                 rd_blocks >>= 1;
@@ -232,7 +232,7 @@ int __init rd_load_image(char *from)
         /*
          * OK, time to copy in the data
          */
-        if (sys_ioctl(in_fd, BLKGETSIZE, (unsigned long)&devblocks) < 0)
+        if (ksys_ioctl(in_fd, BLKGETSIZE, (unsigned long)&devblocks) < 0)
                 devblocks = 0;
         else
                 devblocks >>= 1;