Author: dchagin
Date: Tue Aug 1 03:40:19 2017
New Revision: 321839
URL: https://svnweb.freebsd.org/changeset/base/321839
Log:
Implement proper Linux /dev/fd and /proc/self/fd behavior by adding
Linux specific things to the native fdescfs file system.
Unlike FreeBSD, the Linux fdescfs is a directory containing a symbolic
links to the actual files, which the process has open.
A readlink(2) call on this file returns a full path in case of regular file
or a string in a special format (type:[inode], anon_inode:<file-type>, etc..).
As well as in a FreeBSD, opening the file in the Linux fdescfs directory is
equivalent to duplicating the corresponding file descriptor.
Here we have mutually exclusive requirements:
- in case of readlink(2) call fdescfs lookup() method should return VLNK
vnode otherwise our kern_readlink() fail with EINVAL error;
- in the other calls fdescfs lookup() method should return non VLNK vnode.
For what new vnode v_flag VV_READLINK was added, which is set if fdescfs has
beed
mounted with linrdlnk option an modified kern_readlinkat() to properly handle
it.
For now For Linux ABI compatibility mount fdescfs volume with linrdlnk option:
mount -t fdescfs -o linrdlnk null /compat/linux/dev/fd
Reviewed by: kib@
MFC after: 1 week
Relnotes: yes
Modified:
head/share/man/man4/linux.4
head/share/man/man5/fdescfs.5
head/sys/fs/fdescfs/fdesc.h
head/sys/fs/fdescfs/fdesc_vfsops.c
head/sys/fs/fdescfs/fdesc_vnops.c
head/sys/kern/vfs_syscalls.c
head/sys/sys/vnode.h
Modified: head/share/man/man4/linux.4
==============================================================================
--- head/share/man/man4/linux.4 Tue Aug 1 03:13:43 2017 (r321838)
+++ head/share/man/man4/linux.4 Tue Aug 1 03:40:19 2017 (r321839)
@@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd February 8, 2010
+.Dd August 1, 2017
.Dt LINUX 4
.Os
.Sh NAME
@@ -127,9 +127,11 @@ regardless of whether the
module is statically linked into the kernel
or loaded as a module.
.Sh FILES
-.Bl -tag -width /compat/linux/proc -compact
+.Bl -tag -width /compat/linux/dev/fd -compact
.It Pa /compat/linux
minimal Linux run-time environment
+.It Pa /compat/linux/dev/fd
+limited Linux file-descriptor file system
.It Pa /compat/linux/proc
limited Linux process file system
.It Pa /compat/linux/sys
@@ -138,6 +140,7 @@ limited Linux system file system
.Sh SEE ALSO
.Xr brandelf 1 ,
.Xr elf 5 ,
+.Xr fdescfs 5 ,
.Xr linprocfs 5 ,
.Xr linsysfs 5
.Sh HISTORY
Modified: head/share/man/man5/fdescfs.5
==============================================================================
--- head/share/man/man5/fdescfs.5 Tue Aug 1 03:13:43 2017
(r321838)
+++ head/share/man/man5/fdescfs.5 Tue Aug 1 03:40:19 2017
(r321839)
@@ -34,7 +34,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd September 18, 2010
+.Dd August 1, 2017
.Dt FDESCFS 5
.Os
.Sh NAME
@@ -92,6 +92,14 @@ and
files are created by default when devfs alone is mounted.
.Nm
creates entries for all file descriptors opened by the process.
+.Pp
+For
+.Xr linux 4
+ABI compatibility mount
+.Nm
+volume with
+.Cm linrdlnk
+option.
.Sh FILES
.Bl -tag -width /dev/stderr -compact
.It Pa /dev/fd/#
@@ -103,6 +111,12 @@ volume located on
.Pa /dev/fd :
.Pp
.Dl "mount -t fdescfs null /dev/fd"
+.Pp
+For
+.Xr linux 4
+ABI compatibility:
+.Pp
+.Dl "mount -t fdescfs -o linrdlnk null /compat/linux/dev/fd"
.Sh SEE ALSO
.Xr devfs 5 ,
.Xr mount 8
Modified: head/sys/fs/fdescfs/fdesc.h
==============================================================================
--- head/sys/fs/fdescfs/fdesc.h Tue Aug 1 03:13:43 2017 (r321838)
+++ head/sys/fs/fdescfs/fdesc.h Tue Aug 1 03:40:19 2017 (r321839)
@@ -38,7 +38,9 @@
#define _FS_FDESC_H_
/* Private mount flags for fdescfs. */
-#define FMNT_UNMOUNTF 0x01
+#define FMNT_UNMOUNTF 0x01
+#define FMNT_LINRDLNKF 0x02
+
struct fdescmount {
struct vnode *f_root; /* Root node */
int flags;
Modified: head/sys/fs/fdescfs/fdesc_vfsops.c
==============================================================================
--- head/sys/fs/fdescfs/fdesc_vfsops.c Tue Aug 1 03:13:43 2017
(r321838)
+++ head/sys/fs/fdescfs/fdesc_vfsops.c Tue Aug 1 03:40:19 2017
(r321839)
@@ -101,6 +101,8 @@ fdesc_mount(struct mount *mp)
*/
mp->mnt_data = fmp;
fmp->flags = 0;
+ if (vfs_getopt(mp->mnt_optnew, "linrdlnk", NULL, NULL) == 0)
+ fmp->flags |= FMNT_LINRDLNKF;
error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
if (error) {
free(fmp, M_FDESCMNT);
Modified: head/sys/fs/fdescfs/fdesc_vnops.c
==============================================================================
--- head/sys/fs/fdescfs/fdesc_vnops.c Tue Aug 1 03:13:43 2017
(r321838)
+++ head/sys/fs/fdescfs/fdesc_vnops.c Tue Aug 1 03:40:19 2017
(r321839)
@@ -69,6 +69,7 @@ static vop_getattr_t fdesc_getattr;
static vop_lookup_t fdesc_lookup;
static vop_open_t fdesc_open;
static vop_readdir_t fdesc_readdir;
+static vop_readlink_t fdesc_readlink;
static vop_reclaim_t fdesc_reclaim;
static vop_setattr_t fdesc_setattr;
@@ -81,6 +82,7 @@ static struct vop_vector fdesc_vnodeops = {
.vop_open = fdesc_open,
.vop_pathconf = vop_stdpathconf,
.vop_readdir = fdesc_readdir,
+ .vop_readlink = fdesc_readlink,
.vop_reclaim = fdesc_reclaim,
.vop_setattr = fdesc_setattr,
};
@@ -195,6 +197,8 @@ loop:
fd->fd_type = ftype;
fd->fd_fd = fd_fd;
fd->fd_ix = ix;
+ if (ftype == Fdesc && fmp->flags & FMNT_LINRDLNKF)
+ vp->v_vflag |= VV_READLINK;
error = insmntque1(vp, mp, fdesc_insmntque_dtr, NULL);
if (error != 0) {
*vpp = NULLVP;
@@ -420,7 +424,7 @@ fdesc_getattr(struct vop_getattr_args *ap)
break;
case Fdesc:
- vap->va_type = VCHR;
+ vap->va_type = (vp->v_vflag & VV_READLINK) == 0 ? VCHR : VLNK;
vap->va_nlink = 1;
vap->va_size = 0;
vap->va_rdev = makedev(0, vap->va_fileid);
@@ -490,6 +494,7 @@ fdesc_setattr(struct vop_setattr_args *ap)
static int
fdesc_readdir(struct vop_readdir_args *ap)
{
+ struct fdescmount *fmp;
struct uio *uio = ap->a_uio;
struct filedesc *fdp;
struct dirent d;
@@ -499,6 +504,7 @@ fdesc_readdir(struct vop_readdir_args *ap)
if (VTOFDESC(ap->a_vp)->fd_type != Froot)
panic("fdesc_readdir: not dir");
+ fmp = VFSTOFDESC(ap->a_vp->v_mount);
if (ap->a_ncookies != NULL)
*ap->a_ncookies = 0;
@@ -530,7 +536,8 @@ fdesc_readdir(struct vop_readdir_args *ap)
break;
dp->d_namlen = sprintf(dp->d_name, "%d", fcnt);
dp->d_reclen = UIO_MX;
- dp->d_type = DT_CHR;
+ dp->d_type = (fmp->flags & FMNT_LINRDLNKF) == 0 ?
+ DT_CHR : DT_LNK;
dp->d_fileno = i + FD_DESC;
break;
}
@@ -566,4 +573,53 @@ fdesc_reclaim(struct vop_reclaim_args *ap)
free(vp->v_data, M_TEMP);
vp->v_data = NULL;
return (0);
+}
+
+static int
+fdesc_readlink(struct vop_readlink_args *va)
+{
+ struct vnode *vp, *vn;
+ cap_rights_t rights;
+ struct thread *td;
+ struct uio *uio;
+ struct file *fp;
+ char *freepath, *fullpath;
+ size_t pathlen;
+ int lockflags, fd_fd;
+ int error;
+
+ freepath = NULL;
+ vn = va->a_vp;
+ if (VTOFDESC(vn)->fd_type != Fdesc)
+ panic("fdesc_readlink: not fdescfs link");
+ fd_fd = ((struct fdescnode *)vn->v_data)->fd_fd;
+ lockflags = VOP_ISLOCKED(vn);
+ VOP_UNLOCK(vn, 0);
+
+ td = curthread;
+ error = fget_cap(td, fd_fd, cap_rights_init(&rights), &fp, NULL);
+ if (error != 0)
+ goto out;
+
+ switch (fp->f_type) {
+ case DTYPE_VNODE:
+ vp = fp->f_vnode;
+ error = vn_fullpath(td, vp, &fullpath, &freepath);
+ break;
+ default:
+ fullpath = "anon_inode:[unknown]";
+ break;
+ }
+ if (error == 0) {
+ uio = va->a_uio;
+ pathlen = strlen(fullpath);
+ error = uiomove(fullpath, pathlen, uio);
+ }
+ if (freepath != NULL)
+ free(freepath, M_TEMP);
+ fdrop(fp, td);
+
+out:
+ vn_lock(vn, lockflags | LK_RETRY);
+ return (error);
}
Modified: head/sys/kern/vfs_syscalls.c
==============================================================================
--- head/sys/kern/vfs_syscalls.c Tue Aug 1 03:13:43 2017
(r321838)
+++ head/sys/kern/vfs_syscalls.c Tue Aug 1 03:40:19 2017
(r321839)
@@ -2484,7 +2484,7 @@ kern_readlinkat(struct thread *td, int fd, char *path,
return (error);
}
#endif
- if (vp->v_type != VLNK)
+ if (vp->v_type != VLNK && (vp->v_vflag & VV_READLINK) == 0)
error = EINVAL;
else {
aiov.iov_base = buf;
Modified: head/sys/sys/vnode.h
==============================================================================
--- head/sys/sys/vnode.h Tue Aug 1 03:13:43 2017 (r321838)
+++ head/sys/sys/vnode.h Tue Aug 1 03:40:19 2017 (r321839)
@@ -250,6 +250,7 @@ struct xvnode {
#define VV_DELETED 0x0400 /* should be removed */
#define VV_MD 0x0800 /* vnode backs the md device */
#define VV_FORCEINSMQ 0x1000 /* force the insmntque to succeed */
+#define VV_READLINK 0x2000 /* fdescfs linux vnode */
#define VMP_TMPMNTFREELIST 0x0001 /* Vnode is on mnt's tmp free
list */
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