diff mbox series

[v4,3/8] xen: add basic hypervisor filesystem support

Message ID 20200205101141.24769-4-jgross@suse.com (mailing list archive)
State Superseded
Headers show
Series Add hypervisor sysfs-like support | expand

Commit Message

Jürgen Groß Feb. 5, 2020, 10:11 a.m. UTC
Add the infrastructure for the hypervisor filesystem.

This includes the hypercall interface and the base functions for
entry creation, deletion and modification.

In order not to have to repeat the same pattern multiple times in case
adding a new node should BUG_ON() failure, the helpers for adding a
node (hypfs_add_dir() and hypfs_add_leaf()) get a nofault parameter
causing the BUG() in case of a failure.

When supporting writable leafs the entry's write pointer will need to
be set to the function performing the write to the variable holding the
content. In case there are no special constraints this will be
hypfs_write_bool() for type XEN_HYPFS_TYPE_BOOL and hypfs_write_leaf()
for the other entry types.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V1:
- rename files from filesystem.* to hypfs.*
- add dummy write entry support
- rename hypercall filesystem_op to hypfs_op
- add support for unsigned integer entries

V2:
- test new entry name to be valid

V3:
- major rework, especially by supporting binary contents of entries
- addressed all comments

V4:
- sort #includes alphabetically (Wei Liu)
- add public interface structures to xlat.lst (Jan Beulich)
- let DIRENTRY_SIZE() add 1 for trailing nul byte (Jan Beulich)
- remove hypfs_add_entry() (Jan Beulich)
- len -> ulen (Jan Beulich)
- switch sequence of tests in hypfs_get_entry_rel() (Jan Beulich)
- add const qualifier (Jan Beulich)
- return -ENOBUFS if only direntry but no entry contents are returned
  (Jan Beulich)
- use xmalloc() instead of xzalloc() (Jan Beulich)
- better error handling in hypfs_write_leaf() (Jan Beulich)
- return -EOPNOTSUPP for unknown sub-command (Jan Beulich)
- use plain integers for enum-like constants in public interface
  (Jan Beulich)
- rename XEN_HYPFS_OP_read_contents to XEN_HYPFS_OP_read (Jan Beulich)
- add some comments in include/public/hypfs.h (Jan Beulich)
- use const_char for user parameter path (Jan Beulich)
- add helpers for XEN_HYPFS_TYPE_BOOL and XEN_HYPFS_TYPE_INT entry
  definitions (Jan Beulich)
- make statically defined entries __read_mostly (Jan Beulich)
---
 xen/arch/arm/traps.c         |   1 +
 xen/arch/x86/hvm/hypercall.c |   1 +
 xen/arch/x86/hypercall.c     |   1 +
 xen/arch/x86/pv/hypercall.c  |   1 +
 xen/common/Makefile          |   1 +
 xen/common/hypfs.c           | 358 +++++++++++++++++++++++++++++++++++++++++++
 xen/include/public/hypfs.h   | 127 +++++++++++++++
 xen/include/public/xen.h     |   1 +
 xen/include/xen/hypercall.h  |   8 +
 xen/include/xen/hypfs.h      | 108 +++++++++++++
 xen/include/xlat.lst         |   2 +
 11 files changed, 609 insertions(+)
 create mode 100644 xen/common/hypfs.c
 create mode 100644 xen/include/public/hypfs.h
 create mode 100644 xen/include/xen/hypfs.h
diff mbox series

Patch

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 6f9bec22d3..87af810667 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1382,6 +1382,7 @@  static arm_hypercall_t arm_hypercall_table[] = {
 #ifdef CONFIG_ARGO
     HYPERCALL(argo_op, 5),
 #endif
+    HYPERCALL(hypfs_op, 5),
 };
 
 #ifndef NDEBUG
diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 33dd2d99d2..210dda4f38 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -144,6 +144,7 @@  static const hypercall_table_t hvm_hypercall_table[] = {
 #endif
     HYPERCALL(xenpmu_op),
     COMPAT_CALL(dm_op),
+    HYPERCALL(hypfs_op),
     HYPERCALL(arch_1)
 };
 
diff --git a/xen/arch/x86/hypercall.c b/xen/arch/x86/hypercall.c
index 7f299d45c6..05a3f5e25b 100644
--- a/xen/arch/x86/hypercall.c
+++ b/xen/arch/x86/hypercall.c
@@ -73,6 +73,7 @@  const hypercall_args_t hypercall_args_table[NR_hypercalls] =
     ARGS(hvm_op, 2),
     ARGS(dm_op, 3),
 #endif
+    ARGS(hypfs_op, 5),
     ARGS(mca, 1),
     ARGS(arch_1, 1),
 };
diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index 17ddf9ea1f..83907d4f00 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -85,6 +85,7 @@  const hypercall_table_t pv_hypercall_table[] = {
     HYPERCALL(hvm_op),
     COMPAT_CALL(dm_op),
 #endif
+    HYPERCALL(hypfs_op),
     HYPERCALL(mca),
     HYPERCALL(arch_1),
 };
diff --git a/xen/common/Makefile b/xen/common/Makefile
index 2abb8250b0..3a2c1ae690 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -10,6 +10,7 @@  obj-y += domain.o
 obj-y += event_2l.o
 obj-y += event_channel.o
 obj-y += event_fifo.o
+obj-y += hypfs.o
 obj-$(CONFIG_CRASH_DEBUG) += gdbstub.o
 obj-$(CONFIG_GRANT_TABLE) += grant_table.o
 obj-y += guestcopy.o
diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
new file mode 100644
index 0000000000..c726f89ac9
--- /dev/null
+++ b/xen/common/hypfs.c
@@ -0,0 +1,358 @@ 
+/******************************************************************************
+ *
+ * hypfs.c
+ *
+ * Simple sysfs-like file system for the hypervisor.
+ */
+
+#include <xen/err.h>
+#include <xen/guest_access.h>
+#include <xen/hypercall.h>
+#include <xen/hypfs.h>
+#include <xen/lib.h>
+#include <xen/rwlock.h>
+#include <public/hypfs.h>
+
+#define DIRENTRY_NAME_OFF offsetof(struct xen_hypfs_dirlistentry, name)
+#define DIRENTRY_SIZE(name_len) \
+    (DIRENTRY_NAME_OFF +        \
+     ROUNDUP((name_len) + 1, alignof(struct xen_hypfs_direntry)))
+
+static DEFINE_RWLOCK(hypfs_lock);
+
+HYPFS_DIR_INIT(hypfs_root, "");
+
+static int add_entry(struct hypfs_entry_dir *parent, struct hypfs_entry *new)
+{
+    int ret = -ENOENT;
+    struct hypfs_entry *e;
+
+    write_lock(&hypfs_lock);
+
+    list_for_each_entry ( e, &parent->dirlist, list )
+    {
+        int cmp = strcmp(e->name, new->name);
+
+        if ( cmp > 0 )
+        {
+            ret = 0;
+            list_add_tail(&new->list, &e->list);
+            break;
+        }
+        if ( cmp == 0 )
+        {
+            ret = -EEXIST;
+            break;
+        }
+    }
+
+    if ( ret == -ENOENT )
+    {
+        ret = 0;
+        list_add_tail(&new->list, &parent->dirlist);
+    }
+
+    if ( !ret )
+    {
+        unsigned int sz = strlen(new->name);
+
+        parent->e.size += DIRENTRY_SIZE(sz);
+    }
+
+    write_unlock(&hypfs_lock);
+
+    return ret;
+}
+
+int hypfs_add_dir(struct hypfs_entry_dir *parent,
+                  struct hypfs_entry_dir *dir, bool nofault)
+{
+    int ret;
+
+    ret = add_entry(parent, &dir->e);
+    BUG_ON(nofault && ret);
+
+    return ret;
+}
+
+int hypfs_add_leaf(struct hypfs_entry_dir *parent,
+                   struct hypfs_entry_leaf *leaf, bool nofault)
+{
+    int ret;
+
+    if ( !leaf->content )
+        ret = -EINVAL;
+    else
+        ret = add_entry(parent, &leaf->e);
+    BUG_ON(nofault && ret);
+
+    return ret;
+}
+
+static int hypfs_get_path_user(char *buf,
+                               XEN_GUEST_HANDLE_PARAM(const_char) uaddr,
+                               unsigned long ulen)
+{
+    if ( ulen > XEN_HYPFS_MAX_PATHLEN )
+        return -EINVAL;
+
+    if ( copy_from_guest(buf, uaddr, ulen) )
+        return -EFAULT;
+
+    if ( buf[ulen - 1] )
+        return -EINVAL;
+
+    return 0;
+}
+
+static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
+                                               const char *path)
+{
+    const char *end;
+    struct hypfs_entry *entry;
+    unsigned int name_len;
+
+    if ( dir->e.type != XEN_HYPFS_TYPE_DIR )
+        return NULL;
+
+    if ( !*path )
+        return &dir->e;
+
+    end = strchr(path, '/');
+    if ( !end )
+        end = strchr(path, '\0');
+    name_len = end - path;
+
+    list_for_each_entry ( entry, &dir->dirlist, list )
+    {
+        int cmp = strncmp(path, entry->name, name_len);
+        struct hypfs_entry_dir *d = container_of(entry,
+                                                 struct hypfs_entry_dir, e);
+
+        if ( cmp < 0 )
+            return NULL;
+        if ( !cmp && strlen(entry->name) == name_len )
+            return *end ? hypfs_get_entry_rel(d, end + 1) : entry;
+    }
+
+    return NULL;
+}
+
+struct hypfs_entry *hypfs_get_entry(const char *path)
+{
+    if ( path[0] != '/' )
+        return NULL;
+
+    return hypfs_get_entry_rel(&hypfs_root, path + 1);
+}
+
+int hypfs_read_dir(const struct hypfs_entry *entry,
+                   XEN_GUEST_HANDLE_PARAM(void) uaddr)
+{
+    const struct hypfs_entry_dir *d;
+    const struct hypfs_entry *e;
+    unsigned int size = entry->size;
+
+    d = container_of(entry, const struct hypfs_entry_dir, e);
+
+    list_for_each_entry ( e, &d->dirlist, list )
+    {
+        struct xen_hypfs_dirlistentry direntry;
+        unsigned int e_namelen = strlen(e->name);
+        unsigned int e_len = DIRENTRY_SIZE(e_namelen);
+
+        direntry.e.flags = e->write ? XEN_HYPFS_WRITEABLE : 0;
+        direntry.e.type = e->type;
+        direntry.e.encoding = e->encoding;
+        direntry.e.content_len = e->size;
+        direntry.off_next = list_is_last(&e->list, &d->dirlist) ? 0 : e_len;
+        if ( copy_to_guest(uaddr, &direntry, 1) )
+            return -EFAULT;
+
+        if ( copy_to_guest_offset(uaddr, DIRENTRY_NAME_OFF,
+                                  e->name, e_namelen + 1) )
+            return -EFAULT;
+
+        guest_handle_add_offset(uaddr, e_len);
+
+        ASSERT(e_len <= size);
+        size -= e_len;
+    }
+
+    return 0;
+}
+
+int hypfs_read_leaf(const struct hypfs_entry *entry,
+                    XEN_GUEST_HANDLE_PARAM(void) uaddr)
+{
+    const struct hypfs_entry_leaf *l;
+
+    l = container_of(entry, const struct hypfs_entry_leaf, e);
+
+    return copy_to_guest(uaddr, l->content, entry->size) ? -EFAULT: 0;
+}
+
+static int hypfs_read(const struct hypfs_entry *entry,
+                      XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
+{
+    struct xen_hypfs_direntry e;
+    long ret = -EINVAL;
+
+    if ( ulen < sizeof(e) )
+        goto out;
+
+    e.flags = entry->write ? XEN_HYPFS_WRITEABLE : 0;
+    e.type = entry->type;
+    e.encoding = entry->encoding;
+    e.content_len = entry->size;
+
+    ret = -EFAULT;
+    if ( copy_to_guest(uaddr, &e, 1) )
+        goto out;
+
+    ret = -ENOBUFS;
+    if ( ulen < entry->size + sizeof(e) )
+        goto out;
+
+    guest_handle_add_offset(uaddr, sizeof(e));
+
+    ret = entry->read(entry, uaddr);
+
+ out:
+    return ret;
+}
+
+int hypfs_write_leaf(struct hypfs_entry_leaf *leaf,
+                     XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
+{
+    char *buf;
+    int ret;
+
+    if ( ulen > leaf->e.size )
+        return -ENOSPC;
+
+    buf = xmalloc_array(char, ulen);
+    if ( !buf )
+        return -ENOMEM;
+
+    ret = -EFAULT;
+    if ( copy_from_guest(buf, uaddr, ulen) )
+        goto out;
+
+    ret = -EINVAL;
+    if ( leaf->e.type == XEN_HYPFS_TYPE_STRING && buf[ulen] )
+        goto out;
+
+    ret = 0;
+    memcpy(leaf->write_ptr, buf, ulen);
+
+ out:
+    xfree(buf);
+    return ret;
+}
+
+int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
+                     XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
+{
+    union {
+        char buf[8];
+        uint8_t u8;
+        uint16_t u16;
+        uint32_t u32;
+        uint64_t u64;
+    } u;
+
+    ASSERT(leaf->e.type == XEN_HYPFS_TYPE_UINT && leaf->e.size <= 8);
+
+    if ( ulen != leaf->e.size )
+        return -EDOM;
+
+    if ( copy_from_guest(u.buf, uaddr, ulen) )
+        return -EFAULT;
+
+    switch ( leaf->e.size )
+    {
+    case 1:
+        *(uint8_t *)leaf->write_ptr = !!u.u8;
+        break;
+    case 2:
+        *(uint16_t *)leaf->write_ptr = !!u.u16;
+        break;
+    case 4:
+        *(uint32_t *)leaf->write_ptr = !!u.u32;
+        break;
+    case 8:
+        *(uint64_t *)leaf->write_ptr = !!u.u64;
+        break;
+    }
+
+    return 0;
+}
+
+static int hypfs_write(struct hypfs_entry *entry,
+                       XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
+{
+    struct hypfs_entry_leaf *l;
+
+    if ( !entry->write )
+        return -EACCES;
+
+    l = container_of(entry, struct hypfs_entry_leaf, e);
+
+    return entry->write(l, uaddr, ulen);
+}
+
+long do_hypfs_op(unsigned int cmd,
+                 XEN_GUEST_HANDLE_PARAM(const_char) arg1, unsigned long arg2,
+                 XEN_GUEST_HANDLE_PARAM(void) arg3, unsigned long arg4)
+{
+    int ret;
+    struct hypfs_entry *entry;
+    static char path[XEN_HYPFS_MAX_PATHLEN];
+
+    if ( !is_control_domain(current->domain) &&
+         !is_hardware_domain(current->domain) )
+        return -EPERM;
+
+    if ( cmd == XEN_HYPFS_OP_get_version )
+        return XEN_HYPFS_VERSION;
+
+    if ( cmd == XEN_HYPFS_OP_write_contents )
+        write_lock(&hypfs_lock);
+    else
+        read_lock(&hypfs_lock);
+
+    ret = hypfs_get_path_user(path, arg1, arg2);
+    if ( ret )
+        goto out;
+
+    entry = hypfs_get_entry(path);
+    if ( !entry )
+    {
+        ret = -ENOENT;
+        goto out;
+    }
+
+    switch ( cmd )
+    {
+    case XEN_HYPFS_OP_read:
+        ret = hypfs_read(entry, arg3, arg4);
+        break;
+
+    case XEN_HYPFS_OP_write_contents:
+        ret = hypfs_write(entry, arg3, arg4);
+        break;
+
+    default:
+        ret = -EOPNOTSUPP;
+        break;
+    }
+
+ out:
+    if ( cmd == XEN_HYPFS_OP_write_contents )
+        write_unlock(&hypfs_lock);
+    else
+        read_unlock(&hypfs_lock);
+
+    return ret;
+}
diff --git a/xen/include/public/hypfs.h b/xen/include/public/hypfs.h
new file mode 100644
index 0000000000..4aa2e9449a
--- /dev/null
+++ b/xen/include/public/hypfs.h
@@ -0,0 +1,127 @@ 
+/******************************************************************************
+ * Xen Hypervisor Filesystem
+ *
+ * Copyright (c) 2019, SUSE Software Solutions Germany GmbH
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef __XEN_PUBLIC_HYPFS_H__
+#define __XEN_PUBLIC_HYPFS_H__
+
+#include "xen.h"
+
+/*
+ * Definitions for the __HYPERVISOR_hypfs_op hypercall.
+ */
+
+/* Highest version number of the hypfs interface currently defined. */
+#define XEN_HYPFS_VERSION      1
+
+/* Maximum length of a path in the filesystem. */
+#define XEN_HYPFS_MAX_PATHLEN 1024
+
+struct xen_hypfs_direntry {
+    uint16_t flags;
+#define XEN_HYPFS_WRITEABLE    0x0001
+    uint8_t type;
+#define XEN_HYPFS_TYPE_DIR     0
+#define XEN_HYPFS_TYPE_BLOB    1
+#define XEN_HYPFS_TYPE_STRING  2
+#define XEN_HYPFS_TYPE_UINT    3
+#define XEN_HYPFS_TYPE_INT     4
+#define XEN_HYPFS_TYPE_BOOL    5
+    uint8_t encoding;
+#define XEN_HYPFS_ENC_PLAIN    0
+#define XEN_HYPFS_ENC_GZIP     1
+    uint32_t content_len;
+};
+
+struct xen_hypfs_dirlistentry {
+    struct xen_hypfs_direntry e;
+    /* Offset in bytes to next entry (0 == this is the last entry). */
+    uint16_t off_next;
+    /* Zero terminated entry name, possibly with some padding for alignment. */
+    char name[XEN_FLEX_ARRAY_DIM];
+};
+
+/*
+ * Hypercall operations.
+ */
+
+/*
+ * XEN_HYPFS_OP_get_version
+ *
+ * Read highest interface version supported by the hypervisor.
+ *
+ * Possible return values:
+ * >0: highest supported interface version
+ * <0: negative Xen errno value
+ */
+#define XEN_HYPFS_OP_get_version     0
+
+/*
+ * XEN_HYPFS_OP_read
+ *
+ * Read a filesystem entry.
+ *
+ * Returns the direntry and contents of an entry in the buffer supplied by the
+ * caller (struct xen_hypfs_direntry with the contents following directly
+ * after it).
+ * The data buffer must be at least the size of the direntry returned in order
+ * to have success. If the data buffer was not large enough for all the data
+ * -ENOBUFS and no entry data is returned, but the direntry will contain the
+ * needed size for the returned data.
+ * The format of the contents is according to its entry type and encoding.
+ * The contents of a directory are multiple struct xen_hypfs_dirlistentry
+ * items.
+ *
+ * arg1: XEN_GUEST_HANDLE(path name)
+ * arg2: length of path name (including trailing zero byte)
+ * arg3: XEN_GUEST_HANDLE(data buffer written by hypervisor)
+ * arg4: data buffer size
+ *
+ * Possible return values:
+ * 0: success (at least the direntry was returned)
+ * <0 : negative Xen errno value
+ */
+#define XEN_HYPFS_OP_read              1
+
+/*
+ * XEN_HYPFS_OP_write_contents
+ *
+ * Write contents of a filesystem entry.
+ *
+ * Writes an entry with the contents of a buffer supplied by the caller.
+ * The data type and encoding can't be changed. The size can be changed only
+ * for blobs and strings.
+ *
+ * arg1: XEN_GUEST_HANDLE(path name)
+ * arg2: length of path name (including trailing zero byte)
+ * arg3: XEN_GUEST_HANDLE(content buffer read by hypervisor)
+ * arg4: content buffer size
+ *
+ * Possible return values:
+ * 0: success
+ * <0 : negative Xen errno value
+ */
+#define XEN_HYPFS_OP_write_contents    2
+
+#endif /* __XEN_PUBLIC_HYPFS_H__ */
diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index d2198dffad..bf80f1da8c 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -130,6 +130,7 @@  DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
 #define __HYPERVISOR_argo_op              39
 #define __HYPERVISOR_xenpmu_op            40
 #define __HYPERVISOR_dm_op                41
+#define __HYPERVISOR_hypfs_op             42
 
 /* Architecture-specific hypercall definitions. */
 #define __HYPERVISOR_arch_0               48
diff --git a/xen/include/xen/hypercall.h b/xen/include/xen/hypercall.h
index ad8ad27b23..836a8b1ba8 100644
--- a/xen/include/xen/hypercall.h
+++ b/xen/include/xen/hypercall.h
@@ -150,6 +150,14 @@  do_dm_op(
     unsigned int nr_bufs,
     XEN_GUEST_HANDLE_PARAM(xen_dm_op_buf_t) bufs);
 
+extern long
+do_hypfs_op(
+    unsigned int cmd,
+    XEN_GUEST_HANDLE_PARAM(const_char) arg1,
+    unsigned long arg2,
+    XEN_GUEST_HANDLE_PARAM(void) arg3,
+    unsigned long arg4);
+
 #ifdef CONFIG_COMPAT
 
 extern int
diff --git a/xen/include/xen/hypfs.h b/xen/include/xen/hypfs.h
new file mode 100644
index 0000000000..5b26b2e611
--- /dev/null
+++ b/xen/include/xen/hypfs.h
@@ -0,0 +1,108 @@ 
+#ifndef __XEN_HYPFS_H__
+#define __XEN_HYPFS_H__
+
+#include <xen/list.h>
+#include <xen/string.h>
+#include <public/hypfs.h>
+
+struct hypfs_entry_leaf;
+
+struct hypfs_entry {
+    unsigned short type;
+    unsigned short encoding;
+    unsigned int size;
+    const char *name;
+    struct list_head list;
+    int (*read)(const struct hypfs_entry *entry,
+                XEN_GUEST_HANDLE_PARAM(void) uaddr);
+    int (*write)(struct hypfs_entry_leaf *leaf,
+                 XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen);
+};
+
+struct hypfs_entry_leaf {
+    struct hypfs_entry e;
+    union {
+        const void *content;
+        void *write_ptr;
+    };
+};
+
+struct hypfs_entry_dir {
+    struct hypfs_entry e;
+    struct list_head dirlist;
+};
+
+#define HYPFS_DIR_INIT(var, nam)                  \
+    struct hypfs_entry_dir __read_mostly var = {  \
+        .e.type = XEN_HYPFS_TYPE_DIR,             \
+        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
+        .e.name = nam,                            \
+        .e.size = 0,                              \
+        .e.list = LIST_HEAD_INIT(var.e.list),     \
+        .e.read = hypfs_read_dir,                 \
+        .dirlist = LIST_HEAD_INIT(var.dirlist),   \
+    }
+
+/* Content and size need to be set via hypfs_string_set(). */
+#define HYPFS_STRING_INIT(var, nam)               \
+    struct hypfs_entry_leaf __read_mostly var = { \
+        .e.type = XEN_HYPFS_TYPE_STRING,          \
+        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
+        .e.name = nam,                            \
+        .e.read = hypfs_read_leaf,                \
+    }
+
+static inline void hypfs_string_set(struct hypfs_entry_leaf *leaf,
+                                    const char *str)
+{
+    leaf->content = str;
+    leaf->e.size = strlen(str) + 1;
+}
+
+#define HYPFS_UINT_INIT(var, nam, contvar)        \
+    struct hypfs_entry_leaf __read_mostly var = { \
+        .e.type = XEN_HYPFS_TYPE_UINT,            \
+        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
+        .e.name = nam,                            \
+        .e.size = sizeof(contvar),                \
+        .e.read = hypfs_read_leaf,                \
+        .content = &contvar,                      \
+    }
+
+#define HYPFS_INT_INIT(var, nam, contvar)         \
+    struct hypfs_entry_leaf __read_mostly var = { \
+        .e.type = XEN_HYPFS_TYPE_INT,             \
+        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
+        .e.name = nam,                            \
+        .e.size = sizeof(contvar),                \
+        .e.read = hypfs_read_leaf,                \
+        .content = &contvar,                      \
+    }
+
+#define HYPFS_BOOL_INIT(var, nam, contvar)        \
+    struct hypfs_entry_leaf __read_mostly var = { \
+        .e.type = XEN_HYPFS_TYPE_BOOL,            \
+        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
+        .e.name = nam,                            \
+        .e.size = sizeof(contvar),                \
+        .e.read = hypfs_read_leaf,                \
+        .content = &contvar,                      \
+    }
+
+extern struct hypfs_entry_dir hypfs_root;
+
+struct hypfs_entry *hypfs_get_entry(const char *path);
+int hypfs_add_dir(struct hypfs_entry_dir *parent,
+                  struct hypfs_entry_dir *dir, bool nofault);
+int hypfs_add_leaf(struct hypfs_entry_dir *parent,
+                   struct hypfs_entry_leaf *leaf, bool nofault);
+int hypfs_read_dir(const struct hypfs_entry *entry,
+                   XEN_GUEST_HANDLE_PARAM(void) uaddr);
+int hypfs_read_leaf(const struct hypfs_entry *entry,
+                    XEN_GUEST_HANDLE_PARAM(void) uaddr);
+int hypfs_write_leaf(struct hypfs_entry_leaf *leaf,
+                     XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen);
+int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
+                     XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen);
+
+#endif /* __XEN_HYPFS_H__ */
diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
index 95f5e5592b..228728ba25 100644
--- a/xen/include/xlat.lst
+++ b/xen/include/xlat.lst
@@ -86,6 +86,8 @@ 
 ?	vcpu_hvm_context		hvm/hvm_vcpu.h
 ?	vcpu_hvm_x86_32			hvm/hvm_vcpu.h
 ?	vcpu_hvm_x86_64			hvm/hvm_vcpu.h
+?	xen_hypfs_direntry		hypfs.h
+?	xen_hypfs_dirlistentry		hypfs.h
 ?	kexec_exec			kexec.h
 !	kexec_image			kexec.h
 !	kexec_range			kexec.h