Re: [PATCH v10 04/12] xen: add basic hypervisor filesystem support

[Julien Grall <julien@xen.org>]

Hi Juergen,

On 19/05/2020 08:20, Juergen Gross wrote:
> 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.
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Julien Grall <jgrall@amazon.com>

Cheers,

> ---
> 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)
> 
> V5:
> - switch to xsm for privilege check
> 
> V6:
> - use memchr() for testing correct string length (Jan Beulich)
> - reject writing to non-string leafs with wrong length (Jan Beulich)
> - only support bools of natural size (Julien Grall)
> - adjust blank padding in header (Jan Beulich)
> - adjust comments in public header (Jan Beulich)
> - rename hypfs_string_set() and add comment (Jan Beulich)
> - add common HYPFS_INIT helper macro (Jan Beulich)
> - really check structures added to xlat.lst (Jan Beulich)
> - add missing xsm parts (Jan Beulich)
> 
> V7:
> - simplify compat check (Jan Beulich)
> - add max write size (Jan Beulich)
> - better length testing of written string (Jan Beulich)
> 
> V8:
> - add Kconfig item CONFIG_HYPFS (Jan Beulich)
> - init write pointer in HYPFS_*_INIT_WRITABLE() (Jan Beulich)
> - expand write ASSERT()s (Jan Beulich)
> 
> V9:
> - move hypfs to correct position in Makefile (Jan Beulich)
> - avoid recursion in hypfs_get_entry_rel() (Jan Beulich)
> - make hypfs_get_entry() static (Jan Beulich)
> - assert locking in read/write functions (Jan Beulich)
> - add ASSERT() in hypfs_write_leaf() (Jan Beulich)
> - add encoding test in hypfs_write_leaf() (Jan Beulich)
> - test parameters of XEN_HYPFS_OP_get_version to be zero (Jan Beulich)
> - add parantheses in macro (Jan Beulich)
> - make ulen type unsigned int in functions (Jan Beulich)
> 
> V10:
> - add locking ASSERT()s (Jan Beulich)
> - correct indentation (Jan Beulich)
> 
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
>   tools/flask/policy/modules/dom0.te  |   2 +-
>   xen/arch/arm/traps.c                |   3 +
>   xen/arch/x86/hvm/hypercall.c        |   3 +
>   xen/arch/x86/hypercall.c            |   3 +
>   xen/arch/x86/pv/hypercall.c         |   3 +
>   xen/common/Kconfig                  |  11 +
>   xen/common/Makefile                 |   1 +
>   xen/common/hypfs.c                  | 422 ++++++++++++++++++++++++++++
>   xen/include/Makefile                |   1 +
>   xen/include/public/hypfs.h          | 129 +++++++++
>   xen/include/public/xen.h            |   1 +
>   xen/include/xen/hypercall.h         |  10 +
>   xen/include/xen/hypfs.h             | 121 ++++++++
>   xen/include/xlat.lst                |   2 +
>   xen/include/xsm/dummy.h             |   6 +
>   xen/include/xsm/xsm.h               |   6 +
>   xen/xsm/dummy.c                     |   1 +
>   xen/xsm/flask/hooks.c               |   6 +
>   xen/xsm/flask/policy/access_vectors |   2 +
>   19 files changed, 732 insertions(+), 1 deletion(-)
>   create mode 100644 xen/common/hypfs.c
>   create mode 100644 xen/include/public/hypfs.h
>   create mode 100644 xen/include/xen/hypfs.h
> 
> diff --git a/tools/flask/policy/modules/dom0.te b/tools/flask/policy/modules/dom0.te
> index 272f6a4f75..20925e38a2 100644
> --- a/tools/flask/policy/modules/dom0.te
> +++ b/tools/flask/policy/modules/dom0.te
> @@ -11,7 +11,7 @@ allow dom0_t xen_t:xen {
>   	mtrr_del mtrr_read microcode physinfo quirk writeconsole readapic
>   	writeapic privprofile nonprivprofile kexec firmware sleep frequency
>   	getidle debug getcpuinfo heap pm_op mca_op lockprof cpupool_op
> -	getscheduler setscheduler
> +	getscheduler setscheduler hypfs_op
>   };
>   allow dom0_t xen_t:xen2 {
>   	resource_op psr_cmt_op psr_alloc pmu_ctrl get_symbol
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 30c4c1830b..8f40d0e0b6 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -1381,6 +1381,9 @@ static arm_hypercall_t arm_hypercall_table[] = {
>   #ifdef CONFIG_ARGO
>       HYPERCALL(argo_op, 5),
>   #endif
> +#ifdef CONFIG_HYPFS
> +    HYPERCALL(hypfs_op, 5),
> +#endif
>   };
>   
>   #ifndef NDEBUG
> diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
> index c41c2179c9..b6ccaf4457 100644
> --- a/xen/arch/x86/hvm/hypercall.c
> +++ b/xen/arch/x86/hvm/hypercall.c
> @@ -150,6 +150,9 @@ static const hypercall_table_t hvm_hypercall_table[] = {
>   #endif
>       HYPERCALL(xenpmu_op),
>       COMPAT_CALL(dm_op),
> +#ifdef CONFIG_HYPFS
> +    HYPERCALL(hypfs_op),
> +#endif
>       HYPERCALL(arch_1)
>   };
>   
> diff --git a/xen/arch/x86/hypercall.c b/xen/arch/x86/hypercall.c
> index 7f299d45c6..dd00983005 100644
> --- a/xen/arch/x86/hypercall.c
> +++ b/xen/arch/x86/hypercall.c
> @@ -72,6 +72,9 @@ const hypercall_args_t hypercall_args_table[NR_hypercalls] =
>   #ifdef CONFIG_HVM
>       ARGS(hvm_op, 2),
>       ARGS(dm_op, 3),
> +#endif
> +#ifdef CONFIG_HYPFS
> +    ARGS(hypfs_op, 5),
>   #endif
>       ARGS(mca, 1),
>       ARGS(arch_1, 1),
> diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
> index b0d1d0ed77..53a52360fa 100644
> --- a/xen/arch/x86/pv/hypercall.c
> +++ b/xen/arch/x86/pv/hypercall.c
> @@ -84,6 +84,9 @@ const hypercall_table_t pv_hypercall_table[] = {
>   #ifdef CONFIG_HVM
>       HYPERCALL(hvm_op),
>       COMPAT_CALL(dm_op),
> +#endif
> +#ifdef CONFIG_HYPFS
> +    HYPERCALL(hypfs_op),
>   #endif
>       HYPERCALL(mca),
>       HYPERCALL(arch_1),
> diff --git a/xen/common/Kconfig b/xen/common/Kconfig
> index fe9b41f721..e768ea36b2 100644
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -116,6 +116,17 @@ config SPECULATIVE_HARDEN_BRANCH
>   
>   endmenu
>   
> +config HYPFS
> +	bool "Hypervisor file system support"
> +	default y
> +	---help---
> +	  Support Xen hypervisor file system. This file system is used to
> +	  present various hypervisor internal data to dom0 and in some
> +	  cases to allow modifying settings. Disabling the support might
> +	  result in some features not being available.
> +
> +	  If unsure, say Y.
> +
>   config KEXEC
>   	bool "kexec support"
>   	default y
> diff --git a/xen/common/Makefile b/xen/common/Makefile
> index e8cde65370..bf7d0e25a3 100644
> --- a/xen/common/Makefile
> +++ b/xen/common/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_CRASH_DEBUG) += gdbstub.o
>   obj-$(CONFIG_GRANT_TABLE) += grant_table.o
>   obj-y += guestcopy.o
>   obj-bin-y += gunzip.init.o
> +obj-$(CONFIG_HYPFS) += hypfs.o
>   obj-y += irq.o
>   obj-y += kernel.o
>   obj-y += keyhandler.o
> diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
> new file mode 100644
> index 0000000000..9c2213a068
> --- /dev/null
> +++ b/xen/common/hypfs.c
> @@ -0,0 +1,422 @@
> +/******************************************************************************
> + *
> + * 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>
> +
> +#ifdef CONFIG_COMPAT
> +#include <compat/hypfs.h>
> +CHECK_hypfs_dirlistentry;
> +#endif
> +
> +#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);
> +enum hypfs_lock_state {
> +    hypfs_unlocked,
> +    hypfs_read_locked,
> +    hypfs_write_locked
> +};
> +static DEFINE_PER_CPU(enum hypfs_lock_state, hypfs_locked);
> +
> +HYPFS_DIR_INIT(hypfs_root, "");
> +
> +static void hypfs_read_lock(void)
> +{
> +    ASSERT(this_cpu(hypfs_locked) != hypfs_write_locked);
> +
> +    read_lock(&hypfs_lock);
> +    this_cpu(hypfs_locked) = hypfs_read_locked;
> +}
> +
> +static void hypfs_write_lock(void)
> +{
> +    ASSERT(this_cpu(hypfs_locked) == hypfs_unlocked);
> +
> +    write_lock(&hypfs_lock);
> +    this_cpu(hypfs_locked) = hypfs_write_locked;
> +}
> +
> +static void hypfs_unlock(void)
> +{
> +    enum hypfs_lock_state locked = this_cpu(hypfs_locked);
> +
> +    this_cpu(hypfs_locked) = hypfs_unlocked;
> +
> +    switch ( locked )
> +    {
> +    case hypfs_read_locked:
> +        read_unlock(&hypfs_lock);
> +        break;
> +    case hypfs_write_locked:
> +        write_unlock(&hypfs_lock);
> +        break;
> +    default:
> +        BUG();
> +    }
> +}
> +
> +static int add_entry(struct hypfs_entry_dir *parent, struct hypfs_entry *new)
> +{
> +    int ret = -ENOENT;
> +    struct hypfs_entry *e;
> +
> +    hypfs_write_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);
> +    }
> +
> +    hypfs_unlock();
> +
> +    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 ( memchr(buf, 0, ulen) != 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;
> +    bool again = true;
> +
> +    while ( again )
> +    {
> +        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;
> +
> +        again = false;
> +
> +        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 )
> +            {
> +                if ( !*end )
> +                    return entry;
> +
> +                again = true;
> +                dir = d;
> +                path = end + 1;
> +
> +                break;
> +            }
> +        }
> +    }
> +
> +    return NULL;
> +}
> +
> +static 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;
> +
> +    ASSERT(this_cpu(hypfs_locked) != hypfs_unlocked);
> +
> +    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.pad = 0;
> +        direntry.e.type = e->type;
> +        direntry.e.encoding = e->encoding;
> +        direntry.e.content_len = e->size;
> +        direntry.e.max_write_len = e->max_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;
> +
> +    ASSERT(this_cpu(hypfs_locked) != hypfs_unlocked);
> +
> +    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.pad = 0;
> +    e.type = entry->type;
> +    e.encoding = entry->encoding;
> +    e.content_len = entry->size;
> +    e.max_write_len = entry->max_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 int ulen)
> +{
> +    char *buf;
> +    int ret;
> +
> +    ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
> +    ASSERT(ulen <= leaf->e.max_size);
> +
> +    if ( leaf->e.type != XEN_HYPFS_TYPE_STRING &&
> +         leaf->e.type != XEN_HYPFS_TYPE_BLOB && ulen != leaf->e.size )
> +        return -EDOM;
> +
> +    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 &&
> +         leaf->e.encoding == XEN_HYPFS_ENC_PLAIN &&
> +         memchr(buf, 0, ulen) != (buf + ulen - 1) )
> +        goto out;
> +
> +    ret = 0;
> +    memcpy(leaf->write_ptr, buf, ulen);
> +    leaf->e.size = ulen;
> +
> + out:
> +    xfree(buf);
> +    return ret;
> +}
> +
> +int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
> +                     XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned int ulen)
> +{
> +    bool buf;
> +
> +    ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
> +    ASSERT(leaf->e.type == XEN_HYPFS_TYPE_BOOL &&
> +           leaf->e.size == sizeof(bool) &&
> +           leaf->e.max_size == sizeof(bool) );
> +
> +    if ( ulen != leaf->e.max_size )
> +        return -EDOM;
> +
> +    if ( copy_from_guest(&buf, uaddr, ulen) )
> +        return -EFAULT;
> +
> +    *(bool *)leaf->write_ptr = buf;
> +
> +    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;
> +
> +    ASSERT(entry->max_size);
> +
> +    if ( ulen > entry->max_size )
> +        return -ENOSPC;
> +
> +    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 ( xsm_hypfs_op(XSM_PRIV) )
> +        return -EPERM;
> +
> +    if ( cmd == XEN_HYPFS_OP_get_version )
> +    {
> +        if ( !guest_handle_is_null(arg1) || arg2 ||
> +             !guest_handle_is_null(arg3) || arg4 )
> +            return -EINVAL;
> +
> +        return XEN_HYPFS_VERSION;
> +    }
> +
> +    if ( cmd == XEN_HYPFS_OP_write_contents )
> +        hypfs_write_lock();
> +    else
> +        hypfs_read_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:
> +    hypfs_unlock();
> +
> +    return ret;
> +}
> diff --git a/xen/include/Makefile b/xen/include/Makefile
> index 2a10725d68..089314dc72 100644
> --- a/xen/include/Makefile
> +++ b/xen/include/Makefile
> @@ -9,6 +9,7 @@ headers-y := \
>       compat/event_channel.h \
>       compat/features.h \
>       compat/grant_table.h \
> +    compat/hypfs.h \
>       compat/kexec.h \
>       compat/memory.h \
>       compat/nmi.h \
> diff --git a/xen/include/public/hypfs.h b/xen/include/public/hypfs.h
> new file mode 100644
> index 0000000000..63a5df1629
> --- /dev/null
> +++ b/xen/include/public/hypfs.h
> @@ -0,0 +1,129 @@
> +/******************************************************************************
> + * 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 {
> +    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
> +    uint16_t pad;              /* Returned as 0. */
> +    uint32_t content_len;      /* Current length of data. */
> +    uint32_t max_write_len;    /* Max. length for writes (0 if read-only). */
> +};
> +
> +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.
> + *
> + * arg1 - arg4: all 0/NULL
> + *
> + * 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. 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
> + * <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 75b1619d0d..945ef30273 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 d82a293377..655acc7f47 100644
> --- a/xen/include/xen/hypercall.h
> +++ b/xen/include/xen/hypercall.h
> @@ -150,6 +150,16 @@ do_dm_op(
>       unsigned int nr_bufs,
>       XEN_GUEST_HANDLE_PARAM(xen_dm_op_buf_t) bufs);
>   
> +#ifdef CONFIG_HYPFS
> +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);
> +#endif
> +
>   #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..5c6a0ccece
> --- /dev/null
> +++ b/xen/include/xen/hypfs.h
> @@ -0,0 +1,121 @@
> +#ifndef __XEN_HYPFS_H__
> +#define __XEN_HYPFS_H__
> +
> +#ifdef CONFIG_HYPFS
> +#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;
> +    unsigned int max_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 int 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.max_size = 0,                          \
> +        .e.list = LIST_HEAD_INIT(var.e.list),     \
> +        .e.read = hypfs_read_dir,                 \
> +        .dirlist = LIST_HEAD_INIT(var.dirlist),   \
> +    }
> +
> +#define HYPFS_VARSIZE_INIT(var, typ, nam, msz)    \
> +    struct hypfs_entry_leaf __read_mostly var = { \
> +        .e.type = (typ),                          \
> +        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
> +        .e.name = (nam),                          \
> +        .e.max_size = (msz),                      \
> +        .e.read = hypfs_read_leaf,                \
> +    }
> +
> +/* Content and size need to be set via hypfs_string_set_reference(). */
> +#define HYPFS_STRING_INIT(var, nam)               \
> +    HYPFS_VARSIZE_INIT(var, XEN_HYPFS_TYPE_STRING, nam, 0)
> +
> +/*
> + * Set content and size of a XEN_HYPFS_TYPE_STRING node. The node will point
> + * to str, so any later modification of *str should be followed by a call
> + * to hypfs_string_set_reference() in order to update the size of the node
> + * data.
> + */
> +static inline void hypfs_string_set_reference(struct hypfs_entry_leaf *leaf,
> +                                              const char *str)
> +{
> +    leaf->content = str;
> +    leaf->e.size = strlen(str) + 1;
> +}
> +
> +#define HYPFS_FIXEDSIZE_INIT(var, typ, nam, contvar, wr) \
> +    struct hypfs_entry_leaf __read_mostly var = {        \
> +        .e.type = (typ),                                 \
> +        .e.encoding = XEN_HYPFS_ENC_PLAIN,               \
> +        .e.name = (nam),                                 \
> +        .e.size = sizeof(contvar),                       \
> +        .e.max_size = (wr) ? sizeof(contvar) : 0,        \
> +        .e.read = hypfs_read_leaf,                       \
> +        .e.write = (wr),                                 \
> +        .content = &(contvar),                           \
> +    }
> +
> +#define HYPFS_UINT_INIT(var, nam, contvar)                       \
> +    HYPFS_FIXEDSIZE_INIT(var, XEN_HYPFS_TYPE_UINT, nam, contvar, NULL)
> +#define HYPFS_UINT_INIT_WRITABLE(var, nam, contvar)              \
> +    HYPFS_FIXEDSIZE_INIT(var, XEN_HYPFS_TYPE_UINT, nam, contvar, \
> +                         hypfs_write_leaf)
> +
> +#define HYPFS_INT_INIT(var, nam, contvar)                        \
> +    HYPFS_FIXEDSIZE_INIT(var, XEN_HYPFS_TYPE_INT, nam, contvar, NULL)
> +#define HYPFS_INT_INIT_WRITABLE(var, nam, contvar)               \
> +    HYPFS_FIXEDSIZE_INIT(var, XEN_HYPFS_TYPE_INT, nam, contvar, \
> +                         hypfs_write_leaf)
> +
> +#define HYPFS_BOOL_INIT(var, nam, contvar)                       \
> +    HYPFS_FIXEDSIZE_INIT(var, XEN_HYPFS_TYPE_BOOL, nam, contvar, NULL)
> +#define HYPFS_BOOL_INIT_WRITABLE(var, nam, contvar)              \
> +    HYPFS_FIXEDSIZE_INIT(var, XEN_HYPFS_TYPE_BOOL, nam, contvar, \
> +                         hypfs_write_bool)
> +
> +extern struct hypfs_entry_dir hypfs_root;
> +
> +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 int ulen);
> +int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
> +                     XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned int ulen);
> +#endif
> +
> +#endif /* __XEN_HYPFS_H__ */
> diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
> index 95f5e5592b..0921d4a8d0 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
> +?	hypfs_direntry			hypfs.h
> +?	hypfs_dirlistentry		hypfs.h
>   ?	kexec_exec			kexec.h
>   !	kexec_image			kexec.h
>   !	kexec_range			kexec.h
> diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
> index 295dd67c48..2368acebed 100644
> --- a/xen/include/xsm/dummy.h
> +++ b/xen/include/xsm/dummy.h
> @@ -434,6 +434,12 @@ static XSM_INLINE int xsm_page_offline(XSM_DEFAULT_ARG uint32_t cmd)
>       return xsm_default_action(action, current->domain, NULL);
>   }
>   
> +static XSM_INLINE int xsm_hypfs_op(XSM_DEFAULT_VOID)
> +{
> +    XSM_ASSERT_ACTION(XSM_PRIV);
> +    return xsm_default_action(action, current->domain, NULL);
> +}
> +
>   static XSM_INLINE long xsm_do_xsm_op(XEN_GUEST_HANDLE_PARAM(xsm_op_t) op)
>   {
>       return -ENOSYS;
> diff --git a/xen/include/xsm/xsm.h b/xen/include/xsm/xsm.h
> index e22d6160b5..a80bcf3e42 100644
> --- a/xen/include/xsm/xsm.h
> +++ b/xen/include/xsm/xsm.h
> @@ -127,6 +127,7 @@ struct xsm_operations {
>       int (*resource_setup_misc) (void);
>   
>       int (*page_offline)(uint32_t cmd);
> +    int (*hypfs_op)(void);
>   
>       long (*do_xsm_op) (XEN_GUEST_HANDLE_PARAM(xsm_op_t) op);
>   #ifdef CONFIG_COMPAT
> @@ -536,6 +537,11 @@ static inline int xsm_page_offline(xsm_default_t def, uint32_t cmd)
>       return xsm_ops->page_offline(cmd);
>   }
>   
> +static inline int xsm_hypfs_op(xsm_default_t def)
> +{
> +    return xsm_ops->hypfs_op();
> +}
> +
>   static inline long xsm_do_xsm_op (XEN_GUEST_HANDLE_PARAM(xsm_op_t) op)
>   {
>       return xsm_ops->do_xsm_op(op);
> diff --git a/xen/xsm/dummy.c b/xen/xsm/dummy.c
> index 5705e52791..d4cce68089 100644
> --- a/xen/xsm/dummy.c
> +++ b/xen/xsm/dummy.c
> @@ -103,6 +103,7 @@ void __init xsm_fixup_ops (struct xsm_operations *ops)
>       set_to_dummy_if_null(ops, resource_setup_misc);
>   
>       set_to_dummy_if_null(ops, page_offline);
> +    set_to_dummy_if_null(ops, hypfs_op);
>       set_to_dummy_if_null(ops, hvm_param);
>       set_to_dummy_if_null(ops, hvm_control);
>       set_to_dummy_if_null(ops, hvm_param_nested);
> diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
> index 4649e6fd95..a2c78e445c 100644
> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -1173,6 +1173,11 @@ static inline int flask_page_offline(uint32_t cmd)
>       }
>   }
>   
> +static inline int flask_hypfs_op(void)
> +{
> +    return domain_has_xen(current->domain, XEN__HYPFS_OP);
> +}
> +
>   static int flask_add_to_physmap(struct domain *d1, struct domain *d2)
>   {
>       return domain_has_perm(d1, d2, SECCLASS_MMU, MMU__PHYSMAP);
> @@ -1812,6 +1817,7 @@ static struct xsm_operations flask_ops = {
>       .resource_setup_misc = flask_resource_setup_misc,
>   
>       .page_offline = flask_page_offline,
> +    .hypfs_op = flask_hypfs_op,
>       .hvm_param = flask_hvm_param,
>       .hvm_control = flask_hvm_param,
>       .hvm_param_nested = flask_hvm_param_nested,
> diff --git a/xen/xsm/flask/policy/access_vectors b/xen/xsm/flask/policy/access_vectors
> index c055c14c26..c9e385fb9b 100644
> --- a/xen/xsm/flask/policy/access_vectors
> +++ b/xen/xsm/flask/policy/access_vectors
> @@ -67,6 +67,8 @@ class xen
>       lockprof
>   # XEN_SYSCTL_cpupool_op
>       cpupool_op
> +# hypfs hypercall
> +    hypfs_op
>   # XEN_SYSCTL_scheduler_op with XEN_DOMCTL_SCHEDOP_getinfo, XEN_SYSCTL_sched_id, XEN_DOMCTL_SCHEDOP_getvcpuinfo
>       getscheduler
>   # XEN_SYSCTL_scheduler_op with XEN_DOMCTL_SCHEDOP_putinfo, XEN_DOMCTL_SCHEDOP_putvcpuinfo
> 

-- 
Julien Grall