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Re: [PATCH 2/5] xen/common/domctl: introduce XEN_DOMCTL_get/setdomaincontext
Hi Paul,
On 27/03/2020 18:50, Paul Durrant wrote:
These domctls provide a mechanism to get and set domain context from
the toolstack.
Signed-off-by: Paul Durrant <paul@xxxxxxx>
---
Cc: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Julien Grall <julien@xxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
tools/flask/policy/modules/xen.if | 4 +-
tools/libxc/include/xenctrl.h | 11 +++
tools/libxc/xc_domain.c | 52 +++++++++++++
xen/common/domctl.c | 115 ++++++++++++++++++++++++++++
xen/include/public/domctl.h | 41 +++++++++-
xen/xsm/flask/hooks.c | 6 ++
xen/xsm/flask/policy/access_vectors | 4 +
7 files changed, 230 insertions(+), 3 deletions(-)
diff --git a/tools/flask/policy/modules/xen.if
b/tools/flask/policy/modules/xen.if
index 8eb2293a52..2bc9db4f64 100644
--- a/tools/flask/policy/modules/xen.if
+++ b/tools/flask/policy/modules/xen.if
@@ -53,7 +53,7 @@ define(`create_domain_common', `
allow $1 $2:domain2 { set_cpu_policy settsc setscheduler setclaim
set_vnumainfo get_vnumainfo cacheflush
psr_cmt_op psr_alloc soft_reset
- resource_map get_cpu_policy };
+ resource_map get_cpu_policy setcontext };
allow $1 $2:security check_context;
allow $1 $2:shadow enable;
allow $1 $2:mmu { map_read map_write adjust memorymap physmap pinpage
mmuext_op updatemp };
@@ -97,7 +97,7 @@ define(`migrate_domain_out', `
allow $1 $2:hvm { gethvmc getparam };
allow $1 $2:mmu { stat pageinfo map_read };
allow $1 $2:domain { getaddrsize getvcpucontext pause destroy };
- allow $1 $2:domain2 gettsc;
+ allow $1 $2:domain2 { gettsc getcontext };
allow $1 $2:shadow { enable disable logdirty };
')
diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index fc6e57a1a0..5c0d0d27a4 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -867,6 +867,17 @@ int xc_domain_hvm_setcontext(xc_interface *xch,
uint8_t *hvm_ctxt,
uint32_t size);
+int xc_domain_getcontext(xc_interface *xch,
+ uint32_t domid,
+ uint32_t mask,
+ uint8_t *ctxt_buf,
Why do you use uint8_t rather than void here?
+ uint32_t size);
+int xc_domain_setcontext(xc_interface *xch,
+ uint32_t domid,
+ uint32_t mask,
+ uint8_t *ctxt_buf,
+ uint32_t size);
+
/**
* This function will return guest IO ABI protocol
*
diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
index 71829c2bce..15bcf671fc 100644
--- a/tools/libxc/xc_domain.c
+++ b/tools/libxc/xc_domain.c
@@ -537,6 +537,58 @@ int xc_domain_hvm_setcontext(xc_interface *xch,
return ret;
}
+int xc_domain_getcontext(xc_interface *xch,
+ uint32_t domid,
+ uint32_t mask,
+ uint8_t *ctxt_buf,
+ uint32_t size)
+{
+ int ret;
+ DECLARE_DOMCTL;
+ DECLARE_HYPERCALL_BOUNCE(ctxt_buf, size, XC_HYPERCALL_BUFFER_BOUNCE_OUT);
+
+ if ( xc_hypercall_bounce_pre(xch, ctxt_buf) )
+ return -1;
+
+ domctl.cmd = XEN_DOMCTL_getdomaincontext;
+ domctl.domain = domid;
+ domctl.u.domaincontext.mask = mask;
+ domctl.u.domaincontext.size = size;
+ set_xen_guest_handle(domctl.u.domaincontext.buffer, ctxt_buf);
+
+ ret = do_domctl(xch, &domctl);
+
+ xc_hypercall_bounce_post(xch, ctxt_buf);
+
+ return !ret ? domctl.u.domaincontext.size : -1;
Looking at the domctl interface, size would be a 32-bit unsigned value.
However the return is a 32-bit signed value. This is a call for trouble
if the size is too big.
+}
+
+int xc_domain_setcontext(xc_interface *xch,
+ uint32_t domid,
+ uint32_t mask,
+ uint8_t *ctxt_buf,
The context is not meant to be modified. So this should really be const.
+ uint32_t size)
+{
+ int ret;
+ DECLARE_DOMCTL;
+ DECLARE_HYPERCALL_BOUNCE(ctxt_buf, size, XC_HYPERCALL_BUFFER_BOUNCE_IN);
+
+ if ( xc_hypercall_bounce_pre(xch, ctxt_buf) )
+ return -1;
+
+ domctl.cmd = XEN_DOMCTL_setdomaincontext;
+ domctl.domain = domid;
+ domctl.u.domaincontext.mask = mask;
+ domctl.u.domaincontext.size = size;
+ set_xen_guest_handle(domctl.u.domaincontext.buffer, ctxt_buf);
+
+ ret = do_domctl(xch, &domctl);
+
+ xc_hypercall_bounce_post(xch, ctxt_buf);
+
+ return ret;
+}
+
int xc_vcpu_getcontext(xc_interface *xch,
uint32_t domid,
uint32_t vcpu,
diff --git a/xen/common/domctl.c b/xen/common/domctl.c
index a69b3b59a8..9c39519b04 100644
--- a/xen/common/domctl.c
+++ b/xen/common/domctl.c
@@ -25,6 +25,7 @@
#include <xen/hypercall.h>
#include <xen/vm_event.h>
#include <xen/monitor.h>
+#include <xen/save.h>
#include <asm/current.h>
#include <asm/irq.h>
#include <asm/page.h>
@@ -358,6 +359,111 @@ static struct vnuma_info *vnuma_init(const struct
xen_domctl_vnuma *uinfo,
return ERR_PTR(ret);
}
+struct domctl_context
+{
+ void *buffer;
+ size_t len;
+ size_t cur;
+};
+
+static int accumulate_size(void *priv, void *data, size_t len)
+{
+ struct domctl_context *c = priv;
+
+ c->len += len;
What does prevent overflow?
+
+ return 0;
+}
+
+static int save_data(void *priv, void *data, size_t len)
+{
+ struct domctl_context *c = priv;
+
+ if ( c->len - c->cur < len )
+ return -ENOSPC;
+
+ memcpy(c->buffer + c->cur, data, len);
+ c->cur += len;
+
+ return 0;
+}
+
+static int getdomaincontext(struct domain *d,
+ struct xen_domctl_domaincontext *dc)
+{
+ struct domctl_context c = { };
+ int rc;
+
+ if ( d == current->domain )
+ return -EPERM;
+
+ if ( guest_handle_is_null(dc->buffer) ) /* query for buffer size */
+
+ {
+ if ( dc->size )
+ return -EINVAL;
+
+ /* dry run to acquire buffer size */
+ rc = domain_save(d, accumulate_size, &c, dc->mask, true);
+ if ( rc )
+ return rc;
+
+ dc->size = c.len;
len is a size_t (so 64-bit on 64-bit arch) value, but size is 32-bit. So
we return an error if the stream is going to be bigger than 4G?
+ return 0;
+ }
+
+ c.len = dc->size;
+ c.buffer = xmalloc_bytes(c.len);
+ if ( !c.buffer )
+ return -ENOMEM;
+
+ rc = domain_save(d, save_data, &c, dc->mask, false);
+
+ dc->size = c.cur;
+ if ( !rc && copy_to_guest(dc->buffer, c.buffer, dc->size) )
+ rc = -EFAULT;
+
+ xfree(c.buffer);
+
+ return rc;
+}
+
+static int load_data(void *priv, void *data, size_t len)
+{
+ struct domctl_context *c = priv;
+
+ if ( c->len - c->cur < len )
+ return -ENODATA;
+
+ if ( data )
+ memcpy(data, c->buffer + c->cur, len);
+
+ c->cur += len;
+
+ return 0;
+}
+
+static int setdomaincontext(struct domain *d,
+ const struct xen_domctl_domaincontext *dc)
+{
+ struct domctl_context c = { .len = dc->size };
+ int rc;
+
+ if ( d == current->domain )
+ return -EPERM;
+
+ c.buffer = xmalloc_bytes(c.len);
+ if ( !c.buffer )
+ return -ENOMEM;
+
+ rc = !copy_from_guest(c.buffer, dc->buffer, c.len) ?
+ domain_load(d, load_data, &c, dc->mask) : -EFAULT;
+
+ xfree(c.buffer);
+
+ return rc;
+}
+
long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
{
long ret = 0;
@@ -942,6 +1048,15 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t)
u_domctl)
copyback = 1;
break;
+ case XEN_DOMCTL_getdomaincontext:
+ ret = getdomaincontext(d, &op->u.domaincontext);
+ copyback = !ret;
+ break;
+
+ case XEN_DOMCTL_setdomaincontext:
+ ret = setdomaincontext(d, &op->u.domaincontext);
+ break;
+
default:
ret = arch_do_domctl(op, d, u_domctl);
break;
diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
index 1ad34c35eb..24ed6852cf 100644
--- a/xen/include/public/domctl.h
+++ b/xen/include/public/domctl.h
@@ -38,7 +38,7 @@
#include "hvm/save.h"
#include "memory.h"
-#define XEN_DOMCTL_INTERFACE_VERSION 0x00000012
+#define XEN_DOMCTL_INTERFACE_VERSION 0x00000013
/*
* NB. xen_domctl.domain is an IN/OUT parameter for this operation.
@@ -1129,6 +1129,42 @@ struct xen_domctl_vuart_op {
*/
};
+/*
+ * Get/Set domain PV context. The same struct xen_domctl_domaincontext
+ * is used for both commands but with slightly different field semantics
+ * as follows:
+ *
+ * XEN_DOMCTL_getdomaincontext
+ * ---------------------------
+ *
+ * buffer (IN): The buffer into which the context data should be
+ * copied, or NULL to query the buffer size that should
+ * be allocated.
+ * size (IN/OUT): If 'buffer' is NULL then the value passed in must be
+ * zero, and the value passed out will be the size of the
+ * buffer to allocate.
+ * If 'buffer' is non-NULL then the value passed in must
+ * be the size of the buffer into which data may be copied.
+ * mask (IN): See comment on domain_save/load() in xen/save.h.
+ *
+ * XEN_DOMCTL_setdomaincontext
+ * ---------------------------
+ *
+ * buffer (IN): The buffer from which the context data should be
+ * copied.
+ * size (IN): The size of the buffer from which data may be copied.
+ * This data must include DOMAIN_SAVE_CODE_HEADER at the
+ * start and terminate with a DOMAIN_SAVE_CODE_END record.
+ * Any data beyond the DOMAIN_SAVE_CODE_END record will be
+ * ignored.
+ * mask (IN): See comment on domain_save/load() in xen/save.h.
+ */
+struct xen_domctl_domaincontext {
+ uint32_t size;
+ uint32_t mask;
+ XEN_GUEST_HANDLE_64(uint8) buffer;
Should not it be a void handle?
Also, in the case of XEN_DOMCTL_setdomaincontext, the buffer is not
meant to be modified by the hypervisor. So I would rather introduce two
separate structure so we can enforce the const.
+};
+
struct xen_domctl {
uint32_t cmd;
#define XEN_DOMCTL_createdomain 1
@@ -1210,6 +1246,8 @@ struct xen_domctl {
#define XEN_DOMCTL_vuart_op 81
#define XEN_DOMCTL_get_cpu_policy 82
#define XEN_DOMCTL_set_cpu_policy 83
+#define XEN_DOMCTL_getdomaincontext 84
+#define XEN_DOMCTL_setdomaincontext 85
#define XEN_DOMCTL_gdbsx_guestmemio 1000
#define XEN_DOMCTL_gdbsx_pausevcpu 1001
#define XEN_DOMCTL_gdbsx_unpausevcpu 1002
@@ -1270,6 +1308,7 @@ struct xen_domctl {
struct xen_domctl_monitor_op monitor_op;
struct xen_domctl_psr_alloc psr_alloc;
struct xen_domctl_vuart_op vuart_op;
+ struct xen_domctl_domaincontext domaincontext;
uint8_t pad[128];
} u;
};
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 8af8602b46..d94d0fc125 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -744,6 +744,12 @@ static int flask_domctl(struct domain *d, int cmd)
case XEN_DOMCTL_get_cpu_policy:
return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__GET_CPU_POLICY);
+ case XEN_DOMCTL_setdomaincontext:
+ return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__SETCONTEXT);
+
+ case XEN_DOMCTL_getdomaincontext:
+ return current_has_perm(d, SECCLASS_DOMAIN2, DOMAIN2__GETCONTEXT);
+
default:
return avc_unknown_permission("domctl", cmd);
}
diff --git a/xen/xsm/flask/policy/access_vectors
b/xen/xsm/flask/policy/access_vectors
index c055c14c26..fccfb9de82 100644
--- a/xen/xsm/flask/policy/access_vectors
+++ b/xen/xsm/flask/policy/access_vectors
@@ -245,6 +245,10 @@ class domain2
resource_map
# XEN_DOMCTL_get_cpu_policy
get_cpu_policy
+# XEN_DOMCTL_setdomaincontext
+ setcontext
+# XEN_DOMCTL_getdomaincontext
+ getcontext
}
# Similar to class domain, but primarily contains domctls related to HVM domains
Cheers,
--
Julien Grall
|
