[v4,49/53] xen: add hypercall for setting parameters at runtime

Commit Message

Jürgen Groß Aug. 23, 2017, 5:34 p.m. UTC

Add a sysctl hypercall to support setting parameters similar to
command line parameters, but at runtime. The parameters to set are
specified as a string, just like the boot parameters.

Cc: Daniel De Graaf <[e-mail]>
Cc: Ian Jackson <[e-mail]>
Cc: Wei Liu <[e-mail]>
Cc: Andrew Cooper <[e-mail]>
Cc: George Dunlap <[e-mail]>
Cc: Jan Beulich <[e-mail]>
Cc: Konrad Rzeszutek Wilk <[e-mail]>
Cc: Stefano Stabellini <[e-mail]>
Cc: Tim Deegan <[e-mail]>
Signed-off-by: Juergen Gross <[e-mail]>
Acked-by: Daniel De Graaf <[e-mail]>
---
V4:
- use copy_from_guest() (Jan Beulich)
- add more descriptive comment to sysctl.h (Jan Beulich)

V3:
- check pad[] to be zero (Jan Beulich)
- return E2BIG in case of parameters too long (Jan Beulich)
- move max. parameter size define to sysctl.c (Jan Beulich)

V2:
- corrected XSM test (Daniel De Graaf)
---
 tools/flask/policy/modules/dom0.te  |  2 +-
 xen/common/sysctl.c                 | 36 ++++++++++++++++++++++++++++++++++++
 xen/include/public/sysctl.h         | 20 ++++++++++++++++++++
 xen/xsm/flask/hooks.c               |  3 +++
 xen/xsm/flask/policy/access_vectors |  2 ++
 5 files changed, 62 insertions(+), 1 deletion(-)

Comments

Wei Liu Aug. 24, 2017, 2:28 p.m. UTC | #1

On Wed, Aug 23, 2017 at 07:34:42PM +0200, Juergen Gross wrote:
> Add a sysctl hypercall to support setting parameters similar to
> command line parameters, but at runtime. The parameters to set are
> specified as a string, just like the boot parameters.
> 
> Cc: Daniel De Graaf <[e-mail]>
> Cc: Ian Jackson <[e-mail]>
> Cc: Wei Liu <[e-mail]>
> Cc: Andrew Cooper <[e-mail]>
> Cc: George Dunlap <[e-mail]>
> Cc: Jan Beulich <[e-mail]>
> Cc: Konrad Rzeszutek Wilk <[e-mail]>
> Cc: Stefano Stabellini <[e-mail]>
> Cc: Tim Deegan <[e-mail]>
> Signed-off-by: Juergen Gross <[e-mail]>
> Acked-by: Daniel De Graaf <[e-mail]>

Reviewed-by: Wei Liu <[e-mail]>

Patch

diff --git a/tools/flask/policy/modules/dom0.te b/tools/flask/policy/modules/dom0.te
index d0a4d91ac0..338caaf41e 100644
--- a/tools/flask/policy/modules/dom0.te
+++ b/tools/flask/policy/modules/dom0.te
@@ -16,7 +16,7 @@  allow dom0_t xen_t:xen {
 allow dom0_t xen_t:xen2 {
 	resource_op psr_cmt_op psr_cat_op pmu_ctrl get_symbol
 	get_cpu_levelling_caps get_cpu_featureset livepatch_op
-	gcov_op
+	gcov_op set_parameter
 };
 
 # Allow dom0 to use all XENVER_ subops that have checks.
diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
index ae58a0f650..a6882d1c9d 100644
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -467,6 +467,42 @@  long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
             copyback = 1;
         break;
 
+    case XEN_SYSCTL_set_parameter:
+    {
+#define XEN_SET_PARAMETER_MAX_SIZE 1023
+        char *params;
+
+        if ( op->u.set_parameter.pad[0] || op->u.set_parameter.pad[1] ||
+             op->u.set_parameter.pad[2] )
+        {
+            ret = -EINVAL;
+            break;
+        }
+        if ( op->u.set_parameter.size > XEN_SET_PARAMETER_MAX_SIZE )
+        {
+            ret = -E2BIG;
+            break;
+        }
+        params = xmalloc_bytes(op->u.set_parameter.size + 1);
+        if ( !params )
+        {
+            ret = -ENOMEM;
+            break;
+        }
+        if ( copy_from_guest(params, op->u.set_parameter.params,
+                             op->u.set_parameter.size) )
+            ret = -EFAULT;
+        else
+        {
+            params[op->u.set_parameter.size] = 0;
+            ret = runtime_parse(params);
+        }
+
+        xfree(params);
+
+        break;
+    }
+
     default:
         ret = arch_do_sysctl(op, u_sysctl);
         copyback = 0;
diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h
index 9e51af61e1..7830b987da 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -1096,6 +1096,24 @@  struct xen_sysctl_livepatch_op {
 typedef struct xen_sysctl_livepatch_op xen_sysctl_livepatch_op_t;
 DEFINE_XEN_GUEST_HANDLE(xen_sysctl_livepatch_op_t);
 
+/*
+ * XEN_SYSCTL_set_parameter
+ *
+ * Change hypervisor parameters at runtime.
+ * The input string is parsed similar to the boot parameters.
+ * Parameters are a single string terminated by a NUL byte of max. size
+ * characters. Multiple settings can be specified by separating them
+ * with blanks.
+ */
+
+struct xen_sysctl_set_parameter {
+    XEN_GUEST_HANDLE_64(char) params;       /* IN: pointer to parameters. */
+    uint16_t size;                          /* IN: size of parameters. */
+    uint16_t pad[3];                        /* IN: MUST be zero. */
+};
+typedef struct xen_sysctl_set_parameter xen_sysctl_set_parameter_t;
+DEFINE_XEN_GUEST_HANDLE(xen_sysctl_set_parameter_t);
+
 struct xen_sysctl {
     uint32_t cmd;
 #define XEN_SYSCTL_readconsole                    1
@@ -1124,6 +1142,7 @@  struct xen_sysctl {
 #define XEN_SYSCTL_get_cpu_levelling_caps        25
 #define XEN_SYSCTL_get_cpu_featureset            26
 #define XEN_SYSCTL_livepatch_op                  27
+#define XEN_SYSCTL_set_parameter                 28
     uint32_t interface_version; /* XEN_SYSCTL_INTERFACE_VERSION */
     union {
         struct xen_sysctl_readconsole       readconsole;
@@ -1152,6 +1171,7 @@  struct xen_sysctl {
         struct xen_sysctl_cpu_levelling_caps cpu_levelling_caps;
         struct xen_sysctl_cpu_featureset    cpu_featureset;
         struct xen_sysctl_livepatch_op      livepatch;
+        struct xen_sysctl_set_parameter     set_parameter;
         uint8_t                             pad[128];
     } u;
 };
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 276ca97608..4989335f4a 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -828,6 +828,9 @@  static int flask_sysctl(int cmd)
     case XEN_SYSCTL_gcov_op:
         return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2,
                                     XEN2__GCOV_OP, NULL);
+    case XEN_SYSCTL_set_parameter:
+        return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2,
+                                    XEN2__SET_PARAMETER, NULL);
 
     default:
         return avc_unknown_permission("sysctl", cmd);
diff --git a/xen/xsm/flask/policy/access_vectors b/xen/xsm/flask/policy/access_vectors
index f276f04e29..da9f3dfb2e 100644
--- a/xen/xsm/flask/policy/access_vectors
+++ b/xen/xsm/flask/policy/access_vectors
@@ -101,6 +101,8 @@  class xen2
     livepatch_op
 # XEN_SYSCTL_gcov_op
     gcov_op
+# XEN_SYSCTL_set_parameter
+    set_parameter
 }
 
 # Classes domain and domain2 consist of operations that a domain performs on