[Xen-devel] [PATCH 48/52] xen: add hypercall for setting parameters at runtime

[Juergen Gross <jgross@xxxxxxxx>]

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 <dgdegra@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Tim Deegan <tim@xxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 tools/flask/policy/modules/dom0.te  |  2 +-
 xen/common/sysctl.c                 | 29 +++++++++++++++++++++++++++++
 xen/include/public/sysctl.h         | 19 +++++++++++++++++++
 xen/xsm/flask/hooks.c               |  3 +++
 xen/xsm/flask/policy/access_vectors |  2 ++
 5 files changed, 54 insertions(+), 1 deletion(-)

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..a3237fe9be 100644
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -467,6 +467,35 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) 
u_sysctl)
             copyback = 1;
         break;
 
+    case XEN_SYSCTL_set_parameter:
+    {
+        char *params;
+
+        if ( op->u.set_parameter.size > XEN_SET_PARAMETER_MAX_SIZE )
+        {
+            ret = -EINVAL;
+            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..43b18bdb9b 100644
--- a/xen/include/public/sysctl.h
+++ b/xen/include/public/sysctl.h
@@ -1096,6 +1096,23 @@ 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.
+ */
+
+#define XEN_SET_PARAMETER_MAX_SIZE 1023
+struct xen_sysctl_set_parameter {
+    XEN_GUEST_HANDLE_64(char) params;       /* IN: pointer to parameters. */
+    uint16_t size;                          /* IN: size of parameters. Max.
+                                               XEN_SET_PARAMETER_MAX_SIZE. */
+    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 +1141,7 @@ 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 +1170,7 @@ 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 fd84ac0f09..af709736ac 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -826,6 +826,9 @@ static int flask_sysctl(int cmd)
         return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2,
                                     XEN2__GCOV_OP, NULL);
 
+    case XEN_SYSCTL_set_parameter:
+        return domain_has_xen(current->domain, XEN2__SET_PARAMETER);
+
     default:
         return avc_unknown_permission("sysctl", cmd);
     }
diff --git a/xen/xsm/flask/policy/access_vectors 
b/xen/xsm/flask/policy/access_vectors
index 1f7eb35fc8..b80fca1ec0 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
-- 
2.12.3


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