Re: [Xen-devel] [PATCH v2 48/52] xen: add hypercall for setting parameters at runtime

[Jan Beulich]

>>> On 15.08.17 at 17:57,  wrote:
> On 15/08/17 17:39, Jan Beulich wrote:
> On 14.08.17 at 09:08,  wrote:
>>> +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. 
>>> */
>> 
>> You could even allow querying the size by passing in a null handle
>> and returning the value in the size field.
> 
> Would this help in any way?

Since the caller won't want to dimension the buffer dynamically,
perhaps not much. The only use I could see would be to give a
better error message for too long strings than the one resulting
from strerror(). I.e. ...

> Maybe just returning E2BIG would be enough?

... maybe yes.

Jan


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH v2 48/52] xen: add hypercall for setting parameters at runtime

[Juergen Gross]

On 15/08/17 17:39, Jan Beulich wrote:
 On 14.08.17 at 09:08,  wrote:
>> --- 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
> 
> Does this really need to be in the public interface, i.e. isn't this limit
> an implementation detail?

Hmm, yes.

> 
>> +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. 
>> */
> 
> You could even allow querying the size by passing in a null handle
> and returning the value in the size field.

Would this help in any way?

Maybe just returning E2BIG would be enough?

> 
>> +uint16_t pad[3];/* IN: MUST be zero. */
> 
> But you don't check the field is zero afaics.

Right, I should do this.


Juergen

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH v2 48/52] xen: add hypercall for setting parameters at runtime

[Jan Beulich]

>>> On 14.08.17 at 09:08,  wrote:
> --- 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

Does this really need to be in the public interface, i.e. isn't this limit
an implementation detail?

> +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. */

You could even allow querying the size by passing in a null handle
and returning the value in the size field.

> +uint16_t pad[3];/* IN: MUST be zero. */

But you don't check the field is zero afaics.

Jan


___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

Re: [Xen-devel] [PATCH v2 48/52] xen: add hypercall for setting parameters at runtime

[Daniel De Graaf]

On 08/14/2017 03:08 AM, 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.


Acked-by: Daniel De Graaf 

___
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel

[Xen-devel] [PATCH v2 48/52] xen: add hypercall for setting parameters at runtime

[Juergen Gross]

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 
Cc: Ian Jackson 
Cc: Wei Liu 
Cc: Andrew Cooper 
Cc: George Dunlap 
Cc: Jan Beulich 
Cc: Konrad Rzeszutek Wilk 
Cc: Stefano Stabellini 
Cc: Tim Deegan 
Signed-off-by: Juergen Gross 
---
V2:
- corrected XSM test (Daniel De Graaf)
---
 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_readconsole1
@@ -1124,6 +1141,7 @@ struct xen_sysctl {
 #define XEN_SYSCTL_get_cpu_levelling_caps25
 #define XEN_SYSCTL_get_cpu_featureset26
 #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_featuresetcpu_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..c9c275bf3b 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -825,6 +825,9 @@ 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