[PATCH v5 2/4] xen/console: introduce console input permission

[dmkhn@xxxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx>

Add new flag to domain structure for marking permission to intercept
the physical console input by the domain.

Update console input switch logic accordingly.

No functional change intended.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
Changes since v4:
- kept input_allowed as a separate flag
- updated logic for input_allowed in vpl011
- fixup for console_switch_input()
---
 xen/arch/arm/vpl011.c      |  1 +
 xen/arch/x86/pv/shim.c     |  2 ++
 xen/common/domain.c        |  2 ++
 xen/drivers/char/console.c | 18 +++++++++++++++++-
 xen/include/xen/sched.h    |  8 +++++++-
 5 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c
index 66047bf33c..480fc664fc 100644
--- a/xen/arch/arm/vpl011.c
+++ b/xen/arch/arm/vpl011.c
@@ -713,6 +713,7 @@ int domain_vpl011_init(struct domain *d, struct 
vpl011_init_info *info)
     }
     else
     {
+        d->console.input_allowed = true;
         vpl011->backend_in_domain = false;
 
         vpl011->backend.xen = xzalloc(struct vpl011_xen_backend);
diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index c506cc0bec..bc2a7dd5fa 100644
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -238,6 +238,8 @@ void __init pv_shim_setup_dom(struct domain *d, 
l4_pgentry_t *l4start,
      * guest from depleting the shim memory pool.
      */
     d->max_pages = domain_tot_pages(d);
+
+    d->console.input_allowed = true;
 }
 
 static void write_start_info(struct domain *d)
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 129b4fcb37..d75ece1b61 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -835,6 +835,8 @@ struct domain *domain_create(domid_t domid,
         flags |= CDF_hardware;
         if ( old_hwdom )
             old_hwdom->cdf &= ~CDF_hardware;
+
+        d->console.input_allowed = true;
     }
 
     /* Holding CDF_* internal flags. */
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 30701ae0b0..9a9836ba91 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -512,9 +512,21 @@ static unsigned int __read_mostly console_rx = 0;
 
 struct domain *console_get_domain(void)
 {
+    struct domain *d;
+
     if ( console_rx == 0 )
             return NULL;
-    return rcu_lock_domain_by_id(console_rx - 1);
+
+    d = rcu_lock_domain_by_id(console_rx - 1);
+    if ( !d )
+        return NULL;
+
+    if ( d->console.input_allowed )
+        return d;
+
+    rcu_unlock_domain(d);
+
+    return NULL;
 }
 
 void console_put_domain(struct domain *d)
@@ -551,6 +563,10 @@ static void console_switch_input(void)
         if ( d )
         {
             rcu_unlock_domain(d);
+
+            if ( !d->console.input_allowed )
+                continue;
+
             console_rx = next_rx;
             printk("*** Serial input to DOM%u", domid);
             break;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 559d201e0c..e91c99a8f3 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -512,7 +512,7 @@ struct domain
     bool             auto_node_affinity;
     /* Is this guest fully privileged (aka dom0)? */
     bool             is_privileged;
-    /* Can this guest access the Xen console? */
+    /* XSM: permission to use HYPERCALL_console_io hypercall */
     bool             is_console;
     /* Is this guest being debugged by dom0? */
     bool             debugger_attached;
@@ -651,6 +651,12 @@ struct domain
     unsigned int num_llc_colors;
     const unsigned int *llc_colors;
 #endif
+
+    /* Console settings. */
+    struct {
+        /* Permission to take ownership of the physical console input. */
+        bool input_allowed;
+    } console;
 } __aligned(PAGE_SIZE);
 
 static inline struct page_list_head *page_to_list(
-- 
2.34.1