cpumask <=> xenctl_cpumap: allocate CPU masks and byte maps dynamically

Generally there was a NR_CPUS-bits wide array in these functions and
another (through a cpumask_t) on their callers' stacks, which may get
a little large for big NR_CPUS. As the functions can fail anyway, do
the allocation in there.

For the x86/MCA case this require a little code restructuring: By using
different CPU mask accessors it was possible to avoid allocating a mask
in the broadcast case. Also, this was the only user that failed to
check the return value of the conversion function (which could have led
to undefined behvior).

Also constify the input parameters of the two functions.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/xen/common/trace.c b/xen/common/trace.c
index 2253e3114a..746bf4b750 100644
--- a/xen/common/trace.c
+++ b/xen/common/trace.c
@@ -378,7 +378,16 @@ int tb_control(xen_sysctl_tbuf_op_t *tbc)
         tbc->size = t_info_pages * PAGE_SIZE;
         break;
     case XEN_SYSCTL_TBUFOP_set_cpu_mask:
-        rc = xenctl_cpumap_to_cpumask(&tb_cpu_mask, &tbc->cpu_mask);
+    {
+        cpumask_var_t mask;
+
+        rc = xenctl_cpumap_to_cpumask(&mask, &tbc->cpu_mask);
+        if ( !rc )
+        {
+            cpumask_copy(&tb_cpu_mask, mask);
+            free_cpumask_var(mask);
+        }
+    }
         break;
     case XEN_SYSCTL_TBUFOP_set_evt_mask:
         tb_event_mask = tbc->evt_mask;