[PATCH v2 09/13] libx86: Introduce a helper to deserialise cpuid_policy objects

[Andrew Cooper <andrew.cooper3@citrix.com>]

As with the serialise side, Xen's copy_from_guest API is used, with a
compatibility wrapper for the userspace build.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Sergey Dyasli <sergey.dyasli@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>

v2:
 * Rewrite copy_from_buffer_offset() to avoid multiple evaluation of its
   arguments.
 * Expand boundary justifications.
---
 xen/common/libx86/cpuid.c      | 94 ++++++++++++++++++++++++++++++++++++++++++
 xen/common/libx86/private.h    | 14 +++++++
 xen/include/xen/libx86/cpuid.h | 11 +++++
 3 files changed, 119 insertions(+)

diff --git a/xen/common/libx86/cpuid.c b/xen/common/libx86/cpuid.c
index cf7dbd3..73cd574 100644
--- a/xen/common/libx86/cpuid.c
+++ b/xen/common/libx86/cpuid.c
@@ -123,6 +123,100 @@ int x86_cpuid_copy_to_buffer(const struct cpuid_policy *p,
     return 0;
 }
 
+int x86_cpuid_copy_from_buffer(struct cpuid_policy *p,
+                               const cpuid_leaf_buffer_t leaves,
+                               uint32_t nr_leaves, uint32_t *err_leaf,
+                               uint32_t *err_subleaf)
+{
+    unsigned int i;
+    xen_cpuid_leaf_t data;
+    struct cpuid_leaf *l = (void *)&data.a;
+
+    /*
+     * A well formed caller is expected pass an array with leaves in order,
+     * and without any repetitions.  However, due to per-vendor differences,
+     * and in the case of upgrade or levelled scenarios, we typically expect
+     * fewer than MAX leaves to be passed.
+     *
+     * Detecting repeated entries is prohibitively complicated, so we don't
+     * bother.  That said, one way or another if more than MAX leaves are
+     * passed, something is wrong.
+     */
+    if ( nr_leaves > CPUID_MAX_SERIALISED_LEAVES )
+        return -E2BIG;
+
+    for ( i = 0; i < nr_leaves; ++i )
+    {
+        if ( copy_from_buffer_offset(&data, leaves, i, 1) )
+            return -EFAULT;
+
+        switch ( data.leaf )
+        {
+        case 0 ... ARRAY_SIZE(p->basic.raw) - 1:
+            switch ( data.leaf )
+            {
+            case 0x4:
+                if ( data.subleaf >= ARRAY_SIZE(p->cache.raw) )
+                    goto out_of_range;
+
+                p->cache.raw[data.subleaf] = *l;
+                break;
+
+            case 0x7:
+                if ( data.subleaf >= ARRAY_SIZE(p->feat.raw) )
+                    goto out_of_range;
+
+                p->feat.raw[data.subleaf] = *l;
+                break;
+
+            case 0xb:
+                if ( data.subleaf >= ARRAY_SIZE(p->topo.raw) )
+                    goto out_of_range;
+
+                p->topo.raw[data.subleaf] = *l;
+                break;
+
+            case 0xd:
+                if ( data.subleaf >= ARRAY_SIZE(p->xstate.raw) )
+                    goto out_of_range;
+
+                p->xstate.raw[data.leaf] = *l;
+                break;
+
+            default:
+                p->basic.raw[data.leaf] = *l;
+                break;
+            }
+            break;
+
+        case 0x40000000:
+            p->hv_limit = l->a;
+            break;
+
+        case 0x40000100:
+            p->hv2_limit = l->a;
+            break;
+
+        case 0x80000000 ... 0x80000000 + ARRAY_SIZE(p->extd.raw) - 1:
+            p->extd.raw[data.leaf & 0xffff] = *l;
+            break;
+
+        default:
+            goto out_of_range;
+        }
+    }
+
+    return 0;
+
+ out_of_range:
+    if ( err_leaf )
+        *err_leaf = data.leaf;
+    if ( err_subleaf )
+        *err_subleaf = data.subleaf;
+
+    return -ERANGE;
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/common/libx86/private.h b/xen/common/libx86/private.h
index e874fb6..dc451d0 100644
--- a/xen/common/libx86/private.h
+++ b/xen/common/libx86/private.h
@@ -12,6 +12,7 @@
 #include <asm/msr-index.h>
 
 #define copy_to_buffer_offset copy_to_guest_offset
+#define copy_from_buffer_offset copy_from_guest_offset
 
 #else
 
@@ -44,6 +45,19 @@ static inline bool test_bit(unsigned int bit, const void *vaddr)
     0;                                                  \
 })
 
+/* memcpy(), but with copy_from_guest_offset()'s API. */
+#define copy_from_buffer_offset(dst, src, index, nr)    \
+({                                                      \
+    const typeof(*(dst)) *src_ = (src);                 \
+    typeof(*(dst)) *dst_ = (dst);                       \
+    typeof(index) index_ = (index);                     \
+    typeof(nr) nr_ = (nr), i_;                          \
+                                                        \
+    for ( i_ = 0; i_ < nr_; i_++ )                      \
+        dst_[i_] = src_[index_ + i_];                   \
+    0;                                                  \
+})
+
 #endif /* __XEN__ */
 
 #endif /* XEN_LIBX86_PRIVATE_H */
diff --git a/xen/include/xen/libx86/cpuid.h b/xen/include/xen/libx86/cpuid.h
index 460b102..c4c4bd4 100644
--- a/xen/include/xen/libx86/cpuid.h
+++ b/xen/include/xen/libx86/cpuid.h
@@ -260,6 +260,17 @@ int x86_cpuid_copy_to_buffer(const struct cpuid_policy *p,
                              cpuid_leaf_buffer_t leaves,
                              uint32_t *nr_entries_p);
 
+/*
+ * Copy CPUID data from a buffer, filling in a cpuid_policy object.  Performs
+ * boudary checking of the incomming leaves before filling the appropriate
+ * policy unions, but no content validation is performed.  On an error, the
+ * optional err_* pointers may help identify where the issue lies.
+ */
+int x86_cpuid_copy_from_buffer(struct cpuid_policy *p,
+                               const cpuid_leaf_buffer_t leaves,
+                               uint32_t nr_leaves, uint32_t *err_leaf,
+                               uint32_t *err_subleaf);
+
 #endif /* !XEN_LIBX86_CPUID_H */
 
 /*
-- 
2.1.4


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