Set max cpuid input value to highest emulated value

cpuid(0) and cpuid(0x80000000) should return the highest emulated value instead of the CPU's actual value. This prevents some existing code to try higher leaves. Signed-off-by: Thomas Tendyck <[email protected]>
samuel-lee-msft · Nov 10, 2021 · f16b7c3 · f16b7c3
1 parent dee3c1c
commit f16b7c3
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Showing 3 changed files with 19 additions and 2 deletions.
diff --git a/enclave/core/sgx/cpuid.c b/enclave/core/sgx/cpuid.c
@@ -36,6 +36,12 @@ oe_result_t oe_initialize_cpuid(void)
     if (!(_cpuid_table[1][OE_CPUID_RCX] & OE_CPUID_AESNI_FEATURE))
         oe_abort();
 
+    // set max input value for basic and extended
+    _cpuid_table[oe_get_emulated_cpuid_leaf_index(0)][OE_CPUID_RAX] =
+        OE_CPUID_MAX_BASIC;
+    _cpuid_table[oe_get_emulated_cpuid_leaf_index(0x80000000)][OE_CPUID_RAX] =
+        OE_CPUID_MAX_EXTENDED;
+
     result = OE_OK;
 
 done:

diff --git a/include/openenclave/internal/cpuid.h b/include/openenclave/internal/cpuid.h
@@ -9,6 +9,8 @@
 
 #define OE_CPUID_OPCODE 0xA20F
 #define OE_CPUID_LEAF_COUNT 6 /* 0,1,4,7,0x80000000,0x80000001 */
+#define OE_CPUID_MAX_BASIC 7
+#define OE_CPUID_MAX_EXTENDED 0x80000001
 
 #define OE_CPUID_RAX 0
 #define OE_CPUID_RBX 1

diff --git a/tests/VectorException/host/host.c b/tests/VectorException/host/host.c
@@ -121,9 +121,13 @@ void test_sigill_handling(
 
         for (uint32_t j = 0; j < OE_CPUID_REG_COUNT; j++)
         {
-            if (i == 1 && j == 1)
+            if (leaf == 0 && j == OE_CPUID_RAX)
+            {
+                // The enclave sets this to the highest emulated leaf.
+                OE_TEST(OE_CPUID_MAX_BASIC == cpuid_table[i][j]);
+            }
+            else if (leaf == 1 && j == OE_CPUID_RBX)
             {
-                // Leaf 1. EBX register.
                 // The highest 8 bits indicates the current executing processor
                 // id.
                 // There is no guarantee that the value is the same across
@@ -135,6 +139,11 @@ void test_sigill_handling(
                     (cpuid_info[j] & 0x00FFFFFF) ==
                     (cpuid_table[i][j] & 0x00FFFFFF));
             }
+            else if (leaf == 0x80000000 && j == OE_CPUID_RAX)
+            {
+                // The enclave sets this to the highest emulated leaf.
+                OE_TEST(OE_CPUID_MAX_EXTENDED == cpuid_table[i][j]);
+            }
             else
             {
                 OE_TEST(cpuid_info[j] == cpuid_table[i][j]);