From f16b7c3695ff8a1dbda18c2401212f9da845a240 Mon Sep 17 00:00:00 2001
From: Thomas Tendyck <tt@edgeless.systems>
Date: Wed, 10 Nov 2021 13:51:56 +0100
Subject: [PATCH] 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 <tt@edgeless.systems>
---
 enclave/core/sgx/cpuid.c             |  6 ++++++
 include/openenclave/internal/cpuid.h |  2 ++
 tests/VectorException/host/host.c    | 13 +++++++++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/enclave/core/sgx/cpuid.c b/enclave/core/sgx/cpuid.c
index 1e99252e5f..558f9b9d87 100644
--- 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
index 496671cd15..66e7b48927 100644
--- 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
index 6952e5f957..26427c9a52 100644
--- 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]);