RFR: Out-of-bounds access in cpu_family_description()

[Jinke Fan]

Hi David,
	In VM_Version_Ext::cpu_family_description has out-of-bounds
access on AMD 17h (EPYC) processor.
	
const char* VM_Version_Ext::cpu_family_description(void) {

On AMD 17h (EPYC) processor extended_cpu_family() will return 23,
but array _family_id_amd only has 17 members.

   int cpu_family_id = extended_cpu_family();
   if (is_amd()) {
     return _family_id_amd[cpu_family_id];
   }
...
}

Result of testcase TestCPUInformation.java on AMD Zen:
----------System.out:(15/1615)----------
...
Family: 386 (0x17), Model: <unknown> (0x1), Stepping: 0x1
Ext. family: 0x8, Ext. model: 0x0, Type: 0x0, Signature: 0x00800f11
...
}

The “386” string is incorrectly and comes from Illegal access.

The patch is based on the original repository:
hg.openjdk.java.net/jdk/jdk

changeset:   54520:f48312257bc6
tag:         tip
user:        vromero
date:        Thu Apr 11 22:56:11 2019 -0400
summary:     8222151: refactoring: enhancements to 
java.lang.Class::methodToString and java.lang.Class::getTypeName

*Patch
The out of hg diff -g:
diff --git a/src/hotspot/cpu/x86/vm_version_ext_x86.cpp 
b/src/hotspot/cpu/x86/vm_version_ext_x86.cpp
--- a/src/hotspot/cpu/x86/vm_version_ext_x86.cpp
+++ b/src/hotspot/cpu/x86/vm_version_ext_x86.cpp
@@ -262,6 +262,52 @@
  int VM_Version_Ext::_no_of_cores = 0;
  int VM_Version_Ext::_no_of_packages = 0;

+const char* const VM_Version_Ext::_family_id_intel[] = {
+  "8086/8088",
+  "",
+  "286",
+  "386",
+  "486",
+  "Pentium",
+  "Pentium Pro",   //or Pentium-M/Woodcrest depeding on model
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "Pentium 4"
+};
+
+const char* const VM_Version_Ext::_family_id_amd[] = {
+  "",
+  "",
+  "",
+  "",
+  "5x86",
+  "K5/K6",
+  "Athlon/AthlonXP",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "Opteron/Athlon64",
+  "Opteron QC/Phenom",  // Barcelona et.al.
+  "",
+  "",
+  "",
+  "",
+  "",
+  "",
+  "Zen"
+};
+
  void VM_Version_Ext::initialize(void) {
    ResourceMark rm;

@@ -401,15 +447,19 @@
  }

  const char* VM_Version_Ext::cpu_family_description(void) {
-  int cpu_family_id = extended_cpu_family();
+  uint32_t cpu_family_id = extended_cpu_family();
    if (is_amd()) {
-    return _family_id_amd[cpu_family_id];
+    if (cpu_family_id < sizeof(_family_id_amd)/sizeof(_family_id_amd[0])) {
+      return _family_id_amd[cpu_family_id];
+    }
    }
    if (is_intel()) {
      if (cpu_family_id == CPU_FAMILY_PENTIUMPRO) {
        return cpu_model_description();
      }
-    return _family_id_intel[cpu_family_id];
+    if (cpu_family_id < 
sizeof(_family_id_intel)/sizeof(_family_id_intel[0])) {
+      return _family_id_intel[cpu_family_id];
+    }
    }
    if (is_hygon()) {
      return "Dhyana";
@@ -705,44 +755,6 @@
    return _max_qualified_cpu_frequency;
  }

-const char* const VM_Version_Ext::_family_id_intel[] = {
-  "8086/8088",
-  "",
-  "286",
-  "386",
-  "486",
-  "Pentium",
-  "Pentium Pro",   //or Pentium-M/Woodcrest depeding on model
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "Pentium 4"
-};
-
-const char* const VM_Version_Ext::_family_id_amd[] = {
-  "",
-  "",
-  "",
-  "",
-  "5x86",
-  "K5/K6",
-  "Athlon/AthlonXP",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "",
-  "Opteron/Athlon64",
-  "Opteron QC/Phenom"  // Barcelona et.al.
-};
  // Partially from Intel 64 and IA-32 Architecture Software Developer's 
Manual,
  // September 2013, Vol 3C Table 35-1
  const char* const VM_Version_Ext::_model_id_pentium_pro[] = {

*Test:
After patched,result of testcase TestCPUInformation.java on AMD Zen:
----------System.out:(15/1615)----------
Event: jdk.CPUInformation {
   ...
Family: Zen (0x17), Model: <unknown> (0x1), Stepping: 0x1
Ext. family: 0x8, Ext. model: 0x0, Type: 0x0, Signature: 0x00800f11
Features: ebx: 0x4f400800, ecx: 0x7ed8320b, edx: 0x178bfbff
   ...
}

Is there anything incorrectly?
Please let me know your comments.

Best Regards！
Fanjinke