X-Git-Url: http://git.annexia.org/?a=blobdiff_plain;f=virt-what-cpuid-helper.c;h=0cd4a6f2b168dcdb6d3025828a8d98170f5b68d8;hb=01ea13d9813df93e294b0d9776d4cefd54b1609b;hp=3024c375cb7b71142ded2a6a5836574d5b21f2f5;hpb=fcc68d36da2f3f27beddcc70c99c7a485b08afb4;p=virt-what.git

diff --git a/virt-what-cpuid-helper.c b/virt-what-cpuid-helper.c
index 3024c37..0cd4a6f 100644
--- a/virt-what-cpuid-helper.c
+++ b/virt-what-cpuid-helper.c
@@ -1,5 +1,5 @@
 /* virt-what-cpuid-helper: Are we running inside KVM or Xen HVM?
- * Copyright (C) 2008 Red Hat Inc.
+ * Copyright (C) 2008-2019 Red Hat Inc.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -21,43 +21,92 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
 #include <string.h>
 
 #if defined(__i386__) || defined(__x86_64__)
-void
-cpu_sig (char *sig)
+
+/* Known x86 hypervisor signatures.  Note that if you add a new test
+ * to virt-what.in you may need to update this list.  The signature is
+ * always 12 bytes except in the case of KVM.
+ */
+static int
+known_signature (char *sig)
+{
+  return
+    strcmp (sig, "bhyve bhyve ") == 0 ||
+    strcmp (sig, "KVMKVMKVM") == 0 ||
+    strcmp (sig, "LKVMLKVMLKVM") == 0 ||
+    strcmp (sig, "Microsoft Hv") == 0 ||
+    strcmp (sig, "OpenBSDVMM58") == 0 ||
+    strcmp (sig, "TCGTCGTCGTCG") == 0 ||
+    strcmp (sig, "VMwareVMware") == 0 ||
+    strcmp (sig, "XenVMMXenVMM") == 0 ||
+    0;
+}
+
+static uint32_t
+cpuid (uint32_t eax, char *sig)
 {
-  unsigned int eax = 0x40000000;
-  unsigned int *sig32 = (unsigned int *)sig;
+  uint32_t *sig32 = (uint32_t *) sig;
+
   asm volatile (
-        "xor %%ebx, %%ebx; cpuid"
-        : "=a" (eax), "=b" (sig32[0]), "=c" (sig32[1]), "=d" (sig32[2])
+        "xchgl %%ebx,%1; xor %%ebx,%%ebx; cpuid; xchgl %%ebx,%1"
+        : "=a" (eax), "+r" (sig32[0]), "=c" (sig32[1]), "=d" (sig32[2])
         : "0" (eax));
   sig[12] = 0;
+
+  return eax;
+}
+
+static void
+cpu_sig (void)
+{
+  char sig[13];
+  const uint32_t base = 0x40000000;
+  uint32_t leaf;
+
+  /* Most hypervisors only have information in leaf 0x40000000.
+   *
+   * Some hypervisors have "Viridian [HyperV] extensions", and those
+   * must appear in slot 0x40000000, but they will also have the true
+   * hypervisor in a higher slot.
+   *
+   * CPUID is supposed to return the maximum leaf offset in %eax, but
+   * this is not reliable.  Instead we check the returned signatures
+   * against a known list (the others will be empty or garbage) and
+   * only print the ones we know about.  This is OK because if we add
+   * a new test in virt-what we can update the list.
+   *
+   * By searching backwards we only print the highest entry, thus
+   * ignoring Viridian for Xen (and Nutanix).  If we ever encounter a
+   * hypervisor that has more than 2 entries we may need to revisit
+   * this.
+   */
+  for (leaf = base + 0xff00; leaf >= base; leaf -= 0x100) {
+    memset (sig, 0, sizeof sig);
+    cpuid (leaf, sig);
+    if (known_signature (sig)) {
+      puts (sig);
+      break;
+    }
+  }
 }
-#else
-void
-cpu_sig (char *sig)
+
+#else /* !i386, !x86_64 */
+
+static void
+cpu_sig (void)
 {
   /* nothing for other architectures */
 }
+
 #endif
 
 int
 main()
 {
-  char sig[13];
-
-  memset (sig, 0, sizeof sig);
-
-  cpu_sig (sig);
-
-  puts (sig);
-  /* Possible values:
-   * KVMKVMKVM     KVM guest
-   * XenVMMXenVMM  Xen HVM guest
-   * VMwareVMware  VMware guest
-   */
-
+  cpu_sig ();
   return 0;
 }