x86: Implement SMEP and SMAP

This patch implements Supervisor Mode Execution Prevention (SMEP) and
Supervisor Mode Access Prevention (SMAP) for x86.  The purpose of the
patch, obviously, is to help kernel developers debug the support for
those features.

A fair bit of the code relates to the handling of CPUID features.  The
CPUID code probably would get greatly simplified if all the feature
bit words were unified into a single vector object, but in the
interest of producing a minimal patch for SMEP/SMAP, and because I had
very limited time for this project, I followed the existing style.

[ v2: don't change the definition of the qemu64 CPU shorthand, since
  that breaks loading old snapshots.  Per Anthony Liguori this can be
  fixed once the CPU feature set is snapshot.

  Change the coding style slightly to conform to checkpatch.pl. ]

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 26 insertions, 8 deletions

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index c4e6163c9a..bb1e44eb01 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -104,6 +104,13 @@ static const char *svm_feature_name[] = {
     NULL, NULL, NULL, NULL,
 };
 
+static const char *cpuid_7_0_ebx_feature_name[] = {
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, "smep",
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL, "smap", NULL, NULL, NULL,
+    NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+};
+
 /* collects per-function cpuid data
  */
 typedef struct model_features_t {
@@ -219,14 +226,17 @@ static void add_flagname_to_bitmaps(const char *flagname, uint32_t *features,
                                     uint32_t *ext2_features,
                                     uint32_t *ext3_features,
                                     uint32_t *kvm_features,
-                                    uint32_t *svm_features)
+                                    uint32_t *svm_features,
+                                    uint32_t *cpuid_7_0_ebx_features)
 {
     if (!lookup_feature(features, flagname, NULL, feature_name) &&
         !lookup_feature(ext_features, flagname, NULL, ext_feature_name) &&
         !lookup_feature(ext2_features, flagname, NULL, ext2_feature_name) &&
         !lookup_feature(ext3_features, flagname, NULL, ext3_feature_name) &&
         !lookup_feature(kvm_features, flagname, NULL, kvm_feature_name) &&
-        !lookup_feature(svm_features, flagname, NULL, svm_feature_name))
+        !lookup_feature(svm_features, flagname, NULL, svm_feature_name) &&
+        !lookup_feature(cpuid_7_0_ebx_features, flagname, NULL,
+                        cpuid_7_0_ebx_feature_name))
             fprintf(stderr, "CPU feature %s not found\n", flagname);
 }
 
@@ -287,6 +297,7 @@ typedef struct x86_def_t {
 #define TCG_EXT3_FEATURES (CPUID_EXT3_LAHF_LM | CPUID_EXT3_SVM | \
           CPUID_EXT3_CR8LEG | CPUID_EXT3_ABM | CPUID_EXT3_SSE4A)
 #define TCG_SVM_FEATURES 0
+#define TCG_7_0_EBX_FEATURES (CPUID_7_0_EBX_SMEP | CPUID_7_0_EBX_SMAP)
 
 /* maintains list of cpu model definitions
  */
@@ -1097,10 +1108,12 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
     uint32_t plus_features = 0, plus_ext_features = 0;
     uint32_t plus_ext2_features = 0, plus_ext3_features = 0;
     uint32_t plus_kvm_features = 0, plus_svm_features = 0;
+    uint32_t plus_7_0_ebx_features = 0;
     /* Features to be removed */
     uint32_t minus_features = 0, minus_ext_features = 0;
     uint32_t minus_ext2_features = 0, minus_ext3_features = 0;
     uint32_t minus_kvm_features = 0, minus_svm_features = 0;
+    uint32_t minus_7_0_ebx_features = 0;
     uint32_t numvalue;
 
     for (def = x86_defs; def; def = def->next)
@@ -1127,8 +1140,8 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
 #endif
 
     add_flagname_to_bitmaps("hypervisor", &plus_features,
-        &plus_ext_features, &plus_ext2_features, &plus_ext3_features,
-        &plus_kvm_features, &plus_svm_features);
+            &plus_ext_features, &plus_ext2_features, &plus_ext3_features,
+            &plus_kvm_features, &plus_svm_features,  &plus_7_0_ebx_features);
 
     featurestr = strtok(NULL, ",");
 
@@ -1138,12 +1151,12 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
             add_flagname_to_bitmaps(featurestr + 1, &plus_features,
                             &plus_ext_features, &plus_ext2_features,
                             &plus_ext3_features, &plus_kvm_features,
-                            &plus_svm_features);
+                            &plus_svm_features, &plus_7_0_ebx_features);
         } else if (featurestr[0] == '-') {
             add_flagname_to_bitmaps(featurestr + 1, &minus_features,
                             &minus_ext_features, &minus_ext2_features,
                             &minus_ext3_features, &minus_kvm_features,
-                            &minus_svm_features);
+                            &minus_svm_features, &minus_7_0_ebx_features);
         } else if ((val = strchr(featurestr, '='))) {
             *val = 0; val++;
             if (!strcmp(featurestr, "family")) {
@@ -1249,16 +1262,21 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
     x86_cpu_def->ext3_features |= plus_ext3_features;
     x86_cpu_def->kvm_features |= plus_kvm_features;
     x86_cpu_def->svm_features |= plus_svm_features;
+    x86_cpu_def->cpuid_7_0_ebx_features |= plus_7_0_ebx_features;
     x86_cpu_def->features &= ~minus_features;
     x86_cpu_def->ext_features &= ~minus_ext_features;
     x86_cpu_def->ext2_features &= ~minus_ext2_features;
     x86_cpu_def->ext3_features &= ~minus_ext3_features;
     x86_cpu_def->kvm_features &= ~minus_kvm_features;
     x86_cpu_def->svm_features &= ~minus_svm_features;
+    x86_cpu_def->cpuid_7_0_ebx_features &= ~minus_7_0_ebx_features;
     if (check_cpuid) {
         if (check_features_against_host(x86_cpu_def) && enforce_cpuid)
             goto error;
     }
+    if (x86_cpu_def->cpuid_7_0_ebx_features && x86_cpu_def->level < 7) {
+        x86_cpu_def->level = 7;
+    }
     g_free(s);
     return 0;
 
@@ -1374,7 +1392,7 @@ int cpu_x86_register(X86CPU *cpu, const char *cpu_model)
     env->cpuid_kvm_features = def->kvm_features;
     env->cpuid_svm_features = def->svm_features;
     env->cpuid_ext4_features = def->ext4_features;
-    env->cpuid_7_0_ebx = def->cpuid_7_0_ebx_features;
+    env->cpuid_7_0_ebx_features = def->cpuid_7_0_ebx_features;
     env->cpuid_xlevel2 = def->xlevel2;
     object_property_set_int(OBJECT(cpu), (int64_t)def->tsc_khz * 1000,
                             "tsc-frequency", &error);
@@ -1562,7 +1580,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
         /* Structured Extended Feature Flags Enumeration Leaf */
         if (count == 0) {
             *eax = 0; /* Maximum ECX value for sub-leaves */
-            *ebx = env->cpuid_7_0_ebx; /* Feature flags */
+            *ebx = env->cpuid_7_0_ebx_features; /* Feature flags */
             *ecx = 0; /* Reserved */
             *edx = 0; /* Reserved */
         } else {