target/i386: Implement CPUID_EXT_RDRAND

We now have an interface for guest visible random numbers.

Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

target/i386/cpu.c

@@ -730,13 +730,14 @@ static void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
           CPUID_EXT_MONITOR | CPUID_EXT_SSSE3 | CPUID_EXT_CX16 | \
           CPUID_EXT_SSE41 | CPUID_EXT_SSE42 | CPUID_EXT_POPCNT | \
           CPUID_EXT_XSAVE | /* CPUID_EXT_OSXSAVE is dynamic */   \
-          CPUID_EXT_MOVBE | CPUID_EXT_AES | CPUID_EXT_HYPERVISOR)
+          CPUID_EXT_MOVBE | CPUID_EXT_AES | CPUID_EXT_HYPERVISOR | \
+          CPUID_EXT_RDRAND)
           /* missing:
           CPUID_EXT_DTES64, CPUID_EXT_DSCPL, CPUID_EXT_VMX, CPUID_EXT_SMX,
           CPUID_EXT_EST, CPUID_EXT_TM2, CPUID_EXT_CID, CPUID_EXT_FMA,
           CPUID_EXT_XTPR, CPUID_EXT_PDCM, CPUID_EXT_PCID, CPUID_EXT_DCA,
           CPUID_EXT_X2APIC, CPUID_EXT_TSC_DEADLINE_TIMER, CPUID_EXT_AVX,
-          CPUID_EXT_F16C, CPUID_EXT_RDRAND */
+          CPUID_EXT_F16C */
 
 #ifdef TARGET_X86_64
 #define TCG_EXT2_X86_64_FEATURES (CPUID_EXT2_SYSCALL | CPUID_EXT2_LM)

target/i386/helper.h

@@ -226,3 +226,5 @@ DEF_HELPER_3(rcrl, tl, env, tl, tl)
 DEF_HELPER_3(rclq, tl, env, tl, tl)
 DEF_HELPER_3(rcrq, tl, env, tl, tl)
 #endif
+
+DEF_HELPER_1(rdrand, tl, env)

target/i386/int_helper.c

@@ -22,6 +22,8 @@
 #include "exec/exec-all.h"
 #include "qemu/host-utils.h"
 #include "exec/helper-proto.h"
+#include "qapi/error.h"
+#include "qemu/guest-random.h"
 
 //#define DEBUG_MULDIV
 
@@ -470,3 +472,22 @@ void helper_cr4_testbit(CPUX86State *env, uint32_t bit)
         raise_exception_ra(env, EXCP06_ILLOP, GETPC());
     }
 }
+
+target_ulong HELPER(rdrand)(CPUX86State *env)
+{
+    Error *err = NULL;
+    target_ulong ret;
+
+    if (qemu_guest_getrandom(&ret, sizeof(ret), &err) < 0) {
+        qemu_log_mask(LOG_UNIMP, "rdrand: Crypto failure: %s",
+                      error_get_pretty(err));
+        error_free(err);
+        /* Failure clears CF and all other flags, and returns 0.  */
+        env->cc_src = 0;
+        return 0;
+    }
+
+    /* Success sets CF and clears all others.  */
+    env->cc_src = CC_C;
+    return ret;
+}

target/i386/translate.c

@@ -5332,31 +5332,63 @@ static target_ulong disas_insn(DisasContext *s, CPUState *cpu)
     case 0x1c7: /* cmpxchg8b */
         modrm = x86_ldub_code(env, s);
         mod = (modrm >> 6) & 3;
-        if ((mod == 3) || ((modrm & 0x38) != 0x8))
+        switch ((modrm >> 3) & 7) {
-            goto illegal_op;
+        case 1: /* CMPXCHG8, CMPXCHG16 */
-#ifdef TARGET_X86_64
+            if (mod == 3) {
-        if (dflag == MO_64) {
-            if (!(s->cpuid_ext_features & CPUID_EXT_CX16))
                 goto illegal_op;
-            gen_lea_modrm(env, s, modrm);
-            if ((s->prefix & PREFIX_LOCK) && (tb_cflags(s->base.tb) & CF_PARALLEL)) {
-                gen_helper_cmpxchg16b(cpu_env, s->A0);
-            } else {
-                gen_helper_cmpxchg16b_unlocked(cpu_env, s->A0);
             }
-        } else
+#ifdef TARGET_X86_64
+            if (dflag == MO_64) {
+                if (!(s->cpuid_ext_features & CPUID_EXT_CX16)) {
+                    goto illegal_op;
+                }
+                gen_lea_modrm(env, s, modrm);
+                if ((s->prefix & PREFIX_LOCK) &&
+                    (tb_cflags(s->base.tb) & CF_PARALLEL)) {
+                    gen_helper_cmpxchg16b(cpu_env, s->A0);
+                } else {
+                    gen_helper_cmpxchg16b_unlocked(cpu_env, s->A0);
+                }
+                set_cc_op(s, CC_OP_EFLAGS);
+                break;
+            }
 #endif        
-        {
+            if (!(s->cpuid_features & CPUID_CX8)) {
-            if (!(s->cpuid_features & CPUID_CX8))
                 goto illegal_op;
+            }
             gen_lea_modrm(env, s, modrm);
-            if ((s->prefix & PREFIX_LOCK) && (tb_cflags(s->base.tb) & CF_PARALLEL)) {
+            if ((s->prefix & PREFIX_LOCK) &&
+                (tb_cflags(s->base.tb) & CF_PARALLEL)) {
                 gen_helper_cmpxchg8b(cpu_env, s->A0);
             } else {
                 gen_helper_cmpxchg8b_unlocked(cpu_env, s->A0);
             }
+            set_cc_op(s, CC_OP_EFLAGS);
+            break;
+
+        case 7: /* RDSEED */
+        case 6: /* RDRAND */
+            if (mod != 3 ||
+                (s->prefix & (PREFIX_LOCK | PREFIX_REPZ | PREFIX_REPNZ)) ||
+                !(s->cpuid_ext_features & CPUID_EXT_RDRAND)) {
+                goto illegal_op;
+            }
+            if (tb_cflags(s->base.tb) & CF_USE_ICOUNT) {
+                gen_io_start();
+            }
+            gen_helper_rdrand(s->T0, cpu_env);
+            rm = (modrm & 7) | REX_B(s);
+            gen_op_mov_reg_v(s, dflag, rm, s->T0);
+            set_cc_op(s, CC_OP_EFLAGS);
+            if (tb_cflags(s->base.tb) & CF_USE_ICOUNT) {
+                gen_io_end();
+                gen_jmp(s, s->pc - s->cs_base);
+            }
+            break;
+
+        default:
+            goto illegal_op;
         }
-        set_cc_op(s, CC_OP_EFLAGS);
         break;
 
         /**************************/