target-i386: Check CR4[DE] for processing DR4/DR5

Introduce helper_get_dr so that we don't have to put CR4[DE]
into the scarce HFLAGS resource.  At the same time, rename
helper_movl_drN_T0 to helper_set_dr and set the helper flags.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

target-i386/bpt_helper.c

@@ -242,10 +242,11 @@ void helper_single_step(CPUX86State *env)
     raise_exception(env, EXCP01_DB);
 }
 
-void helper_movl_drN_T0(CPUX86State *env, int reg, target_ulong t0)
+void helper_set_dr(CPUX86State *env, int reg, target_ulong t0)
 {
 #ifndef CONFIG_USER_ONLY
-    if (reg < 4) {
+    switch (reg) {
+    case 0: case 1: case 2: case 3:
         if (hw_breakpoint_enabled(env->dr[7], reg)
             && hw_breakpoint_type(env->dr[7], reg) != DR7_TYPE_IO_RW) {
             hw_breakpoint_remove(env, reg);
@@ -254,14 +255,49 @@ void helper_movl_drN_T0(CPUX86State *env, int reg, target_ulong t0)
         } else {
             env->dr[reg] = t0;
         }
-    } else if (reg == 7) {
+        return;
+    case 4:
+        if (env->cr[4] & CR4_DE_MASK) {
+            break;
+        }
+        /* fallthru */
+    case 6:
+        env->dr[6] = t0;
+        return;
+    case 5:
+        if (env->cr[4] & CR4_DE_MASK) {
+            break;
+        }
+        /* fallthru */
+    case 7:
         cpu_x86_update_dr7(env, t0);
-    } else {
-        env->dr[reg] = t0;
+        return;
     }
+    raise_exception_err_ra(env, EXCP06_ILLOP, 0, GETPC());
 #endif
 }
 
+target_ulong helper_get_dr(CPUX86State *env, int reg)
+{
+    switch (reg) {
+    case 0: case 1: case 2: case 3: case 6: case 7:
+        return env->dr[reg];
+    case 4:
+        if (env->cr[4] & CR4_DE_MASK) {
+            break;
+        } else {
+            return env->dr[6];
+        }
+    case 5:
+        if (env->cr[4] & CR4_DE_MASK) {
+            break;
+        } else {
+            return env->dr[7];
+        }
+    }
+    raise_exception_err_ra(env, EXCP06_ILLOP, 0, GETPC());
+}
+
 /* Check if Port I/O is trapped by a breakpoint.  */
 void helper_bpt_io(CPUX86State *env, uint32_t port,
                    uint32_t size, target_ulong next_eip)

target-i386/cpu.h

@@ -920,7 +920,7 @@ typedef struct CPUX86State {
     int error_code;
     int exception_is_int;
     target_ulong exception_next_eip;
-    target_ulong dr[8]; /* debug registers */
+    target_ulong dr[8]; /* debug registers; note dr4 and dr5 are unused */
     union {
         struct CPUBreakpoint *cpu_breakpoint[4];
         struct CPUWatchpoint *cpu_watchpoint[4];

target-i386/helper.h

@@ -40,7 +40,8 @@ DEF_HELPER_2(read_crN, tl, env, int)
 DEF_HELPER_3(write_crN, void, env, int, tl)
 DEF_HELPER_2(lmsw, void, env, tl)
 DEF_HELPER_1(clts, void, env)
-DEF_HELPER_3(movl_drN_T0, void, env, int, tl)
+DEF_HELPER_FLAGS_3(set_dr, TCG_CALL_NO_WG, void, env, int, tl)
+DEF_HELPER_FLAGS_2(get_dr, TCG_CALL_NO_WG, tl, env, int)
 DEF_HELPER_2(invlpg, void, env, tl)
 
 DEF_HELPER_4(enter_level, void, env, int, int, tl)

target-i386/translate.c

@@ -7627,18 +7627,20 @@ static target_ulong disas_insn(CPUX86State *env, DisasContext *s,
                 ot = MO_64;
             else
                 ot = MO_32;
-            /* XXX: do it dynamically with CR4.DE bit */
-            if (reg == 4 || reg == 5 || reg >= 8)
+            if (reg >= 8) {
                 goto illegal_op;
+            }
             if (b & 2) {
                 gen_svm_check_intercept(s, pc_start, SVM_EXIT_WRITE_DR0 + reg);
                 gen_op_mov_v_reg(ot, cpu_T[0], rm);
-                gen_helper_movl_drN_T0(cpu_env, tcg_const_i32(reg), cpu_T[0]);
+                tcg_gen_movi_i32(cpu_tmp2_i32, reg);
+                gen_helper_set_dr(cpu_env, cpu_tmp2_i32, cpu_T[0]);
                 gen_jmp_im(s->pc - s->cs_base);
                 gen_eob(s);
             } else {
                 gen_svm_check_intercept(s, pc_start, SVM_EXIT_READ_DR0 + reg);
-                tcg_gen_ld_tl(cpu_T[0], cpu_env, offsetof(CPUX86State,dr[reg]));
+                tcg_gen_movi_i32(cpu_tmp2_i32, reg);
+                gen_helper_get_dr(cpu_T[0], cpu_env, cpu_tmp2_i32);
                 gen_op_mov_reg_v(ot, rm, cpu_T[0]);
             }
         }