Remove the outdated hack to zero all code gen buffer

This shall also improve performance

Fix #2001

Author: wtdcode

qemu/tcg/tcg.c

@@ -407,7 +407,7 @@ static void tcg_region_assign(TCGContext *s, size_t curr_region)
     s->code_gen_ptr = start;
     s->code_gen_buffer_size = (char *)end - (char *)start;
 
-    memset(s->code_gen_buffer, 0x00, s->code_gen_buffer_size);
+    // memset(s->code_gen_buffer, 0x00, s->code_gen_buffer_size); // Outdated Unicorn hacks
     s->code_gen_highwater = (char *)end - TCG_HIGHWATER;
 }
 
@@ -812,6 +812,7 @@ TranslationBlock *tcg_tb_alloc(TCGContext *s)
     }
     s->code_gen_ptr = next;
     s->data_gen_ptr = NULL;
+    // memset((void*)tb, 0x00, sizeof(TranslationBlock)); // not necessary as both tb and tb->tc.ptr is reused here
     return tb;
 }
 

qemu/unicorn_common.h

@@ -40,6 +40,10 @@ static void release_common(void *t)
     int i;
 #endif
 
+    // Clear bps
+    cpu_watchpoint_remove_all(CPU(s->uc->cpu), BP_CPU);
+    cpu_breakpoint_remove_all(CPU(s->uc->cpu), BP_CPU);
+
     // Clean TCG.
     TCGOpDef* def = s->tcg_op_defs;
     g_free(def->args_ct);
@@ -72,8 +76,6 @@ static void release_common(void *t)
     /* qemu/util/qht.c:264: map = qht_map_create(n_buckets); */
     qht_destroy(&s->tb_ctx.htable);
 
-    cpu_watchpoint_remove_all(CPU(s->uc->cpu), BP_CPU);
-    cpu_breakpoint_remove_all(CPU(s->uc->cpu), BP_CPU);
 
 #if TCG_TARGET_REG_BITS == 32
     for(i = 0; i < s->nb_globals; i++) {

tests/unit/test_x86.c

@@ -2019,6 +2019,17 @@ static void test_x86_hook_insn_rdtscp(void)
     OK(uc_close(uc));
 }
 
+static void test_x86_dr7() {
+    uc_engine *uc;
+    char code[] =
+        "\x48\xC7\xC0\x05\x00\x01\x00\x0F\x23\xF8"; // mov rax, 0x10005
+                                                    // mov dr7, rax
+    uc_common_setup(&uc, UC_ARCH_X86, UC_MODE_64, code, sizeof(code) - 1);
+    OK(uc_emu_start(uc, code_start, code_start + sizeof(code) - 1, 0, 0));
+
+    OK(uc_close(uc));
+}
+
 TEST_LIST = {
     {"test_x86_in", test_x86_in},
     {"test_x86_out", test_x86_out},
@@ -2079,4 +2090,5 @@ TEST_LIST = {
     {"test_x86_ro_segfault", test_x86_ro_segfault},
     {"test_x86_hook_insn_rdtsc", test_x86_hook_insn_rdtsc},
     {"test_x86_hook_insn_rdtscp", test_x86_hook_insn_rdtscp},
+    {"test_x86_dr7", test_x86_dr7},
     {NULL, NULL}};