A stronger test and handle addr_end = 0

qemu/accel/tcg/translate-all.c

@@ -1753,7 +1753,8 @@ void tb_invalidate_phys_range(struct uc_struct *uc, ram_addr_t start, ram_addr_t
 
     pages = page_collection_lock(uc, start, end);
     for (next = (start & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
-         start < end;
+         //start < end; Unicorn: Fix possible wrap around
+         (intptr_t)(end - start) > 0;
          start = next, next += TARGET_PAGE_SIZE) {
         PageDesc *pd = page_find(uc, start >> TARGET_PAGE_BITS);
         tb_page_addr_t bound = MIN(next, end);

qemu/softmmu/cpus.c

@@ -174,7 +174,7 @@ void cpu_stop_current(struct uc_struct *uc)
 void resume_all_vcpus(struct uc_struct* uc)
 {
     CPUState *cpu = uc->cpu;
-    tb_page_addr_t addr;
+    tb_page_addr_t start, end;
     cpu->halted = 0;
     cpu->exit_request = 0;
     cpu->exception_index = -1;
@@ -190,15 +190,20 @@ void resume_all_vcpus(struct uc_struct* uc)
     // clear the cache of the addr_end address, since the generated code
     // at that address is to exit emulation, but not for the instruction there.
     // if we dont do this, next time we cannot emulate at that address
+    if (uc->addr_end != 0) {
+        // GVA to GPA (GPA -> HVA via page_find, HVA->HPA via host mmu)
+        end = get_page_addr_code(uc->cpu->env_ptr, uc->addr_end);
 
-    // GVA to GPA (GPA -> HVA via page_find, HVA->HPA via host mmu)
-    addr = get_page_addr_code(uc->cpu->env_ptr, uc->addr_end);
-    // Unicorn: Why addr - 1?
-    // 0: INC ecx
-    // 1: DEC edx <--- We put exit here, then the range of TB is [0, 1)
-    //
-    // While tb_invalidate_phys_range invalides [start, end)
-    tb_invalidate_phys_range(uc, addr - 1, addr - 1 + 8);
+        // For 32bit target.
+        start = (end - 1) & (target_ulong)(-1);
+        end = end & (target_ulong)(-1);
+        // Unicorn: Why start - 1?
+        // 0: INC ecx
+        // 1: DEC edx <--- We put exit here, then the range of TB is [0, 1)
+        //
+        // While tb_invalidate_phys_range invalides [start, end)
+        tb_invalidate_phys_range(uc, start, end);
+    }
 
     cpu->created = false;
 }

tests/unit/test_x86.c

@@ -633,7 +633,7 @@ static void test_x86_hook_cpuid()
 static void test_x86_clear_tb_cache()
 {
     uc_engine *uc;
-    char code[] = "\x83\xc1\x01\x4a"; // INC ecx; DEC edx;
+    char code[] = "\x83\xc1\x01\x4a"; // ADD ecx, 1; DEC edx;
     int r_ecx = 0x1234;
     int r_edx = 0x7890;
     uint64_t code_start = 0x1240; // Choose this address by design
@@ -645,6 +645,10 @@ static void test_x86_clear_tb_cache()
     OK(uc_reg_write(uc, UC_X86_REG_ECX, &r_ecx));
     OK(uc_reg_write(uc, UC_X86_REG_EDX, &r_edx));
 
+    // This emulation should take no effect at all.
+    OK(uc_emu_start(uc, code_start, code_start, 0, 0));
+
+    // Emulate ADD ecx, 1.
     OK(uc_emu_start(uc, code_start, code_start + 3, 0, 0));
 
     // If tb cache is not cleared, edx would be still 0x7890

uc.c

@@ -639,6 +639,12 @@ uc_err uc_emu_start(uc_engine *uc, uint64_t begin, uint64_t until,
     uc->timed_out = false;
     uc->first_tb = true;
 
+    // In this case, we don't do any emulation because it will generate
+    // an empty translation block which we can't invalidate.
+    if (begin == until) {
+        return UC_ERR_OK;
+    }
+    
     switch (uc->arch) {
     default:
         break;