diff --git a/include/unicorn/unicorn.h b/include/unicorn/unicorn.h
index 556b6c17..ce887aa3 100755
--- a/include/unicorn/unicorn.h
+++ b/include/unicorn/unicorn.h
@@ -151,6 +151,7 @@ typedef enum uc_mem_type {
     UC_MEM_READ_WRITE,  // Memory is accessed (either READ or WRITE)
     UC_MEM_WRITE_NW,    // write to non-writable
     UC_MEM_READ_NR,     // read from non-readable
+    UC_MEM_NX,          // read from non-readable
 } uc_mem_type;
 
 // All type of hooks for uc_hook_add() API.
@@ -391,12 +392,13 @@ uc_err uc_hook_del(uch handle, uch *h2);
 typedef enum uc_prot {
    UC_PROT_READ = 1,
    UC_PROT_WRITE = 2,
+   UC_PROT_EXEC = 4,
 } uc_prot;
 
 /*
  Map memory in for emulation.
  This API adds a memory region that can be used by emulation. The region is mapped
- with permissions UC_PROT_READ | UC_PROT_WRITE.
+ with permissions UC_PROT_READ | UC_PROT_WRITE | UC_PROT_EXEC.
 
  @handle: handle returned by uc_open()
  @address: starting address of the new memory region to be mapped in.
@@ -420,7 +422,7 @@ uc_err uc_mem_map(uch handle, uint64_t address, size_t size);
  @size: size of the new memory region to be mapped in.
     This size must be multiple of 4KB, or this will return with UC_ERR_MAP error.
  @perms: Permissions for the newly mapped region.
-    This must be some combination of UC_PROT_READ | UC_PROT_WRITE,
+    This must be some combination of UC_PROT_READ | UC_PROT_WRITE | UC_PROT_EXEC,
     or this will return with UC_ERR_MAP error.
 
  @return UC_ERR_OK on success, or other value on failure (refer to uc_err enum
@@ -429,6 +431,25 @@ uc_err uc_mem_map(uch handle, uint64_t address, size_t size);
 UNICORN_EXPORT
 uc_err uc_mem_map_ex(uch handle, uint64_t address, size_t size, uint32_t perms);
 
+/*
+ Set memory permissions for emulation memory.
+ This API changes permissions on an existing memory region.
+
+ @handle: handle returned by uc_open()
+ @start: starting address of the memory region to be modified.
+    This address must be aligned to 4KB, or this will return with UC_ERR_MAP error.
+ @block_size: size of the memory region to be modified.
+    This size must be multiple of 4KB, or this will return with UC_ERR_MAP error.
+ @perms: New permissions for the mapped region.
+    This must be some combination of UC_PROT_READ | UC_PROT_WRITE | UC_PROT_EXEC,
+    or this will return with UC_ERR_MAP error.
+
+ @return UC_ERR_OK on success, or other value on failure (refer to uc_err enum
+ for detailed error).
+*/
+UNICORN_EXPORT
+uc_err uc_mem_protect(uch handle, uint64_t start, size_t block_size, uint32_t perms);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/qemu/softmmu_template.h b/qemu/softmmu_template.h
index 56f657a4..8c181824 100755
--- a/qemu/softmmu_template.h
+++ b/qemu/softmmu_template.h
@@ -181,6 +181,24 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, target_ulong addr, int mmu_idx,
     struct uc_struct *uc = env->uc;
     MemoryRegion *mr = memory_mapping(uc, addr);
 
+#if defined(SOFTMMU_CODE_ACCESS)
+    // Unicorn: callback on fetch from NX
+    if (mr != NULL && !(mr->perms & UC_PROT_EXEC)) {  //non-executable
+        if (uc->hook_mem_idx != 0 && ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
+                                       (uch)uc, UC_MEM_NX, addr, DATA_SIZE, 0,
+                                       uc->hook_callbacks[uc->hook_mem_idx].user_data)) {
+            env->invalid_error = UC_ERR_OK;
+        }
+        else {
+            env->invalid_addr = addr;
+            env->invalid_error = UC_ERR_MEM_READ;
+            // printf("***** Invalid memory read (non-readable) at " TARGET_FMT_lx "\n", addr);
+            cpu_exit(uc->current_cpu);
+            return 0;
+        }
+    }
+#endif
+
     // Unicorn: callback on memory read
     if (env->uc->hook_mem_read && READ_ACCESS_TYPE == MMU_DATA_LOAD) {
         struct hook_struct *trace = hook_find((uch)env->uc, UC_MEM_READ, addr);
@@ -206,15 +224,11 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, target_ulong addr, int mmu_idx,
         }
     }
 
-    // Unicorn: callback on read only memory
+    // Unicorn: callback on non-readable memory
     if (mr != NULL && !(mr->perms & UC_PROT_READ)) {  //non-readable
-        bool result = false;
-        if (uc->hook_mem_idx) {
-            result = ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
-                        (uch)uc, UC_MEM_READ_NR, addr, DATA_SIZE, 0,
-                        uc->hook_callbacks[uc->hook_mem_idx].user_data);
-        }
-        if (result) {
+        if (uc->hook_mem_idx != 0 && ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
+                                       (uch)uc, UC_MEM_READ_NR, addr, DATA_SIZE, 0,
+                                       uc->hook_callbacks[uc->hook_mem_idx].user_data)) {
             env->invalid_error = UC_ERR_OK;
         }
         else {
@@ -326,6 +340,24 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, target_ulong addr, int mmu_idx,
     struct uc_struct *uc = env->uc;
     MemoryRegion *mr = memory_mapping(uc, addr);
 
+#if defined(SOFTMMU_CODE_ACCESS)
+    // Unicorn: callback on fetch from NX
+    if (mr != NULL && !(mr->perms & UC_PROT_EXEC)) {  //non-executable
+        if (uc->hook_mem_idx != 0 && ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
+                                       (uch)uc, UC_MEM_NX, addr, DATA_SIZE, 0,
+                                       uc->hook_callbacks[uc->hook_mem_idx].user_data)) {
+            env->invalid_error = UC_ERR_OK;
+        }
+        else {
+            env->invalid_addr = addr;
+            env->invalid_error = UC_ERR_MEM_READ;
+            // printf("***** Invalid memory read (non-readable) at " TARGET_FMT_lx "\n", addr);
+            cpu_exit(uc->current_cpu);
+            return 0;
+        }
+    }
+#endif
+
     // Unicorn: callback on memory read
     if (env->uc->hook_mem_read && READ_ACCESS_TYPE == MMU_DATA_LOAD) {
         struct hook_struct *trace = hook_find((uch)env->uc, UC_MEM_READ, addr);
@@ -351,15 +383,11 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, target_ulong addr, int mmu_idx,
         }
     }
 
-    // Unicorn: callback on read only memory
+    // Unicorn: callback on non-readable memory
     if (mr != NULL && !(mr->perms & UC_PROT_READ)) {  //non-readable
-        bool result = false;
-        if (uc->hook_mem_idx) {
-            result = ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
-                        (uch)uc, UC_MEM_READ_NR, addr, DATA_SIZE, 0,
-                        uc->hook_callbacks[uc->hook_mem_idx].user_data);
-        }
-        if (result) {
+        if (uc->hook_mem_idx != 0 && ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
+                                       (uch)uc, UC_MEM_READ_NR, addr, DATA_SIZE, 0,
+                                       uc->hook_callbacks[uc->hook_mem_idx].user_data)) {
             env->invalid_error = UC_ERR_OK;
         }
         else {
@@ -534,15 +562,11 @@ void helper_le_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
         }
     }
 
-    // Unicorn: callback on read only memory
-    if (mr != NULL && !(mr->perms & UC_PROT_WRITE)) {  //read only memory
-        bool result = false;
-        if (uc->hook_mem_idx) {
-            result = ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
-                        (uch)uc, UC_MEM_WRITE_NW, addr, DATA_SIZE, (int64_t)val,
-                        uc->hook_callbacks[uc->hook_mem_idx].user_data);
-        }
-        if (result) {
+    // Unicorn: callback on non-writable memory
+    if (mr != NULL && !(mr->perms & UC_PROT_WRITE)) {  //non-writable
+        if (uc->hook_mem_idx != 0 && ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
+                                       (uch)uc, UC_MEM_WRITE_NW, addr, DATA_SIZE, (int64_t)val,
+                                       uc->hook_callbacks[uc->hook_mem_idx].user_data)) {
             env->invalid_error = UC_ERR_OK;
         }
         else {
@@ -672,15 +696,11 @@ void helper_be_st_name(CPUArchState *env, target_ulong addr, DATA_TYPE val,
         }
     }
 
-    // Unicorn: callback on read only memory
-    if (mr != NULL && !(mr->perms & UC_PROT_WRITE)) {  //read only memory
-        bool result = false;
-        if (uc->hook_mem_idx) {
-            result = ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
-                        (uch)uc, UC_MEM_WRITE_NW, addr, DATA_SIZE, (int64_t)val,
-                        uc->hook_callbacks[uc->hook_mem_idx].user_data);
-        }
-        if (result) {
+    // Unicorn: callback on non-writable memory
+    if (mr != NULL && !(mr->perms & UC_PROT_WRITE)) {  //non-writable
+        if (uc->hook_mem_idx != 0 && ((uc_cb_eventmem_t)uc->hook_callbacks[uc->hook_mem_idx].callback)(
+                                       (uch)uc, UC_MEM_WRITE_NW, addr, DATA_SIZE, (int64_t)val,
+                                       uc->hook_callbacks[uc->hook_mem_idx].user_data)) {
             env->invalid_error = UC_ERR_OK;
         }
         else {
diff --git a/uc.c b/uc.c
index 3192c627..18d70b63 100755
--- a/uc.c
+++ b/uc.c
@@ -568,7 +568,7 @@ uc_err uc_mem_map_ex(uch handle, uint64_t address, size_t size, uint32_t perms)
         return UC_ERR_MAP;
 
     // check for only valid permissions
-    if ((perms & ~(UC_PROT_READ | UC_PROT_WRITE)) != 0)
+    if ((perms & ~(UC_PROT_READ | UC_PROT_WRITE | UC_PROT_EXEC)) != 0)
         return UC_ERR_MAP;
 
     if ((uc->mapped_block_count & (MEM_BLOCK_INCR - 1)) == 0) {  //time to grow
@@ -588,7 +588,91 @@ UNICORN_EXPORT
 uc_err uc_mem_map(uch handle, uint64_t address, size_t size)
 {
     //old api, maps RW by default
-    return uc_mem_map_ex(handle, address, size, UC_PROT_READ | UC_PROT_WRITE);
+    return uc_mem_map_ex(handle, address, size, UC_PROT_READ | UC_PROT_WRITE | UC_PROT_EXEC);
+}
+
+UNICORN_EXPORT
+uc_err uc_mem_protect(uch handle, uint64_t start, size_t block_size, uint32_t perms)
+{
+    uint64_t address;
+    uint64_t size;
+    struct uc_struct* uc = (struct uc_struct *)handle;
+
+    if (handle == 0)
+        // invalid handle
+        return UC_ERR_UCH;
+
+    if (block_size == 0)
+        // invalid memory mapping
+        return UC_ERR_MAP;
+
+    // address must be aligned to 4KB
+    if ((start & (4*1024 - 1)) != 0)
+        return UC_ERR_MAP;
+
+    // size must be multiple of 4KB
+    if ((block_size & (4*1024 - 1)) != 0)
+        return UC_ERR_MAP;
+
+    // check for only valid permissions
+    if ((perms & ~(UC_PROT_READ | UC_PROT_WRITE | UC_PROT_EXEC)) != 0)
+        return UC_ERR_MAP;
+        
+    //check that users entire requested block is mapped
+    address = start;
+    size = block_size;
+    while (size > 0) {
+        uint64_t region_size;
+        MemoryRegion *mr = memory_mapping(uc, address);
+        if (mr == NULL) {
+            return UC_ERR_MAP;
+        }
+        region_size = int128_get64(mr->size);
+        if (address > mr->addr) {
+            //in case start address is not aligned with start of region
+            region_size -= address - mr->addr;
+        }
+        if (size < region_size) {
+            //entire region is covered
+            break;
+        }
+        size -= region_size;
+        address += region_size;
+    }
+
+    //Now we know entire region is mapped, so change permissions
+    address = start;
+    size = block_size;
+    while (size > 0) {
+        MemoryRegion *mr = memory_mapping(uc, address);
+        uint64_t region_size = int128_get64(mr->size);
+        if (address > mr->addr) {
+            //in case start address is not aligned with start of region
+            region_size -= address - mr->addr;
+            //TODO Learn how to split regions
+            //In this case some proper subset of the region is having it's permissions changed
+            //need to split region and add new portions into uc->mapped_blocks list
+            //In this case, there is a portion of the region with original perms: mr->addr..start
+            //and a portion getting new perms: start..start+block_size
+
+            //split the block and stay in the loop
+        }
+        if (size < int128_get64(mr->size)) {
+            //TODO Learn how to split regions
+            //In this case some proper subset of the region is having it's permissions changed
+            //need to split region and add new portions into uc->mapped_blocks list
+            //In this case, there is a portion of the region with new perms: start..start+block_size
+            //and a portion getting new perms: mr->addr+size..mr->addr+mr->size
+
+            //split the block and break
+            break;
+        }
+        size -= int128_get64(mr->size);
+        address += int128_get64(mr->size);
+        mr->perms = perms;
+        uc->readonly_mem(mr, (perms & UC_PROT_WRITE) == 0);
+    }
+    return UC_ERR_OK;
 }
 
 MemoryRegion *memory_mapping(struct uc_struct* uc, uint64_t address)