diff --git a/riscemu/CPU.py b/riscemu/CPU.py
index e2fd594..12fdc91 100644
--- a/riscemu/CPU.py
+++ b/riscemu/CPU.py
@@ -10,7 +10,7 @@ import sys
 from typing import Tuple, List, Dict, Callable, Type
 
 from .Tokenizer import RiscVTokenizer
-
+from .Executable import MemoryFlags
 from .Syscall import SyscallInterface, get_syscall_symbols
 from .Exceptions import RiscemuBaseException, LaunchDebuggerException
 from .MMU import MMU
@@ -85,6 +85,12 @@ class CPU:
         Run a loaded executable
         """
         self.pc = le.run_ptr
+
+        if self.conf.stack_size > 0:
+            stack = self.mmu.allocate_section("stack", self.conf.stack_size, MemoryFlags(False, False))
+            self.regs.set('sp', stack.base + stack.size)
+            print(FMT_CPU + '[CPU] Allocated {} bytes of stack'.format(stack.size) + FMT_NONE)
+
         print(FMT_CPU + '[CPU] Started running from 0x{:08X} ({})'.format(le.run_ptr, le.name) + FMT_NONE)
         self.__run()
 
diff --git a/riscemu/Config.py b/riscemu/Config.py
index 6946de9..b710677 100644
--- a/riscemu/Config.py
+++ b/riscemu/Config.py
@@ -10,7 +10,7 @@ from typing import Optional
 
 @dataclass(frozen=True, init=True)
 class RunConfig:
-    preffered_stack_size: Optional[int] = None
+    stack_size: int = 0     # 8 * 1024 * 1024 * 8 # for 8MB stack
     include_scall_symbols: bool = True
     add_accept_imm: bool = False
     # debugging
diff --git a/riscemu/Exceptions.py b/riscemu/Exceptions.py
index cf7017d..4bba2c0 100644
--- a/riscemu/Exceptions.py
+++ b/riscemu/Exceptions.py
@@ -90,12 +90,28 @@ class OutOfMemoryException(RiscemuBaseException):
         self.action = action
 
     def message(self):
-        return + FMT_MEM + '{}(Ran out of memory during {})'.format(
+        return FMT_MEM + '{}(Ran out of memory during {})'.format(
             self.__class__.__name__,
             self.action
         ) + FMT_NONE
 
 
+class InvalidAllocationException(RiscemuBaseException):
+    def __init__(self, msg, name, size, flags):
+        self.msg = msg
+        self.name = name
+        self.size = size
+        self.flags = flags
+
+    def message(self):
+        return FMT_MEM + '{}[{}](name={}, size={}, flags={})'.format(
+            self.__class__.__name__,
+            self.msg,
+            self.name,
+            self.size,
+            self.flags
+        )
+
 # CPU Exceptions
 
 
diff --git a/riscemu/MMU.py b/riscemu/MMU.py
index a63d3f0..211df7c 100644
--- a/riscemu/MMU.py
+++ b/riscemu/MMU.py
@@ -7,7 +7,7 @@ SPDX-License-Identifier: BSD-2-Clause
 from .Config import RunConfig
 from .Executable import Executable, LoadedExecutable, LoadedMemorySection, LoadedInstruction, MemoryFlags
 from .helpers import align_addr
-from .Exceptions import OutOfMemoryException
+from .Exceptions import OutOfMemoryException, InvalidAllocationException
 from .colors import *
 from typing import Dict, List, Tuple, Optional
 
@@ -22,6 +22,11 @@ class MMU:
     The maximum size of the memory in bytes
     """
 
+    max_alloc_size = 8 * 1024 * 1024 * 64
+    """
+    No single allocation can be bigger than 64 MB
+    """
+
     sections: List[LoadedMemorySection]
     """
     A list of all loaded memory sections
@@ -84,6 +89,32 @@ class MMU:
 
         return loaded_bin
 
+    def allocate_section(self, name: str, req_size: int, flag: MemoryFlags):
+        """
+        Used to allocate a memory region (data only). Use `load_bin` if you want to load a binary, this is used for
+        stack and maybe malloc in the future.
+
+        :param name: Name of the section to allocate
+        :param req_size: The requested size
+        :param flag: The flags protecting this memory section
+        :return: The LoadedMemorySection
+        """
+        if flag.executable:
+            raise InvalidAllocationException('cannot allocate executable section', name, req_size, flag)
+
+        if req_size < 0:
+            raise InvalidAllocationException('Invalid size request', name, req_size, flag)
+
+        if req_size > self.max_alloc_size:
+            raise InvalidAllocationException('Cannot allocate more than {} bytes at a time'.format(self.max_alloc_size), name, req_size, flag)
+
+        base = align_addr(self.first_free_addr)
+        size = align_addr(req_size)
+        sec = LoadedMemorySection(name, base, size, bytearray(size), flag, "<runtime>")
+        self.sections.append(sec)
+        self.first_free_addr = base + size
+        return sec
+
     def get_sec_containing(self, addr: int) -> Optional[LoadedMemorySection]:
         """
         Returns the section that contains the address addr
diff --git a/riscemu/__main__.py b/riscemu/__main__.py
index 1aa5966..9ec6d4d 100644
--- a/riscemu/__main__.py
+++ b/riscemu/__main__.py
@@ -62,13 +62,13 @@ if __name__ == '__main__':
                         help="Instruction sets to load, available are: {}. All are enabled by default"
                         .format(", ".join(all_ins_names)), keys={k: True for k in all_ins_names}, omit_empty=True)
 
-    parser.add_argument('--default_stack_size', type=int, help='Default stack size of loaded programs', default=None,
-                        metavar='default-stack-size', nargs='?')
+    parser.add_argument('--stack_size', type=int, help='Stack size of loaded programs, defaults to 8MB', nargs='?')
 
     args = parser.parse_args()
 
-    cfg = RunConfig(
-        preffered_stack_size=args.default_stack_size,
+    # create a RunConfig from the cli args
+    cfg_dict = dict(
+        stack_size=args.stack_size,
         debug_instruction=not args.options['disable_debug'],
         include_scall_symbols=not args.options['no_syscall_symbols'],
         debug_on_exception=not args.options['fail_on_ex'],
@@ -76,6 +76,11 @@ if __name__ == '__main__':
         scall_fs=args.syscall_opts['fs_access'],
         scall_input=not args.syscall_opts['disable_input']
     )
+    for k, v in dict(cfg_dict).items():
+        if v is None:
+            del cfg_dict[k]
+
+    cfg = RunConfig(**cfg_dict)
 
     if not hasattr(args, 'ins'):
         setattr(args, 'ins', {k: True for k in all_ins_names})