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GH-137573: Add test to check that the margin used for overflow protection is larger than the stack space used by the interpreter #137724

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GH-137573: Add test to check that the margin used for overflow protection is larger than the stack space used by the interpreter #137724

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16 changes: 16 additions & 0 deletions Lib/test/test_call.py
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,10 @@
import _testlimitedcapi
except ImportError:
_testlimitedcapi = None
try:
import _testinternalcapi
except ImportError:
_testinternalcapi = None
import struct
import collections
import itertools
Expand Down Expand Up @@ -1037,6 +1041,18 @@ def test_unexpected_keyword_suggestion_via_getargs(self):
@cpython_only
class TestRecursion(unittest.TestCase):

def test_margin_is_sufficient(self):

def get_sp():
return _testinternalcapi.get_stack_pointer()

this_sp = _testinternalcapi.get_stack_pointer()
lower_sp = _testcapi.pyobject_vectorcall(get_sp, (), ())
self.assertLess(lower_sp, this_sp)
# Add an (arbitrary) extra 25% for safety
safe_margin = (this_sp - lower_sp) * 5 / 4
self.assertLess(safe_margin, _testinternalcapi.get_stack_margin())

@skip_on_s390x
@unittest.skipIf(is_wasi and Py_DEBUG, "requires deep stack")
@skip_if_sanitizer("requires deep stack", thread=True)
Expand Down
14 changes: 14 additions & 0 deletions Modules/_testinternalcapi.c
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Expand Up @@ -125,6 +125,18 @@ get_c_recursion_remaining(PyObject *self, PyObject *Py_UNUSED(args))
return PyLong_FromLong(remaining);
}

static PyObject*
get_stack_pointer(PyObject *self, PyObject *Py_UNUSED(args))
{
uintptr_t here_addr = _Py_get_machine_stack_pointer();
return PyLong_FromSize_t(here_addr);
}

static PyObject*
get_stack_margin(PyObject *self, PyObject *Py_UNUSED(args))
{
return PyLong_FromSize_t(_PyOS_STACK_MARGIN_BYTES);
}

static PyObject*
test_bswap(PyObject *self, PyObject *Py_UNUSED(args))
Expand Down Expand Up @@ -2380,6 +2392,8 @@ static PyMethodDef module_functions[] = {
{"get_configs", get_configs, METH_NOARGS},
{"get_recursion_depth", get_recursion_depth, METH_NOARGS},
{"get_c_recursion_remaining", get_c_recursion_remaining, METH_NOARGS},
{"get_stack_pointer", get_stack_pointer, METH_NOARGS},
{"get_stack_margin", get_stack_margin, METH_NOARGS},
{"test_bswap", test_bswap, METH_NOARGS},
{"test_popcount", test_popcount, METH_NOARGS},
{"test_bit_length", test_bit_length, METH_NOARGS},
Expand Down
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