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gh-139653: Add PyUnstable_ThreadState_SetStackProtection() (#139668)

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Add PyUnstable_ThreadState_SetStackProtection() and
PyUnstable_ThreadState_ResetStackProtection() functions
to set the stack base address and stack size of a Python
thread state.

Co-authored-by: Petr Viktorin <encukou@gmail.com>
This commit is contained in:
Victor Stinner
2025-11-13 17:30:50 +01:00
committed by GitHub
parent d7862e9b1b
commit b99db92dde
10 changed files with 199 additions and 7 deletions
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77
Python/ceval.c
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@@ -443,7 +443,7 @@ int pthread_attr_destroy(pthread_attr_t *a)
#endif
static void
hardware_stack_limits(uintptr_t *top, uintptr_t *base)
hardware_stack_limits(uintptr_t *base, uintptr_t *top)
{
#ifdef WIN32
ULONG_PTR low, high;
@@ -486,23 +486,86 @@ hardware_stack_limits(uintptr_t *top, uintptr_t *base)
#endif
}
void
_Py_InitializeRecursionLimits(PyThreadState *tstate)
static void
tstate_set_stack(PyThreadState *tstate,
uintptr_t base, uintptr_t top)
{
uintptr_t top;
uintptr_t base;
hardware_stack_limits(&top, &base);
assert(base < top);
assert((top - base) >= _PyOS_MIN_STACK_SIZE);
#ifdef _Py_THREAD_SANITIZER
// Thread sanitizer crashes if we use more than half the stack.
uintptr_t stacksize = top - base;
base += stacksize/2;
base += stacksize / 2;
#endif
_PyThreadStateImpl *_tstate = (_PyThreadStateImpl *)tstate;
_tstate->c_stack_top = top;
_tstate->c_stack_hard_limit = base + _PyOS_STACK_MARGIN_BYTES;
_tstate->c_stack_soft_limit = base + _PyOS_STACK_MARGIN_BYTES * 2;
#ifndef NDEBUG
// Sanity checks
_PyThreadStateImpl *ts = (_PyThreadStateImpl *)tstate;
assert(ts->c_stack_hard_limit <= ts->c_stack_soft_limit);
assert(ts->c_stack_soft_limit < ts->c_stack_top);
#endif
}
void
_Py_InitializeRecursionLimits(PyThreadState *tstate)
{
uintptr_t base, top;
hardware_stack_limits(&base, &top);
assert(top != 0);
tstate_set_stack(tstate, base, top);
_PyThreadStateImpl *ts = (_PyThreadStateImpl *)tstate;
ts->c_stack_init_base = base;
ts->c_stack_init_top = top;
// Test the stack pointer
#if !defined(NDEBUG) && !defined(__wasi__)
uintptr_t here_addr = _Py_get_machine_stack_pointer();
assert(ts->c_stack_soft_limit < here_addr);
assert(here_addr < ts->c_stack_top);
#endif
}
int
PyUnstable_ThreadState_SetStackProtection(PyThreadState *tstate,
void *stack_start_addr, size_t stack_size)
{
if (stack_size < _PyOS_MIN_STACK_SIZE) {
PyErr_Format(PyExc_ValueError,
"stack_size must be at least %zu bytes",
_PyOS_MIN_STACK_SIZE);
return -1;
}
uintptr_t base = (uintptr_t)stack_start_addr;
uintptr_t top = base + stack_size;
tstate_set_stack(tstate, base, top);
return 0;
}
void
PyUnstable_ThreadState_ResetStackProtection(PyThreadState *tstate)
{
_PyThreadStateImpl *ts = (_PyThreadStateImpl *)tstate;
if (ts->c_stack_init_top != 0) {
tstate_set_stack(tstate,
ts->c_stack_init_base,
ts->c_stack_init_top);
return;
}
_Py_InitializeRecursionLimits(tstate);
}
/* The function _Py_EnterRecursiveCallTstate() only calls _Py_CheckRecursiveCall()
if the recursion_depth reaches recursion_limit. */
int