GH-96421: Insert shim frame on entry to interpreter (GH-96319)

* Adds EXIT_INTERPRETER instruction to exit PyEval_EvalDefault()

* Simplifies RETURN_VALUE, YIELD_VALUE and RETURN_GENERATOR instructions as they no longer need to check for entry frames.

1 files changed, 20 insertions, 1 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 51192bd5bb9..13519762fa8 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -29,6 +29,7 @@
 #include "pycore_tuple.h"         // _PyTuple_InitTypes()
 #include "pycore_typeobject.h"    // _PyTypes_InitTypes()
 #include "pycore_unicodeobject.h" // _PyUnicode_InitTypes()
+#include "opcode.h"
 
 extern void _PyIO_Fini(void);
 
@@ -779,6 +780,21 @@ pycore_init_types(PyInterpreterState *interp)
     return _PyStatus_OK();
 }
 
+static const uint8_t INTERPRETER_TRAMPOLINE_INSTRUCTIONS[] = {
+    /* Put a NOP at the start, so that the IP points into
+    * the code, rather than before it */
+    NOP, 0,
+    INTERPRETER_EXIT, 0,
+    /* RESUME at end makes sure that the frame appears incomplete */
+    RESUME, 0
+};
+
+static const _PyShimCodeDef INTERPRETER_TRAMPOLINE_CODEDEF = {
+    INTERPRETER_TRAMPOLINE_INSTRUCTIONS,
+    sizeof(INTERPRETER_TRAMPOLINE_INSTRUCTIONS),
+    1,
+    "<interpreter trampoline>"
+};
 
 static PyStatus
 pycore_init_builtins(PyThreadState *tstate)
@@ -812,7 +828,10 @@ pycore_init_builtins(PyThreadState *tstate)
     PyObject *object__getattribute__ = _PyType_Lookup(&PyBaseObject_Type, &_Py_ID(__getattribute__));
     assert(object__getattribute__);
     interp->callable_cache.object__getattribute__ = object__getattribute__;
-
+    interp->interpreter_trampoline = _Py_MakeShimCode(&INTERPRETER_TRAMPOLINE_CODEDEF);
+    if (interp->interpreter_trampoline == NULL) {
+        return _PyStatus_ERR("failed to create interpreter trampoline.");
+    }
     if (_PyBuiltins_AddExceptions(bimod) < 0) {
         return _PyStatus_ERR("failed to add exceptions to builtins");
     }