Strengthen JIT GDB backtrace tests

Author: diegorusso

Lib/test/test_gdb/test_jit.py

@@ -15,10 +15,15 @@
 # This bound is just a generous upper limit so the test fails clearly if the
 # expected stack shape changes.
 MAX_FINISH_STEPS = 20
+# Break directly on the lazy shim entry in the binary, then single-step just
+# enough to let it install the compiled shim and set a temporary breakpoint on
+# the resulting JIT entry address.
+MAX_SHIM_SETUP_STEPS = 20
 # After landing on the executor frame, single-step a little further into the
 # blob so the backtrace is taken from executor code itself rather than the
 # immediate helper-return site.
 EXECUTOR_SINGLE_STEPS = 2
+EVAL_FRAME_RE = r"(_PyEval_EvalFrameDefault|_PyEval_Vector)"
 
 FINISH_TO_JIT_EXECUTOR = (
     "python exec(\"import gdb\\n"
@@ -31,6 +36,18 @@
     "else:\\n"
     "    raise RuntimeError('did not reach %s' % target)\\n\")"
 )
+BREAK_IN_COMPILED_SHIM = (
+    "python exec(\"import gdb\\n"
+    "lazy = int(gdb.parse_and_eval('(void*)_Py_LazyJitShim'))\\n"
+    f"for _ in range({MAX_SHIM_SETUP_STEPS}):\\n"
+    "    entry = int(gdb.parse_and_eval('(void*)_Py_jit_entry'))\\n"
+    "    if entry != lazy:\\n"
+    "        gdb.execute('tbreak *0x%x' % entry)\\n"
+    "        break\\n"
+    "    gdb.execute('next')\\n"
+    "else:\\n"
+    "    raise RuntimeError('compiled shim was not installed')\\n\")"
+)
 
 
 def setUpModule():
@@ -42,17 +59,38 @@ def setUpModule():
     "requires a JIT-enabled build",
 )
 class JitBacktraceTests(DebuggerTests):
+    def test_bt_shows_compiled_jit_shim(self):
+        gdb_output = self.get_stack_trace(
+            script=JIT_SAMPLE_SCRIPT,
+            breakpoint="_Py_LazyJitShim",
+            cmds_after_breakpoint=[
+                BREAK_IN_COMPILED_SHIM,
+                "continue",
+                "bt",
+            ],
+            PYTHON_JIT="1",
+        )
+        self.assertRegex(
+            gdb_output,
+            re.compile(
+                rf"#0\s+py::jit_shim:<jit>.*{EVAL_FRAME_RE}",
+                re.DOTALL,
+            ),
+        )
+
     def test_bt_unwinds_through_jit_frames(self):
         gdb_output = self.get_stack_trace(
             script=JIT_SAMPLE_SCRIPT,
             cmds_after_breakpoint=["bt"],
             PYTHON_JIT="1",
         )
+        # The executor should appear as a named JIT frame and unwind back into
+        # the eval loop. Whether GDB also materializes a separate shim frame is
+        # an implementation detail of the synthetic executor CFI.
         self.assertRegex(
             gdb_output,
             re.compile(
-                r"py::jit_executor:<jit>.*py::jit_shim:<jit>.*"
-                r"(_PyEval_EvalFrameDefault|_PyEval_Vector)",
+                rf"py::jit_executor:<jit>.*{EVAL_FRAME_RE}",
                 re.DOTALL,
             ),
         )
@@ -67,11 +105,12 @@ def test_bt_unwinds_from_inside_jit_executor(self):
             ],
             PYTHON_JIT="1",
         )
+        # Once the selected PC is inside the executor, we only require that
+        # GDB can identify the JIT frame and keep unwinding into _PyEval_*.
         self.assertRegex(
             gdb_output,
             re.compile(
-                r"#0\s+py::jit_executor:<jit>.*#1\s+py::jit_shim:<jit>.*"
-                r"(_PyEval_EvalFrameDefault|_PyEval_Vector)",
+                rf"#0\s+py::jit_executor:<jit>.*{EVAL_FRAME_RE}",
                 re.DOTALL,
             ),
         )

Modules/_testinternalcapi.c

@@ -1220,7 +1220,7 @@ write_perf_map_entry(PyObject *self, PyObject *args)
         return NULL;
     }
 
-    int ret = PyUnstable_WritePerfMapEntry(code_addr, code_size, entry_name);
+    int ret = PyUnstable_WritePerfMapEntry(code_addr, (unsigned int)code_size, entry_name);
     if (ret < 0) {
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;