gh-149619: Fix `_remote_debugging` permissions error on Linux (#150012)

When running profiling on Linux without sudo, attempts to read
process memory would fail with the misleading error 'Failed to find
the PyRuntime section in process <pid> on Linux platform'.

The actual issue is a permissions error because profiling was not
run with sudo. We were clearing the exception on Linux when trying
to read memory, instead, we should bubble up the permissions error
and show it properly.

diff --git a/Python/remote_debug.h b/Python/remote_debug.h
index 7b2c4f3bcb8077a8377fb35f47ec4538c53f208c..53bbd571ad3cef4c38758983e6b391a83098afa3 100644 (file)
--- a/Python/remote_debug.h
+++ b/Python/remote_debug.h
@@ -170,7 +170,9 @@ _Py_RemoteDebug_ValidatePyRuntimeCookie(proc_handle_t *handle, uintptr_t address
     }
     char buf[sizeof(_Py_Debug_Cookie) - 1];
     if (_Py_RemoteDebug_ReadRemoteMemory(handle, address, sizeof(buf), buf) != 0) {
-        PyErr_Clear();
+        if (!PyErr_ExceptionMatches(PyExc_PermissionError)) {
+            PyErr_Clear();
+        }
         return 0;
     }
     return memcmp(buf, _Py_Debug_Cookie, sizeof(buf)) == 0;
@@ -785,6 +787,10 @@ search_linux_map_for_section(proc_handle_t *handle, const char* secname, const c
         }
 
         if (strstr(filename, substr)) {
+            if (PyErr_ExceptionMatches(PyExc_PermissionError)) {
+                retval = 0;
+                break;
+            }
             PyErr_Clear();
             retval = search_elf_file_for_section(handle, secname, start, path);
             if (retval
@@ -960,12 +966,14 @@ _Py_RemoteDebug_GetPyRuntimeAddress(proc_handle_t* handle)
     address = search_linux_map_for_section(handle, "PyRuntime", "python",
                                            _Py_RemoteDebug_ValidatePyRuntimeCookie);
     if (address == 0) {
-        // Error out: 'python' substring covers both executable and DLL
-        PyObject *exc = PyErr_GetRaisedException();
-        PyErr_Format(PyExc_RuntimeError,
-            "Failed to find the PyRuntime section in process %d on Linux platform",
-            handle->pid);
-        _PyErr_ChainExceptions1(exc);
+        if (!PyErr_ExceptionMatches(PyExc_PermissionError)) {
+            // Error out: 'python' substring covers both executable and DLL
+            PyObject *exc = PyErr_GetRaisedException();
+            PyErr_Format(PyExc_RuntimeError,
+                "Failed to find the PyRuntime section in process %d on Linux platform",
+                handle->pid);
+            _PyErr_ChainExceptions1(exc);
+        }
     }
 #elif defined(__APPLE__) && defined(TARGET_OS_OSX) && TARGET_OS_OSX
     // On macOS, try libpython first, then fall back to python