[3.15] gh-149619: Fix _remote_debugging permissions error on Linux (GH-150012) (#150339)

gh-149619: Fix `_remote_debugging` permissions error on Linux (GH-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.
(cherry picked from commit 0563890)

Co-authored-by: ivonastojanovic <80911834+ivonastojanovic@users.noreply.github.com>

Author: miss-islington

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