Improve ReadRemoteMemory error handling on macOS

Improve the return value check to be able to raise a ProcessLookupError
when the remote process is not available.

Mach uses composite error values where higher error values indicate
specific subsystems. We can use the err_get_code function to mask the
higher bits to make our error checking more robust in case the subsystem
bits are set. For example, in some situations if the process is in zombie
state, we can get KERN_NO_SPACE (0x3) but the actual return value is
0x10000003 which indicates a specific subsystem, thus we need to
use err_get_code to extract the error value.

This also improves how KERN_INVALID_ARGUMENT is handled to check whether
we got a generic invalid argument error, or if the process is no longer
accessible.

Author: lkollar

Lib/test/test_sample_profiler.py

@@ -1723,12 +1723,11 @@ def test_is_process_running(self):
             self.assertIsNotNone(profiler.unwinder.get_stack_trace())
             proc.kill()
             proc.wait()
-            # ValueError on MacOS (yeah I know), ProcessLookupError on Linux and Windows
-            self.assertRaises((ValueError, ProcessLookupError), profiler.unwinder.get_stack_trace)
+            self.assertRaises(ProcessLookupError, profiler.unwinder.get_stack_trace)
 
         # Exit the context manager to ensure the process is terminated
         self.assertFalse(profiler._is_process_running())
-        self.assertRaises((ValueError, ProcessLookupError), profiler.unwinder.get_stack_trace)
+        self.assertRaises(ProcessLookupError, profiler.unwinder.get_stack_trace)
 
     @unittest.skipUnless(sys.platform == "linux", "Only valid on Linux")
     def test_esrch_signal_handling(self):

Python/remote_debug.h

@@ -50,6 +50,7 @@ extern "C" {
 #  include <mach-o/fat.h>
 #  include <mach-o/loader.h>
 #  include <mach-o/nlist.h>
+#  include <mach/error.h>
 #  include <mach/mach.h>
 #  include <mach/mach_vm.h>
 #  include <mach/machine.h>
@@ -1053,18 +1054,37 @@ _Py_RemoteDebug_ReadRemoteMemory(proc_handle_t *handle, uintptr_t remote_address
         (mach_vm_size_t*)&result);
 
     if (kr != KERN_SUCCESS) {
-        switch (kr) {
+        switch (err_get_code(kr)) {
         case KERN_PROTECTION_FAILURE:
             PyErr_Format(PyExc_PermissionError,
                 "Memory protection failure reading from PID %d at address "
                 "0x%lx (size %zu): insufficient permissions",
                 handle->pid, remote_address, len);
             break;
         case KERN_INVALID_ARGUMENT:
-            PyErr_Format(PyExc_ValueError,
-                "Invalid argument to mach_vm_read_overwrite for PID %d at "
-                "address 0x%lx (size %zu)",
-                handle->pid, remote_address, len);
+            // Perform a task_info check to see if the invalid argument is due
+            // to the process being terminated
+            task_basic_info_data_t task_basic_info;
+            mach_msg_type_number_t task_info_count = TASK_BASIC_INFO_COUNT;
+            kern_return_t task_valid_check = task_info(handle->task, TASK_BASIC_INFO,
+                                                        (task_info_t)&task_basic_info,
+                                                        &task_info_count);
+            if (task_valid_check == KERN_INVALID_ARGUMENT) {
+                PyErr_Format(PyExc_ProcessLookupError,
+                    "Process %d is no longer accessible (process terminated)",
+                    handle->pid);
+            } else {
+                PyErr_Format(PyExc_PermissionError,
+                    "Invalid argument to mach_vm_read_overwrite for PID %d at "
+                    "address 0x%lx (size %zu) - check memory permissions",
+                    handle->pid, remote_address, len);
+            }
+            break;
+        case KERN_NO_SPACE:
+        case KERN_MEMORY_ERROR:
+            PyErr_Format(PyExc_ProcessLookupError,
+                "Process %d memory space no longer available (process terminated)",
+                handle->pid);
             break;
         default:
             PyErr_Format(PyExc_RuntimeError,