Re: [PATCH] Fix crash in gdbpy_parse_register_id

[Tom Tromey <tom@tromey.com>]

>> +    PyErr_SetString (PyExc_ValueError, _("Invalid type for register"));

Simon> I think this one should be a TypeError.

Fixed.

>> +    PyErr_SetString (PyExc_ValueError, "Bad register");

Simon> It seems like you kept the wrong line here?  If this is really an error
Simon> and no test has caught this, it means we're lacking some coverage.

Yeah, oops.  I added a test.

>> +# This previously caused a crash.

Simon> This comment is a bit too broad, can you make it a bit more precise?
Simon> What is it we are testing exactly?  I suppose "passing an object with an
Simon> unexpected type to read_register".

I did this.

New patch appended.

Tom

commit 310a3620ac6f86bbc0bc2c400a3df4202adcfe41
Author: Tom Tromey <tom@tromey.com>
Date:   Wed Apr 27 15:22:56 2022 -0600

    Fix crash in gdbpy_parse_register_id
    
    I noticed that gdbpy_parse_register_id would assert if passed a Python
    object of a type it was not expecting.  The included test case shows
    this crash.  This patch fixes the problem and also changes
    gdbpy_parse_register_id to be more "Python-like" -- it always ensures
    the Python error is set when it fails, and the callers now simply
    propagate the existing exception.

diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
index 9a28c36c1cc..8bd2e0bc6da 100644
--- a/gdb/python/py-frame.c
+++ b/gdb/python/py-frame.c
@@ -253,10 +253,7 @@ frapy_read_register (PyObject *self, PyObject *args)
 
       if (!gdbpy_parse_register_id (get_frame_arch (frame), pyo_reg_id,
 				    &regnum))
-	{
-	  PyErr_SetString (PyExc_ValueError, "Bad register");
-	  return NULL;
-	}
+	return nullptr;
 
       gdb_assert (regnum >= 0);
       val = value_of_register (regnum, frame);
diff --git a/gdb/python/py-registers.c b/gdb/python/py-registers.c
index bbb322f068c..bac85c1ecff 100644
--- a/gdb/python/py-registers.c
+++ b/gdb/python/py-registers.c
@@ -386,21 +386,27 @@ gdbpy_parse_register_id (struct gdbarch *gdbarch, PyObject *pyo_reg_id,
 	{
 	  *reg_num = user_reg_map_name_to_regnum (gdbarch, reg_name.get (),
 						  strlen (reg_name.get ()));
-	  return *reg_num >= 0;
+	  if (*reg_num >= 0)
+	    return true;
+	  PyErr_SetString (PyExc_ValueError, "Bad register");
 	}
     }
   /* The register could be its internal GDB register number.  */
   else if (PyLong_Check (pyo_reg_id))
     {
       long value;
-      if (gdb_py_int_as_long (pyo_reg_id, &value) && (int) value == value)
+      if (gdb_py_int_as_long (pyo_reg_id, &value) == 0)
 	{
-	  if (user_reg_map_regnum_to_name (gdbarch, value) != NULL)
-	    {
-	      *reg_num = (int) value;
-	      return true;
-	    }
+	  /* Nothing -- error.  */
 	}
+      else if ((int) value == value
+	       && user_reg_map_regnum_to_name (gdbarch, value) != NULL)
+	{
+	  *reg_num = (int) value;
+	  return true;
+	}
+      else
+	PyErr_SetString (PyExc_ValueError, "Bad register");
     }
   /* The register could be a gdb.RegisterDescriptor object.  */
   else if (PyObject_IsInstance (pyo_reg_id,
@@ -417,6 +423,8 @@ gdbpy_parse_register_id (struct gdbarch *gdbarch, PyObject *pyo_reg_id,
 	PyErr_SetString (PyExc_ValueError,
 			 _("Invalid Architecture in RegisterDescriptor"));
     }
+  else
+    PyErr_SetString (PyExc_TypeError, _("Invalid type for register"));
 
   gdb_assert (PyErr_Occurred ());
   return false;
diff --git a/gdb/python/py-unwind.c b/gdb/python/py-unwind.c
index b2fd1402e93..15b22ab9b30 100644
--- a/gdb/python/py-unwind.c
+++ b/gdb/python/py-unwind.c
@@ -262,10 +262,7 @@ unwind_infopy_add_saved_register (PyObject *self, PyObject *args)
 			  &pyo_reg_id, &pyo_reg_value))
     return NULL;
   if (!gdbpy_parse_register_id (pending_frame->gdbarch, pyo_reg_id, &regnum))
-    {
-      PyErr_SetString (PyExc_ValueError, "Bad register");
-      return NULL;
-    }
+    return nullptr;
 
   /* If REGNUM identifies a user register then *maybe* we can convert this
      to a real (i.e. non-user) register.  The maybe qualifier is because we
@@ -383,10 +380,7 @@ pending_framepy_read_register (PyObject *self, PyObject *args)
   if (!PyArg_UnpackTuple (args, "read_register", 1, 1, &pyo_reg_id))
     return NULL;
   if (!gdbpy_parse_register_id (pending_frame->gdbarch, pyo_reg_id, &regnum))
-    {
-      PyErr_SetString (PyExc_ValueError, "Bad register");
-      return NULL;
-    }
+    return nullptr;
 
   try
     {
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 217bc15bb28..2136c72faae 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -799,7 +799,8 @@ typedef std::unique_ptr<Py_buffer, Py_buffer_deleter> Py_buffer_up;
 
    If a register is parsed successfully then *REG_NUM will have been
    updated, and true is returned.  Otherwise the contents of *REG_NUM are
-   undefined, and false is returned.
+   undefined, and false is returned.  When false is returned, the
+   Python error is set.
 
    The PYO_REG_ID object can be a string, the name of the register.  This
    is the slowest approach as GDB has to map the name to a number for each
diff --git a/gdb/testsuite/gdb.python/py-frame.exp b/gdb/testsuite/gdb.python/py-frame.exp
index 4991e8a0c5d..56e1ecdcedd 100644
--- a/gdb/testsuite/gdb.python/py-frame.exp
+++ b/gdb/testsuite/gdb.python/py-frame.exp
@@ -134,3 +134,9 @@ gdb_test "python print(gdb.selected_frame().language())" "c"
 gdb_test "set language ada"
 gdb_test "python print(gdb.selected_frame().language())" "c" \
     "frame language is not affected by global language"
+
+# This previously caused a crash -- the implementation was missing the
+# case where a register had an unexpected type.
+gdb_test "python print(gdb.selected_frame().read_register(list()))" \
+    ".*Invalid type for register.*" \
+    "test Frame.read_register with list"
diff --git a/gdb/testsuite/gdb.python/py-unwind.exp b/gdb/testsuite/gdb.python/py-unwind.exp
index cdf9034b1bd..798e76525db 100644
--- a/gdb/testsuite/gdb.python/py-unwind.exp
+++ b/gdb/testsuite/gdb.python/py-unwind.exp
@@ -57,3 +57,9 @@ gdb_test_sequence "where"  "Backtrace restored by unwinder" {
 
 # Check that the Python unwinder frames can be flushed / released.
 gdb_test "maint flush register-cache" "Register cache flushed\\." "flush frames"
+
+# Check that invalid register names cause errors.
+gdb_test "python print(add_saved_register_error)" "True" \
+    "add_saved_register error"
+gdb_test "python print(read_register_error)" "True" \
+    "read_register error"
diff --git a/gdb/testsuite/gdb.python/py-unwind.py b/gdb/testsuite/gdb.python/py-unwind.py
index 15dba59f624..319bb630c1c 100644
--- a/gdb/testsuite/gdb.python/py-unwind.py
+++ b/gdb/testsuite/gdb.python/py-unwind.py
@@ -17,6 +17,11 @@ import gdb
 from gdb.unwinder import Unwinder
 
 
+# These are set to test whether invalid register names cause an error.
+add_saved_register_error = False
+read_register_error = False
+
+
 class FrameId(object):
     def __init__(self, sp, pc):
         self._sp = sp
@@ -101,6 +106,12 @@ class TestUnwinder(Unwinder):
             previous_ip = self._read_word(bp + 8)
             previous_sp = bp + 16
 
+            try:
+                pending_frame.read_register("nosuchregister")
+            except ValueError:
+                global read_register_error
+                read_register_error = True
+
             frame_id = FrameId(
                 pending_frame.read_register(TestUnwinder.AMD64_RSP),
                 pending_frame.read_register(TestUnwinder.AMD64_RIP),
@@ -109,6 +120,11 @@ class TestUnwinder(Unwinder):
             unwind_info.add_saved_register(TestUnwinder.AMD64_RBP, previous_bp)
             unwind_info.add_saved_register("rip", previous_ip)
             unwind_info.add_saved_register("rsp", previous_sp)
+            try:
+                unwind_info.add_saved_register("nosuchregister", previous_sp)
+            except ValueError:
+                global add_saved_register_error
+                add_saved_register_error = True
             return unwind_info
         except (gdb.error, RuntimeError):
             return None