binutils-gdb/gdb/python/py-frame.c
Andrew Burgess 43d5901ded gdb/python: make more use of RegisterDescriptors
This commit unifies all of the Python register lookup code (used by
Frame.read_register, PendingFrame.read_register, and
gdb.UnwindInfo.add_saved_register), and adds support for using a
gdb.RegisterDescriptor for register lookup.

Currently the register unwind code (PendingFrame and UnwindInfo) allow
registers to be looked up either by name, or by GDB's internal
number.  I suspect the number was added for performance reasons, when
unwinding we don't want to repeatedly map from name to number for
every unwind.  However, this kind-of sucks, it means Python scripts
could include GDB's internal register numbers, and if we ever change
this numbering in the future users scripts will break in unexpected
ways.

Meanwhile, the Frame.read_register method only supports accessing
registers using a string, the register name.

This commit unifies all of the register to register-number lookup code
in our Python bindings, and adds a third choice into the mix, the use
of gdb.RegisterDescriptor.

The register descriptors can be looked up by name, but once looked up,
they contain GDB's register number, and so provide all of the
performance benefits of using a register number directly.  However, as
they are looked up by name we are no longer tightly binding the Python
API to GDB's internal numbering scheme.

As we may already have scripts in the wild that are using the register
numbers directly I have kept support for this in the API, but I have
listed this method last in the manual, and I have tried to stress that
this is NOT a good method to use and that users should use either a
string or register descriptor approach.

After this commit all existing Python code should function as before,
but users now have new options for how to identify registers.

gdb/ChangeLog:

	* python/py-frame.c: Remove 'user-regs.h' include.
	(frapy_read_register): Rewrite to make use of
	gdbpy_parse_register_id.
	* python/py-registers.c (gdbpy_parse_register_id): New function,
	moved here from python/py-unwind.c.  Updated the return type, and
	also accepts register descriptor objects.
	* python/py-unwind.c: Remove 'user-regs.h' include.
	(pyuw_parse_register_id): Moved to python/py-registers.c.
	(unwind_infopy_add_saved_register): Update to use
	gdbpy_parse_register_id.
	(pending_framepy_read_register): Likewise.
	* python/python-internal.h (gdbpy_parse_register_id): Declare.

gdb/testsuite/ChangeLog:

	* gdb.python/py-unwind.py: Update to make use of a register
	descriptor.

gdb/doc/ChangeLog:

	* python.texi (Unwinding Frames in Python): Update descriptions
	for PendingFrame.read_register and
	gdb.UnwindInfo.add_saved_register.
	(Frames In Python): Update description of Frame.read_register.
2020-07-28 10:27:54 +01:00

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/* Python interface to stack frames
Copyright (C) 2008-2020 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "defs.h"
#include "charset.h"
#include "block.h"
#include "frame.h"
#include "symtab.h"
#include "stack.h"
#include "value.h"
#include "python-internal.h"
#include "symfile.h"
#include "objfiles.h"
typedef struct {
PyObject_HEAD
struct frame_id frame_id;
struct gdbarch *gdbarch;
/* Marks that the FRAME_ID member actually holds the ID of the frame next
to this, and not this frames' ID itself. This is a hack to permit Python
frame objects which represent invalid frames (i.e., the last frame_info
in a corrupt stack). The problem arises from the fact that this code
relies on FRAME_ID to uniquely identify a frame, which is not always true
for the last "frame" in a corrupt stack (it can have a null ID, or the same
ID as the previous frame). Whenever get_prev_frame returns NULL, we
record the frame_id of the next frame and set FRAME_ID_IS_NEXT to 1. */
int frame_id_is_next;
} frame_object;
/* Require a valid frame. This must be called inside a TRY_CATCH, or
another context in which a gdb exception is allowed. */
#define FRAPY_REQUIRE_VALID(frame_obj, frame) \
do { \
frame = frame_object_to_frame_info (frame_obj); \
if (frame == NULL) \
error (_("Frame is invalid.")); \
} while (0)
/* Returns the frame_info object corresponding to the given Python Frame
object. If the frame doesn't exist anymore (the frame id doesn't
correspond to any frame in the inferior), returns NULL. */
struct frame_info *
frame_object_to_frame_info (PyObject *obj)
{
frame_object *frame_obj = (frame_object *) obj;
struct frame_info *frame;
frame = frame_find_by_id (frame_obj->frame_id);
if (frame == NULL)
return NULL;
if (frame_obj->frame_id_is_next)
frame = get_prev_frame (frame);
return frame;
}
/* Called by the Python interpreter to obtain string representation
of the object. */
static PyObject *
frapy_str (PyObject *self)
{
string_file strfile;
fprint_frame_id (&strfile, ((frame_object *) self)->frame_id);
return PyString_FromString (strfile.c_str ());
}
/* Implementation of gdb.Frame.is_valid (self) -> Boolean.
Returns True if the frame corresponding to the frame_id of this
object still exists in the inferior. */
static PyObject *
frapy_is_valid (PyObject *self, PyObject *args)
{
struct frame_info *frame = NULL;
try
{
frame = frame_object_to_frame_info (self);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
if (frame == NULL)
Py_RETURN_FALSE;
Py_RETURN_TRUE;
}
/* Implementation of gdb.Frame.name (self) -> String.
Returns the name of the function corresponding to this frame. */
static PyObject *
frapy_name (PyObject *self, PyObject *args)
{
struct frame_info *frame;
gdb::unique_xmalloc_ptr<char> name;
enum language lang;
PyObject *result;
try
{
FRAPY_REQUIRE_VALID (self, frame);
name = find_frame_funname (frame, &lang, NULL);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
if (name)
{
result = PyUnicode_Decode (name.get (), strlen (name.get ()),
host_charset (), NULL);
}
else
{
result = Py_None;
Py_INCREF (Py_None);
}
return result;
}
/* Implementation of gdb.Frame.type (self) -> Integer.
Returns the frame type, namely one of the gdb.*_FRAME constants. */
static PyObject *
frapy_type (PyObject *self, PyObject *args)
{
struct frame_info *frame;
enum frame_type type = NORMAL_FRAME;/* Initialize to appease gcc warning. */
try
{
FRAPY_REQUIRE_VALID (self, frame);
type = get_frame_type (frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return PyInt_FromLong (type);
}
/* Implementation of gdb.Frame.architecture (self) -> gdb.Architecture.
Returns the frame's architecture as a gdb.Architecture object. */
static PyObject *
frapy_arch (PyObject *self, PyObject *args)
{
struct frame_info *frame = NULL; /* Initialize to appease gcc warning. */
frame_object *obj = (frame_object *) self;
try
{
FRAPY_REQUIRE_VALID (self, frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return gdbarch_to_arch_object (obj->gdbarch);
}
/* Implementation of gdb.Frame.unwind_stop_reason (self) -> Integer.
Returns one of the gdb.FRAME_UNWIND_* constants. */
static PyObject *
frapy_unwind_stop_reason (PyObject *self, PyObject *args)
{
struct frame_info *frame = NULL; /* Initialize to appease gcc warning. */
enum unwind_stop_reason stop_reason;
try
{
FRAPY_REQUIRE_VALID (self, frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
stop_reason = get_frame_unwind_stop_reason (frame);
return PyInt_FromLong (stop_reason);
}
/* Implementation of gdb.Frame.pc (self) -> Long.
Returns the frame's resume address. */
static PyObject *
frapy_pc (PyObject *self, PyObject *args)
{
CORE_ADDR pc = 0; /* Initialize to appease gcc warning. */
struct frame_info *frame;
try
{
FRAPY_REQUIRE_VALID (self, frame);
pc = get_frame_pc (frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return gdb_py_long_from_ulongest (pc);
}
/* Implementation of gdb.Frame.read_register (self, register) -> gdb.Value.
Returns the value of a register in this frame. */
static PyObject *
frapy_read_register (PyObject *self, PyObject *args)
{
PyObject *pyo_reg_id;
struct value *val = NULL;
if (!PyArg_UnpackTuple (args, "read_register", 1, 1, &pyo_reg_id))
return NULL;
try
{
struct frame_info *frame;
int regnum;
FRAPY_REQUIRE_VALID (self, frame);
if (!gdbpy_parse_register_id (get_frame_arch (frame), pyo_reg_id,
&regnum))
{
PyErr_SetString (PyExc_ValueError, "Bad register");
return NULL;
}
gdb_assert (regnum >= 0);
val = value_of_register (regnum, frame);
if (val == NULL)
PyErr_SetString (PyExc_ValueError, _("Can't read register."));
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return val == NULL ? NULL : value_to_value_object (val);
}
/* Implementation of gdb.Frame.block (self) -> gdb.Block.
Returns the frame's code block. */
static PyObject *
frapy_block (PyObject *self, PyObject *args)
{
struct frame_info *frame;
const struct block *block = NULL, *fn_block;
try
{
FRAPY_REQUIRE_VALID (self, frame);
block = get_frame_block (frame, NULL);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
for (fn_block = block;
fn_block != NULL && BLOCK_FUNCTION (fn_block) == NULL;
fn_block = BLOCK_SUPERBLOCK (fn_block))
;
if (block == NULL || fn_block == NULL || BLOCK_FUNCTION (fn_block) == NULL)
{
PyErr_SetString (PyExc_RuntimeError,
_("Cannot locate block for frame."));
return NULL;
}
if (block)
{
return block_to_block_object
(block, symbol_objfile (BLOCK_FUNCTION (fn_block)));
}
Py_RETURN_NONE;
}
/* Implementation of gdb.Frame.function (self) -> gdb.Symbol.
Returns the symbol for the function corresponding to this frame. */
static PyObject *
frapy_function (PyObject *self, PyObject *args)
{
struct symbol *sym = NULL;
struct frame_info *frame;
try
{
enum language funlang;
FRAPY_REQUIRE_VALID (self, frame);
gdb::unique_xmalloc_ptr<char> funname
= find_frame_funname (frame, &funlang, &sym);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
if (sym)
return symbol_to_symbol_object (sym);
Py_RETURN_NONE;
}
/* Convert a frame_info struct to a Python Frame object.
Sets a Python exception and returns NULL on error. */
PyObject *
frame_info_to_frame_object (struct frame_info *frame)
{
gdbpy_ref<frame_object> frame_obj (PyObject_New (frame_object,
&frame_object_type));
if (frame_obj == NULL)
return NULL;
try
{
/* Try to get the previous frame, to determine if this is the last frame
in a corrupt stack. If so, we need to store the frame_id of the next
frame and not of this one (which is possibly invalid). */
if (get_prev_frame (frame) == NULL
&& get_frame_unwind_stop_reason (frame) != UNWIND_NO_REASON
&& get_next_frame (frame) != NULL)
{
frame_obj->frame_id = get_frame_id (get_next_frame (frame));
frame_obj->frame_id_is_next = 1;
}
else
{
frame_obj->frame_id = get_frame_id (frame);
frame_obj->frame_id_is_next = 0;
}
frame_obj->gdbarch = get_frame_arch (frame);
}
catch (const gdb_exception &except)
{
gdbpy_convert_exception (except);
return NULL;
}
return (PyObject *) frame_obj.release ();
}
/* Implementation of gdb.Frame.older (self) -> gdb.Frame.
Returns the frame immediately older (outer) to this frame, or None if
there isn't one. */
static PyObject *
frapy_older (PyObject *self, PyObject *args)
{
struct frame_info *frame, *prev = NULL;
PyObject *prev_obj = NULL; /* Initialize to appease gcc warning. */
try
{
FRAPY_REQUIRE_VALID (self, frame);
prev = get_prev_frame (frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
if (prev)
prev_obj = frame_info_to_frame_object (prev);
else
{
Py_INCREF (Py_None);
prev_obj = Py_None;
}
return prev_obj;
}
/* Implementation of gdb.Frame.newer (self) -> gdb.Frame.
Returns the frame immediately newer (inner) to this frame, or None if
there isn't one. */
static PyObject *
frapy_newer (PyObject *self, PyObject *args)
{
struct frame_info *frame, *next = NULL;
PyObject *next_obj = NULL; /* Initialize to appease gcc warning. */
try
{
FRAPY_REQUIRE_VALID (self, frame);
next = get_next_frame (frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
if (next)
next_obj = frame_info_to_frame_object (next);
else
{
Py_INCREF (Py_None);
next_obj = Py_None;
}
return next_obj;
}
/* Implementation of gdb.Frame.find_sal (self) -> gdb.Symtab_and_line.
Returns the frame's symtab and line. */
static PyObject *
frapy_find_sal (PyObject *self, PyObject *args)
{
struct frame_info *frame;
PyObject *sal_obj = NULL; /* Initialize to appease gcc warning. */
try
{
FRAPY_REQUIRE_VALID (self, frame);
symtab_and_line sal = find_frame_sal (frame);
sal_obj = symtab_and_line_to_sal_object (sal);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return sal_obj;
}
/* Implementation of gdb.Frame.read_var_value (self, variable,
[block]) -> gdb.Value. If the optional block argument is provided
start the search from that block, otherwise search from the frame's
current block (determined by examining the resume address of the
frame). The variable argument must be a string or an instance of a
gdb.Symbol. The block argument must be an instance of gdb.Block. Returns
NULL on error, with a python exception set. */
static PyObject *
frapy_read_var (PyObject *self, PyObject *args)
{
struct frame_info *frame;
PyObject *sym_obj, *block_obj = NULL;
struct symbol *var = NULL; /* gcc-4.3.2 false warning. */
const struct block *block = NULL;
struct value *val = NULL;
if (!PyArg_ParseTuple (args, "O|O", &sym_obj, &block_obj))
return NULL;
if (PyObject_TypeCheck (sym_obj, &symbol_object_type))
var = symbol_object_to_symbol (sym_obj);
else if (gdbpy_is_string (sym_obj))
{
gdb::unique_xmalloc_ptr<char>
var_name (python_string_to_target_string (sym_obj));
if (!var_name)
return NULL;
if (block_obj)
{
block = block_object_to_block (block_obj);
if (!block)
{
PyErr_SetString (PyExc_RuntimeError,
_("Second argument must be block."));
return NULL;
}
}
try
{
struct block_symbol lookup_sym;
FRAPY_REQUIRE_VALID (self, frame);
if (!block)
block = get_frame_block (frame, NULL);
lookup_sym = lookup_symbol (var_name.get (), block, VAR_DOMAIN, NULL);
var = lookup_sym.symbol;
block = lookup_sym.block;
}
catch (const gdb_exception &except)
{
gdbpy_convert_exception (except);
return NULL;
}
if (!var)
{
PyErr_Format (PyExc_ValueError,
_("Variable '%s' not found."), var_name.get ());
return NULL;
}
}
else
{
PyErr_SetString (PyExc_TypeError,
_("Argument must be a symbol or string."));
return NULL;
}
try
{
FRAPY_REQUIRE_VALID (self, frame);
val = read_var_value (var, block, frame);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return value_to_value_object (val);
}
/* Select this frame. */
static PyObject *
frapy_select (PyObject *self, PyObject *args)
{
struct frame_info *fi;
try
{
FRAPY_REQUIRE_VALID (self, fi);
select_frame (fi);
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
Py_RETURN_NONE;
}
/* Implementation of gdb.newest_frame () -> gdb.Frame.
Returns the newest frame object. */
PyObject *
gdbpy_newest_frame (PyObject *self, PyObject *args)
{
struct frame_info *frame = NULL;
try
{
frame = get_current_frame ();
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return frame_info_to_frame_object (frame);
}
/* Implementation of gdb.selected_frame () -> gdb.Frame.
Returns the selected frame object. */
PyObject *
gdbpy_selected_frame (PyObject *self, PyObject *args)
{
struct frame_info *frame = NULL;
try
{
frame = get_selected_frame ("No frame is currently selected.");
}
catch (const gdb_exception &except)
{
GDB_PY_HANDLE_EXCEPTION (except);
}
return frame_info_to_frame_object (frame);
}
/* Implementation of gdb.stop_reason_string (Integer) -> String.
Return a string explaining the unwind stop reason. */
PyObject *
gdbpy_frame_stop_reason_string (PyObject *self, PyObject *args)
{
int reason;
const char *str;
if (!PyArg_ParseTuple (args, "i", &reason))
return NULL;
if (reason < UNWIND_FIRST || reason > UNWIND_LAST)
{
PyErr_SetString (PyExc_ValueError,
_("Invalid frame stop reason."));
return NULL;
}
str = unwind_stop_reason_to_string ((enum unwind_stop_reason) reason);
return PyUnicode_Decode (str, strlen (str), host_charset (), NULL);
}
/* Implements the equality comparison for Frame objects.
All other comparison operators will throw a TypeError Python exception,
as they aren't valid for frames. */
static PyObject *
frapy_richcompare (PyObject *self, PyObject *other, int op)
{
int result;
if (!PyObject_TypeCheck (other, &frame_object_type)
|| (op != Py_EQ && op != Py_NE))
{
Py_INCREF (Py_NotImplemented);
return Py_NotImplemented;
}
if (frame_id_eq (((frame_object *) self)->frame_id,
((frame_object *) other)->frame_id))
result = Py_EQ;
else
result = Py_NE;
if (op == result)
Py_RETURN_TRUE;
Py_RETURN_FALSE;
}
/* Sets up the Frame API in the gdb module. */
int
gdbpy_initialize_frames (void)
{
frame_object_type.tp_new = PyType_GenericNew;
if (PyType_Ready (&frame_object_type) < 0)
return -1;
/* Note: These would probably be best exposed as class attributes of
Frame, but I don't know how to do it except by messing with the
type's dictionary. That seems too messy. */
if (PyModule_AddIntConstant (gdb_module, "NORMAL_FRAME", NORMAL_FRAME) < 0
|| PyModule_AddIntConstant (gdb_module, "DUMMY_FRAME", DUMMY_FRAME) < 0
|| PyModule_AddIntConstant (gdb_module, "INLINE_FRAME", INLINE_FRAME) < 0
|| PyModule_AddIntConstant (gdb_module, "TAILCALL_FRAME",
TAILCALL_FRAME) < 0
|| PyModule_AddIntConstant (gdb_module, "SIGTRAMP_FRAME",
SIGTRAMP_FRAME) < 0
|| PyModule_AddIntConstant (gdb_module, "ARCH_FRAME", ARCH_FRAME) < 0
|| PyModule_AddIntConstant (gdb_module, "SENTINEL_FRAME",
SENTINEL_FRAME) < 0)
return -1;
#define SET(name, description) \
if (PyModule_AddIntConstant (gdb_module, "FRAME_"#name, name) < 0) \
return -1;
#include "unwind_stop_reasons.def"
#undef SET
return gdb_pymodule_addobject (gdb_module, "Frame",
(PyObject *) &frame_object_type);
}
static PyMethodDef frame_object_methods[] = {
{ "is_valid", frapy_is_valid, METH_NOARGS,
"is_valid () -> Boolean.\n\
Return true if this frame is valid, false if not." },
{ "name", frapy_name, METH_NOARGS,
"name () -> String.\n\
Return the function name of the frame, or None if it can't be determined." },
{ "type", frapy_type, METH_NOARGS,
"type () -> Integer.\n\
Return the type of the frame." },
{ "architecture", frapy_arch, METH_NOARGS,
"architecture () -> gdb.Architecture.\n\
Return the architecture of the frame." },
{ "unwind_stop_reason", frapy_unwind_stop_reason, METH_NOARGS,
"unwind_stop_reason () -> Integer.\n\
Return the reason why it's not possible to find frames older than this." },
{ "pc", frapy_pc, METH_NOARGS,
"pc () -> Long.\n\
Return the frame's resume address." },
{ "read_register", frapy_read_register, METH_VARARGS,
"read_register (register_name) -> gdb.Value\n\
Return the value of the register in the frame." },
{ "block", frapy_block, METH_NOARGS,
"block () -> gdb.Block.\n\
Return the frame's code block." },
{ "function", frapy_function, METH_NOARGS,
"function () -> gdb.Symbol.\n\
Returns the symbol for the function corresponding to this frame." },
{ "older", frapy_older, METH_NOARGS,
"older () -> gdb.Frame.\n\
Return the frame that called this frame." },
{ "newer", frapy_newer, METH_NOARGS,
"newer () -> gdb.Frame.\n\
Return the frame called by this frame." },
{ "find_sal", frapy_find_sal, METH_NOARGS,
"find_sal () -> gdb.Symtab_and_line.\n\
Return the frame's symtab and line." },
{ "read_var", frapy_read_var, METH_VARARGS,
"read_var (variable) -> gdb.Value.\n\
Return the value of the variable in this frame." },
{ "select", frapy_select, METH_NOARGS,
"Select this frame as the user's current frame." },
{NULL} /* Sentinel */
};
PyTypeObject frame_object_type = {
PyVarObject_HEAD_INIT (NULL, 0)
"gdb.Frame", /* tp_name */
sizeof (frame_object), /* tp_basicsize */
0, /* tp_itemsize */
0, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_compare */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
frapy_str, /* tp_str */
0, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT, /* tp_flags */
"GDB frame object", /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
frapy_richcompare, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
frame_object_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
};