Re: [PATCH] Add Frame.read_register to Python API

[Alexander Smundak <asmundak@google.com>]

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On Mon, Jun 9, 2014 at 12:25 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> When 2 changes are in the same node, write them one after the other,
> and have only one "(Node Name)" thing.
Done.

>> +* Python Scripting
>> +  Access frame registers
>
> This is an incomplete sentence.  I guess you meant something like
>   You can now access frame registers from Python scripts.
Done.

>> +Return the value of @var{register} in this frame. The @var{register}
>> +argument must be a string (e.g., 'rsp' or 'r1'), or a register number.
>                                     ^^^^^^^^^^^^^
> These should be in @code instead of quotes.
Added the code but retained the quotes, because it's string literal.

>> +Returns @code{Gdb.Value} object.
>           ^
> "a" missing here.
Done.
Here it is again:

The ability to read registers is needed to use Frame Filter API to
display the frames created by JIT compilers.

gdb/Changelog
2014-06-09  Sasha Smundak  <asmundak@google.com>

* python/py-frame.c (frapy_read_register): New function.

2014-06-09  Sasha Smundak  <asmundak@google.com>

* python.texi (Writing a Frame Filter): Fix example code.
(Frames in Python): Fix reference in find_sal description.
Add read_register description.

2014-06-09  Sasha Smundak  <asmundak@google.com>

* gdb.python/py-frame.exp: Test Frame.read_register.

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diff --git a/gdb/NEWS b/gdb/NEWS
index 1397e8b..3db458b 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,9 @@
 
 *** Changes since GDB 7.7
 
+* Python Scripting
+  You can now access frame registers from Python scripts.
+
 * New command line options
 
 -D data-directory
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index 4688783..14564eb 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -2046,9 +2046,10 @@ class InlinedFrameDecorator(FrameDecorator):
 
     def __init__(self, fobj):
         super(InlinedFrameDecorator, self).__init__(fobj)
+        self.fobj = fobj
 
     def function(self):
-        frame = fobj.inferior_frame()
+        frame = self.fobj.inferior_frame()
         name = str(frame.name())
 
         if frame.type() == gdb.INLINE_FRAME:
@@ -3585,10 +3586,16 @@ Return the frame called by this frame.
 @end defun
 
 @defun Frame.find_sal ()
-Return the frame's symtab and line object.
+Return the frame's @code{gdb.Symtab_and_line} object.
 @xref{Symbol Tables In Python}.
 @end defun
 
+@defun Frame.read_register (register)
+Return the value of @var{register} in this frame. The @var{register}
+argument must be a string (e.g., @code{'rsp'} or @code{'r1'}), or a
+register number. Returns a @code{Gdb.Value} object.
+@end defun
+
 @defun Frame.read_var (variable @r{[}, block@r{]})
 Return the value of @var{variable} in this frame.  If the optional
 argument @var{block} is provided, search for the variable from that
diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
index 77077d3..4375541 100644
--- a/gdb/python/py-frame.c
+++ b/gdb/python/py-frame.c
@@ -28,6 +28,7 @@
 #include "python-internal.h"
 #include "symfile.h"
 #include "objfiles.h"
+#include "user-regs.h"
 
 typedef struct {
   PyObject_HEAD
@@ -235,6 +236,38 @@ frapy_pc (PyObject *self, PyObject *args)
   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)
+{
+  struct frame_info *frame;
+  volatile struct gdb_exception except;
+  int regnum = -1;
+  struct value *val = NULL;
+  TRY_CATCH (except, RETURN_MASK_ALL)
+    {
+      FRAPY_REQUIRE_VALID (self, frame);
+      if (!PyArg_ParseTuple (args, "i", &regnum))
+	{
+	  const char *regnum_str;
+	  PyErr_Clear();  /* Clear PyArg_ParseTuple failure above.  */
+	  if (PyArg_ParseTuple (args, "s", &regnum_str))
+	    {
+	      regnum = user_reg_map_name_to_regnum (get_frame_arch (frame),
+						    regnum_str,
+						    strlen (regnum_str));
+	    }
+	}
+      if (regnum >= 0)
+	{
+	  val = value_of_register (regnum, frame);
+	}
+    }
+  GDB_PY_HANDLE_EXCEPTION (except);
+  return val ? value_to_value_object (val) : NULL;
+}
+
 /* Implementation of gdb.Frame.block (self) -> gdb.Block.
    Returns the frame's code block.  */
 
@@ -674,6 +707,9 @@ 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) -> 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." },
diff --git a/gdb/testsuite/gdb.python/py-frame.exp b/gdb/testsuite/gdb.python/py-frame.exp
index 3517824..6034fff 100644
--- a/gdb/testsuite/gdb.python/py-frame.exp
+++ b/gdb/testsuite/gdb.python/py-frame.exp
@@ -94,3 +94,16 @@ gdb_test "python print ('result = %s' % f0.read_var ('variable_which_surely_does
 gdb_test "python print ('result = %s' % f0.read_var ('a'))" " = 1" "test Frame.read_var - success"
 
 gdb_test "python print ('result = %s' % (gdb.selected_frame () == f1))" " = True" "test gdb.selected_frame"
+
+# Can read SP register.
+gdb_test "python print ('result = %s' % f0.read_register('sp'))" \
+  " = 0x\[0-9a-fA-F\]+" \
+  "test Frame.read_register(fp)"
+# PC value obtained via read_register is as expected.
+gdb_test "python print ('result = %s' % (f0.read_register('pc').cast(gdb.lookup_type('unsigned long')) == f0.pc()))" \
+  "True" \
+  "test Frame.read_register(pc)"
+# On x86-64, PC is register 16.
+gdb_test "python print ('result = %s' % ((f0.architecture().name() != 'i386:x86-64') or f0.read_register('pc') == f0.read_register(16)))" \
+  "True" \
+  "test Frame.read_register(regnum)"