From d11916aa89c43071c08c1f9b4550a01f8eec78e3 Mon Sep 17 00:00:00 2001 From: Sasha Smundak Date: Wed, 1 Apr 2015 11:49:12 -0700 Subject: Add support for writing unwinders in Python. gdb/ChangeLog: * Makefile.in (SUBDIR_PYTHON_OBJS): Add py-unwind.o. (SUBDIR_PYTHON_SRCS): Add py-unwind.c. (py-unwind.o): New recipe. * NEWS: mention Python frame unwinding. * data-directory/Makefile.in (PYTHON_FILE_LIST): Add gdb/unwinder.py and gdb/command/unwinder.py * python/lib/gdb/__init__.py (packages): Add frame_unwinders list. (execute_unwinders): New function. * python/lib/gdb/command/unwinders.py: New file. * python/lib/gdb/unwinder.py: New file. * python/py-objfile.c (objfile_object): Add frame_unwinders field. (objfpy_dealloc): Decrement frame_unwinders reference count. (objfpy_initialize): Create frame_unwinders list. (objfpy_get_frame_unwinders): New function. (objfpy_set_frame_unwinders): Ditto. (objfile_getset): Add frame_unwinders attribute to Objfile. * python/py-progspace.c (pspace_object): Add frame_unwinders field. (pspy_dealloc): Decrement frame_unwinders reference count. (pspy_initialize): Create frame_unwinders list. (pspy_get_frame_unwinders): New function. (pspy_set_frame_unwinders): Ditto. (pspy_getset): Add frame_unwinders attribute to gdb.Progspace. * python/py-unwind.c: New file. * python/python-internal.h (pspy_get_name_unwinders): New prototype. (objpy_get_frame_unwinders): New prototype. (gdbpy_initialize_unwind): New prototype. * python/python.c (gdbpy_apply_type_printers): Call gdbpy_initialize_unwind. gdb/doc/ChangeLog: * doc/python.texi (Writing a Frame Unwinder in Python): Add section. gdb/testsuite/ChangeLog: * gdb.python/py-unwind-maint.c: New file. * gdb.python/py-unwind-maint.exp: New test. * gdb.python/py-unwind-maint.py: New file. * gdb.python/py-unwind.c: New file. * gdb.python/py-unwind.exp: New test. * gdb.python/py-unwind.py: New test. --- gdb/testsuite/gdb.python/py-unwind.py | 99 +++++++++++++++++++++++++++++++++++ 1 file changed, 99 insertions(+) create mode 100644 gdb/testsuite/gdb.python/py-unwind.py (limited to 'gdb/testsuite/gdb.python/py-unwind.py') diff --git a/gdb/testsuite/gdb.python/py-unwind.py b/gdb/testsuite/gdb.python/py-unwind.py new file mode 100644 index 0000000..6257fd7 --- /dev/null +++ b/gdb/testsuite/gdb.python/py-unwind.py @@ -0,0 +1,99 @@ +# Copyright (C) 2015 Free Software Foundation, Inc. + +# 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 . + +import gdb +from gdb.unwinder import Unwinder + +class FrameId(object): + + def __init__(self, sp, pc): + self._sp = sp + self._pc = pc + + @property + def sp(self): + return self._sp + + @property + def pc(self): + return self._pc + + +class TestUnwinder(Unwinder): + AMD64_RBP = 6 + AMD64_RSP = 7 + AMD64_RIP = 16 + + def __init__(self): + Unwinder.__init__(self, "test unwinder") + self.char_ptr_t = gdb.lookup_type("unsigned char").pointer() + self.char_ptr_ptr_t = self.char_ptr_t.pointer() + + def _read_word(self, address): + return address.cast(self.char_ptr_ptr_t).dereference() + + def __call__(self, pending_frame): + """Test unwinder written in Python. + + This unwinder can unwind the frames that have been deliberately + corrupted in a specific way (functions in the accompanying + py-unwind.c file do that.) + This code is only on AMD64. + On AMD64 $RBP points to the innermost frame (unless the code + was compiled with -fomit-frame-pointer), which contains the + address of the previous frame at offset 0. The functions + deliberately corrupt their frames as follows: + Before After + Corruption: Corruption: + +--------------+ +--------------+ + RBP-8 | | | Previous RBP | + +--------------+ +--------------+ + RBP + Previous RBP | | RBP | + +--------------+ +--------------+ + RBP+8 | Return RIP | | Return RIP | + +--------------+ +--------------+ + Old SP | | | | + + This unwinder recognizes the corrupt frames by checking that + *RBP == RBP, and restores previous RBP from the word above it. + """ + try: + # NOTE: the registers in Unwinder API can be referenced + # either by name or by number. The code below uses both + # to achieve more coverage. + bp = pending_frame.read_register("rbp").cast(self.char_ptr_t) + if self._read_word(bp) != bp: + return None + # Found the frame that the test program has corrupted for us. + # The correct BP for the outer frame has been saved one word + # above, previous IP and SP are at the expected places. + previous_bp = self._read_word(bp - 8) + previous_ip = self._read_word(bp + 8) + previous_sp = bp + 16 + + frame_id = FrameId( + pending_frame.read_register(TestUnwinder.AMD64_RSP), + pending_frame.read_register(TestUnwinder.AMD64_RIP)) + unwind_info = pending_frame.create_unwind_info(frame_id) + 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) + return unwind_info + except (gdb.error, RuntimeError): + return None + +gdb.unwinder.register_unwinder(None, TestUnwinder(), True) +print("Python script imported") -- cgit v1.1