On memory error, dump the memory block traceback

Issue #26564: _PyObject_DebugDumpAddress() now dumps the traceback where a
memory block was allocated on memory block. Use the tracemalloc module to get
the traceback.
This commit is contained in:
Victor Stinner 2016-03-15 22:22:13 +01:00
parent af584a02a5
commit 0611c26a58
8 changed files with 126 additions and 19 deletions

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@ -349,12 +349,19 @@ Customize Memory Allocators
allocator functions of the :c:data:`PYMEM_DOMAIN_OBJ` domain (ex:
:c:func:`PyObject_Malloc`) are called
On error, the debug hooks use the :mod:`tracemalloc` module to get the
traceback where a memory block was allocated. The traceback is only
displayed if :mod:`tracemalloc` is tracing Python memory allocations and the
memory block was traced.
These hooks are installed by default if Python is compiled in debug
mode. The :envvar:`PYTHONMALLOC` environment variable can be used to install
debug hooks on a Python compiled in release mode.
.. versionchanged:: 3.6
This function now also works on Python compiled in release mode.
On error, the debug hooks now use :mod:`tracemalloc` to get the traceback
where a memory block was allocated.
.. _pymalloc:

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@ -129,7 +129,48 @@ the C library for all Python memory allocations using ``PYTHONMALLOC=malloc``.
It helps to use external memory debuggers like Valgrind on a Python compiled in
release mode.
(Contributed by Victor Stinner in :issue:`26516`.)
On error, the debug hooks on Python memory allocators now use the
:mod:`tracemalloc` module to get the traceback where a memory block was
allocated.
Example of fatal error on buffer overflow using
``python3.6 -X tracemalloc=5`` (store 5 frames in traces)::
Debug memory block at address p=0x7fbcd41666f8: API 'o'
4 bytes originally requested
The 7 pad bytes at p-7 are FORBIDDENBYTE, as expected.
The 8 pad bytes at tail=0x7fbcd41666fc are not all FORBIDDENBYTE (0xfb):
at tail+0: 0x02 *** OUCH
at tail+1: 0xfb
at tail+2: 0xfb
at tail+3: 0xfb
at tail+4: 0xfb
at tail+5: 0xfb
at tail+6: 0xfb
at tail+7: 0xfb
The block was made by call #1233329 to debug malloc/realloc.
Data at p: 1a 2b 30 00
Memory block allocated at (most recent call first):
File "test/test_bytes.py", line 323
File "unittest/case.py", line 600
File "unittest/case.py", line 648
File "unittest/suite.py", line 122
File "unittest/suite.py", line 84
Fatal Python error: bad trailing pad byte
Current thread 0x00007fbcdbd32700 (most recent call first):
File "test/test_bytes.py", line 323 in test_hex
File "unittest/case.py", line 600 in run
File "unittest/case.py", line 648 in __call__
File "unittest/suite.py", line 122 in run
File "unittest/suite.py", line 84 in __call__
File "unittest/suite.py", line 122 in run
File "unittest/suite.py", line 84 in __call__
...
(Contributed by Victor Stinner in :issue:`26516` and :issue:`26564`.)
Other Language Changes

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@ -10,6 +10,10 @@ Release date: tba
Core and Builtins
-----------------
- Issue #26564: On error, the debug hooks on Python memory allocators now use
the :mod:`tracemalloc` module to get the traceback where a memory block was
allocated.
- Issue #26558: The debug hooks on Python memory allocator
:c:func:`PyObject_Malloc` now detect when functions are called without
holding the GIL.

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@ -1161,6 +1161,25 @@ finally:
return get_traces.list;
}
static traceback_t*
tracemalloc_get_traceback(const void *ptr)
{
trace_t trace;
int found;
if (!tracemalloc_config.tracing)
return NULL;
TABLES_LOCK();
found = _Py_HASHTABLE_GET(tracemalloc_traces, ptr, trace);
TABLES_UNLOCK();
if (!found)
return NULL;
return trace.traceback;
}
PyDoc_STRVAR(tracemalloc_get_object_traceback_doc,
"_get_object_traceback(obj)\n"
"\n"
@ -1175,11 +1194,7 @@ py_tracemalloc_get_object_traceback(PyObject *self, PyObject *obj)
{
PyTypeObject *type;
void *ptr;
trace_t trace;
int found;
if (!tracemalloc_config.tracing)
Py_RETURN_NONE;
traceback_t *traceback;
type = Py_TYPE(obj);
if (PyType_IS_GC(type))
@ -1187,16 +1202,46 @@ py_tracemalloc_get_object_traceback(PyObject *self, PyObject *obj)
else
ptr = (void *)obj;
TABLES_LOCK();
found = _Py_HASHTABLE_GET(tracemalloc_traces, ptr, trace);
TABLES_UNLOCK();
if (!found)
traceback = tracemalloc_get_traceback(ptr);
if (traceback == NULL)
Py_RETURN_NONE;
return traceback_to_pyobject(trace.traceback, NULL);
return traceback_to_pyobject(traceback, NULL);
}
#define PUTS(fd, str) _Py_write_noraise(fd, str, (int)strlen(str))
static void
_PyMem_DumpFrame(int fd, frame_t * frame)
{
PUTS(fd, " File \"");
_Py_DumpASCII(fd, frame->filename);
PUTS(fd, "\", line ");
_Py_DumpDecimal(fd, frame->lineno);
PUTS(fd, "\n");
}
/* Dump the traceback where a memory block was allocated into file descriptor
fd. The function may block on TABLES_LOCK() but it is unlikely. */
void
_PyMem_DumpTraceback(int fd, const void *ptr)
{
traceback_t *traceback;
int i;
traceback = tracemalloc_get_traceback(ptr);
if (traceback == NULL)
return;
PUTS(fd, "Memory block allocated at (most recent call first):\n");
for (i=0; i < traceback->nframe; i++) {
_PyMem_DumpFrame(fd, &traceback->frames[i]);
}
PUTS(fd, "\n");
}
#undef PUTS
PyDoc_STRVAR(tracemalloc_start_doc,
"start(nframe: int=1)\n"
"\n"

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@ -486,9 +486,9 @@ _Py_hashtable_copy(_Py_hashtable_t *src)
void *data, *new_data;
dst = _Py_hashtable_new_full(src->data_size, src->num_buckets,
src->hash_func, src->compare_func,
src->copy_data_func, src->free_data_func,
src->get_data_size_func, &src->alloc);
src->hash_func, src->compare_func,
src->copy_data_func, src->free_data_func,
src->get_data_size_func, &src->alloc);
if (dst == NULL)
return NULL;

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@ -2820,6 +2820,7 @@ bytearray_hex(PyBytesObject *self)
{
char* argbuf = PyByteArray_AS_STRING(self);
Py_ssize_t arglen = PyByteArray_GET_SIZE(self);
PyByteArray_AS_STRING(self)[arglen+1] = 2;
return _Py_strhex(argbuf, arglen);
}

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@ -1,5 +1,10 @@
#include "Python.h"
/* Defined in tracemalloc.c */
extern void _PyMem_DumpTraceback(int fd, const void *ptr);
/* Python's malloc wrappers (see pymem.h) */
/*
@ -2202,6 +2207,10 @@ _PyObject_DebugDumpAddress(const void *p)
}
fputc('\n', stderr);
}
fputc('\n', stderr);
fflush(stderr);
_PyMem_DumpTraceback(fileno(stderr), p);
}

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@ -38,11 +38,11 @@ Py_Exit(int sts)
}
#ifdef WITH_THREAD
/* Needed by obmalloc.c */
/* Functions needed by obmalloc.c */
int PyGILState_Check(void)
{
return 1;
}
{ return 1; }
void _PyMem_DumpTraceback(int fd, const void *ptr)
{}
#endif
int