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python: clean up exception handling
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Python uses exceptions in a similar fashion to how C APIs use errno.  It's
important use an appropriate exception so that exception handling can
key off it properly.

This patch updates the python interface to provide more detailed exceptions
through better choice of exception types and its own kdump_err_str interface.

We also pass exceptions up untouched and return NULL instead of Py_None where
necessary.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
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@jeffmahoney
jeffmahoney committed Feb 9, 2016
1 parent aaa323e commit 9488340
Showing 1 changed file with 59 additions and 36 deletions.
95 changes: 59 additions & 36 deletions python/kdumpfile.c
View file
Expand Up @@ -62,16 +62,18 @@ kdumpfile_new (PyTypeObject *type, PyObject *args, PyObject *kw)

self->ctx = kdump_init();

if (! self->ctx) {
PyErr_SetString(PyExc_RuntimeError, "Cannot kdump_init()");
if (!self->ctx) {
PyErr_SetString(PyExc_MemoryError,
"Could not create kdump context");
Py_XDECREF(self);
Py_XDECREF(fo);
self = NULL;
goto end;
}

if (kdump_set_fd(self->ctx, fd)) {
PyErr_SetString(PyExc_RuntimeError, "Cannot kdump_set_fd()");
PyErr_Format(PyExc_RuntimeError, "kdump_set_fd failed: %s",
kdump_err_str(self->ctx));
Py_XDECREF(self);
Py_XDECREF(fo);
self = NULL;
Expand Down Expand Up @@ -101,35 +103,59 @@ kdumpfile_dealloc(PyObject *_self)
self->ob_type->tp_free((PyObject*)self);
}

static PyObject *exception_map(kdump_status status)
{
switch (status) {
case kdump_ok: return NULL;
case kdump_syserr: return PyExc_SystemError;
case kdump_unsupported: return PyExc_TypeError;
case kdump_nodata: return PyExc_IndexError;
case kdump_dataerr: return PyExc_IOError;
case kdump_invalid: return PyExc_IOError;
case kdump_nokey: return PyExc_KeyError;
case kdump_eof: return PyExc_EOFError;
default: return PyExc_RuntimeError;
};
}

static PyObject *kdumpfile_read (PyObject *_self, PyObject *args, PyObject *kw)
{
kdumpfile_object *self = (kdumpfile_object*)_self;
PyObject *obj;
kdump_paddr_t addr;
kdump_status status;
int addrspace;
unsigned long size;
static char *keywords[] = {"addrspace", "address", "size", NULL};
size_t r;

if (! PyArg_ParseTupleAndKeywords(args, kw, "ikk:", keywords, &addrspace, &addr, &size)) {
Py_RETURN_NONE;
}
if (!PyArg_ParseTupleAndKeywords(args, kw, "ikk:", keywords,
&addrspace, &addr, &size))
return NULL;

if (! size) {
PyErr_SetString(PyExc_RuntimeError, "Zero size");
if (!size) {
PyErr_SetString(PyExc_ValueError, "Zero size buffer");
return NULL;
}

obj = PyByteArray_FromStringAndSize(0, size);
obj = PyByteArray_FromStringAndSize(NULL, size);
if (!obj)
return NULL;

if (! obj) {
PyErr_SetString(PyExc_RuntimeError, "Cannot create buffer");
r = size;
status = kdump_readp(self->ctx, addrspace, addr,
PyByteArray_AS_STRING(obj), &r);
if (status != kdump_ok) {
Py_XDECREF(obj);
PyErr_Format(exception_map(status), "Cannot read: %s",
kdump_err_str(self->ctx));
return NULL;
}

if ((r = kdump_read(self->ctx, addrspace, addr, PyByteArray_AS_STRING(obj), size)) != size) {
if (r != size) {
Py_XDECREF(obj);
PyErr_SetString(PyExc_RuntimeError, "Cannot read");
PyErr_Format(PyExc_IOError, "Cannot read: %s",
kdump_err_str(self->ctx));
return NULL;
}
return obj;
Expand All @@ -146,7 +172,7 @@ static int kdumpfile_dir2obj_it(void *data, const char *key, const struct kdump_
{
struct attr2obj_data *cb_data = (struct attr2obj_data *)data;
PyObject *v = kdumpfile_attr2obj(cb_data->ctx, valp);
if (! v) return 1;
if (!v) return 1;
PyDict_SetItem(cb_data->dict, PyString_FromString(key), v);
return 0;
}
Expand All @@ -163,10 +189,12 @@ static PyObject *kdumpfile_dir2obj(kdump_ctx *ctx, const struct kdump_attr *attr
return NULL;
}

/* This dictionary will be mutable. Is that intended? */
return cb_data.dict;
}

static PyObject *kdumpfile_attr2obj(kdump_ctx *ctx, const struct kdump_attr *attr)
static PyObject *kdumpfile_attr2obj(kdump_ctx *ctx,
const struct kdump_attr *attr)
{
switch (attr->type) {
case kdump_number:
Expand All @@ -177,25 +205,26 @@ static PyObject *kdumpfile_attr2obj(kdump_ctx *ctx, const struct kdump_attr *att
return PyString_FromString(attr->val.string);
case kdump_directory:
return kdumpfile_dir2obj(ctx, attr);
default:
PyErr_SetString(PyExc_RuntimeError, "Unhandled attr type");
return NULL;
}

PyErr_Format(PyExc_TypeError, "Unhandled attr type (%d)", attr->type);
return NULL;
}

static PyObject *kdumpfile_getattr(PyObject *_self, PyObject *args, PyObject *kw)
static PyObject *kdumpfile_getattr(PyObject *_self, PyObject *args,
PyObject *kw)
{
kdumpfile_object *self = (kdumpfile_object*)_self;
static char *keywords[] = {"name", NULL};
struct kdump_attr attr;
const char *name;

if (! PyArg_ParseTupleAndKeywords(args, kw, "s:", keywords, &name)) {
Py_RETURN_NONE;
}
if (!PyArg_ParseTupleAndKeywords(args, kw, "s:", keywords, &name))
return NULL;

if (kdump_get_attr(self->ctx, name, &attr) != kdump_ok) {
Py_RETURN_NONE;
PyErr_Format(PyExc_KeyError, "no such attribute `%s'", name);
return NULL;
}

return kdumpfile_attr2obj(self->ctx, &attr);
Expand Down Expand Up @@ -230,24 +259,23 @@ static PyObject *kdumpfile_get_symbol_func (PyObject *_self, void *_data)
{
kdumpfile_object *self = (kdumpfile_object*)_self;

if (! self->cb_get_symbol)
if (!self->cb_get_symbol)
Py_RETURN_NONE;
Py_INCREF(self->cb_get_symbol);

Py_INCREF(self->cb_get_symbol);
return self->cb_get_symbol;
}

int kdumpfile_set_symbol_func(PyObject *_self, PyObject *_set, void *_data)
{
kdumpfile_object *self = (kdumpfile_object*)_self;

if (! PyCallable_Check(_set)) {
PyErr_SetString(PyExc_RuntimeError, "Argument must be callable");
return 1;
if (!PyCallable_Check(_set)) {
PyErr_SetString(PyExc_TypeError, "value must be callable");
return -1;
}

if (self->cb_get_symbol)
Py_XDECREF(self->cb_get_symbol);
Py_XDECREF(self->cb_get_symbol);
self->cb_get_symbol = _set;
Py_INCREF(self->cb_get_symbol);
return 0;
Expand Down Expand Up @@ -315,11 +343,6 @@ static PyTypeObject kdumpfile_object_type =
kdumpfile_new, /* tp_new */
};

static inline void pyncref(char* c)
{
Py_INCREF((PyObject*)c);
}

PyMODINIT_FUNC
init_kdumpfile (void)
{
Expand All @@ -333,6 +356,6 @@ init_kdumpfile (void)

if (!mod) return;

pyncref((char*)&kdumpfile_object_type);
Py_INCREF((PyObject *)&kdumpfile_object_type);
PyModule_AddObject(mod, "kdumpfile", (PyObject*)&kdumpfile_object_type);
}

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