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2ee6c960ee
unicorn/qemu/qapi/qmp-input-visitor.c
Eric Blake 2ee6c960ee
qapi: Simplify visiting of alternate types 
Previously, working with alternates required two lookup arrays
and some indirection: for type Foo, we created Foo_qtypes[]
which maps each qtype to a value of the generated FooKind enum,
then look up that value in FooKind_lookup[] like we do for other
union types.

This has a couple of subtle bugs. First, the generator was
creating a call with a parameter '(int *) &(*obj)->type' where
type is an enum type; this is unsafe if the compiler chooses
to store the enum type in a different size than int, where
assigning through the wrong size pointer can corrupt data or
cause a SIGBUS.

Related bug, not not fixed in this patch: qapi-visit.py's
gen_visit_enum() generates a cast of its enum * argument to
int *. Marked FIXME.

Second, since the values of the FooKind enum start at zero, all
entries of the Foo_qtypes[] array that were not explicitly
initialized will map to the same branch of the union as the
first member of the alternate, rather than triggering a desired
failure in visit_get_next_type(). Fortunately, the bug seldom
bites; the very next thing the input visitor does is try to
parse the incoming JSON with the wrong parser, which normally
fails; the output visitor is not used with a C struct in that
state, and the dealloc visitor has nothing to clean up (so
there is no leak).

However, the second bug IS observable in one case: parsing an
integer causes unusual behavior in an alternate that contains
at least a 'number' member but no 'int' member, because the
'number' parser accepts QTYPE_QINT in addition to the expected
QTYPE_QFLOAT (that is, since 'int' is not a member, the type
QTYPE_QINT accidentally maps to FooKind 0; if this enum value
is the 'number' branch the integer parses successfully, but if
the 'number' branch is not first, some other branch tries to
parse the integer and rejects it). A later patch will worry
about fixing alternates to always parse all inputs that a
non-alternate 'number' would accept, for now this is still
marked FIXME in the updated test-qmp-input-visitor.c, to
merely point out that new undesired behavior of 'ans' matches
the existing undesired behavior of 'asn'.

This patch fixes the default-initialization bug by deleting the
indirection, and modifying get_next_type() to directly assign a
QTypeCode parameter. This in turn fixes the type-casting bug,
as we are no longer casting a pointer to enum to a questionable
size. There is no longer a need to generate an implicit FooKind
enum associated with the alternate type (since the QMP wire
format never uses the stringized counterparts of the C union
member names). Since the updated visit_get_next_type() does not
know which qtypes are expected, the generated visitor is
modified to generate an error statement if an unexpected type is
encountered.

Callers now have to know the QTYPE_* mapping when looking at the
discriminator; but so far, only the testsuite was even using the
C struct of an alternate types. I considered the possibility of
keeping the internal enum FooKind, but initialized differently
than most generated arrays, as in:
typedef enum FooKind {
FOO_KIND_A = QTYPE_QDICT,
FOO_KIND_B = QTYPE_QINT,
} FooKind;
to create nicer aliases for knowing when to use foo->a or foo->b
when inspecting foo->type; but it turned out to add too much
complexity, especially without a client.

There is a user-visible side effect to this change, but I
consider it to be an improvement. Previously,
the invalid QMP command:
{"execute":"blockdev-add", "arguments":{"options":
{"driver":"raw", "id":"a", "file":true}}}
failed with:
{"error": {"class": "GenericError",
"desc": "Invalid parameter type for 'file', expected: QDict"}}
(visit_get_next_type() succeeded, and the error comes from the
visit_type_BlockdevOptions() expecting {}; there is no mention of
the fact that a string would also work). Now it fails with:
{"error": {"class": "GenericError",
"desc": "Invalid parameter type for 'file', expected: BlockdevRef"}}
(the error when the next type doesn't match any expected types for
the overall alternate).

Backports commit 0426d53c6530606bf7641b83f2b755fe61c280ee from qemu
2018-02-19 21:52:39 -05:00

382 lines
9.6 KiB
C
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/*
* Input Visitor
*
* Copyright IBM, Corp. 2011
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qapi/qmp-input-visitor.h"
#include "qapi/visitor-impl.h"
#include "qemu/queue.h"
#include "qemu-common.h"
#include "qapi/qmp/types.h"
#include "qapi/qmp/qerror.h"
#define QIV_STACK_SIZE 1024
typedef struct StackObject
{
QObject *obj;
const QListEntry *entry;
GHashTable *h;
} StackObject;
struct QmpInputVisitor
{
Visitor visitor;
StackObject stack[QIV_STACK_SIZE];
int nb_stack;
bool strict;
};
static QmpInputVisitor *to_qiv(Visitor *v)
{
return container_of(v, QmpInputVisitor, visitor);
}
static QObject *qmp_input_get_object(QmpInputVisitor *qiv,
const char *name,
bool consume)
{
QObject *qobj = qiv->stack[qiv->nb_stack - 1].obj;
if (qobj) {
if (name && qobject_type(qobj) == QTYPE_QDICT) {
if (qiv->stack[qiv->nb_stack - 1].h && consume) {
g_hash_table_remove(qiv->stack[qiv->nb_stack - 1].h, name);
}
return qdict_get(qobject_to_qdict(qobj), name);
} else if (qiv->stack[qiv->nb_stack - 1].entry) {
return qlist_entry_obj(qiv->stack[qiv->nb_stack - 1].entry);
}
}
return qobj;
}
static void qdict_add_key(const char *key, QObject *obj, void *opaque)
{
GHashTable *h = opaque;
g_hash_table_insert(h, (gpointer) key, NULL);
}
static void qmp_input_push(QmpInputVisitor *qiv, QObject *obj, Error **errp)
{
GHashTable *h;
if (qiv->nb_stack >= QIV_STACK_SIZE) {
error_setg(errp, "An internal buffer overran");
return;
}
qiv->stack[qiv->nb_stack].obj = obj;
qiv->stack[qiv->nb_stack].entry = NULL;
qiv->stack[qiv->nb_stack].h = NULL;
if (qiv->strict && qobject_type(obj) == QTYPE_QDICT) {
h = g_hash_table_new(g_str_hash, g_str_equal);
qdict_iter(qobject_to_qdict(obj), qdict_add_key, h);
qiv->stack[qiv->nb_stack].h = h;
}
qiv->nb_stack++;
}
/** Only for qmp_input_pop. */
static gboolean always_true(gpointer key, gpointer val, gpointer user_pkey)
{
*(const char **)user_pkey = (const char *)key;
return TRUE;
}
static void qmp_input_pop(QmpInputVisitor *qiv, Error **errp)
{
assert(qiv->nb_stack > 0);
if (qiv->strict) {
GHashTable * const top_ht = qiv->stack[qiv->nb_stack - 1].h;
if (top_ht) {
if (g_hash_table_size(top_ht)) {
const char *key;
g_hash_table_find(top_ht, always_true, (gpointer)&key);
error_setg(errp, QERR_QMP_EXTRA_MEMBER, key);
}
g_hash_table_unref(top_ht);
}
}
qiv->nb_stack--;
}
static void qmp_input_start_struct(Visitor *v, void **obj, const char *kind,
const char *name, size_t size, Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QObject *qobj = qmp_input_get_object(qiv, name, true);
Error *err = NULL;
if (!qobj || qobject_type(qobj) != QTYPE_QDICT) {
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"QDict");
return;
}
qmp_input_push(qiv, qobj, &err);
if (err) {
error_propagate(errp, err);
return;
}
if (obj) {
*obj = g_malloc0(size);
}
}
static void qmp_input_end_struct(Visitor *v, Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
qmp_input_pop(qiv, errp);
}
static void qmp_input_start_implicit_struct(Visitor *v, void **obj,
size_t size, Error **errp)
{
if (obj) {
*obj = g_malloc0(size);
}
}
static void qmp_input_end_implicit_struct(Visitor *v)
{
}
static void qmp_input_start_list(Visitor *v, const char *name, Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QObject *qobj = qmp_input_get_object(qiv, name, true);
if (!qobj || qobject_type(qobj) != QTYPE_QLIST) {
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"list");
return;
}
qmp_input_push(qiv, qobj, errp);
}
static GenericList *qmp_input_next_list(Visitor *v, GenericList **list)
{
QmpInputVisitor *qiv = to_qiv(v);
GenericList *entry;
StackObject *so = &qiv->stack[qiv->nb_stack - 1];
bool first;
if (so->entry == NULL) {
so->entry = qlist_first(qobject_to_qlist(so->obj));
first = true;
} else {
so->entry = qlist_next(so->entry);
first = false;
}
if (so->entry == NULL) {
return NULL;
}
entry = g_malloc0(sizeof(*entry));
if (first) {
*list = entry;
} else {
(*list)->next = entry;
}
return entry;
}
static void qmp_input_end_list(Visitor *v)
{
QmpInputVisitor *qiv = to_qiv(v);
qmp_input_pop(qiv, &error_abort);
}
static void qmp_input_get_next_type(Visitor *v, QType *type,
const char *name, Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QObject *qobj = qmp_input_get_object(qiv, name, false);
if (!qobj) {
error_setg(errp, QERR_MISSING_PARAMETER, name ? name : "null");
return;
}
*type = qobject_type(qobj);
}
static void qmp_input_type_int64(Visitor *v, int64_t *obj, const char *name,
Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QInt *qint = qobject_to_qint(qmp_input_get_object(qiv, name, true));
if (!qint) {
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"integer");
return;
}
*obj = qint_get_int(qint);
}
static void qmp_input_type_uint64(Visitor *v, uint64_t *obj, const char *name,
Error **errp)
{
/* FIXME: qobject_to_qint mishandles values over INT64_MAX */
QmpInputVisitor *qiv = to_qiv(v);
QInt *qint = qobject_to_qint(qmp_input_get_object(qiv, name, true));
if (!qint) {
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"integer");
return;
}
*obj = qint_get_int(qint);
}
static void qmp_input_type_bool(Visitor *v, bool *obj, const char *name,
Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QBool *qbool = qobject_to_qbool(qmp_input_get_object(qiv, name, true));
if (!qbool) {
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"boolean");
return;
}
*obj = qbool_get_bool(qbool);
}
static void qmp_input_type_str(Visitor *v, char **obj, const char *name,
Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QString *qstr = qobject_to_qstring(qmp_input_get_object(qiv, name, true));
if (!qstr) {
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"string");
return;
}
*obj = g_strdup(qstring_get_str(qstr));
}
static void qmp_input_type_number(Visitor *v, double *obj, const char *name,
Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QObject *qobj = qmp_input_get_object(qiv, name, true);
QInt *qint;
QFloat *qfloat;
qint = qobject_to_qint(qobj);
if (qint) {
*obj = qint_get_int(qobject_to_qint(qobj));
return;
}
qfloat = qobject_to_qfloat(qobj);
if (qfloat) {
*obj = qfloat_get_double(qobject_to_qfloat(qobj));
return;
}
error_setg(errp, QERR_INVALID_PARAMETER_TYPE, name ? name : "null",
"number");
}
static void qmp_input_type_any(Visitor *v, QObject **obj, const char *name,
Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QObject *qobj = qmp_input_get_object(qiv, name, true);
qobject_incref(qobj);
*obj = qobj;
}
static void qmp_input_optional(Visitor *v, bool *present, const char *name,
Error **errp)
{
QmpInputVisitor *qiv = to_qiv(v);
QObject *qobj = qmp_input_get_object(qiv, name, true);
if (!qobj) {
*present = false;
return;
}
*present = true;
}
Visitor *qmp_input_get_visitor(QmpInputVisitor *v)
{
return &v->visitor;
}
void qmp_input_visitor_cleanup(QmpInputVisitor *v)
{
qobject_decref(v->stack[0].obj);
g_free(v);
}
QmpInputVisitor *qmp_input_visitor_new(QObject *obj)
{
QmpInputVisitor *v;
v = g_malloc0(sizeof(*v));
v->visitor.start_struct = qmp_input_start_struct;
v->visitor.end_struct = qmp_input_end_struct;
v->visitor.start_implicit_struct = qmp_input_start_implicit_struct;
v->visitor.end_implicit_struct = qmp_input_end_implicit_struct;
v->visitor.start_list = qmp_input_start_list;
v->visitor.next_list = qmp_input_next_list;
v->visitor.end_list = qmp_input_end_list;
v->visitor.type_enum = input_type_enum;
v->visitor.type_int64 = qmp_input_type_int64;
v->visitor.type_uint64 = qmp_input_type_uint64;
v->visitor.type_bool = qmp_input_type_bool;
v->visitor.type_str = qmp_input_type_str;
v->visitor.type_number = qmp_input_type_number;
v->visitor.type_any = qmp_input_type_any;
v->visitor.optional = qmp_input_optional;
v->visitor.get_next_type = qmp_input_get_next_type;
qmp_input_push(v, obj, NULL);
qobject_incref(obj);
return v;
}
QmpInputVisitor *qmp_input_visitor_new_strict(QObject *obj)
{
QmpInputVisitor *v;
v = qmp_input_visitor_new(obj);
v->strict = true;
return v;
}
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