qemu/backends/rng-random.c
Markus Armbruster d2623129a7 qom: Drop parameter @errp of object_property_add() & friends
The only way object_property_add() can fail is when a property with
the same name already exists.  Since our property names are all
hardcoded, failure is a programming error, and the appropriate way to
handle it is passing &error_abort.

Same for its variants, except for object_property_add_child(), which
additionally fails when the child already has a parent.  Parentage is
also under program control, so this is a programming error, too.

We have a bit over 500 callers.  Almost half of them pass
&error_abort, slightly fewer ignore errors, one test case handles
errors, and the remaining few callers pass them to their own callers.

The previous few commits demonstrated once again that ignoring
programming errors is a bad idea.

Of the few ones that pass on errors, several violate the Error API.
The Error ** argument must be NULL, &error_abort, &error_fatal, or a
pointer to a variable containing NULL.  Passing an argument of the
latter kind twice without clearing it in between is wrong: if the
first call sets an error, it no longer points to NULL for the second
call.  ich9_pm_add_properties(), sparc32_ledma_realize(),
sparc32_dma_realize(), xilinx_axidma_realize(), xilinx_enet_realize()
are wrong that way.

When the one appropriate choice of argument is &error_abort, letting
users pick the argument is a bad idea.

Drop parameter @errp and assert the preconditions instead.

There's one exception to "duplicate property name is a programming
error": the way object_property_add() implements the magic (and
undocumented) "automatic arrayification".  Don't drop @errp there.
Instead, rename object_property_add() to object_property_try_add(),
and add the obvious wrapper object_property_add().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200505152926.18877-15-armbru@redhat.com>
[Two semantic rebase conflicts resolved]
2020-05-15 07:07:58 +02:00

154 lines
3.6 KiB
C

/*
* QEMU Random Number Generator Backend
*
* Copyright IBM, Corp. 2012
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "sysemu/rng-random.h"
#include "sysemu/rng.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qemu/main-loop.h"
#include "qemu/module.h"
struct RngRandom
{
RngBackend parent;
int fd;
char *filename;
};
/**
* A simple and incomplete backend to request entropy from /dev/random.
*
* This backend exposes an additional "filename" property that can be used to
* set the filename to use to open the backend.
*/
static void entropy_available(void *opaque)
{
RngRandom *s = RNG_RANDOM(opaque);
while (!QSIMPLEQ_EMPTY(&s->parent.requests)) {
RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
ssize_t len;
len = read(s->fd, req->data, req->size);
if (len < 0 && errno == EAGAIN) {
return;
}
g_assert(len != -1);
req->receive_entropy(req->opaque, req->data, len);
rng_backend_finalize_request(&s->parent, req);
}
/* We've drained all requests, the fd handler can be reset. */
qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
}
static void rng_random_request_entropy(RngBackend *b, RngRequest *req)
{
RngRandom *s = RNG_RANDOM(b);
if (QSIMPLEQ_EMPTY(&s->parent.requests)) {
/* If there are no pending requests yet, we need to
* install our fd handler. */
qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
}
}
static void rng_random_opened(RngBackend *b, Error **errp)
{
RngRandom *s = RNG_RANDOM(b);
if (s->filename == NULL) {
error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
"filename", "a valid filename");
} else {
s->fd = qemu_open(s->filename, O_RDONLY | O_NONBLOCK);
if (s->fd == -1) {
error_setg_file_open(errp, errno, s->filename);
}
}
}
static char *rng_random_get_filename(Object *obj, Error **errp)
{
RngRandom *s = RNG_RANDOM(obj);
return g_strdup(s->filename);
}
static void rng_random_set_filename(Object *obj, const char *filename,
Error **errp)
{
RngBackend *b = RNG_BACKEND(obj);
RngRandom *s = RNG_RANDOM(obj);
if (b->opened) {
error_setg(errp, QERR_PERMISSION_DENIED);
return;
}
g_free(s->filename);
s->filename = g_strdup(filename);
}
static void rng_random_init(Object *obj)
{
RngRandom *s = RNG_RANDOM(obj);
object_property_add_str(obj, "filename",
rng_random_get_filename,
rng_random_set_filename);
s->filename = g_strdup("/dev/urandom");
s->fd = -1;
}
static void rng_random_finalize(Object *obj)
{
RngRandom *s = RNG_RANDOM(obj);
if (s->fd != -1) {
qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
qemu_close(s->fd);
}
g_free(s->filename);
}
static void rng_random_class_init(ObjectClass *klass, void *data)
{
RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
rbc->request_entropy = rng_random_request_entropy;
rbc->opened = rng_random_opened;
}
static const TypeInfo rng_random_info = {
.name = TYPE_RNG_RANDOM,
.parent = TYPE_RNG_BACKEND,
.instance_size = sizeof(RngRandom),
.class_init = rng_random_class_init,
.instance_init = rng_random_init,
.instance_finalize = rng_random_finalize,
};
static void register_types(void)
{
type_register_static(&rng_random_info);
}
type_init(register_types);