qemu/backends/rng-egd.c
Markus Armbruster ff92444884 backends: Improve error messages when property can no longer be set
When you try to set virtio-rng property "filename" after the backend
has been completed with user_creatable_complete(), the error message
blames "insufficient permission":

    $ qemu-system-x86_64 -S -display none -nodefaults -monitor stdio -object rng-random,id=rng0 -device virtio-rng,id=vrng0,rng=rng0
    QEMU 7.1.50 monitor - type 'help' for more information
    (qemu) qom-set /objects/rng0 filename /dev/random
    Error: Insufficient permission to perform this operation

This implies it could work with "sufficient permission".  It can't.
Change the error message to:

    Error: Property 'filename' can no longer be set

Same for cryptodev-vhost-user property "chardev", rng-egd property
"chardev", and vhost-user-backend property "chardev".

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221012153801.2604340-3-armbru@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
[Commit message tidied up]
2022-10-27 07:56:56 +02:00

170 lines
4.1 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.h"
#include "chardev/char-fe.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qemu/module.h"
#include "qom/object.h"
#define TYPE_RNG_EGD "rng-egd"
OBJECT_DECLARE_SIMPLE_TYPE(RngEgd, RNG_EGD)
struct RngEgd {
RngBackend parent;
CharBackend chr;
char *chr_name;
};
static void rng_egd_request_entropy(RngBackend *b, RngRequest *req)
{
RngEgd *s = RNG_EGD(b);
size_t size = req->size;
while (size > 0) {
uint8_t header[2];
uint8_t len = MIN(size, 255);
/* synchronous entropy request */
header[0] = 0x02;
header[1] = len;
/* XXX this blocks entire thread. Rewrite to use
* qemu_chr_fe_write and background I/O callbacks */
qemu_chr_fe_write_all(&s->chr, header, sizeof(header));
size -= len;
}
}
static int rng_egd_chr_can_read(void *opaque)
{
RngEgd *s = RNG_EGD(opaque);
RngRequest *req;
int size = 0;
QSIMPLEQ_FOREACH(req, &s->parent.requests, next) {
size += req->size - req->offset;
}
return size;
}
static void rng_egd_chr_read(void *opaque, const uint8_t *buf, int size)
{
RngEgd *s = RNG_EGD(opaque);
size_t buf_offset = 0;
while (size > 0 && !QSIMPLEQ_EMPTY(&s->parent.requests)) {
RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
int len = MIN(size, req->size - req->offset);
memcpy(req->data + req->offset, buf + buf_offset, len);
buf_offset += len;
req->offset += len;
size -= len;
if (req->offset == req->size) {
req->receive_entropy(req->opaque, req->data, req->size);
rng_backend_finalize_request(&s->parent, req);
}
}
}
static void rng_egd_opened(RngBackend *b, Error **errp)
{
RngEgd *s = RNG_EGD(b);
Chardev *chr;
if (s->chr_name == NULL) {
error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
"chardev", "a valid character device");
return;
}
chr = qemu_chr_find(s->chr_name);
if (chr == NULL) {
error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
"Device '%s' not found", s->chr_name);
return;
}
if (!qemu_chr_fe_init(&s->chr, chr, errp)) {
return;
}
/* FIXME we should resubmit pending requests when the CDS reconnects. */
qemu_chr_fe_set_handlers(&s->chr, rng_egd_chr_can_read,
rng_egd_chr_read, NULL, NULL, s, NULL, true);
}
static void rng_egd_set_chardev(Object *obj, const char *value, Error **errp)
{
RngBackend *b = RNG_BACKEND(obj);
RngEgd *s = RNG_EGD(b);
if (b->opened) {
error_setg(errp, "Property 'chardev' can no longer be set");
} else {
g_free(s->chr_name);
s->chr_name = g_strdup(value);
}
}
static char *rng_egd_get_chardev(Object *obj, Error **errp)
{
RngEgd *s = RNG_EGD(obj);
Chardev *chr = qemu_chr_fe_get_driver(&s->chr);
if (chr && chr->label) {
return g_strdup(chr->label);
}
return NULL;
}
static void rng_egd_finalize(Object *obj)
{
RngEgd *s = RNG_EGD(obj);
qemu_chr_fe_deinit(&s->chr, false);
g_free(s->chr_name);
}
static void rng_egd_class_init(ObjectClass *klass, void *data)
{
RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
rbc->request_entropy = rng_egd_request_entropy;
rbc->opened = rng_egd_opened;
object_class_property_add_str(klass, "chardev",
rng_egd_get_chardev, rng_egd_set_chardev);
}
static const TypeInfo rng_egd_info = {
.name = TYPE_RNG_EGD,
.parent = TYPE_RNG_BACKEND,
.instance_size = sizeof(RngEgd),
.class_init = rng_egd_class_init,
.instance_finalize = rng_egd_finalize,
};
static void register_types(void)
{
type_register_static(&rng_egd_info);
}
type_init(register_types);