2012-06-25 23:34:09 +08:00
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/*
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* QEMU Random Number Generator Backend
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*
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* Copyright IBM, Corp. 2012
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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2016-01-30 01:49:54 +08:00
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#include "qemu/osdep.h"
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2013-04-08 22:55:25 +08:00
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#include "sysemu/rng-random.h"
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#include "sysemu/rng.h"
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include/qemu/osdep.h: Don't include qapi/error.h
Commit 57cb38b included qapi/error.h into qemu/osdep.h to get the
Error typedef. Since then, we've moved to include qemu/osdep.h
everywhere. Its file comment explains: "To avoid getting into
possible circular include dependencies, this file should not include
any other QEMU headers, with the exceptions of config-host.h,
compiler.h, os-posix.h and os-win32.h, all of which are doing a
similar job to this file and are under similar constraints."
qapi/error.h doesn't do a similar job, and it doesn't adhere to
similar constraints: it includes qapi-types.h. That's in excess of
100KiB of crap most .c files don't actually need.
Add the typedef to qemu/typedefs.h, and include that instead of
qapi/error.h. Include qapi/error.h in .c files that need it and don't
get it now. Include qapi-types.h in qom/object.h for uint16List.
Update scripts/clean-includes accordingly. Update it further to match
reality: replace config.h by config-target.h, add sysemu/os-posix.h,
sysemu/os-win32.h. Update the list of includes in the qemu/osdep.h
comment quoted above similarly.
This reduces the number of objects depending on qapi/error.h from "all
of them" to less than a third. Unfortunately, the number depending on
qapi-types.h shrinks only a little. More work is needed for that one.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
[Fix compilation without the spice devel packages. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-03-14 16:01:28 +08:00
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#include "qapi/error.h"
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2012-12-18 01:19:43 +08:00
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#include "qapi/qmp/qerror.h"
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2012-12-18 01:20:00 +08:00
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#include "qemu/main-loop.h"
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2019-05-23 22:35:07 +08:00
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#include "qemu/module.h"
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2012-06-25 23:34:09 +08:00
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2016-04-15 09:36:08 +08:00
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struct RngRandom
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2012-06-25 23:34:09 +08:00
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{
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RngBackend parent;
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int fd;
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char *filename;
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};
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/**
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* A simple and incomplete backend to request entropy from /dev/random.
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*
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* This backend exposes an additional "filename" property that can be used to
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* set the filename to use to open the backend.
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*/
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static void entropy_available(void *opaque)
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{
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(opaque);
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2012-06-25 23:34:09 +08:00
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2016-03-03 21:16:11 +08:00
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while (!QSIMPLEQ_EMPTY(&s->parent.requests)) {
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RngRequest *req = QSIMPLEQ_FIRST(&s->parent.requests);
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2016-03-03 16:37:18 +08:00
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ssize_t len;
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2012-06-25 23:34:09 +08:00
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2016-03-03 16:37:18 +08:00
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len = read(s->fd, req->data, req->size);
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if (len < 0 && errno == EAGAIN) {
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return;
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}
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g_assert(len != -1);
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2012-06-25 23:34:09 +08:00
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2016-03-03 16:37:18 +08:00
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req->receive_entropy(req->opaque, req->data, len);
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rng_backend_finalize_request(&s->parent, req);
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}
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/* We've drained all requests, the fd handler can be reset. */
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2012-06-25 23:34:09 +08:00
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qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
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}
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2016-03-03 16:37:18 +08:00
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static void rng_random_request_entropy(RngBackend *b, RngRequest *req)
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2012-06-25 23:34:09 +08:00
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{
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(b);
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2012-06-25 23:34:09 +08:00
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2016-03-03 21:16:11 +08:00
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if (QSIMPLEQ_EMPTY(&s->parent.requests)) {
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2016-03-03 16:37:18 +08:00
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/* If there are no pending requests yet, we need to
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* install our fd handler. */
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qemu_set_fd_handler(s->fd, entropy_available, NULL, s);
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2012-06-25 23:34:09 +08:00
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}
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}
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static void rng_random_opened(RngBackend *b, Error **errp)
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{
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(b);
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2012-06-25 23:34:09 +08:00
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if (s->filename == NULL) {
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2015-03-17 18:54:50 +08:00
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error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
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"filename", "a valid filename");
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2012-06-25 23:34:09 +08:00
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} else {
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2013-03-01 20:53:55 +08:00
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s->fd = qemu_open(s->filename, O_RDONLY | O_NONBLOCK);
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2012-06-25 23:34:09 +08:00
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if (s->fd == -1) {
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2013-06-08 02:28:02 +08:00
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error_setg_file_open(errp, errno, s->filename);
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2012-06-25 23:34:09 +08:00
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}
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}
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}
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static char *rng_random_get_filename(Object *obj, Error **errp)
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{
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(obj);
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2012-06-25 23:34:09 +08:00
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2014-12-04 17:26:55 +08:00
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return g_strdup(s->filename);
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2012-06-25 23:34:09 +08:00
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}
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static void rng_random_set_filename(Object *obj, const char *filename,
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Error **errp)
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{
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RngBackend *b = RNG_BACKEND(obj);
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(obj);
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2012-06-25 23:34:09 +08:00
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if (b->opened) {
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2015-03-17 18:54:50 +08:00
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error_setg(errp, QERR_PERMISSION_DENIED);
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2012-06-25 23:34:09 +08:00
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return;
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}
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2014-05-31 04:02:18 +08:00
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g_free(s->filename);
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2012-06-25 23:34:09 +08:00
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s->filename = g_strdup(filename);
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}
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static void rng_random_init(Object *obj)
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{
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(obj);
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2012-06-25 23:34:09 +08:00
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object_property_add_str(obj, "filename",
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rng_random_get_filename,
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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]
2020-05-05 23:29:22 +08:00
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rng_random_set_filename);
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2012-06-25 23:34:09 +08:00
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VirtIO-RNG: Update default entropy source to `/dev/urandom`
When QEMU exposes a VirtIO-RNG device to the guest, that device needs a
source of entropy, and that source needs to be "non-blocking", like
`/dev/urandom`. However, currently QEMU defaults to the problematic
`/dev/random`, which on Linux is "blocking" (as in, it waits until
sufficient entropy is available).
Why prefer `/dev/urandom` over `/dev/random`?
---------------------------------------------
The man pages of urandom(4) and random(4) state:
"The /dev/random device is a legacy interface which dates back to a
time where the cryptographic primitives used in the implementation
of /dev/urandom were not widely trusted. It will return random
bytes only within the estimated number of bits of fresh noise in the
entropy pool, blocking if necessary. /dev/random is suitable for
applications that need high quality randomness, and can afford
indeterminate delays."
Further, the "Usage" section of the said man pages state:
"The /dev/random interface is considered a legacy interface, and
/dev/urandom is preferred and sufficient in all use cases, with the
exception of applications which require randomness during early boot
time; for these applications, getrandom(2) must be used instead,
because it will block until the entropy pool is initialized.
"If a seed file is saved across reboots as recommended below (all
major Linux distributions have done this since 2000 at least), the
output is cryptographically secure against attackers without local
root access as soon as it is reloaded in the boot sequence, and
perfectly adequate for network encryption session keys. Since reads
from /dev/random may block, users will usually want to open it in
nonblocking mode (or perform a read with timeout), and provide some
sort of user notification if the desired entropy is not immediately
available."
And refer to random(7) for a comparison of `/dev/random` and
`/dev/urandom`.
What about other OSes?
----------------------
`/dev/urandom` exists and works on OS-X, FreeBSD, DragonFlyBSD, NetBSD
and OpenBSD, which cover all the non-Linux platforms we explicitly
support, aside from Windows.
On Windows `/dev/random` doesn't work either so we don't regress.
This is actually another argument in favour of using the newly
proposed 'rng-builtin' backend by default, as that will work on
Windows.
- - -
Given the above, change the entropy source for VirtIO-RNG device to
`/dev/urandom`.
Related discussion in these[1][2] past threads.
[1] https://lists.nongnu.org/archive/html/qemu-devel/2018-06/msg08335.html
-- "RNG: Any reason QEMU doesn't default to `/dev/urandom`?"
[2] https://lists.nongnu.org/archive/html/qemu-devel/2018-09/msg02724.html
-- "[RFC] Virtio RNG: Consider changing the default entropy source to
/dev/urandom"
Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20190529143106.11789-2-lvivier@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
2019-05-29 22:31:03 +08:00
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s->filename = g_strdup("/dev/urandom");
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2013-12-21 06:21:06 +08:00
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s->fd = -1;
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2012-06-25 23:34:09 +08:00
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}
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static void rng_random_finalize(Object *obj)
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{
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2016-04-15 09:36:08 +08:00
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RngRandom *s = RNG_RANDOM(obj);
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2012-06-25 23:34:09 +08:00
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if (s->fd != -1) {
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2013-12-21 06:21:06 +08:00
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qemu_set_fd_handler(s->fd, NULL, NULL, NULL);
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2013-03-01 20:53:55 +08:00
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qemu_close(s->fd);
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2012-06-25 23:34:09 +08:00
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}
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g_free(s->filename);
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}
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static void rng_random_class_init(ObjectClass *klass, void *data)
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{
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RngBackendClass *rbc = RNG_BACKEND_CLASS(klass);
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rbc->request_entropy = rng_random_request_entropy;
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rbc->opened = rng_random_opened;
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}
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2013-01-10 23:19:07 +08:00
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static const TypeInfo rng_random_info = {
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2012-06-25 23:34:09 +08:00
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.name = TYPE_RNG_RANDOM,
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.parent = TYPE_RNG_BACKEND,
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2016-04-15 09:36:08 +08:00
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.instance_size = sizeof(RngRandom),
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2012-06-25 23:34:09 +08:00
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.class_init = rng_random_class_init,
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.instance_init = rng_random_init,
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.instance_finalize = rng_random_finalize,
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};
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static void register_types(void)
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{
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type_register_static(&rng_random_info);
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}
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type_init(register_types);
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