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qemu/replay/replay.c
Alex Bennée 982263ce71 replay: assert time only goes forward 
If we find ourselves trying to add an event to the log where time has
gone backwards it is because a vCPU event has occurred and the
main-loop is not yet aware of time moving forward. This should not
happen and if it does its better to fail early than generate a log
that will have weird behaviour.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
2017-04-10 10:23:38 +01:00

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/*
* replay.c
*
* Copyright (c) 2010-2015 Institute for System Programming
* of the Russian Academy of Sciences.
*
* 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 "qapi/error.h"
#include "qemu-common.h"
#include "sysemu/replay.h"
#include "replay-internal.h"
#include "qemu/timer.h"
#include "qemu/main-loop.h"
#include "sysemu/cpus.h"
#include "sysemu/sysemu.h"
#include "qemu/error-report.h"
/* Current version of the replay mechanism.
Increase it when file format changes. */
#define REPLAY_VERSION 0xe02006
/* Size of replay log header */
#define HEADER_SIZE (sizeof(uint32_t) + sizeof(uint64_t))
ReplayMode replay_mode = REPLAY_MODE_NONE;
char *replay_snapshot;
/* Name of replay file */
static char *replay_filename;
ReplayState replay_state;
static GSList *replay_blockers;
bool replay_next_event_is(int event)
{
bool res = false;
/* nothing to skip - not all instructions used */
if (replay_state.instructions_count != 0) {
assert(replay_state.data_kind == EVENT_INSTRUCTION);
return event == EVENT_INSTRUCTION;
}
while (true) {
if (event == replay_state.data_kind) {
res = true;
}
switch (replay_state.data_kind) {
case EVENT_SHUTDOWN:
replay_finish_event();
qemu_system_shutdown_request();
break;
default:
/* clock, time_t, checkpoint and other events */
return res;
}
}
return res;
}
uint64_t replay_get_current_step(void)
{
return cpu_get_icount_raw();
}
int replay_get_instructions(void)
{
int res = 0;
replay_mutex_lock();
if (replay_next_event_is(EVENT_INSTRUCTION)) {
res = replay_state.instructions_count;
}
replay_mutex_unlock();
return res;
}
void replay_account_executed_instructions(void)
{
if (replay_mode == REPLAY_MODE_PLAY) {
replay_mutex_lock();
if (replay_state.instructions_count > 0) {
int count = (int)(replay_get_current_step()
- replay_state.current_step);
/* Time can only go forward */
assert(count >= 0);
replay_state.instructions_count -= count;
replay_state.current_step += count;
if (replay_state.instructions_count == 0) {
assert(replay_state.data_kind == EVENT_INSTRUCTION);
replay_finish_event();
/* Wake up iothread. This is required because
timers will not expire until clock counters
will be read from the log. */
qemu_notify_event();
}
}
replay_mutex_unlock();
}
}
bool replay_exception(void)
{
if (replay_mode == REPLAY_MODE_RECORD) {
replay_save_instructions();
replay_mutex_lock();
replay_put_event(EVENT_EXCEPTION);
replay_mutex_unlock();
return true;
} else if (replay_mode == REPLAY_MODE_PLAY) {
bool res = replay_has_exception();
if (res) {
replay_mutex_lock();
replay_finish_event();
replay_mutex_unlock();
}
return res;
}
return true;
}
bool replay_has_exception(void)
{
bool res = false;
if (replay_mode == REPLAY_MODE_PLAY) {
replay_account_executed_instructions();
replay_mutex_lock();
res = replay_next_event_is(EVENT_EXCEPTION);
replay_mutex_unlock();
}
return res;
}
bool replay_interrupt(void)
{
if (replay_mode == REPLAY_MODE_RECORD) {
replay_save_instructions();
replay_mutex_lock();
replay_put_event(EVENT_INTERRUPT);
replay_mutex_unlock();
return true;
} else if (replay_mode == REPLAY_MODE_PLAY) {
bool res = replay_has_interrupt();
if (res) {
replay_mutex_lock();
replay_finish_event();
replay_mutex_unlock();
}
return res;
}
return true;
}
bool replay_has_interrupt(void)
{
bool res = false;
if (replay_mode == REPLAY_MODE_PLAY) {
replay_account_executed_instructions();
replay_mutex_lock();
res = replay_next_event_is(EVENT_INTERRUPT);
replay_mutex_unlock();
}
return res;
}
void replay_shutdown_request(void)
{
if (replay_mode == REPLAY_MODE_RECORD) {
replay_mutex_lock();
replay_put_event(EVENT_SHUTDOWN);
replay_mutex_unlock();
}
}
bool replay_checkpoint(ReplayCheckpoint checkpoint)
{
bool res = false;
assert(EVENT_CHECKPOINT + checkpoint <= EVENT_CHECKPOINT_LAST);
replay_save_instructions();
if (!replay_file) {
return true;
}
replay_mutex_lock();
if (replay_mode == REPLAY_MODE_PLAY) {
if (replay_next_event_is(EVENT_CHECKPOINT + checkpoint)) {
replay_finish_event();
} else if (replay_state.data_kind != EVENT_ASYNC) {
res = false;
goto out;
}
replay_read_events(checkpoint);
/* replay_read_events may leave some unread events.
Return false if not all of the events associated with
checkpoint were processed */
res = replay_state.data_kind != EVENT_ASYNC;
} else if (replay_mode == REPLAY_MODE_RECORD) {
replay_put_event(EVENT_CHECKPOINT + checkpoint);
replay_save_events(checkpoint);
res = true;
}
out:
replay_mutex_unlock();
return res;
}
static void replay_enable(const char *fname, int mode)
{
const char *fmode = NULL;
assert(!replay_file);
switch (mode) {
case REPLAY_MODE_RECORD:
fmode = "wb";
break;
case REPLAY_MODE_PLAY:
fmode = "rb";
break;
default:
fprintf(stderr, "Replay: internal error: invalid replay mode\n");
exit(1);
}
atexit(replay_finish);
replay_mutex_init();
replay_file = fopen(fname, fmode);
if (replay_file == NULL) {
fprintf(stderr, "Replay: open %s: %s\n", fname, strerror(errno));
exit(1);
}
replay_filename = g_strdup(fname);
replay_mode = mode;
replay_state.data_kind = -1;
replay_state.instructions_count = 0;
replay_state.current_step = 0;
replay_state.has_unread_data = 0;
/* skip file header for RECORD and check it for PLAY */
if (replay_mode == REPLAY_MODE_RECORD) {
fseek(replay_file, HEADER_SIZE, SEEK_SET);
} else if (replay_mode == REPLAY_MODE_PLAY) {
unsigned int version = replay_get_dword();
if (version != REPLAY_VERSION) {
fprintf(stderr, "Replay: invalid input log file version\n");
exit(1);
}
/* go to the beginning */
fseek(replay_file, HEADER_SIZE, SEEK_SET);
replay_fetch_data_kind();
}
replay_init_events();
}
void replay_configure(QemuOpts *opts)
{
const char *fname;
const char *rr;
ReplayMode mode = REPLAY_MODE_NONE;
Location loc;
if (!opts) {
return;
}
loc_push_none(&loc);
qemu_opts_loc_restore(opts);
rr = qemu_opt_get(opts, "rr");
if (!rr) {
/* Just enabling icount */
goto out;
} else if (!strcmp(rr, "record")) {
mode = REPLAY_MODE_RECORD;
} else if (!strcmp(rr, "replay")) {
mode = REPLAY_MODE_PLAY;
} else {
error_report("Invalid icount rr option: %s", rr);
exit(1);
}
fname = qemu_opt_get(opts, "rrfile");
if (!fname) {
error_report("File name not specified for replay");
exit(1);
}
replay_snapshot = g_strdup(qemu_opt_get(opts, "rrsnapshot"));
replay_vmstate_register();
replay_enable(fname, mode);
out:
loc_pop(&loc);
}
void replay_start(void)
{
if (replay_mode == REPLAY_MODE_NONE) {
return;
}
if (replay_blockers) {
error_reportf_err(replay_blockers->data, "Record/replay: ");
exit(1);
}
if (!use_icount) {
error_report("Please enable icount to use record/replay");
exit(1);
}
/* Timer for snapshotting will be set up here. */
replay_enable_events();
}
void replay_finish(void)
{
if (replay_mode == REPLAY_MODE_NONE) {
return;
}
replay_save_instructions();
/* finalize the file */
if (replay_file) {
if (replay_mode == REPLAY_MODE_RECORD) {
/* write end event */
replay_put_event(EVENT_END);
/* write header */
fseek(replay_file, 0, SEEK_SET);
replay_put_dword(REPLAY_VERSION);
}
fclose(replay_file);
replay_file = NULL;
}
if (replay_filename) {
g_free(replay_filename);
replay_filename = NULL;
}
g_free(replay_snapshot);
replay_snapshot = NULL;
replay_finish_events();
replay_mutex_destroy();
}
void replay_add_blocker(Error *reason)
{
replay_blockers = g_slist_prepend(replay_blockers, reason);
}
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