static void emulate_signal_delivery()
{
/* We are now at the exact point in the child where the signal
* was recorded, emulate it using the next trace line (records
* the state at sighandler entry). */
struct context* ctx = rep_sched_get_thread();
pid_t tid = ctx->child_tid;
struct trace_frame* trace = &ctx->trace;
/* Restore the signal-hander frame data, if there was one. */
if (!set_child_data(ctx)) {
/* No signal handler. Advance execution to the point
* we recorded. */
reset_hpc(ctx, 0);
/* TODO what happens if we step on a breakpoint? */
advance_to(ctx, ctx->trace.rbc, &trace->recorded_regs,
/*no signal*/0, DONT_STEPI);
/* (|advance_to()| just asserted that the registers
* match what was recorded.) */
} else {
/* Signal handler; we just set up the callframe.
* Continuing execution will run that code. */
write_child_main_registers(tid, &trace->recorded_regs);
}
/* Delivered the signal. */
ctx->child_sig = 0;
validate_args(ctx->trace.stop_reason, -1, ctx);
}
static void replay_one_trace_frame(struct dbg_context* dbg,
struct context* ctx)
{
struct dbg_request req;
struct rep_trace_step step;
int event = ctx->trace.stop_reason;
int stop_sig = 0;
debug("%d: replaying event %s, state %s",
ctx->rec_tid,
strevent(event), statename(ctx->trace.state));
if (ctx->syscallbuf_hdr) {
debug(" (syscllbufsz:%u, abrtcmt:%u)",
ctx->syscallbuf_hdr->num_rec_bytes,
ctx->syscallbuf_hdr->abort_commit);
}
/* Advance the trace until we've exec()'d the tracee before
* processing debugger requests. Otherwise the debugger host
* will be confused about the initial executable image,
* rr's. */
if (validate) {
req = process_debugger_requests(dbg, ctx);
assert(dbg_is_resume_request(&req));
}
/* print some kind of progress */
if (ctx->trace.global_time % 10000 == 0) {
fprintf(stderr, "time: %u\n",ctx->trace.global_time);
}
if (ctx->child_sig != 0) {
assert(event == -ctx->child_sig
|| event == -(ctx->child_sig | DET_SIGNAL_BIT));
ctx->child_sig = 0;
}
/* Ask the trace-interpretation code what to do next in order
* to retire the current frame. */
memset(&step, 0, sizeof(step));
switch (event) {
case USR_INIT_SCRATCH_MEM: {
/* for checksumming: make a note that this area is
* scratch and need not be validated. */
struct mmapped_file file;
read_next_mmapped_file_stats(&file);
replay_init_scratch_memory(ctx, &file);
add_scratch((void*)ctx->trace.recorded_regs.eax,
file.end - file.start);
step.action = TSTEP_RETIRE;
break;
}
case USR_EXIT:
rep_sched_deregister_thread(&ctx);
/* Early-return because |ctx| is gone now. */
return;
case USR_ARM_DESCHED:
case USR_DISARM_DESCHED:
rep_skip_desched_ioctl(ctx);
/* TODO */
step.action = TSTEP_RETIRE;
break;
case USR_SYSCALLBUF_ABORT_COMMIT:
ctx->syscallbuf_hdr->abort_commit = 1;
step.action = TSTEP_RETIRE;
break;
case USR_SYSCALLBUF_FLUSH:
rep_process_flush(ctx, rr_flags->redirect);
/* TODO */
step.action = TSTEP_RETIRE;
break;
case USR_SYSCALLBUF_RESET:
ctx->syscallbuf_hdr->num_rec_bytes = 0;
step.action = TSTEP_RETIRE;
break;
case USR_SCHED:
step.action = TSTEP_PROGRAM_ASYNC_SIGNAL_INTERRUPT;
step.target.rcb = ctx->trace.rbc;
step.target.regs = &ctx->trace.recorded_regs;
step.target.signo = 0;
break;
case SIG_SEGV_RDTSC:
step.action = TSTEP_DETERMINISTIC_SIGNAL;
step.signo = SIGSEGV;
break;
default:
/* Pseudosignals are handled above. */
assert(event > LAST_RR_PSEUDOSIGNAL);
if (FIRST_DET_SIGNAL <= event && event <= LAST_DET_SIGNAL) {
step.action = TSTEP_DETERMINISTIC_SIGNAL;
step.signo = (-event & ~DET_SIGNAL_BIT);
stop_sig = step.signo;
} else if (event < 0) {
assert(FIRST_ASYNC_SIGNAL <= event
&& event <= LAST_ASYNC_SIGNAL);
step.action = TSTEP_PROGRAM_ASYNC_SIGNAL_INTERRUPT;
step.target.rcb = ctx->trace.rbc;
step.target.regs = &ctx->trace.recorded_regs;
step.target.signo = -event;
stop_sig = step.target.signo;
} else {
assert(event > 0);
/* XXX not so pretty ... */
validate |= (ctx->trace.state == STATE_SYSCALL_EXIT
&& event == SYS_execve);
rep_process_syscall(ctx, rr_flags->redirect, &step);
}
}
/* See the comment below about *not* resetting the hpc for
* buffer flushes. Here, we're processing the *other* event,
* just after the buffer flush, where the rcb matters. To
* simplify the advance-to-target code that follows (namely,
* making debugger interrupts simpler), pretend like the
* execution in the BUFFER_FLUSH didn't happen by resetting
* the rbc and compensating down the target rcb. */
if (TSTEP_PROGRAM_ASYNC_SIGNAL_INTERRUPT == step.action) {
uint64_t rcb_now = read_rbc(ctx->hpc);
assert(step.target.rcb >= rcb_now);
step.target.rcb -= rcb_now;
reset_hpc(ctx, 0);
}
/* Advance until |step| has been fulfilled. */
while (try_one_trace_step(ctx, &step, &req)) {
struct user_regs_struct regs;
/* Currently we only understand software breakpoints
* and successful stepi's. */
assert(SIGTRAP == ctx->child_sig && "Unknown trap");
read_child_registers(ctx->child_tid, ®s);
if (ip_is_breakpoint((void*)regs.eip)) {
/* SW breakpoint: $ip is just past the
* breakpoint instruction. Move $ip back
* right before it. */
regs.eip -= sizeof(int_3_insn);
write_child_registers(ctx->child_tid, ®s);
} else {
/* Successful stepi. Nothing else to do. */
assert(DREQ_STEP == req.type
&& req.target == get_threadid(ctx));
}
/* Don't restart with SIGTRAP anywhere. */
ctx->child_sig = 0;
/* Notify the debugger and process any new requests
* that might have triggered before resuming. */
dbg_notify_stop(dbg, get_threadid(ctx), 0x05/*gdb mandate*/);
req = process_debugger_requests(dbg, ctx);
assert(dbg_is_resume_request(&req));
}
if (dbg && stop_sig) {
dbg_notify_stop(dbg, get_threadid(ctx), stop_sig);
}
/* We flush the syscallbuf in response to detecting *other*
* events, like signal delivery. Flushing the syscallbuf is a
* sort of side-effect of reaching the other event. But once
* we've flushed the syscallbuf during replay, we still must
* reach the execution point of the *other* event. For async
* signals, that requires us to have an "intact" rbc, with the
* same value as it was when the last buffered syscall was
* retired during replay. We'll be continuing from that rcb
* to reach the rcb we recorded at signal delivery. So don't
* reset the counter for buffer flushes. (It doesn't matter
* for non-async-signal types, which are deterministic.) */
switch (ctx->trace.stop_reason) {
case USR_SYSCALLBUF_ABORT_COMMIT:
case USR_SYSCALLBUF_FLUSH:
case USR_SYSCALLBUF_RESET:
break;
default:
reset_hpc(ctx, 0);
}
debug_memory(ctx);
}
/**
* Run execution forwards for |ctx| until |ctx->trace.rbc| is reached,
* and the $ip reaches the recorded $ip. Return 0 if successful or 1
* if an unhandled interrupt occurred. |sig| is the pending signal to
* be delivered; it's only used to distinguish debugger-related traps
* from traps related to replaying execution.
*/
static int advance_to(struct context* ctx, uint64_t rcb,
const struct user_regs_struct* regs, int sig,
int stepi)
{
pid_t tid = ctx->child_tid;
uint64_t rcb_now;
assert(ctx->hpc->rbc.fd > 0);
assert(ctx->child_sig == 0);
/* Step 1: advance to the target rcb (minus a slack region) as
* quickly as possible by programming the hpc. */
rcb_now = read_rbc(ctx->hpc);
debug("Advancing to rcb:%llu/eip:%p from rcb:%llu",
rcb, (void*)regs->eip, rcb_now);
/* XXX should we only do this if (rcb > 10000)? */
while (rcb > SKID_SIZE && rcb_now < rcb - SKID_SIZE) {
if (SIGTRAP == ctx->child_sig) {
/* We proved we're not at the execution target
* and we're not single-stepping execution, so
* this must have been meant for the debugger.
* (The debugging code will verify that.) */
return 1;
}
ctx->child_sig = 0;
reset_hpc(ctx, rcb - rcb_now - SKID_SIZE);
continue_or_step(ctx, stepi);
if (SIGIO == ctx->child_sig || SIGCHLD == ctx->child_sig) {
/* Tracees can receive SIGCHLD at pretty much
* any time during replay. If we recorded
* delivery, we'll manually replay it
* eventually (or already have). Just ignore
* here. */
ctx->child_sig = 0;
}
guard_unexpected_signal(ctx);
if (fcntl(ctx->hpc->rbc.fd, F_GETOWN) != tid) {
fatal("Scheduled task %d doesn't own hpc; replay divergence", tid);
}
rcb_now = read_rbc(ctx->hpc);
}
guard_overshoot(ctx, rcb, rcb_now);
/* Step 2: Slowly single-step our way to the target rcb.
*
* This is apparently needed because hpc interrupts can
* overshoot. */
while (rcb > 0 && rcb_now < rcb) {
if (SIGTRAP == ctx->child_sig
&& is_debugger_trap(ctx, sig, ASYNC, NOT_AT_TARGET,
stepi)) {
/* We proved that we're not at the execution
* target, but we're single-stepping now so
* have to check whether this was a debugger
* trap. */
return 1;
}
continue_or_step(ctx, STEPI);
if (SIGCHLD == ctx->child_sig) {
/* See above. */
ctx->child_sig = 0;
}
guard_unexpected_signal(ctx);
rcb_now = read_rbc(ctx->hpc);
}
guard_overshoot(ctx, rcb, rcb_now);
/* Step 3: Slowly single-step our way to the target $ip.
*
* What we really want to do is set a retired-instruction
* interrupt and do away with all this cruft. */
while (rcb == rcb_now) {
struct user_regs_struct cur_regs;
read_child_registers(ctx->child_tid, &cur_regs);
if (0 == compare_register_files("rep interrupt", &cur_regs,
"rec", regs, 0, 0)) {
if (SIGTRAP == ctx->child_sig
&& is_debugger_trap(ctx, sig, ASYNC, AT_TARGET,
stepi)) {
return 1;
}
ctx->child_sig = 0;
break;
}
debug("Stepping from ip %p to %p",
(void*)cur_regs.eip, (void*)regs->eip);
if (SIGTRAP == ctx->child_sig
&& is_debugger_trap(ctx, ASYNC, sig, NOT_AT_TARGET,
stepi)) {
/* See above. */
return 1;
}
continue_or_step(ctx, STEPI);
if (SIGCHLD == ctx->child_sig) {
/* See above. */
ctx->child_sig = 0;
}
guard_unexpected_signal(ctx);
rcb_now = read_rbc(ctx->hpc);
}
guard_overshoot(ctx, rcb, rcb_now);
return 0;
}
void rep_process_signal(struct context *ctx)
{
struct trace* trace = &(ctx->trace);
int tid = ctx->child_tid;
int sig = -trace->stop_reason;
/* if the there is still a signal pending here, two signals in a row must be delivered?\n */
assert(ctx->child_sig == 0);
switch (sig) {
/* set the eax and edx register to the recorded values */
case -SIG_SEGV_RDTSC:
{
struct user_regs_struct regs;
int size;
/* goto the event */
goto_next_event(ctx);
/* make sure we are there */
assert(WSTOPSIG(ctx->status) == SIGSEGV);
char* inst = get_inst(tid, 0, &size);
assert(strncmp(inst,"rdtsc",5) == 0);
read_child_registers(tid, ®s);
regs.eax = trace->recorded_regs.eax;
regs.edx = trace->recorded_regs.edx;
regs.eip += size;
write_child_registers(tid, ®s);
sys_free((void**) &inst);
compare_register_files("rdtsv_now", ®s, "rdsc_rec", &ctx->trace.recorded_regs, 1, 1);
/* this signal should not be recognized by the application */
ctx->child_sig = 0;
break;
}
case -USR_SCHED:
{
assert(trace->rbc_up > 0);
/* if the current architecture over-counts the event in question,
* substract the overcount here */
reset_hpc(ctx, trace->rbc_up - SKID_SIZE);
goto_next_event(ctx);
/* make sure that the signal came from hpc */
if (fcntl(ctx->hpc->rbc_down.fd, F_GETOWN) == ctx->child_tid) {
/* this signal should not be recognized by the application */
ctx->child_sig = 0;
stop_hpc_down(ctx);
compensate_branch_count(ctx, sig);
stop_hpc(ctx);
} else {
fprintf(stderr, "internal error: next event should be: %d but it is: %d -- bailing out\n", -USR_SCHED, ctx->event);
sys_exit();
}
break;
}
case SIGIO:
case SIGCHLD:
{
/* synchronous signal (signal received in a system call) */
if (trace->rbc_up == 0) {
ctx->replay_sig = sig;
return;
}
// setup and start replay counters
reset_hpc(ctx, trace->rbc_up - SKID_SIZE);
/* single-step if the number of instructions to the next event is "small" */
if (trace->rbc_up <= 10000) {
stop_hpc_down(ctx);
compensate_branch_count(ctx, sig);
stop_hpc(ctx);
} else {
printf("large count\n");
sys_ptrace_syscall(tid);
sys_waitpid(tid, &ctx->status);
// make sure we ere interrupted by ptrace
assert(WSTOPSIG(ctx->status) == SIGIO);
/* reset the penig sig, since it did not occur in the original execution */
ctx->child_sig = 0;
ctx->status = 0;
//DO NOT FORGET TO STOP HPC!!!
compensate_branch_count(ctx, sig);
stop_hpc(ctx);
stop_hpc_down(ctx);
}
break;
}
case SIGSEGV:
{
/* synchronous signal (signal received in a system call) */
if (trace->rbc_up == 0 && trace->page_faults == 0) {
ctx->replay_sig = sig;
return;
}
sys_ptrace_syscall(ctx->child_tid);
sys_waitpid(ctx->child_tid, &ctx->status);
assert(WSTOPSIG(ctx->status) == SIGSEGV);
struct user_regs_struct regs;
read_child_registers(ctx->child_tid, ®s);
assert(compare_register_files("now", ®s, "rec", &ctx->trace.recorded_regs, 1, 1) == 0);
/* deliver the signal */
singlestep(ctx, SIGSEGV, 0x57f);
break;
}
default:
printf("unknown signal %d -- bailing out\n", sig);
sys_exit();
break;
}
}
