bool isVMFrame(const ActRec* ar) {
assert(ar);
// Determine whether the frame pointer is outside the native stack, cleverly
// using a single unsigned comparison to do both halves of the bounds check.
bool ret = uintptr_t(ar) - s_stackLimit >= s_stackSize;
assert(!ret || isValidVMStackAddress(ar) ||
(ar->m_func->validate(), ar->resumed()));
return ret;
}
void FixupMap::fixupWorkSimulated(ExecutionContext* ec) const {
TRACE(1, "fixup(begin):\n");
auto isVMFrame = [] (ActRec* ar, const vixl::Simulator* sim) {
// If this assert is failing, you may have forgotten a sync point somewhere
assertx(ar);
bool ret =
uintptr_t(ar) - s_stackLimit >= s_stackSize &&
!sim->is_on_stack(ar);
assertx(!ret || isValidVMStackAddress(ar) || ar->resumed());
return ret;
};
// For each nested simulator (corresponding to nested VM invocations), look at
// its PC to find a potential fixup key.
//
// Callstack walking is necessary, because we may get called from a
// uniqueStub.
for (int i = ec->m_activeSims.size() - 1; i >= 0; --i) {
auto const* sim = ec->m_activeSims[i];
auto const fp = arm::x2a(arm::rvmfp());
auto* rbp = reinterpret_cast<ActRec*>(sim->xreg(fp.code()));
auto tca = reinterpret_cast<TCA>(sim->pc());
TRACE(2, "considering frame %p, %p\n", rbp, tca);
while (rbp && !isVMFrame(rbp, sim)) {
tca = reinterpret_cast<TCA>(rbp->m_savedRip);
rbp = rbp->m_sfp;
}
if (!rbp) continue;
auto* ent = m_fixups.find(tca);
if (!ent) {
continue;
}
if (ent->isIndirect()) {
not_implemented();
}
VMRegs regs;
regsFromActRec(tca, rbp, ent->fixup, ®s);
TRACE(2, "fixup(end): func %s fp %p sp %p pc %p\b",
regs.fp->m_func->name()->data(),
regs.fp, regs.sp, regs.pc);
auto& vmRegs = vmRegsUnsafe();
vmRegs.fp = const_cast<ActRec*>(regs.fp);
vmRegs.pc = reinterpret_cast<PC>(regs.pc);
vmRegs.stack.top() = regs.sp;
return;
}
// This shouldn't be reached.
always_assert(false);
}
void enterTC(TCA start, ActRec* stashedAR) {
if (debug) {
fflush(stdout);
fflush(stderr);
}
assertx(tc::isValidCodeAddress(start));
assertx(((uintptr_t)vmsp() & (sizeof(Cell) - 1)) == 0);
assertx(((uintptr_t)vmfp() & (sizeof(Cell) - 1)) == 0);
INC_TPC(enter_tc);
if (Trace::moduleEnabled(Trace::ringbuffer, 1)) {
auto skData = SrcKey{liveFunc(), vmpc(), liveResumed()}.toAtomicInt();
Trace::ringbufferEntry(Trace::RBTypeEnterTC, skData, (uint64_t)start);
}
tl_regState = VMRegState::DIRTY;
enterTCImpl(start, stashedAR);
tl_regState = VMRegState::CLEAN;
assertx(isValidVMStackAddress(vmsp()));
vmfp() = nullptr;
}
