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
assert(ar);
bool ret =
uintptr_t(ar) - s_stackLimit >= s_stackSize &&
!sim->is_on_stack(ar);
assert(!ret ||
(ar >= vmStack().getStackLowAddress() &&
ar < vmStack().getStackHighAddress()) ||
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* rbp = reinterpret_cast<ActRec*>(sim->xreg(JIT::ARM::rVmFp.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.m_fp->m_func->name()->data(),
regs.m_fp, regs.m_sp, regs.m_pc);
vmfp() = const_cast<ActRec*>(regs.m_fp);
vmpc() = reinterpret_cast<PC>(regs.m_pc);
vmsp() = regs.m_sp;
return;
}
// This shouldn't be reached.
always_assert(false);
}
bool FixupMap::getFrameRegs(const ActRec* ar,
const ActRec* prevAr,
VMRegs* outVMRegs) const {
CTCA tca = (CTCA)ar->m_savedRip;
// Non-obvious off-by-one fun: if the *return address* points into the TC,
// then the frame we were running on in the TC is actually the previous
// frame.
ar = ar->m_sfp;
auto* ent = m_fixups.find(tca);
if (!ent) return false;
if (ent->isIndirect()) {
// Note: if indirect fixups happen frequently enough, we could
// just compare savedRip to be less than some threshold where
// stubs in a.code stop.
assertx(prevAr);
auto pRealRip = ent->indirect.returnIpDisp +
uintptr_t(prevAr->m_sfp);
ent = m_fixups.find(*reinterpret_cast<CTCA*>(pRealRip));
assertx(ent && !ent->isIndirect());
}
regsFromActRec(tca, ar, ent->fixup, outVMRegs);
return true;
}
