// Place internal breakpoints to get out of the current function. This may place
// multiple internal breakpoints, and it may place them more than one frame up.
// Some instructions can cause PHP to be invoked without an explicit call. A set
// which causes a destructor to run, a iteration init which causes an object's
// next() method to run, a RetC which causes destructors to run, etc. This
// recgonizes such cases and ensures we have internal breakpoints to cover the
// destination(s) of such instructions.
void CmdFlowControl::setupStepOuts() {
// Existing step outs should be cleaned up before making new ones.
assert(!hasStepOuts());
auto fp = g_context->getFP();
if (!fp) return; // No place to step out to!
Offset returnOffset;
bool fromVMEntry;
while (!hasStepOuts()) {
fp = g_context->getPrevVMState(fp, &returnOffset, nullptr, &fromVMEntry);
// If we've run off the top of the stack, just return having setup no
// step outs. This will cause cmds like Next and Out to just let the program
// run, which is appropriate.
if (!fp) break;
Unit* returnUnit = fp->m_func->unit();
PC returnPC = returnUnit->at(returnOffset);
TRACE(2, "CmdFlowControl::setupStepOuts: at '%s' offset %d opcode %s\n",
fp->m_func->fullName()->data(), returnOffset,
opcodeToName(*reinterpret_cast<const Op*>(returnPC)));
// Don't step out to generated functions, keep looking.
if (fp->m_func->line1() == 0) continue;
if (fromVMEntry) {
TRACE(2, "CmdFlowControl::setupStepOuts: VM entry\n");
// We only execute this for opcodes which invoke more PHP, and that does
// not include switches. Thus, we'll have at most two destinations.
assert(!isSwitch(*reinterpret_cast<const Op*>(returnPC)) &&
(numSuccs(reinterpret_cast<const Op*>(returnPC)) <= 2));
// Set an internal breakpoint after the instruction if it can fall thru.
if (instrAllowsFallThru(*reinterpret_cast<const Op*>(returnPC))) {
Offset nextOffset = returnOffset + instrLen((Op*)returnPC);
TRACE(2, "CmdFlowControl: step out to '%s' offset %d (fall-thru)\n",
fp->m_func->fullName()->data(), nextOffset);
m_stepOut1 = StepDestination(returnUnit, nextOffset);
}
// Set an internal breakpoint at the target of a control flow instruction.
// A good example of a control flow op that invokes PHP is IterNext.
if (instrIsControlFlow(*reinterpret_cast<const Op*>(returnPC))) {
Offset target =
instrJumpTarget(reinterpret_cast<const Op*>(returnPC), 0);
if (target != InvalidAbsoluteOffset) {
Offset targetOffset = returnOffset + target;
TRACE(2, "CmdFlowControl: step out to '%s' offset %d (jump target)\n",
fp->m_func->fullName()->data(), targetOffset);
m_stepOut2 = StepDestination(returnUnit, targetOffset);
}
}
// If we have no place to step out to, then unwind another frame and try
// again. The most common case that leads here is Ret*, which does not
// fall-thru and has no encoded target.
} else {
TRACE(2, "CmdFlowControl: step out to '%s' offset %d\n",
fp->m_func->fullName()->data(), returnOffset);
m_stepOut1 = StepDestination(returnUnit, returnOffset);
}
}
}
void CmdNext::onBeginInterrupt(DebuggerProxy& proxy, CmdInterrupt& interrupt) {
TRACE(2, "CmdNext::onBeginInterrupt\n");
assertx(!m_complete); // Complete cmds should not be asked to do work.
ActRec *fp = vmfp();
if (!fp) {
// If we have no frame just wait for the next instruction to be interpreted.
m_needsVMInterrupt = true;
return;
}
PC pc = vmpc();
Unit* unit = fp->m_func->unit();
Offset offset = unit->offsetOf(pc);
TRACE(2, "CmdNext: pc %p, opcode %s at '%s' offset %d\n",
pc,
opcodeToName(peek_op(pc)),
fp->m_func->fullName()->data(),
offset);
int currentVMDepth = g_context->m_nesting;
int currentStackDepth = proxy.getStackDepth();
TRACE(2, "CmdNext: original depth %d:%d, current depth %d:%d\n",
m_vmDepth, m_stackDepth, currentVMDepth, currentStackDepth);
// Where are we on the stack now vs. when we started? Breaking the answer down
// into distinct variables helps the clarity of the algorithm below.
bool deeper = false;
bool originalDepth = false;
if ((currentVMDepth == m_vmDepth) && (currentStackDepth == m_stackDepth)) {
originalDepth = true;
} else if ((currentVMDepth > m_vmDepth) ||
((currentVMDepth == m_vmDepth) &&
(currentStackDepth > m_stackDepth))) {
deeper = true;
}
m_needsVMInterrupt = false; // Will be set again below if still needed.
// First consider if we've got internal breakpoints setup. These are used when
// we can make an accurate prediction of where execution should flow,
// eventually, and when we want to let the program run normally until we get
// there.
if (hasStepOuts() || hasStepResumable()) {
TRACE(2, "CmdNext: checking internal breakpoint(s)\n");
if (atStepOutOffset(unit, offset)) {
if (deeper) return; // Recursion
TRACE(2, "CmdNext: hit step-out\n");
} else if (atStepResumableOffset(unit, offset)) {
if (m_stepResumableId != getResumableId(fp)) return;
TRACE(2, "CmdNext: hit step-cont\n");
// We're in the resumable we expect. This may be at a
// different stack depth, though, especially if we've moved from
// the original function to the resumable. Update the depth
// accordingly.
if (!originalDepth) {
m_vmDepth = currentVMDepth;
m_stackDepth = currentStackDepth;
deeper = false;
originalDepth = true;
}
} else if (interrupt.getInterruptType() == ExceptionHandler) {
// Entering an exception handler may take us someplace we weren't
// expecting. Adjust internal breakpoints accordingly. First case is easy.
if (deeper) {
TRACE(2, "CmdNext: exception handler, deeper\n");
return;
}
// For step-conts, we ignore handlers at the original level if we're not
// in the original resumable. We don't care about exception handlers
// in resumables being driven at the same level.
if (hasStepResumable() && originalDepth &&
(m_stepResumableId != getResumableId(fp))) {
TRACE(2, "CmdNext: exception handler, original depth, wrong cont\n");
return;
}
// Sometimes we have handlers in generated code, i.e., Continuation::next.
// These just help propagate exceptions so ignore those.
if (fp->m_func->line1() == 0) {
TRACE(2, "CmdNext: exception handler, ignoring func with no source\n");
return;
}
if (fp->m_func->isBuiltin()) {
TRACE(2, "CmdNext: exception handler, ignoring builtin functions\n");
return;
}
TRACE(2, "CmdNext: exception handler altering expected flow\n");
} else {
// We have internal breakpoints setup, but we haven't hit one yet. Keep
// running until we reach one.
TRACE(2, "CmdNext: waiting to hit internal breakpoint...\n");
return;
}
// We've hit one internal breakpoint at a useful place, or decided we don't,
// need them, so we can remove them all now.
cleanupStepOuts();
cleanupStepResumable();
}
if (interrupt.getInterruptType() == ExceptionHandler) {
// If we're about to enter an exception handler we turn interrupts on to
// ensure we stop when control reaches the handler. The normal logic below
// will decide if we're done at that point or not.
TRACE(2, "CmdNext: exception handler\n");
removeLocationFilter();
m_needsVMInterrupt = true;
return;
}
if (m_skippingAwait) {
m_skippingAwait = false;
stepAfterAwait();
return;
}
if (deeper) {
TRACE(2, "CmdNext: deeper, setup step out to get back to original line\n");
setupStepOuts();
// We can nuke the entire location filter here since we'll re-install it
// when we get back to the old level. Keeping it installed may be more
// efficient if we were on a large line, but there is a penalty for every
// opcode executed while it's installed and that's bad if there's a lot of
// code called from that line.
removeLocationFilter();
return;
}
if (originalDepth && (m_loc == interrupt.getFileLine())) {
TRACE(2, "CmdNext: not complete, still on same line\n");
stepCurrentLine(interrupt, fp, pc);
return;
}
TRACE(2, "CmdNext: operation complete.\n");
m_complete = (decCount() == 0);
if (!m_complete) {
TRACE(2, "CmdNext: repeat count > 0, start fresh.\n");
onSetup(proxy, interrupt);
}
}
