Handle implicit stack overflow without affecting stack walks
This changes the way in which implicit stack overflows are handled
to satisfy concerns about changes to the stack walk code.
Instead of creating a gap in the stack and checking for it in
the stack walker, use the ManagedStack infrastructure to concoct
an invisible gap that will never be seen by a stack walk.
Also, this uses madvise to tell the kernel that the main stack's
protected region will probably never be accessed, and instead
of using memset to map the pages in, use memcpy to read from
them. This will save 32K on the main stack.
Also adds a 'signals' verbosity level as per a review request.
Bug: 14066862
Change-Id: I5257305feeaea241d11e6aa6f021d2a81da20b81
diff --git a/compiler/dex/quick/arm/call_arm.cc b/compiler/dex/quick/arm/call_arm.cc
index 163c0fe..d3477c9 100644
--- a/compiler/dex/quick/arm/call_arm.cc
+++ b/compiler/dex/quick/arm/call_arm.cc
@@ -360,6 +360,22 @@
if (Runtime::Current()->ExplicitStackOverflowChecks()) {
/* Load stack limit */
Load32Disp(rs_rARM_SELF, Thread::StackEndOffset<4>().Int32Value(), rs_r12);
+ } else {
+ // Implicit stack overflow check.
+ // Generate a load from [sp, #-overflowsize]. If this is in the stack
+ // redzone we will get a segmentation fault.
+ //
+ // Caveat coder: if someone changes the kStackOverflowReservedBytes value
+ // we need to make sure that it's loadable in an immediate field of
+ // a sub instruction. Otherwise we will get a temp allocation and the
+ // code size will increase.
+ //
+ // This is done before the callee save instructions to avoid any possibility
+ // of these overflowing. This uses r12 and that's never saved in a callee
+ // save.
+ OpRegRegImm(kOpSub, rs_r12, rs_rARM_SP, Thread::kStackOverflowReservedBytes);
+ Load32Disp(rs_r12, 0, rs_r12);
+ MarkPossibleStackOverflowException();
}
}
/* Spill core callee saves */
@@ -418,17 +434,8 @@
AddSlowPath(new(arena_)StackOverflowSlowPath(this, branch, false, frame_size_));
}
} else {
- // Implicit stack overflow check.
- // Generate a load from [sp, #-overflowsize]. If this is in the stack
- // redzone we will get a segmentation fault.
- //
- // Caveat coder: if someone changes the kStackOverflowReservedBytes value
- // we need to make sure that it's loadable in an immediate field of
- // a sub instruction. Otherwise we will get a temp allocation and the
- // code size will increase.
- OpRegRegImm(kOpSub, rs_r12, rs_rARM_SP, Thread::kStackOverflowReservedBytes);
- Load32Disp(rs_r12, 0, rs_r12);
- MarkPossibleStackOverflowException();
+ // Implicit stack overflow check has already been done. Just make room on the
+ // stack for the frame now.
OpRegImm(kOpSub, rs_rARM_SP, frame_size_without_spills);
}
} else {
diff --git a/runtime/arch/arm/fault_handler_arm.cc b/runtime/arch/arm/fault_handler_arm.cc
index eddaa0b..f81e2f9 100644
--- a/runtime/arch/arm/fault_handler_arm.cc
+++ b/runtime/arch/arm/fault_handler_arm.cc
@@ -34,7 +34,7 @@
namespace art {
extern "C" void art_quick_throw_null_pointer_exception();
-extern "C" void art_quick_throw_stack_overflow(void*);
+extern "C" void art_quick_throw_stack_overflow_from_signal();
extern "C" void art_quick_implicit_suspend();
// Get the size of a thumb2 instruction in bytes.
@@ -50,7 +50,7 @@
struct ucontext *uc = (struct ucontext *)context;
struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
*out_sp = static_cast<uintptr_t>(sc->arm_sp);
- LOG(DEBUG) << "sp: " << *out_sp;
+ VLOG(signals) << "sp: " << *out_sp;
if (*out_sp == 0) {
return;
}
@@ -74,7 +74,7 @@
// Need to work out the size of the instruction that caused the exception.
uint8_t* ptr = reinterpret_cast<uint8_t*>(sc->arm_pc);
- LOG(DEBUG) << "pc: " << std::hex << static_cast<void*>(ptr);
+ VLOG(signals) << "pc: " << std::hex << static_cast<void*>(ptr);
uint32_t instr_size = GetInstructionSize(ptr);
*out_return_pc = (sc->arm_pc + instr_size) | 1;
@@ -95,7 +95,7 @@
uint32_t instr_size = GetInstructionSize(ptr);
sc->arm_lr = (sc->arm_pc + instr_size) | 1; // LR needs to point to gc map location
sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_throw_null_pointer_exception);
- LOG(DEBUG) << "Generating null pointer exception";
+ VLOG(signals) << "Generating null pointer exception";
return true;
}
@@ -117,10 +117,10 @@
struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
uint8_t* ptr2 = reinterpret_cast<uint8_t*>(sc->arm_pc);
uint8_t* ptr1 = ptr2 - 4;
- LOG(DEBUG) << "checking suspend";
+ VLOG(signals) << "checking suspend";
uint16_t inst2 = ptr2[0] | ptr2[1] << 8;
- LOG(DEBUG) << "inst2: " << std::hex << inst2 << " checkinst2: " << checkinst2;
+ VLOG(signals) << "inst2: " << std::hex << inst2 << " checkinst2: " << checkinst2;
if (inst2 != checkinst2) {
// Second instruction is not good, not ours.
return false;
@@ -132,7 +132,7 @@
bool found = false;
while (ptr1 > limit) {
uint32_t inst1 = ((ptr1[0] | ptr1[1] << 8) << 16) | (ptr1[2] | ptr1[3] << 8);
- LOG(DEBUG) << "inst1: " << std::hex << inst1 << " checkinst1: " << checkinst1;
+ VLOG(signals) << "inst1: " << std::hex << inst1 << " checkinst1: " << checkinst1;
if (inst1 == checkinst1) {
found = true;
break;
@@ -140,7 +140,7 @@
ptr1 -= 2; // Min instruction size is 2 bytes.
}
if (found) {
- LOG(DEBUG) << "suspend check match";
+ VLOG(signals) << "suspend check match";
// This is a suspend check. Arrange for the signal handler to return to
// art_quick_implicit_suspend. Also set LR so that after the suspend check it
// will resume the instruction (current PC + 2). PC points to the
@@ -148,14 +148,14 @@
// NB: remember that we need to set the bottom bit of the LR register
// to switch to thumb mode.
- LOG(DEBUG) << "arm lr: " << std::hex << sc->arm_lr;
- LOG(DEBUG) << "arm pc: " << std::hex << sc->arm_pc;
+ VLOG(signals) << "arm lr: " << std::hex << sc->arm_lr;
+ VLOG(signals) << "arm pc: " << std::hex << sc->arm_pc;
sc->arm_lr = sc->arm_pc + 3; // +2 + 1 (for thumb)
sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_implicit_suspend);
// Now remove the suspend trigger that caused this fault.
Thread::Current()->RemoveSuspendTrigger();
- LOG(DEBUG) << "removed suspend trigger invoking test suspend";
+ VLOG(signals) << "removed suspend trigger invoking test suspend";
return true;
}
return false;
@@ -174,103 +174,60 @@
// on the stack.
//
// If we determine this is a stack overflow we need to move the stack pointer
-// to the overflow region below the protected region. Because we now have
-// a gap in the stack (skips over protected region), we need to arrange
-// for the rest of the system to be unaware of the new stack arrangement
-// and behave as if there is a fully valid stack. We do this by placing
-// a unique address onto the stack followed by
-// the size of the gap. The stack walker will detect this and skip over the
-// gap.
-
-// NB. We also need to be careful of stack alignment as the ARM EABI specifies that
-// stack must be 8 byte aligned when making any calls.
-
-// NB. The size of the gap is the difference between the previous frame's SP and
-// the SP at which the size word is pushed.
+// to the overflow region below the protected region.
bool StackOverflowHandler::Action(int sig, siginfo_t* info, void* context) {
struct ucontext *uc = (struct ucontext *)context;
struct sigcontext *sc = reinterpret_cast<struct sigcontext*>(&uc->uc_mcontext);
- LOG(DEBUG) << "stack overflow handler with sp at " << std::hex << &uc;
- LOG(DEBUG) << "sigcontext: " << std::hex << sc;
+ VLOG(signals) << "stack overflow handler with sp at " << std::hex << &uc;
+ VLOG(signals) << "sigcontext: " << std::hex << sc;
- uint8_t* sp = reinterpret_cast<uint8_t*>(sc->arm_sp);
- LOG(DEBUG) << "sp: " << static_cast<void*>(sp);
+ uintptr_t sp = sc->arm_sp;
+ VLOG(signals) << "sp: " << std::hex << sp;
- uintptr_t* fault_addr = reinterpret_cast<uintptr_t*>(sc->fault_address);
- LOG(DEBUG) << "fault_addr: " << std::hex << fault_addr;
- LOG(DEBUG) << "checking for stack overflow, sp: " << std::hex << static_cast<void*>(sp) <<
+ uintptr_t fault_addr = sc->fault_address;
+ VLOG(signals) << "fault_addr: " << std::hex << fault_addr;
+ VLOG(signals) << "checking for stack overflow, sp: " << std::hex << sp <<
", fault_addr: " << fault_addr;
- uintptr_t* overflow_addr = reinterpret_cast<uintptr_t*>(sp - Thread::kStackOverflowReservedBytes);
+
+ uintptr_t overflow_addr = sp - Thread::kStackOverflowReservedBytes;
+
+ Thread* self = reinterpret_cast<Thread*>(sc->arm_r9);
+ CHECK_EQ(self, Thread::Current());
+ uintptr_t pregion = reinterpret_cast<uintptr_t>(self->GetStackEnd()) -
+ Thread::kStackOverflowProtectedSize;
// Check that the fault address is the value expected for a stack overflow.
if (fault_addr != overflow_addr) {
- LOG(DEBUG) << "Not a stack overflow";
+ VLOG(signals) << "Not a stack overflow";
return false;
}
// We know this is a stack overflow. We need to move the sp to the overflow region
- // the exists below the protected region. R9 contains the current Thread* so
- // we can read the stack_end from that and subtract the size of the
- // protected region. This creates a gap in the stack that needs to be marked.
- Thread* self = reinterpret_cast<Thread*>(sc->arm_r9);
+ // the exists below the protected region. Determine the address of the next
+ // available valid address below the protected region.
+ uintptr_t prevsp = sp;
+ sp = pregion;
+ VLOG(signals) << "setting sp to overflow region at " << std::hex << sp;
- uint8_t* prevsp = sp;
- sp = self->GetStackEnd() - Thread::kStackOverflowProtectedSize;
- LOG(DEBUG) << "setting sp to overflow region at " << std::hex << static_cast<void*>(sp);
-
- // We need to find the previous frame. Remember that
- // this has not yet been fully constructed because the SP has not been
- // decremented. So we need to work out the size of the spill portion of the
- // frame. This consists of something like:
- //
- // 0xb6a1d49c: e92d40e0 push {r5, r6, r7, lr}
- // 0xb6a1d4a0: ed2d8a06 vpush.f32 {s16-s21}
- //
- // The first is encoded in the ArtMethod as the spill_mask, the second as the
- // fp_spill_mask. A population count on each will give the number of registers
- // in each mask. Each register is 4 bytes on ARM32.
-
- mirror::ArtMethod* method = reinterpret_cast<mirror::ArtMethod*>(sc->arm_r0);
- uint32_t spill_mask = method->GetCoreSpillMask();
- uint32_t numcores = POPCOUNT(spill_mask);
- uint32_t fp_spill_mask = method->GetFpSpillMask();
- uint32_t numfps = POPCOUNT(fp_spill_mask);
- uint32_t spill_size = (numcores + numfps) * 4;
- LOG(DEBUG) << "spill size: " << spill_size;
- uint8_t* prevframe = prevsp + spill_size;
- LOG(DEBUG) << "previous frame: " << static_cast<void*>(prevframe);
-
- // NOTE: the ARM EABI needs an 8 byte alignment. In the case of ARM32 a pointer
- // is 4 bytes so that, together with the offset to the previous frame is 8
- // bytes. On other architectures we will need to align the stack.
-
- // Push a marker onto the stack to tell the stack walker that there is a stack
- // overflow and the stack is not contiguous.
-
- // First the offset from SP to the previous frame.
- sp -= sizeof(uint32_t);
- LOG(DEBUG) << "push gap of " << static_cast<uint32_t>(prevframe - sp);
- *reinterpret_cast<uint32_t*>(sp) = static_cast<uint32_t>(prevframe - sp);
-
- // Now the gap marker (pointer sized).
- sp -= sizeof(mirror::ArtMethod*);
- *reinterpret_cast<void**>(sp) = stack_overflow_gap_marker;
+ // Since the compiler puts the implicit overflow
+ // check before the callee save instructions, the SP is already pointing to
+ // the previous frame.
+ VLOG(signals) << "previous frame: " << std::hex << prevsp;
// Now establish the stack pointer for the signal return.
- sc->arm_sp = reinterpret_cast<uintptr_t>(sp);
+ sc->arm_sp = prevsp;
- // Now arrange for the signal handler to return to art_quick_throw_stack_overflow.
- // We need the LR to point to the GC map just after the fault instruction.
- uint8_t* ptr = reinterpret_cast<uint8_t*>(sc->arm_pc);
- uint32_t instr_size = GetInstructionSize(ptr);
- sc->arm_lr = (sc->arm_pc + instr_size) | 1; // LR needs to point to gc map location
- sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow);
+ // Tell the stack overflow code where the new stack pointer should be.
+ sc->arm_ip = sp; // aka r12
- // The kernel will now return to the address in sc->arm_pc. We have arranged the
- // stack pointer to be in the overflow region. Throwing the exception will perform
- // a longjmp which will restore the stack pointer to the correct location for the
- // exception catch.
+ // Now arrange for the signal handler to return to art_quick_throw_stack_overflow_from_signal.
+ // The value of LR must be the same as it was when we entered the code that
+ // caused this fault. This will be inserted into a callee save frame by
+ // the function to which this handler returns (art_quick_throw_stack_overflow_from_signal).
+ sc->arm_pc = reinterpret_cast<uintptr_t>(art_quick_throw_stack_overflow_from_signal);
+
+ // The kernel will now return to the address in sc->arm_pc.
return true;
}
} // namespace art
diff --git a/runtime/arch/arm/quick_entrypoints_arm.S b/runtime/arch/arm/quick_entrypoints_arm.S
index bc80644..dcf4561 100644
--- a/runtime/arch/arm/quick_entrypoints_arm.S
+++ b/runtime/arch/arm/quick_entrypoints_arm.S
@@ -235,6 +235,31 @@
*/
ONE_ARG_RUNTIME_EXCEPTION art_quick_throw_no_such_method, artThrowNoSuchMethodFromCode
+ /*
+ * Invoke stack overflow exception from signal handler.
+ * On entry:
+ * r9: thread
+ * sp: address of last known frame
+ * r12: address of next valid SP below protected region in stack
+ *
+ * This is deceptively simple but hides some complexity. It is called in the case of
+ * a stack overflow condition during implicit checks. The signal handler has been
+ * called by the kernel due to a load from the protected stack region. The handler
+ * works out the address of the previous frame and passes this in SP. However there
+ * is a piece of memory somewhere below the current SP that is not accessible (the
+ * memory that caused the signal). The signal handler works out the next
+ * accessible value of SP and passes this in r12. This code then sets up the SP
+ * to be this new value and calls the code to create and throw the stack overflow
+ * exception.
+ */
+ENTRY art_quick_throw_stack_overflow_from_signal
+ SETUP_SAVE_ALL_CALLEE_SAVE_FRAME // save all registers as basis for long jump context
+ mov r0, r9 @ pass Thread::Current
+ mov r1, sp @ pass SP
+ mov sp, r12 @ move SP down to below protected region.
+ b artThrowStackOverflowFromCode @ artThrowStackOverflowFromCode(Thread*, SP)
+END art_quick_throw_stack_overflow_from_signal
+
/*
* All generated callsites for interface invokes and invocation slow paths will load arguments
* as usual - except instead of loading arg0/r0 with the target Method*, arg0/r0 will contain
diff --git a/runtime/base/logging.h b/runtime/base/logging.h
index bd5ae85..c4461fa 100644
--- a/runtime/base/logging.h
+++ b/runtime/base/logging.h
@@ -296,6 +296,7 @@
bool startup;
bool third_party_jni; // Enabled with "-verbose:third-party-jni".
bool threads;
+ bool signals;
};
extern LogVerbosity gLogVerbosity;
diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index b8093bc..1304b04 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -106,23 +106,23 @@
bool FaultManager::IsInGeneratedCode(void* context, bool check_dex_pc) {
// We can only be running Java code in the current thread if it
// is in Runnable state.
- LOG(DEBUG) << "Checking for generated code";
+ VLOG(signals) << "Checking for generated code";
Thread* thread = Thread::Current();
if (thread == nullptr) {
- LOG(DEBUG) << "no current thread";
+ VLOG(signals) << "no current thread";
return false;
}
ThreadState state = thread->GetState();
if (state != kRunnable) {
- LOG(DEBUG) << "not runnable";
+ VLOG(signals) << "not runnable";
return false;
}
// Current thread is runnable.
// Make sure it has the mutator lock.
if (!Locks::mutator_lock_->IsSharedHeld(thread)) {
- LOG(DEBUG) << "no lock";
+ VLOG(signals) << "no lock";
return false;
}
@@ -135,9 +135,9 @@
GetMethodAndReturnPCAndSP(context, &method_obj, &return_pc, &sp);
// If we don't have a potential method, we're outta here.
- LOG(DEBUG) << "potential method: " << method_obj;
+ VLOG(signals) << "potential method: " << method_obj;
if (method_obj == 0 || !IsAligned<kObjectAlignment>(method_obj)) {
- LOG(DEBUG) << "no method";
+ VLOG(signals) << "no method";
return false;
}
@@ -147,36 +147,36 @@
// TODO: Method might be not a heap address, and GetClass could fault.
mirror::Class* cls = method_obj->GetClass<kVerifyNone>();
if (cls == nullptr) {
- LOG(DEBUG) << "not a class";
+ VLOG(signals) << "not a class";
return false;
}
if (!IsAligned<kObjectAlignment>(cls)) {
- LOG(DEBUG) << "not aligned";
+ VLOG(signals) << "not aligned";
return false;
}
if (!VerifyClassClass(cls)) {
- LOG(DEBUG) << "not a class class";
+ VLOG(signals) << "not a class class";
return false;
}
// Now make sure the class is a mirror::ArtMethod.
if (!cls->IsArtMethodClass()) {
- LOG(DEBUG) << "not a method";
+ VLOG(signals) << "not a method";
return false;
}
// We can be certain that this is a method now. Check if we have a GC map
// at the return PC address.
if (true || kIsDebugBuild) {
- LOG(DEBUG) << "looking for dex pc for return pc " << std::hex << return_pc;
+ VLOG(signals) << "looking for dex pc for return pc " << std::hex << return_pc;
const void* code = Runtime::Current()->GetInstrumentation()->GetQuickCodeFor(method_obj);
uint32_t sought_offset = return_pc - reinterpret_cast<uintptr_t>(code);
- LOG(DEBUG) << "pc offset: " << std::hex << sought_offset;
+ VLOG(signals) << "pc offset: " << std::hex << sought_offset;
}
uint32_t dexpc = method_obj->ToDexPc(return_pc, false);
- LOG(DEBUG) << "dexpc: " << dexpc;
+ VLOG(signals) << "dexpc: " << dexpc;
return !check_dex_pc || dexpc != DexFile::kDexNoIndex;
}
diff --git a/runtime/parsed_options.cc b/runtime/parsed_options.cc
index 9cf8785..f6a98e1 100644
--- a/runtime/parsed_options.cc
+++ b/runtime/parsed_options.cc
@@ -232,6 +232,7 @@
// gLogVerbosity.startup = true; // TODO: don't check this in!
// gLogVerbosity.third_party_jni = true; // TODO: don't check this in!
// gLogVerbosity.threads = true; // TODO: don't check this in!
+// gLogVerbosity.signals = true; // TODO: don't check this in!
method_trace_ = false;
method_trace_file_ = "/data/method-trace-file.bin";
@@ -464,6 +465,8 @@
gLogVerbosity.third_party_jni = true;
} else if (verbose_options[i] == "threads") {
gLogVerbosity.threads = true;
+ } else if (verbose_options[i] == "signals") {
+ gLogVerbosity.signals = true;
} else {
Usage("Unknown -verbose option %s\n", verbose_options[i].c_str());
return false;
diff --git a/runtime/stack.cc b/runtime/stack.cc
index 9c709ae..5e64e59 100644
--- a/runtime/stack.cc
+++ b/runtime/stack.cc
@@ -32,14 +32,6 @@
namespace art {
-// Define a piece of memory, the address of which can be used as a marker
-// for the gap in the stack added during stack overflow handling.
-static uint32_t stack_overflow_object;
-
-// The stack overflow gap marker is simply a valid unique address.
-void* stack_overflow_gap_marker = &stack_overflow_object;
-
-
mirror::Object* ShadowFrame::GetThisObject() const {
mirror::ArtMethod* m = GetMethod();
if (m->IsStatic()) {
@@ -305,56 +297,23 @@
bool exit_stubs_installed = Runtime::Current()->GetInstrumentation()->AreExitStubsInstalled();
uint32_t instrumentation_stack_depth = 0;
- bool kDebugStackWalk = false;
- bool kDebugStackWalkVeryVerbose = false; // The name says it all.
-
- if (kDebugStackWalk) {
- LOG(INFO) << "walking stack";
- }
for (const ManagedStack* current_fragment = thread_->GetManagedStack(); current_fragment != NULL;
current_fragment = current_fragment->GetLink()) {
cur_shadow_frame_ = current_fragment->GetTopShadowFrame();
cur_quick_frame_ = current_fragment->GetTopQuickFrame();
cur_quick_frame_pc_ = current_fragment->GetTopQuickFramePc();
- if (kDebugStackWalkVeryVerbose) {
- LOG(INFO) << "cur_quick_frame: " << cur_quick_frame_;
- LOG(INFO) << "cur_quick_frame_pc: " << std::hex << cur_quick_frame_pc_;
- }
if (cur_quick_frame_ != NULL) { // Handle quick stack frames.
// Can't be both a shadow and a quick fragment.
DCHECK(current_fragment->GetTopShadowFrame() == NULL);
mirror::ArtMethod* method = *cur_quick_frame_;
while (method != NULL) {
- // Check for a stack overflow gap marker.
- if (method == reinterpret_cast<mirror::ArtMethod*>(stack_overflow_gap_marker)) {
- // Marker for a stack overflow. This is followed by the offset from the
- // current SP to the next frame. There is a gap in the stack here. Jump
- // the gap silently.
- // Caveat coder: the layout of the overflow marker depends on the architecture.
- // The first element is address sized (8 bytes on a 64 bit machine). The second
- // element is 32 bits. So be careful with those address calculations.
-
- // Get the address of the offset, just beyond the marker pointer.
- byte* gapsizeaddr = reinterpret_cast<byte*>(cur_quick_frame_) + sizeof(uintptr_t);
- uint32_t gap = *reinterpret_cast<uint32_t*>(gapsizeaddr);
- CHECK_GT(gap, Thread::kStackOverflowProtectedSize);
- mirror::ArtMethod** next_frame = reinterpret_cast<mirror::ArtMethod**>(
- reinterpret_cast<byte*>(gapsizeaddr) + gap);
- if (kDebugStackWalk) {
- LOG(INFO) << "stack overflow marker hit, gap: " << gap << ", next_frame: " <<
- next_frame;
- }
- cur_quick_frame_ = next_frame;
- method = *next_frame;
- CHECK(method != nullptr);
- } else {
- SanityCheckFrame();
- bool should_continue = VisitFrame();
- if (UNLIKELY(!should_continue)) {
- return;
- }
+ SanityCheckFrame();
+ bool should_continue = VisitFrame();
+ if (UNLIKELY(!should_continue)) {
+ return;
}
+
if (context_ != NULL) {
context_->FillCalleeSaves(*this);
}
@@ -363,9 +322,6 @@
size_t return_pc_offset = method->GetReturnPcOffsetInBytes();
byte* return_pc_addr = reinterpret_cast<byte*>(cur_quick_frame_) + return_pc_offset;
uintptr_t return_pc = *reinterpret_cast<uintptr_t*>(return_pc_addr);
- if (kDebugStackWalkVeryVerbose) {
- LOG(INFO) << "frame size: " << frame_size << ", return_pc: " << std::hex << return_pc;
- }
if (UNLIKELY(exit_stubs_installed)) {
// While profiling, the return pc is restored from the side stack, except when walking
// the stack for an exception where the side stack will be unwound in VisitFrame.
@@ -398,10 +354,6 @@
cur_quick_frame_ = reinterpret_cast<mirror::ArtMethod**>(next_frame);
cur_depth_++;
method = *cur_quick_frame_;
- if (kDebugStackWalkVeryVerbose) {
- LOG(INFO) << "new cur_quick_frame_: " << cur_quick_frame_;
- LOG(INFO) << "new cur_quick_frame_pc_: " << std::hex << cur_quick_frame_pc_;
- }
}
} else if (cur_shadow_frame_ != NULL) {
do {
diff --git a/runtime/stack.h b/runtime/stack.h
index 73a823a..88ef78f 100644
--- a/runtime/stack.h
+++ b/runtime/stack.h
@@ -102,14 +102,6 @@
kVRegNonSpecialTempBaseReg = -3,
};
-// Special object used to mark the gap in the stack placed when a stack
-// overflow fault occurs during implicit stack checking. This is not
-// a real object - it is used simply as a valid address to which a
-// mirror::ArtMethod* can be compared during a stack walk. It is inserted
-// into the stack during the stack overflow signal handling to mark the gap
-// in which the memory is protected against read and write.
-extern void* stack_overflow_gap_marker;
-
// A reference from the shadow stack to a MirrorType object within the Java heap.
template<class MirrorType>
class MANAGED StackReference : public mirror::ObjectReference<false, MirrorType> {
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 23a6779..3a62cd5 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -243,10 +243,16 @@
pregion -= kStackOverflowProtectedSize;
// Touch the pages in the region to map them in. Otherwise mprotect fails. Only
- // need to do this on the main stack.
+ // need to do this on the main stack. We only need to touch one byte per page.
if (is_main_stack) {
- memset(pregion, 0x55, kStackOverflowProtectedSize);
+ byte* start = pregion;
+ byte* end = pregion + kStackOverflowProtectedSize;
+ while (start < end) {
+ *start = static_cast<byte>(0);
+ start += kPageSize;
+ }
}
+
VLOG(threads) << "installing stack protected region at " << std::hex <<
static_cast<void*>(pregion) << " to " <<
static_cast<void*>(pregion + kStackOverflowProtectedSize - 1);
@@ -255,6 +261,11 @@
LOG(FATAL) << "Unable to create protected region in stack for implicit overflow check. Reason:"
<< strerror(errno);
}
+
+ // Tell the kernel that we won't be needing these pages any more.
+ if (is_main_stack) {
+ madvise(pregion, kStackOverflowProtectedSize, MADV_DONTNEED);
+ }
}
void Thread::CreateNativeThread(JNIEnv* env, jobject java_peer, size_t stack_size, bool is_daemon) {