Implicit null/suspend checks (oat version bump)

This adds the ability to use SEGV signals
to throw NullPointerException exceptions from Java code rather
than having the compiler generate explicit comparisons and
branches.  It does this by using sigaction to trap SIGSEGV and when triggered
makes sure it's in compiled code and if so, sets the return
address to the entry point to throw the exception.

It also uses this signal mechanism to determine whether to check
for thread suspension.  Instead of the compiler generating calls
to a function to check for threads being suspended, the compiler
will now load indirect via an address in the TLS area.  To trigger
a suspend, the contents of this address are changed from something
valid to 0.  A SIGSEGV will occur and the handler will check
for a valid instruction pattern before invoking the thread
suspension check code.

If a user program taps SIGSEGV it will prevent our signal handler
working.  This will cause a failure in the runtime.

There are two signal handlers at present.  You can control them
individually using the flags -implicit-checks: on the runtime
command line.  This takes a string parameter, a comma
separated set of strings.  Each can be one of:

none        switch off
null        null pointer checks
suspend     suspend checks
all         all checks

So to switch only suspend checks on, pass:
-implicit-checks:suspend

There is also -explicit-checks to provide the reverse once
we change the default.

For dalvikvm, pass --runtime-arg -implicit-checks:foo,bar

The default is -implicit-checks:none

There is also a property 'dalvik.vm.implicit_checks' whose value is the same
string as the command option.  The default is 'none'.  For example to switch on
null checks using the option:

setprop dalvik.vm.implicit_checks null

It only works for ARM right now.

Bumps OAT version number due to change to Thread offsets.

Bug: 13121132
Change-Id: If743849138162f3c7c44a523247e413785677370

1 files changed, 4 insertions, 0 deletions

diff --git a/runtime/thread.cc b/runtime/thread.cc
index fbdf95f..f4b9d9a 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -302,6 +302,7 @@ void Thread::Init(ThreadList* thread_list, JavaVMExt* java_vm) {
   SetUpAlternateSignalStack();
   InitCpu();
   InitTlsEntryPoints();
+  RemoveSuspendTrigger();
   InitCardTable();
   InitTid();
   // Set pthread_self_ ahead of pthread_setspecific, that makes Thread::Current function, this
@@ -576,6 +577,7 @@ void Thread::ModifySuspendCount(Thread* self, int delta, bool for_debugger) {
     AtomicClearFlag(kSuspendRequest);
   } else {
     AtomicSetFlag(kSuspendRequest);
+    TriggerSuspend();
   }
 }
 
@@ -643,6 +645,7 @@ bool Thread::RequestCheckpoint(Closure* function) {
     checkpoint_functions_[available_checkpoint] = nullptr;
   } else {
     CHECK_EQ(ReadFlag(kCheckpointRequest), true);
+    TriggerSuspend();
   }
   return succeeded == 0;
 }
@@ -1774,6 +1777,7 @@ void Thread::DumpThreadOffset(std::ostream& os, uint32_t offset, size_t size_of_
   // DO_THREAD_OFFSET(top_of_managed_stack_);
   // DO_THREAD_OFFSET(top_of_managed_stack_pc_);
   DO_THREAD_OFFSET(top_sirt_);
+  DO_THREAD_OFFSET(suspend_trigger_);
 #undef DO_THREAD_OFFSET
 
   size_t entry_point_count = arraysize(gThreadEntryPointInfo);