1 files changed, 12 insertions, 5 deletions
diff --git a/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc b/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
index d7fa5f6451d1..0f543d2d7c87 100644
--- a/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
+++ b/lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -57,6 +57,14 @@
 #include "sanitizer_mutex.h"
 #include "sanitizer_placement_new.h"
 
+// Sufficiently old kernel headers don't provide this value, but we can still
+// call prctl with it. If the runtime kernel is new enough, the prctl call will
+// have the desired effect; if the kernel is too old, the call will error and we
+// can ignore said error.
+#ifndef PR_SET_PTRACER
+#define PR_SET_PTRACER 0x59616d61
+#endif
+
 // This module works by spawning a Linux task which then attaches to every
 // thread in the caller process with ptrace. This suspends the threads, and
 // PTRACE_GETREGS can then be used to obtain their register state. The callback
@@ -245,8 +253,9 @@ static void TracerThreadDieCallback() {
 }
 
 // Signal handler to wake up suspended threads when the tracer thread dies.
-static void TracerThreadSignalHandler(int signum, void *siginfo, void *uctx) {
-  SignalContext ctx = SignalContext::Create(siginfo, uctx);
+static void TracerThreadSignalHandler(int signum, __sanitizer_siginfo *siginfo,
+                                      void *uctx) {
+  SignalContext ctx(siginfo, uctx);
   Printf("Tracer caught signal %d: addr=0x%zx pc=0x%zx sp=0x%zx\n", signum,
          ctx.addr, ctx.pc, ctx.sp);
   ThreadSuspender *inst = thread_suspender_instance;
@@ -263,7 +272,7 @@ static void TracerThreadSignalHandler(int signum, void *siginfo, void *uctx) {
 }
 
 // Size of alternative stack for signal handlers in the tracer thread.
-static const int kHandlerStackSize = 4096;
+static const int kHandlerStackSize = 8192;
 
 // This function will be run as a cloned task.
 static int TracerThread(void* argument) {
@@ -433,9 +442,7 @@ void StopTheWorld(StopTheWorldCallback callback, void *argument) {
     ScopedSetTracerPID scoped_set_tracer_pid(tracer_pid);
     // On some systems we have to explicitly declare that we want to be traced
     // by the tracer thread.
-#ifdef PR_SET_PTRACER
     internal_prctl(PR_SET_PTRACER, tracer_pid, 0, 0, 0);
-#endif
     // Allow the tracer thread to start.
     tracer_thread_argument.mutex.Unlock();
     // NOTE: errno is shared between this thread and the tracer thread.