1 files changed, 101 insertions, 47 deletions

diff --git a/contrib/llvm/lib/Support/Unix/Signals.inc b/contrib/llvm/lib/Support/Unix/Signals.inc
index 061cdb3..55fd76d 100644
--- a/contrib/llvm/lib/Support/Unix/Signals.inc
+++ b/contrib/llvm/lib/Support/Unix/Signals.inc
@@ -45,6 +45,17 @@
 #if HAVE_LINK_H
 #include <link.h>
 #endif
+#if HAVE_UNWIND_BACKTRACE
+// FIXME: We should be able to use <unwind.h> for any target that has an
+// _Unwind_Backtrace function, but on FreeBSD the configure test passes
+// despite the function not existing, and on Android, <unwind.h> conflicts
+// with <link.h>.
+#ifdef __GLIBC__
+#include <unwind.h>
+#else
+#undef HAVE_UNWIND_BACKTRACE
+#endif
+#endif
 
 using namespace llvm;
 
@@ -57,6 +68,8 @@ static void (*InterruptFunction)() = nullptr;
 
 static ManagedStatic<std::vector<std::string>> FilesToRemove;
 
+static StringRef Argv0;
+
 // IntSigs - Signals that represent requested termination. There's no bug
 // or failure, or if there is, it's not our direct responsibility. For whatever
 // reason, our continued execution is no longer desirable.
@@ -96,7 +109,7 @@ static void RegisterHandler(int Signal) {
   struct sigaction NewHandler;
 
   NewHandler.sa_handler = SignalHandler;
-  NewHandler.sa_flags = SA_NODEFER|SA_RESETHAND;
+  NewHandler.sa_flags = SA_NODEFER | SA_RESETHAND | SA_ONSTACK;
   sigemptyset(&NewHandler.sa_mask);
 
   // Install the new handler, save the old one in RegisteredSignalInfo.
@@ -106,6 +119,35 @@ static void RegisterHandler(int Signal) {
   ++NumRegisteredSignals;
 }
 
+#if defined(HAVE_SIGALTSTACK)
+// Hold onto the old alternate signal stack so that it's not reported as a leak.
+// We don't make any attempt to remove our alt signal stack if we remove our
+// signal handlers; that can't be done reliably if someone else is also trying
+// to do the same thing.
+static stack_t OldAltStack;
+
+static void CreateSigAltStack() {
+  const size_t AltStackSize = MINSIGSTKSZ + 8192;
+
+  // If we're executing on the alternate stack, or we already have an alternate
+  // signal stack that we're happy with, there's nothing for us to do. Don't
+  // reduce the size, some other part of the process might need a larger stack
+  // than we do.
+  if (sigaltstack(nullptr, &OldAltStack) != 0 ||
+      OldAltStack.ss_flags & SS_ONSTACK ||
+      (OldAltStack.ss_sp && OldAltStack.ss_size >= AltStackSize))
+    return;
+
+  stack_t AltStack = {};
+  AltStack.ss_sp = reinterpret_cast<char *>(malloc(AltStackSize));
+  AltStack.ss_size = AltStackSize;
+  if (sigaltstack(&AltStack, &OldAltStack) != 0)
+    free(AltStack.ss_sp);
+}
+#else
+static void CreateSigAltStack() {}
+#endif
+
 static void RegisterHandlers() {
   // We need to dereference the signals mutex during handler registration so
   // that we force its construction. This is to prevent the first use being
@@ -116,6 +158,10 @@ static void RegisterHandlers() {
   // If the handlers are already registered, we're done.
   if (NumRegisteredSignals != 0) return;
 
+  // Create an alternate stack for signal handling. This is necessary for us to
+  // be able to reliably handle signals due to stack overflow.
+  CreateSigAltStack();
+
   for (auto S : IntSigs) RegisterHandler(S);
   for (auto S : KillSigs) RegisterHandler(S);
 }
@@ -309,20 +355,64 @@ static bool findModulesAndOffsets(void **StackTrace, int Depth,
 }
 #endif // defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES) && ...
 
+#if defined(ENABLE_BACKTRACES) && defined(HAVE_UNWIND_BACKTRACE)
+static int unwindBacktrace(void **StackTrace, int MaxEntries) {
+  if (MaxEntries < 0)
+    return 0;
+
+  // Skip the first frame ('unwindBacktrace' itself).
+  int Entries = -1;
+
+  auto HandleFrame = [&](_Unwind_Context *Context) -> _Unwind_Reason_Code {
+    // Apparently we need to detect reaching the end of the stack ourselves.
+    void *IP = (void *)_Unwind_GetIP(Context);
+    if (!IP)
+      return _URC_END_OF_STACK;
+
+    assert(Entries < MaxEntries && "recursively called after END_OF_STACK?");
+    if (Entries >= 0)
+      StackTrace[Entries] = IP;
+
+    if (++Entries == MaxEntries)
+      return _URC_END_OF_STACK;
+    return _URC_NO_REASON;
+  };
+
+  _Unwind_Backtrace(
+      [](_Unwind_Context *Context, void *Handler) {
+        return (*static_cast<decltype(HandleFrame) *>(Handler))(Context);
+      },
+      static_cast<void *>(&HandleFrame));
+  return std::max(Entries, 0);
+}
+#endif
+
 // PrintStackTrace - In the case of a program crash or fault, print out a stack
 // trace so that the user has an indication of why and where we died.
 //
 // On glibc systems we have the 'backtrace' function, which works nicely, but
 // doesn't demangle symbols.
 void llvm::sys::PrintStackTrace(raw_ostream &OS) {
-#if defined(HAVE_BACKTRACE) && defined(ENABLE_BACKTRACES)
-  static void* StackTrace[256];
+#if defined(ENABLE_BACKTRACES)
+  static void *StackTrace[256];
+  int depth = 0;
+#if defined(HAVE_BACKTRACE)
   // Use backtrace() to output a backtrace on Linux systems with glibc.
-  int depth = backtrace(StackTrace,
+  if (!depth)
+    depth = backtrace(StackTrace, static_cast<int>(array_lengthof(StackTrace)));
+#endif
+#if defined(HAVE_UNWIND_BACKTRACE)
+  // Try _Unwind_Backtrace() if backtrace() failed.
+  if (!depth)
+    depth = unwindBacktrace(StackTrace,
                         static_cast<int>(array_lengthof(StackTrace)));
-  if (printSymbolizedStackTrace(StackTrace, depth, OS))
+#endif
+  if (!depth)
+    return;
+
+  if (printSymbolizedStackTrace(Argv0, StackTrace, depth, OS))
     return;
-#if HAVE_DLFCN_H && __GNUG__
+#if HAVE_DLFCN_H && __GNUG__ && !defined(__CYGWIN__)
   int width = 0;
   for (int i = 0; i < depth; ++i) {
     Dl_info dlinfo;
@@ -369,7 +459,7 @@ void llvm::sys::PrintStackTrace(raw_ostream &OS) {
     }
     OS << '\n';
   }
-#else
+#elif defined(HAVE_BACKTRACE)
   backtrace_symbols_fd(StackTrace, depth, STDERR_FILENO);
 #endif
 #endif
@@ -383,7 +473,10 @@ void llvm::sys::DisableSystemDialogsOnCrash() {}
 
 /// PrintStackTraceOnErrorSignal - When an error signal (such as SIGABRT or
 /// SIGSEGV) is delivered to the process, print a stack trace and then exit.
-void llvm::sys::PrintStackTraceOnErrorSignal(bool DisableCrashReporting) {
+void llvm::sys::PrintStackTraceOnErrorSignal(StringRef Argv0,
+                                             bool DisableCrashReporting) {
+  ::Argv0 = Argv0;
+
   AddSignalHandler(PrintStackTraceSignalHandler, nullptr);
 
 #if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
@@ -402,42 +495,3 @@ void llvm::sys::PrintStackTraceOnErrorSignal(bool DisableCrashReporting) {
   }
 #endif
 }
-
-
-/***/
-
-// On Darwin, raise sends a signal to the main thread instead of the current
-// thread. This has the unfortunate effect that assert() and abort() will end up
-// bypassing our crash recovery attempts. We work around this for anything in
-// the same linkage unit by just defining our own versions of the assert handler
-// and abort.
-
-#if defined(__APPLE__) && defined(ENABLE_CRASH_OVERRIDES)
-
-#include <signal.h>
-#include <pthread.h>
-
-int raise(int sig) {
-  return pthread_kill(pthread_self(), sig);
-}
-
-void __assert_rtn(const char *func,
-                  const char *file,
-                  int line,
-                  const char *expr) {
-  if (func)
-    fprintf(stderr, "Assertion failed: (%s), function %s, file %s, line %d.\n",
-            expr, func, file, line);
-  else
-    fprintf(stderr, "Assertion failed: (%s), file %s, line %d.\n",
-            expr, file, line);
-  abort();
-}
-
-void abort() {
-  raise(SIGABRT);
-  usleep(1000);
-  __builtin_trap();
-}
-
-#endif