1 files changed, 45 insertions, 0 deletions
diff --git a/mfbt/LinuxSignal.h b/mfbt/LinuxSignal.h
new file mode 100644
index 000000000..83c2bf81f
--- /dev/null
+++ b/mfbt/LinuxSignal.h
@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_LinuxSignal_h
+#define mozilla_LinuxSignal_h
+
+namespace mozilla {
+
+#if defined(__arm__)
+
+// Some (old) Linux kernels on ARM have a bug where a signal handler
+// can be called without clearing the IT bits in CPSR first. The result
+// is that the first few instructions of the handler could be skipped,
+// ultimately resulting in crashes. To workaround this bug, the handler
+// on ARM is a trampoline that starts with enough NOP instructions, so
+// that even if the IT bits are not cleared, only the NOP instructions
+// will be skipped over.
+
+template <void (*H)(int, siginfo_t*, void*)>
+__attribute__((naked)) void
+SignalTrampoline(int aSignal, siginfo_t* aInfo, void* aContext)
+{
+  asm volatile (
+    "nop; nop; nop; nop"
+    : : : "memory");
+
+  asm volatile (
+    "b %0"
+    :
+    : "X"(H)
+    : "memory");
+}
+
+# define MOZ_SIGNAL_TRAMPOLINE(h) (mozilla::SignalTrampoline<h>)
+
+#else // __arm__
+
+# define MOZ_SIGNAL_TRAMPOLINE(h) (h)
+
+#endif // __arm__
+
+} // namespace mozilla
+
+#endif // mozilla_LinuxSignal_h