diff --git a/ABI-bugs.txt b/ABI-bugs.txt
--- /dev/null
+++ b/ABI-bugs.txt
@@ -0,0 +1,15 @@
+KNOWN ABI BUGS
+--------------
+
+ time_t is 32-bit. http://b/5819737
+
+ off_t is 32-bit. There is off64_t, but no _FILE_OFFSET_BITS support.
+
+ sigset_t is too small on ARM and x86 (but correct on MIPS), so support
+ for real-time signals is broken. http://b/5828899
+
+ Too few TLS slots mean we can't allocate 128 pthread_key_t instances,
+ which POSIX says should be the minimum.
+
+ atexit(3) handlers registered by a shared library aren't called on
+ dlclose(3); this only affects ARM. http://b/4998315